Progress 10/01/02 to 09/30/07
Outputs
Phylloxera research explored the nature of grapevine damage and durability of resistance of rootstocks. Virulence of soil fungal isolates is associated with phylloxera damage to vines. However, rootstocks resist the insect building its population, and not fungal infection. Of 8 cultivars tested, some including V. vinifera none had different fungal susceptibility. Similarly, vine stress did not change vine susceptibility to the fungi. Petri dish tests showed that phylloxera probing spread fungal infections to tertiary roots that were not susceptible to tuberosities. However, these results were not supported by whole plant greenhouse and field experiments: phylloxera vectoring of pathogens through probing is not a field issue. A study of vine genome through an AXR#1-like cross showed that nodosity and tuberosity formation are controlled by distinct sets of genes. Seasonal field tests showed that gall formation is the limiting factor for phylloxera populations.
These findings were considered when we found high nodosity populations on 3 strongly resistant rootstocks in vineyards in Napa and Sonoma Co. A nodosity bioassay was developed and showed that strains from these fields were phenotypically characterizable: Strong nodosity population growth was seen on an array of pure American rootstocks but not on root types that incorporated V. vinifera. These findings question the conventional definitions of susceptibility and resistance. Damage seen in some of the fields initially appeared to be associated with the nodosity populations, however, in the 2006 work this was not the case. We did a survey of random fields in Sonoma, Napa and Yolo Co. CA focusing on the rootstock 101-14 Mgt and found about half the fields with nodosities, but with no attributable damage. Without the possibility that probing can spread fungal associated phylloxera damage, we know of no mechanism by which the nodosity populations could cause vine damage. It is likely that
the damage we saw previously was caused by early season root growth out-pacing late irrigation. California phylloxera are diverse genotypically. Over 3 years about 300 phylloxera populations were SSR fingerprinted finding >80 genotypes. Single founder colonies from 3 strongly resistant rootstocks did not differ in virulence spectrum on hosts of origin suggesting they are all a single phenotypic strain. Hints of this rootstock strain had been seen a decade previous, so this strain is not new and is in all surveyed regions. This strain is distinct from biotype B both in phenotypical behavior on rootstocks as well as in genotyping using SSRs. It did not arise from existing populations but was introduced, possibly at planting. Genotypes of phylloxera colonies originating on AXR#1 appear to be distinct from strains on the strongly resistant rootstocks. A test of sexual recombination on whole greenhouse vines is in process to help determine how the variation seen arises. Phylloxera
forming leaf galls in Yolo Co. were not genetically distinct from close by or remote root feeders. Two-quart bowls with TanglefootTM were used as emergence traps and identified rootstocks as hosts for alates and crawlers.
Impacts
Knowledge that phylloxera damage to vines is associated with and possibly caused by virulent fungal pathogens suggests ways to minimize damage to susceptible rootstocks and increase their durability. Minimizing infections can be done using composts (though we do not know the mechanism in the phylloxera associated situation), decreasing root pruning via plowing, and possibly chemical controls. This perspective on the nature of damage is useful for farmers who want to use the newer insecticides for phylloxera damage control: our work suggests that early preventative treatments would be relevant but that continued treatments will be necessary. An important rootstock issue concerns durability of resistance. We showed that the newly quantified nodosity populations were not a known cause of damage seen. The fact that these populations have been around for decades, are numerous, and are completely without tuberosity damage suggests that phylloxera is not rapidly being
selected to overcome tuberosity resistance. High nodosity populations do not indicate rootstock failure. Our bioassays showed that strains do not vary appreciably based on root type of field origin even though they differ genetically as seen by SSRs. Lack of obvious selection from existing phylloxera populations suggests that limiting human movement of the insect is a key strategy. However, we need to know how the high genetic variability arises. Our new trapping method and nodosity bioassay will be useful in the work of other researchers in characterizing phylloxera populations in the field and laboratory.
Publications
- J. Granett, 2004. Ruling out the wine plague. Nature 428:20 (a book review)
- T.L. Roush. 2006. Genetic analysis of galling responses in Vitis vinifera x V. rupestris hybrids to grape phylloxera (Daktulosphaira vitifoliae) PhD Thesis, Univ. of Calif. Davis, 90pp.
- M.A. Fossen. 2006. Biological constraints affecting root damage on grapevines infested with grape phylloxera (Daktulosphaira vitifoliae (Fitch) [Hemiptera: Phylloxeridae] PhD Thesis, Univ of Calif. Davis, 64 pp.
- Powell., K.,S., Burns, A., Granett, J. and G. McGourty. 2006. Influence of composted green waste on grapevine phylloxera (Daktulosphaira vitifoliae Fitch) management, Poster, 6th International Cool Climate Symp. Vitic. Oenol., 6-10 Feb 2006, Christchurch New Zealand.
- Powell., K.,S., Burns, A., Granett, J., Norng, S., and G. McGourty. 2006. Influence of composted green waste on the population dynamics and dispersal of grapevine phylloxera Daktulosphaira vitifoliae. Agric. Ecosys. Environ. (in press).
- Edwards, J., Powell, K., Granett, J. 2006. Tritrophic interactions between grapevines, phylloxera, and pathogenic fungi--establishing the root cause of grapevine decline. Australian & New Zealand Grapegrower & Winemaker. Oct.: 33-37.
|
Progress 01/01/05 to 12/31/05
Outputs
1. Fields with damage to phylloxera-resistant rootstocks (with M.A. Walker, Vit. & Enol., UCDavis): Of the vineyard blocks identified as showing damage associated with nodosity phylloxera last year, the two Sonoma blocks were removed from experiments by the owners. One of the Napa sites was removed from consideration by discovery of AXR#1 in the block and some scion rooting. We found one additional genuine 101-14 Mgt block in Napa with significant nodosity populations. One untested hypothesis for the cause of damage in this latter site was a root system too large to be supported by midsummer irrigation.
2. Does phylloxera probing vector fungal necrosis to cause vine damage? We set up greenhouse and field tests to determine if nodosity associated damage is caused by a spreading of fungal necrosis as a result of phylloxera probing on storage roots. 101-14 Mgt vines were treated with a virulent Fusarium strain or not. In addition the vines were infested with Type A
phylloxera, a 101-14 phylloxera strain, or none. Ten of the greenhouse plants were evaluated in the fall. Increased fungal necrosis was not associated with the presence of the 101-14 Mgt adapted phylloxera. Rather than completing the test in the fall we let the vines overwinter in case the vectoring activity was enhanced by spring conditions. Similarly, the field-plants will be evaluated summer 2006.
3. Bioassays and DNA fingerprinting: We used the nodosity bioassay method developed last year to test the virulence of 6 phylloxera colonies against up to 26 rootstocks and V. vinifera cv 'Chardonnay.' First, observations of activity on field growing vines and the bioassays suggest the phenotypes of 3 strains colonized from 101-14 Mgt roots caused strong nodosities on this root type unlike Type A or B phylloxera. Site conditions likely mediate this activity. Second, root sensitivity of strains is similar in June and August. Third, the three colonies which had a 101-14 Mgt host of
origin responded to many rootstocks similarly. They tended to be more virulent on rootstocks with V. rupestris, V. riparia or V. berlandieri parentage while they tended to be inhibited on V. vinifera parentage rootstocks. The reverse response was seen with Types A and B. These parentage correlations are somewhat subjective since each plant parent contributes only half of its traits to hybrids. The mechanism for virulence on the V. rupestris and V. riparia hybrids appears to be ability to form the nodosity. Fourth, the 101-14 colonies had higher phylloxera survivorship, development, and fecundity on the 101-14 Mgt rootstock. However, these colonies were less strong in all three parameters on the V. vinifera and AXR#1. Conversely, for the Type A and B colonies V. vinifera susceptibility is seen clearly and the non-V. vinifera rootstock 101-14 Mgt retains resistance. These data indicate that V. vinifera has non-host traits within its genome and rootstocks have host traits. We had
difficulty with the DNA fingerprinting because of inadequate extraction. However, with 4 primers we saw a complete separation of 6 genotypes between AXR#1 and 5C field plantings.
Impacts
This work investigates a previously unknown damage scenario for phylloxera. The past understanding was that vine damage was limited to storage root (tuberosity) phylloxera populations. Since tuberosities are not seen on resistant roots, resistance of currently used rootstocks has remained durable. Our observations of high feeder root (nodosity) infestations seemingly associated with vine damage question this understanding. Our bioassays demonstrate a nodosity-virulent phenotype that is clearly associated with field populations on roots. The phenotypes select for rootstocks that previously have been resistant to nodosities, and preliminary data indicate that genotypes reflect this distribution. Our probing experiment will disprove or support the contention that nodosity populations cause damage via spread of fungal infections through probing. If the hypothesis is disproved, we will need to look for other reasons for poor vine health in some of the infested sites. If it
is supported, we must then determine whether spread of the problem is occurring. The former outcome will minimize the impact and suggest that the nodosity virulence at this point is not of great significance. However it does not rule out the possibility that this virulence will lead eventually to damaging tuberosity virulence. On the other hand, if probing is damaging via spread of fungal infections, this will suggest that these nodosity strains of phylloxera are sufficient as they are to be very problematical for the grape industry, though further selection, would be even worse.
Publications
- Granett, J., Kocsis, L., Horvath, L., Horvathne, E.B. 2005. Grape phylloxera gallicole and radicicole activity on grape rootstock vines. HortScience 40(1):150-153.
- Lin, H., M. A.Walker, R. Hu, and J. Granett. New simple sequence repeat loci for the study of grape phylloxera (Daktulosphaira vitifoliae) genetics and host adaptation. American Journal of Enology and Viticulture 57(1), 33-40, 2006
|
Progress 01/01/04 to 12/31/04
Outputs
1. C02: We previously documented that grape phylloxera kill grape roots by allowing fungal infections at feeding wounds and last year began testing CO2 production and O2 utilization by roots under these circumstances in laboratory experiments. We demonstrated depletion of O2 in a few weeks in glass containers with the CO2 concentration exceeding 20% of the gas volume. We found that packed clay soil inhibited diffusion of CO2 away from roots in these laboratory experiments. We began developing methods to test this with intact field vines. We hypothesize that diffusion methods for measuring soil CO2 are invalid because of relatively impervious pores around clay-bound roots, especially roots that are fungi-infected. 2. Field damage of grape phylloxera-resistant rootstocks (with M. A. Walker, Dept of Vit. & Enol., UCDavis): We have found vineyard blocks in Napa, Sonoma, and Mendocino Co. in which strongly resistant rootstocks (101-14 Mgt and Teleki 5C) have developed
easily observable feeder root phylloxera populations and exhibit above ground reduced cane growth that appears to be phylloxera-like damage. Nematode populations in soil samples from affected vineyard sites are not sufficient to cause the observed damage. We hypothesized that the local conditions caused the phylloxera population build up which then allowed first instars to probe but not survive on mature roots. We suggest that the probing may have been sufficient to allow pathogenic fungus infections to harm mature roots. To test this scenario we set up experiments of probing in the laboratory and in enclosures on attached roots in the field. These tests demonstrated that phylloxera probing on resistant roots was capable of allowing fungal infections of mature 101-14 and 5C roots. In addition, we determined in laboratory bioassays that soil fungal community in damaged areas of vineyards was virulent against grape roots in comparison with the low virulence of soil fungi in vineyard
sites not showing vine damage. These observations support our hypotheses but do not prove it. We will continue with whole-vine, relatively non-invasive experiments. 3. Emergence trapping of phylloxera: We tested inverted 2 liter Tupper TM bowls as emergence traps for phylloxera in the infected vineyards monitored in the previously described work. A strip of double sided tape coated with Tanglefoot TM was placed on the inside bottom of the bowls. These traps were placed inverted in vine rows and collected emerging phylloxera over two week periods. Traps were evaluated in infested rootstock vineyards described above as well as vineyard blocks with susceptible V. vinifera and AXR#1 roots. Populations were highest in early summer declining thereafter with a second peak in late summer in some vineyards. Catch was predominantly of first instar crawlers however some vineyard sites had very high winged-adult populations emerging in late summer. Moist soil conditions produce more emerging
phylloxera than dry soil conditions.
Impacts
1. Grape phylloxera is a worldwide pest. It kills roots by creating wounds that permit infection by fungi. These pathogens cause necrosis, girdling storage roots, killing them. Our laboratory experiments showed that considerable CO2 is produced by the fungi in the process of causing the necrosis. We hypothesize that some of the CO2 is trapped around the roots by impervious clay-soil pores. If we can test for clay soil pores that do not permit CO2 or O2 diffusion, it is possible that saprophytic as well as pathogenic fungi may cause destructively high CO2 and low O2 concentrations around these roots. This would alter animal populations in the soil, change the microbial ecology around roots, and, if unsuitable gas concentrations were held long, this would negatively impact root health. Although soil biologists do not believe that impermeable pores can form around roots, such a condition has not been disproved. If we can demonstrate low-diffusion pores in the field, this
result would have wide ramifications for agriculture. 2. Grapevines are protected from phylloxera by phylloxera-resistant rootstocks. Our study of field damage by phylloxera to strongly resistant rootstocks, may be a first unequivocal demonstration of this anywhere in the world. We do not know how severely this circumstance will affect rootstocks long term. If damage is harsh and spreads, consequences for viticulture will be severe. On the other hand, if the damage is related to the replanting on previously phylloxera-damaged sites, than consequences are circumstantial and less ominous.
Publications
- No publications reported this period
|
Progress 01/01/03 to 12/31/03
Outputs
We studied high and low virulence secondary fungal pathogens (Fusarium oxysporum) from phylloxera-infested vines. 1) We tested virulence on 2 year grape rootstocks and a Vitis vinifera cultivar. They were inoculated last year and evaluated in spring this year. All rootstocks were susceptible and the low and high virulence was confirmed. No differences between rootstocks were seen. This field confirmation completes work indicating that F. oxysporum virulence is variable and predictable from lab bioassays. 2) We did replicated water stress and crop load stress tests on Cabernet vines at the UC field station in Hopland, CA to determine whether fungal virulence is influenced. The experiment achieved stress as indicted by pressure bomb measurements of leaf stem water retention for water stress and crop measurements for crop load stress. Results suggest that these stresses do not increase virulence of F. oxysporum isolates. A parallel test on the UC Davis campus suggested
that water stress does not influence phylloxera vigor, either. These results were unexpected and suggest that viticulturally relevant stress physiology is not important to infection or infestation. Stress is frequently used in vineyard management for grape quality. These results suggest the hypothesis that field differences in vineyard decline from phylloxera activity is not based on vine physiology, but rather ecological conditions. The fourth year of the field trial using compost to ameliorate phylloxera vine damage in a mature vineyard was completed. Treatments included plots with and without compost cover, hay cover, and tillage. Treatment effects with regard to phylloxera populations, root necrosis, and vine production and vigor were not seen. We will terminate this experiment. The results suggest that the cause of slow vine decline in phylloxerated organic vineyards is not simply soil organic matter. We are conducting laboratory tests of ethylene and ethylene inhibitor on
phylloxera gall formation. Although treatments clearly impact callus production, the effects on the insect are not clear. We will continue trying to identify regulating mechanisms of phylloxera gall formation. This is important because gall formation is the limiting factor for phylloxera survival and population growth. We have begun collaborating with D. Smart (UCDavis Dept of Viticulture & Enology) on phylloxera populations on rootstocks as observed in vineyards in buried tubes. Phylloxera were found on 3 rootstocks at the Napa field station by visual observation and emergence traps on the vineyard surface. These results suggest mechanisms by which rootstocks might prevent selection of virulent phylloxera strains. We are planning ways to test this suggestion. We began testing root and fungus CO2 production and O2 utilization as mediating factors for insect and possibly root health. Excised root pieces infected with F. oxysporum in closed containers can produce a sufficiently high
CO2/O2 ratio in one week to inhibit phylloxera. We will continue these tests to determine whether this mechanism plays a positive or negative role in vineyards.
Impacts
Severe phylloxera-caused vine damage is prevented by rootstocks. Since we do not know how rootstocks work and have limited knowledge of the grapevine-insect interaction, we can not trouble-shoot problems. The goal of this research is to understand the nature of phylloxera damage and the plant-insect-soil microbiology interactions. This knowledge will help maintain trouble-free rootstock use.
Publications
- Granett, J., M. A. Walker, L. Kocsis. 2003. Grape phylloxera damage, ecology, variability, and management. 6th Slovenian Conf. Plant Protection, Zrece, 4-6 March 2003, Ljubljana. pp 409-413
- Granett, J., Huisman, O. C., McGourty, G. 2003. Compost and Mulch Demonstration Project, Mendocino County: Use of Compost and Mulches for North Coast Vineyards. http://www.ciwmb.ca.gov/publications/organics/44203002.pdf
|
Progress 01/01/02 to 12/31/02
Outputs
We studied the Fusarium oxysporum isolates collected in 2001 from phylloxerated vines and ranked as high, medium, or low virulence. 1) We began to confirm isolate virulence level on vines newly planted in a Davis, CA field. Six grape rootstocks and a Vitis vinifera cultivar were planted in early summer and in autumn were inoculated with low or high virulence fungal strains or no fungus using single-root cloth enclosures held in place with clips. The study will be evaluated in 2003. 2) Natural selection of low or high virulence characteristics from a mix of the fungal isolates by pathogenic or non pathogenic culture conditions was tested in Petri dish experiments. Results suggest that selection did not occur. The experiment will be replicated in 2003. 3) A small vineyard trial in Hopland, CA tested whether water stress applied to vines changed apparent virulence of fungal inoculations on roots. Results suggest that stress increases virulence of F. oxysporum isolates.
4) Fungal isolates that have been used were originally extracted from partially necrotic vineyard roots without regard to where in the root the isolate arose. We tested the hypothesis that isolates from necrotic tissue will be less virulent than isolates from tissue that is not yet necrotic at the leading edge of an infection. Results falsified the hypothesis. Virulence was independent of necrotic state of the tissue from which the isolate was taken. L. Kocsis (Vesperim U., Hungary) and I evaluated data collected in 2000 on phylloxera leaf galls suggesting that leaf infestations come from insects overwintering in the soil and that leaf galling is synergized by presence of other leaf galls. These discoveries explain the enigma that populations of leaf galls are very uneven in susceptible vineyards. The rate limiting factor for leaf phylloxera populations is gall formation (this was previously shown with root feeding phylloxera). A common physiological interaction exists between
phylloxera and plant independent of feeding site. Preliminary data for both roots and leaves suggest feeding attractants/arrestants may be involved as well as the physiological factors inducing gall formation. We will now focus on identifying factors. We evaluated fungal isolates from Vitis labrusca cultivars in NY in conjunction with G. English-Loeb (NYAES). We had hypothesized that the low level of damage of those cultivars by phylloxera infestations was due to resistance of the roots to fungal infections. This hypothesis was disproved. Instead the low level of damage appears to be due to the lack of phylloxera feeding on the mature roots - their infestation appears to be limited to immature feeder roots which result in considerably less vine damage than does feeding on mature roots. We continued the large field trial using compost to ameliorate phylloxera vine damage in a mature vineyard for the third year. Treatments include plots with and without compost cover, hay cover, and
tillage. To date treatment effects with regard to phylloxera populations or root necrosis have not been seen. However treatments with tillage appear to be healthier. This experiment will be continued into 2003.
Impacts
Severe phylloxera-caused vine damage is prevented by rootstocks. Since we don't know how rootstocks work and have limited knowledge of the grapevine-insect interaction, we can not trouble shoot problems. This research provides a basic understanding of the nature of phylloxera damage and the plant-insect-soil microbiology interactions. This knowledge will help maintain trouble-free rootstock use.
Publications
- M. A. Fossen. 2002. Resistance of grapevine rootstocks to root-pathogenic fungi vectored by grape phylloxera (Daktulosphaira vitifoliae Fitch). MS Thesis. Plant Protection and Pest Management, University of California, Davis.
- Kocsis, L., Granett, J., and Walker, M. A. 2002. Performance of Hungarian phylloxera strains in bioassays of Vitis riparia and rootstocks. Georgikon for Agriculture 13:1-15.
- Omer, A. D., Granett, J., and Walker, M. A. 2002. Influence of plant growth stage on grape phylloxera (Homoptera: Phylloxeridae) populations. Environmental Entomology. 31: 120-126.
- Kocsis, L., Granett, J., and Walker, M. A. 2002. Performance of Hungarian phylloxera strains on Vitis riparia rootstocks. Journal of Applied Entomology. 126: 567-571.
|
Progress 01/01/01 to 12/31/01
Outputs
1) We collected phylloxera-infested roots from 27 vineyards in 8 California counties and isolated fungi responsible for root necrosis from the phylloxera feeding sites. After confirming pathogenicity of each isolate on Vitis vinifera L., we have begun to screen them for virulence on rootstocks (3309C, O 39-16, Freedom, Teleki 5C, 101-14 Mgt, AXR#1). Virulence varies with isolate and root type. Necrosis on V. vinifera roots average 26% (with some isolates ranging to 80%) and while rootstocks average about 13% (ranging to 50%). Individual isolates that are ranked high, medium, or low virulence on V. vinifera, average the same ranking on rootstocks suggesting that the level of damage on V. vinifera predicts the level on rootstocks. These results suggest that rootstocks might be damaged if virulent fungi as well as aggressive grape phylloxera biotypes were to co-exist. 2) We hypothesize that management of soil organic matter will alter susceptibility of grapevine roots to
these necrosis-causing fungi. This was the 3rd and terminal year of a field trial of this hypothesis with young grapevines in compost-amended soil. Though the second year results were promising, showing significantly less root necrosis with sterilized or living composts, the third year results showed that the vines outgrew any early protection. The results are reported in the termination report under CA-D*-ENT-6520-CG. A second field trial established last year with mature vines and surface compost treatments is also testing tillage. Second year results have yet to show strong treatment effects with compost, however, the tillage treatments are beginning to show enhanced growth. We worried about the high root necrosis in this trial and set up a third trial in a part of the vineyard with less root necrosis. 3) In greenhouse tests we evaluated vineyard soils and compost for ability to suppress the necrosis. We found that vineyard soils from sites with a high level of phylloxera damage
cause a high level of necrosis to wounded vines. However, mixing such soils with compost or soils from vineyard sites with low levels of phylloxera-related root necrosis, decreased that virulence. These results demonstrate that some soils as well as compost suppress root necrosis. 4) Second year field trials with the commercial systemic insecticide, imidocloprid and with the fungicide Ridomil showed little or no protection against root necrosis. 5) Data on overwintering survival of grape phylloxera on vineyard vines showed that it was low but measurable. 6) We began tests with plant hormone treatments of excised roots to determine impact on phylloxera survival. In sealed Petri dishes, indole acetic acid (auxin) and BAP (a kinetin analog) killed phylloxera or caused failure of feeding sites. In contrast Ethrel (a commercial ethylene releasing product) increased phylloxera survival over controls. Ventilation of dishes suggested that the auxin and kinetin results worked directly on the
treated roots. The Ethrel results occurred by vapor and on directly treated roots. These experiments will be continued with whole plants.
Impacts
The work with fungal isolates suggest that strongly resistant rootstocks are not immune to damage. Although strongly resistant rootstocks have not failed to grape phylloxera, our work suggests they are subject to failure if a virulent fungal isolate and an aggressive phylloxera biotype were to co-exist. Our compost work demonstrates that addition of organic matter to soils will not prevent phylloxera damage. Our work with the plant hormones gives us insights into the way phylloxera form feeding sites.
Publications
- Downie, D., and Granett, J. 2000. Genetic divergence in geographically isolated populations of native grape phylloxera, Daktulosphaira vitifoliae (Fitch). southwestern Entomologist 25 (4):255-263.
- Granett, J., Omer, A.D., Walker, M.A. 2001. Seasonal capacity of attached and detached vineyard roots to support grape phylloxera (Homoptera: Phylloxeridae). Journal Economic Entomology 94(10:138-144.
- Omer, A.D., Granett, J., Karban, R., and Vila, E.M. 2001. Chemical induced resistance against multiple pests in cotton. International Journal of Pest Management 47(1):49-54.
- Downie, D.A., Fisher, J.R., Granett, J. 2001. Grapes, galls, and geography: The distribution of nuclear and mitochondrial DNA variation across host-plant species and regions in a specialist herbivore. Evolution. 55(7): 1345-1362.
|
Progress 01/01/00 to 12/31/00
Outputs
1) This year, we surveyed phylloxera-infested, organically and conventionally managed vineyards (Mendocino Co, Calif.). Organically managed vineyards had half the level of root necrosis as conventionally managed vineyards. This work independently confirmed last year's report. We set up an experiment using soil from a highly necrotic, conventionally managed phylloxera vineyard and showed that we could detect differences in pathogen virulence from this vineyard relative to virulence of pathogens from a close by, organically managed, low-necrosis vineyard. This experiment suggests that pathogen virulence is a variable in phylloxera related vine damage. 2) The 1999-established field trial has been infested a full year with various soil treatments. Data from June 2000 indicated no treatment effects relative to phylloxera populations or root necrosis for the following treatments: Live compost, sterile compost, high nitrogen, low nitrogen, control. However, the September
data found that both compost treatments suppressed root necrosis and resulted in greater root and cane growth in comparison with the nitrogen and control treatments. Phylloxera population levels were not distinguishable between treatments. These data confirm greenhouse experiments and suggest that vineyard soil management can influence phylloxera-related vine damage. This experiment will be concluded next year. This work is also reported under CA-D*-ENT-6520-CG. 3) We established a field experiment to determine whether the results from 2) have relevance in a mature vineyard. Variables were compost, fertilization, and tillage and the experiment was set up in Mendocino Co., Calif. Data collection will include phylloxera population level, root necrosis, and vine productivity over 2-3 years and we will relate disease to microbial ecology in the soil and rhizosphere. First treatment data will be collected in 2001. 4) A field trial with Platinum, a commercial systemic insecticide, Platinum
plus Ridomil, and Platinum plus BTH, a non-pesticidal chemical that is reported to induce plants to resist pathogen attack was set up in Lodi, Calif. Applications were made in early July and August. All treatments depressed phylloxera population a month after applications. The combination treatments also depressed fungal necrosis at phylloxera feeding sites on roots. This is the third year for Platinum tests showing phylloxera population suppression and the first time we have been able to depress root necrosis. Combination treatments represent a new strategy for management of phylloxera damage. 5) We set up an experiment to confirm that fruit removal does not appreciably affect phylloxera populations on vine roots. Results confirmed that phylloxera populations were not strongly affected by fruit removal. 6) We set up an experiment to determine overwintering survival of grape phylloxera in vineyard soils. Data will be collected in 2001. 7) We compiled and analyzed literature on biology
and management of grape phylloxera for the Annual Review of Entomology (2001).
Impacts
Economic losses from grape phylloxera are prevented by use of resistant rootstocks. However, no back up methods are available should rootstocks fail again as they did in California in the 1990s. Our long-term goal is to develop backup technologies for such a contingency. Current work suggests that we should emphasize research on methods relating to soil management and certain pesticides.
Publications
- Downie, D. A. and Granett, J. 1999. Distribution, abundance, and short term persistence of grape phylloxera in two regions of the native range. Environmental Entomology 28: 1004-1013.
- Omer, A. D. and Granett, J. 2000. Relationship between grape phylloxera and fungal infection in grape vine roots. Journal of Plant Diseases & Protection 107: 285-294.
- Omer, A. D., Thaler, J. S., Granett, J. and Karban, R. 2000. Jasmonic acid induced resistance in grapes to a root and leaf feeder. Journal of Economic Entomology 93: 840-845.
- Granett, J. and Kocsis, L. 2000. Populations of grape phylloxera gallicoles on rootstock foliage in Hungary. Vitis 39: 37-41.
- Downie, D. A., Granett J., and Fisher, J. R. 2000, Distribution and abundance of leaf galling and foliar sexual morphs of grape phylloxera (Hemiptera: Phylloxeridae) and VITIS species in central and eastern United States. Environmental Entomology 29: 979-986.
|
Progress 01/01/99 to 12/31/99
Outputs
1. Phylloxera life table experiments on mature, field-living grapevine roots attached to the vine, showed that the insect was influenced by plant phenology with greater survival after harvest than at the cool, early-spring vegetative growth stage or summer time post veraison stage. By comparing phylloxera populations and demography on attached roots in comparison with identical roots under similar conditions that were detached from the same vines, we showed that attachment inhibited populations. The life table demography showed that inhibition focuses on the 1st and 2nd instar stage of the phylloxera and this is the time of the insect's life cycle when galls due to feeding are forming. This work suggests that a better understanding of gall formation might lead to knowledge of its prevention. 2. Some soils are known to inhibit plant pathogens. Our experiments showed that mechanisms of vineyard soil suppressiveness to Fusarium root necrosis induced by phylloxera feeding
involves pathogen antagonists, Trichoderma and pseudomonads, but also other microbial components of soil must be involved. Suppressiveness of soils is influenced by the organic farming management classification, use of composts, and may be influenced by no-till conditions. All organically managed vineyards did not have suppressive soils and we are searching for the underlying cause. 3. We have planted a replicated vineyard experiment to test the influence of nitrogen and compost on vine growth, phylloxera populations and root necrosis associated with phylloxera feeding. The vines have been infested and the soil amendments added. Data collection will commence in summer 2000. However, we completed an initial greenhouse test of these same factors. Results suggested that, as expected, nitrogen and compost (living or sterile) increased vine growth. Increased growth stimulated phylloxera population growth. However, live compost reduced phylloxera associated root necrosis, while sterile
compost did so only slightly. These greenhouse results will guide us in data collection for the field experiment. This work is under CA-D*-ENT-6520-CG. 4. We replicated last year's tests with a systemic insecticide using drip irrigation and confirmed a 4 week residual activity. In addition, I tested the same material on leaf-gall phylloxera while in Hungary and found a 2 week residual activity. If tests continue to be positive, this material will add a needed component to phylloxera IPM. 5. Other work in Hungary included testing the relationship between phylloxera populations on leaves and depressed vine growth, seasonal life history of the insect in a place where the sexual parts of the life cycle occur, the relationship between insect virulence and domestication of phylloxera, and leaf chemicals which correlate with populations. Data for these projects have not been fully collected and therefore results are too tentative to report.
Impacts
Knowledge of the biology of phylloxera and phylloxera damage allows us to think about new ways to control this insect. We are testing the influence of soil management practices but have not excluded chemicals (insecticides, fungicides and inducers of plant resistance). These alternatives will provide back-up tools to prevent massive vineyard losses that occur when resistant rootstocks fail.
Publications
- Hong, L., Downie, D. A., Walker, M. A., Granett, J., English-Loeb, G. 1999. Genetic structure in native populations of grape phylloxera (Homoptera: Phylloxeridae). Annals of the Entomological Society of America 92 (3): 376-381.
- Kocsis, L., Granett, J., Walker, M. A. Lin, H., Omer, A. D. 1999. Grape phylloxera populations adapted to VITIS BERLANDIERI X V. RIPARIA rootstocks. American Journal of Enology and Viticulture 50(1): 101-106.
- Lotter, D. W., Granett, J., Omer, A. D., Differences in grape phylloxera-related grapevine root damage in organically and conventionally managed vineyards in California. 1999. HortScience 34: 1108-1111.
- Omer, A. D., Granett, J., Kocsis, L., Downie, D. A. 1999. Preference and performance responses of California grape phylloxera to different VITIS rootstocks. Journal of Applied Entomology 123: 341-346.
- Omer, A. D., Granett, J., Shebelut, C. W. 1999. Effect of attack intensity on host utilization in grape phylloxera. Crop Protection 18: 341-347.
- Omer, A. D., Granett, J., Wakeman, R. J. 1999. Pathogenicity of FUSARIUM OXYSPORUM on different VITIS rootstocks. Journal of Phytopathology. 147: 433-436.
|
Progress 01/01/98 to 12/31/98
Outputs
1) Phylloxera population growth is influenced by vine phenology. We infested field VITIS VINIFERA c. Thompson Seedless roots in sequential months from May-Sept. and determined populations one month after each infestation. Population was higher on excised roots than attached roots. Three timings of harvest did not influence phylloxera populations disproving the hypothesis that harvest influences population growth. 2) We surveyed organic and conventionally managed vineyards over two years: Phylloxera populations in conventionally managed vineyards correlated with root necrosis, a measure of damage. Organic vineyards had variable phylloxera populations but root fungal necrosis was low. We need to investigate the mechanisms of this root protection. 3) Field tests with an experimental systemic insecticide showed that root populations were decreased by drench treatments. We will replicate this work and use this tool to begin to determine what populations cause economic
injury. 4) Greenhouse tests with jasmonic acid treatment of grape vines demonstrated decreased phylloxera fecundity. 5) We completed a test of Koch's postulates to demonstrate that FUSARIUM caused root necrosis at phylloxera feeding wounds. Rootstocks resistant to phylloxera also have resistance to FUSARIUM. 6) Rootstocks resistant to grape phylloxera include a component of antixenosis. 7) Population dynamics of phylloxera in leaf galls of resistant cultivars was studied in Hungary. Populations appeared to spread from epicenters.
Impacts
(N/A)
Publications
- GRANETT, J., OMER, A.D., PESSEREAU, P. AND WALKER, M. A. 1998. Fungal infections of grapevine roots in phylloxera-infested vineyards. Vitis
- OMER, A.D., GRANETT, J., DOWNIE, D.A. AND WALKER, M.A. 1997. Population dynamics of grape phylloxera in California vineyards.
- KOCSIS, L., LIN, H., GRANETT, J., OMER, A.D. AND WALKER, M.A. 1998. Variability of grape phylloxera in Hungary. Hort. Sci. 29(3-4):73-77
- DOWNIE, D. AND GRANETT, J. 1998. A life cycle variation in grape phylloxera DAKTULOSPHAIRA VITIFOLIAE (Fitch). Southwestern Entomol.
- WALKER, M.A., GRANETT, J., OMER, A., HONG, L., KOCSIS, L., FORNECK, A. AND PORTEN, M. 1998. Are phylloxera feeding on 5C rootstock in Europe? Practical Vineyards and Wineries (March/April):21-26.
- PARRELLA, M.P., GRANETT, J., DUFFEY, S.S., AND KITTERMAN, D. 1998. Exploiting the "Entomology Advantage." Amer. Entomol. 44:198-201.
|
Progress 01/01/97 to 12/01/97
Outputs
Grape phylloxera: 1) We infested roots of mature VITIS VINIFERA c. Carignane monthly from May-Sept., and determined population after one month. Infested roots were left physiologically attached to the vines and buried in place in Petri dishes. Controls were similarly treated excised roots. From May-Aug., the phylloxera on attached roots decreased in development and reproduction. After harvest, populations recovered. In contrast, the excised roots had stable population growth. Results suggest that phylloxera compete with vine sinks for nutrients. 2) Histology of parenchyma tissues of excised roots suggests that phylloxera activity decreases starch reserves over time, with the reserves being depleted at the feeding site first, then depleted at distances from the feeding. 3) Studies comparing phylloxera-infested organically managed vineyards with conventionally managed vineyards found that fungal root infection (the cause of damage) was not correlated with phylloxera
populations in the former but was in the latter. Results suggest that soil components in the former suppress the damage. 4) With M.A. Walker, we studied the DNA variability of phylloxera on a transect from Arizona to Missouri and in a single site in New York. Within-site variability was low at all sites but there were large differences between sites. These data, along with differences seen with the sexual aspect of the life cycle (present in leaves in Arizona but not elsewhere) open the question of distinct grape phylloxera species.
Impacts
(N/A)
Publications
- Murphy, B.C., Rosenheim, J.A. and Granett, J. 1996. Habitat diversification for improving biological control: Abundance of ANAGRUS EPOS (Hymenoptera: Mymaridae) in grape vineyards.
|
Progress 01/01/96 to 12/30/96
Outputs
Grape phylloxera DAKTULOSPHAIRA VITIFOLIAE; grapes: Populations were low overwinter, reached a peak midsummer after which they declined except for a peak with the root flush postharvest. That the decline in midsummer was not due to temperature suggests a host-related cause. Mortality between instars was indicated by there being fewer adults than immatures, suggesting that (unknown) field factors slow phylloxera populations. Preliminary tests showed inhibitory factors in organic soils. Phylloxera in spring, summer, and fall predominate on immature, mature, and immature roots, respectively. Populations overwinter as first instar hibrinants which begin to appear as populations decline beginning midsummer. A high % of fungal infections (FUSARIUM, PYTHIUM, and CEPHALOSPORUM) of feeding sites on roots was seen in spring, the infection rate decreasing to <10% by midsummer. A smaller rise in % infection was seen with the fall root flush. The summer decline in % infection
appears due to death of severely infected roots. Whether the fungi are pathogenic or saprophytic in the field is unknown. Phylloxera collected from the rootstocks 5C or SO4 in California, Germany and Hungary had variable vigor on those rootstocks in lab assays. Vigor in some cases was greater on the rootstock than on VITIS VINIFERA roots. The variability is amplified by host-race selection and may eventually lead to strains able to harm mature field vines.
Impacts
(N/A)
Publications
- TURLEY, M., GRANETT, J., OMER, A. D., AND DEBENEDICTIS, J.A. 1996. Grape phylloxera (Homoptera: Phylloxeridae) temperature threshold for establishment offeeding sites and degree-day calculations. Environmental Entomology 25:842-847.
- WEBER, E., DEBENEDICTIS, J., SMITH, R., GRANETT, J., AND ZACCONE, D. 1996. Enzone applications do little to improve phylloxera-infested vineyards. California Agriculture 50(4):19-23.
- GRANETT, J., WALKER, M. A., AND WEBER, E. 1996. California grape phylloxera are more variable than expected. Will this variability affect replacement rootstocksCalifornia Agriculture 50(4):9-13.
- DEBENEDICTIS, J. A., GRANETT, J., AND TAORMINO, S.P. 1996. Differences in host utilization by California strains of grape phylloxera. American Journal of Enology and Viticulture 47:373-379.
- OMER, A.D., GRANETT, J., DANDEKAR, A.M., DRIVER, J.A., URATSU, S. L., AND TANG, F.A. 1996. Effects of transgenic petunia expressing BACILLUS THURINGIENSIS toxinon selected lepidopteran pests. Biocontrol Science and Technology. In press.
|
Progress 01/01/95 to 12/30/95
Outputs
GRAPE PHYLLOXERA DAKTULOSPHAIRA VITIFOLIAE: RUPESTRIS X VINIFERA CROSSES: Roots of approximately 200+ accessions of a seedling population of these crosses plus selections of both parents were screened for resistance against phylloxera. An array of bioassay responses within vine type indicated that multiple genes are involved in the resistance mechanism(s). We will use a subset of these vines to study physiological mechanisms of resistance. POPULATION STUDY: A Lodi, CA, population was sampled at 3-wk intervals from May-Dec. Exponential population rise through July suggests density independent growth. A slow decline followed. These data indicated that phylloxera's withdrawal of nutrients alone does not damage vines appreciably. This study will continue in 1996. LEAF GALLS FROM ARIZ. & NY: Wild grape vine leaf galls from Ariz. and NY were collected and phylloxera DNA variability determined by PCR. Less than 5% variability was observed within state, indicating some unknown
mechanism for depressing variability of these populations which have sexual reproduction. We observed sexual forms in Arizona leaf galls that did not arise from alates, an observation that goes counter to published understandings of phylloxera biology. BOX SELECTION: Field planter boxes with various rootstock plants were infested with phylloxera strains over the past 3 years. Insects recovered from the boxes this year were of several different strains, indicating selection by the rootstocks over this short time frame.
Impacts
(N/A)
Publications
|
Progress 01/01/94 to 12/30/94
Outputs
Grape phylloxera DAKTULOSPHAIRA VITIFOLIAE: A series of greenhouse tests demonstrated that exclusion of the fungi PYTHIUM and FUSARIUM from phylloxera infested roots resulted in approximately half the grapevine damage as in situations with fungi present. These fungi are common in vineyards; results suggest the important role of secondary pathogens in phylloxera-related vine damage. Field tests were initiated. Phylloxera variability was studied with laboratory root-bioassays and DNA analysis with PCR techniques. We have 4 strains of phylloxera that are neither biotype A nor B, are generally weak on VITIS VINIFERA roots and have variably increased virulence on specific rootstocks. The bioassays suggest that all but one would do no acute damage to vineyard rootstocks. One, however, had elevated bioassay virulence on the rootstock Harmony and in the field (collaboration with E. Weber) was damaging this cultivar in one rootstock trial block in Napa Co., CA. This is a new
biotype. The PCR work (collaboration M.A. Walker) evaluated 12 colonies of phylloxera of both biotypes and several strains. All were different from one another and no markers for biotypes were distinguished. The bioassay and PCR analyses did not give complementary results. Remote sensing (Collaborative work with NASA, Chico State U. and Mondavi) completed the second field season. We are able to distinguish probabilistically leaf reflectances for several types of stresses.
Impacts
(N/A)
Publications
|
Progress 01/01/93 to 12/30/93
Outputs
Grape Phylloxera: Biotype B was confirmed in two additional counties, Sacramentoand Mendocino. We continued studying the weak strains discovered last year and collected additional ones. No rootstock allow these strains to outbreak, though they survive in immature roots. We continue providing phylloxera eggs to MA Walker (Viticulture and Enology) for PCR (DNA) analyses of biotypes and strains. We have collaborated with NASA/Ames, Mondavi Winery and Chico State to determine whether remote sensing can detect phylloxera before visual vine symptoms are seen. Initial analyses suggest that leaf reflectances may presage phylloxera damage and very low populations may cause a systemic physiological plant change. A greenhouse experiment tested whether fungal infections cause the root damage associated with phylloxera populations: exclusion of fungi from phylloxera feeding sites prevents some damage associated with phylloxera. Field trials of the soil insecticide Enzone continued
with E Weber (Napa Co.) and Unocal. Vine damage is slowed but not to a great extent. Lab screening of other chemical and biological agents against phylloxera produced no candidates for further testing. Lab trials with electric shock have been negative. Tests with heat and microwaves have given baseline data on lethal dosages. ANAGRUS and Grape Leafhopper: Field tests have been completed on the effect of prune refuges on efficiency of the parasite for controlling leafhopper populations.
Impacts
(N/A)
Publications
|
Progress 01/01/92 to 12/30/92
Outputs
Grape phylloxera: Biotype B has increased its range with new finds in Santa Clara, San Joaquin, Lake and Alameda counties. We have continued to study variability of phylloxera by finding new strains that differ from our standard colonies with regard to host preferences. Two new strains, for example, are not strong feeders on mature roots but do well on immature roots and differ from previous descriptions of A and B by being able to survive on immature roots of resistant rootstocks such as 5C. We are collaborating with M.A. Walker who is subjecting phylloxera from our colonies to enzyme and PCR (DNA) analyses and is finding high variability. Variability in the state is much greater than previously thought. We are continuing to assay therapeutic control tactics with laboratory tests (SO2, Mocap, electric shock, x-rays and various ion solutions) and field tests (Enzone, SO2). We have begun large planter box experiments to determine economic injury levels. We will
determine which parts of the root system need protection and determine the significance for damage of the strains that feed preferentially on immature roots. ANAGRUS and grape leafhopper: A student with J. Rosenheim and myself is studying use of prune trees as an overwintering habitat for the leafhopper parasite. A large field experiment in ten sites with and without trees found that the trees enhanced parasitism.
Impacts
(N/A)
Publications
|
Progress 01/01/91 to 12/30/91
Outputs
Phylloxera assays in the laboratory were used 1) to determine resistance of rootstocks to biotypes A and B, 2) identify biotypes at specific sites, 3) recognize possible new biotypes, and 4) test control tactics. As previously, insect survival, rate of development and fecundity were measured in 45-day bioassays. An overall index of the potential growth of the population, the egg multiplication index (EMI) was formulated and simulated r using 45-day bioassay data. 1) The only rootstocks with less than strong resistance to biotype B were AXR#1, 41B, 04343. V. CALIFORNICA plants had resistance which varied from low to high. 2) Biotype B is still restricted to Napa and Sonoma Co. and damage is increasing; biotype A is found widely. Phylloxera from Oregon and Washington appeared to be similar to biotype A on AXR#1, Cabernet sauvignon (CS) and three Concord cultivars. 3) A phylloxera collection from the rootstock Freedom in Napa Co. was found to exhibit properties
different from A and B and is being called C. On AXR#1 EMI values of B>>A=C and CS, B=A>C. On Freedom and Harmony rootstocks, C>A=B and C formed tuberosities occasionally but nodosities commonly. Virulence was not sufficient to predict field decline of these rootstocks. 4) Electrocat (Trademark), a machine which purported to disrupt pests by vibrations, has no effect on phylloxera survival, growth or reproduction.
Impacts
(N/A)
Publications
|
Progress 01/01/90 to 12/30/90
Outputs
Biotype B, the new grape phylloxera, is devastating the rootstock AxR#1 in many parts of Napa and Sonoma Counties. Survey and assays to determine the California distribution of the normal phylloxera (biotype A) and the new one were completed. Biotype B remains limited to Napa and Sonoma; biotype A is in all other California viticultural regions where phylloxera are found. Phylloxera from Oregon appear similar to biotype A. An analysis of the survey data indicates that there are only two biotypes in the viticultural regions and that these have low variability. Assays with a series of other root cultivars indicates that within- and between-biotype variation is very low except with regard to the former on the wild grape species V. CALIFORNICA and the latter on AxR#1 and the wild grape. These results suggest a single lineage for all biotype B's in the state, that biotype B arose from a biotype A population and that biotype B is a host race. The group studying phylloxera
are considering the field recommendations that arise from these interpretations. We have tested Enzone, an experimental insecticide. Although it is of high toxicity to grape phylloxera, field trials with furrow irrigation applications give insufficient control. We are exploring various aspects of grape phylloxera biology and interaction with hosts. I am becoming involved in cooperative grape leafhopper research looking at the efficacy and optimization of prune trees as an overwintering site for parasites.
Impacts
(N/A)
Publications
|
Progress 01/01/89 to 12/30/89
Outputs
The number of purported AxR #1 vineyards with declining blocks with high phylloxera populations increased from 32 to more than 50 this year. We sought to determine whether the decline was due to biotype B, anomolous rootstocks or stress on the vines. We collected phylloxera in 12 grape growing counties. Of 108 colonies started, 54 have been bioassayed. All collections from declining AxR #1 vines were biotype B and were in Napa or Sonoma Counties. A test of two AxR #1 accessions at Davis indicated that they were almost equally resistant to phylloxera A and B. Stress tests (with Kasimatis) have been initiated. As a result of the work completed AxR #1 has been removed from the recommendations for phylloxera resistance. Collections from wild grapes (Vitis californica, hybrids with V. vinifera and V. girdiana) were made n 4 counties and are being biotyped. Tests for morphological distinctions between biotypes and geographically separated colonies are being done.
Field and laboratory trials with GY-81 (Unocal), a formulation of carbon bisulfide, are being conducted.
Impacts
(N/A)
Publications
|
Progress 01/01/88 to 12/30/88
Outputs
Phylloxera: Several populations of grape phylloxera from declining AxR #1 vineyards in Napa and Sonoma Counties were studied; B biotype phylloxera were not the only cause of the declines. An off-type AxR #1 from one vineyard was found to have ampulographic characteristics similar to an AxR #1 accession. Differences between phylloxera resistance levels of two AxR #1 accessions are suggested by preliminary results. Parasites (Anagrus epos) of the grape leafhopper and variegated leafhopper were imported from various locations in Arizona, Colorado, Mexico and southern California. Initial field testing suggests that a major increase in the level of parasitism against the variegated leafhopper can be expected. The majority of our effort in this area for this coming year will be directed at quantifying the ability of these parasites to overwinter and build up on the prune leafhopper, an alternate host for Anagrus epos.
Impacts
(N/A)
Publications
|
Progress 01/01/87 to 12/30/87
Outputs
Phylloxera: A biotype in France was discovered which could utilize 41B as host. For this biotype, survivorship percentage was higher than normal phylloxera. This biotype appears to be a host race adapted to this V. berlandieri hybrid. The mechanism of resistance for this hybrid does not appear to be related to indole acetic acid levels. Preformed tuberosities are preferred sites for establishment of phylloxera crawlers. Parasites of the grape leafhopper and variegated leafhopper were imported from various locations in Arizona, Colorado, Mexico and southern California. Initial field testing suggests that a major increase in the level of parasitism against the variegated leafhopper can be expected. The majority of our effort in this area for this coming year will be directed at quantifying the degree of preference shown by each parasite for each leafhopper species; at evaluating the degree of field control provided by each parasite; and at quantifying the ability
of each parasite to parasitize and overwinter on alternate leafhopper hosts.
Impacts
(N/A)
Publications
|
Progress 01/01/86 to 12/30/86
Outputs
Phylloxera: The field trial in the phylloxera type B infested vineyard was readand terminated. The resistant or immune rootstocks were SO4, 0-39-16, 0-44-4, and St. George. Ganzin 1 was clearly susceptible. The grower has now planted a commercial block test of these rootstocks. Additional sites of possible type B infestations were investigated. Although new sites have been found, the type B is clustered around three epicenters. Aerial survey of the Napa and Sonoma County vineyards was repeated for a second year 1) to follow the spread of the type B phylloxera within identified infestation on sites and 2) as a means of locating hereto undetected infestation sites. Chemical analysis (isozymes, amino acids, IAA) was continued to differentiate between biotypes and geographical strains. Grape leafhopper (GLH) and variegated leafhopper (VLH): Extensive field trials were conducted aimed at quantifying distribution and phenology of both species as affected by grape
cultivar, rootstock, cover crop, and crop phenology. A trial was initiated to develop a damage response function for VLH. Major emphasis was placed on foreign exploration, colonization, release and evaluation of parasites of both species. We are developing a crop-linked VLH model for use in management. Pacific and Willamette spider mites: Field trials were conducted aimed at quantifying distribution and phenology of both species on Thompson seedless grapes.
Impacts
(N/A)
Publications
|
Progress 01/01/85 to 12/30/85
Outputs
Phylloxera: The field trial in the phylloxera type B infested vineyard was readafter 1.5 years: Ganzin 1 is susceptible but SO4, 1202 and St. George are resistant or tolerant. Additional rootstocks were added to the field trial. Twenty-three rootstocks were screened for resistance to type B in the laboratory. Two additional sites with possible type B infestations were investigated, both in Sonoma County. All finds of type B are coincidental with a moderate to high frequency of an off-type rootstock, XX (believed Couderc 93-5) mixed in with Ganzin 1. Electrophoretic work was initiated to differentiate between biotypes and geographical strains. Stability and transmissibility of the type B characters are being studied. Grape leafhopper (GLH) and variegated leafhopper (VLH): Extensive field trials were conducted aimed at quantifying distribution and phenology of both species as affected by grape cultivar, rootstock, cover crop, and crop phenology. A trial was
initiated to develop a damage response function for VLH. Major emphasis was placed on foreign exploration, colonization, release and evaluation of parasites of both species. We are developing a crop-linked VLH model for use in management. Pacific and Willamette spider mites: Field trials were conducted aimed at quantifying distribution and phenology of both species on Thompson seedless grapes. Detailed fecundity trials addressed the effects of leaf position, age, and crop phenology.
Impacts
(N/A)
Publications
|
Progress 01/01/84 to 12/30/84
Outputs
Phylloxera: A strain of phylloxera (B biotype) was collected from Napa Valley and was able to survive and grow well on the resistant rootstock, Ganzin I. This strain was demonstrated through life-table experiments to be different from other strains of phylloxera (A biotype). The B biotype was also considerably more active on the highly resistant rootstock St. George in laboratory tests. A small field trial was established to determine activity of the B biotype on other rootstocks in the field. Insecticide tests were conducted with carbofuran in the field and laboratory. In the field, carbofuran at registered rates somewhat inhibited the spread of phylloxera but did not kill existing populations. In the laboratory, bioassays were conducted to establish baseline susceptibilities with eggs and nymphs with 8 clone colonies from Salinas Valley. These tests will be of value should resistance to carbofuran develop. In addition, life-table experiments demonstrated that
carbofuran had no effect on phylloxera fecundity at sublethal treatment concentrations. Sticky panels were placed in Salinas Valley vineyards in June, August and October and demonstrated that first instar phylloxera appear in the windstream. It is not known whether windblown phylloxera are viable.
Impacts
(N/A)
Publications
|
Progress 01/01/83 to 12/30/83
Outputs
Phylloxera: The phylloxera work falls into 2 areas, phylloxera biology and chemical control of phylloxera. In the biology area, phylloxera population response to temperature was studied in the laboratory and complementary work was initiated in the field. In the laboratory lifetable experiments indicated that populations would grow between about 65 F and 90 F. Temperatures at depths in vineyards indicate that in Davis and Napa there is probably a vertical movement of populations to attain these temperatures between May and October. Trenches in a Napa vineyard dug at different seasons so far confirm the laboratory findings. This work is continuing. Work on the resistant-rootstock bioassay has been completed in the laboratory and will not be confirmed in the field. Several laboratory experiments are underway with chemicals. In particular egg hatch, 1st instar establishment, and immature/adult mortality bioassays inresponse to the chemicals oxamyl and carbofuran
have been conducted. Confirmatory work is being done or has been done in the greenhouse and field. These experiments should indicate whether chemicals are a possible option in phylloxera management.
Impacts
(N/A)
Publications
|
Progress 01/01/82 to 12/30/82
Outputs
Grape phylloxera, Viteus vitifolii Shimer, were reared on excised grape roots maintained in petri dish chambers. Life tables were constructed using 2 susceptible grape rootstocks, Cabernet Sauvignon and Muscat of Alexandria and 2 resistant rootstocks, V. rupestris St. George and Ganzin 1. Phylloxera on resistant varieties had lower rates of 1st instar establishment than on susceptible varieties. Gross reproductive rates (GRR) and net reproductive rates (R(o)) on resistant varieties were lower than susceptible varieties. Mean generation times (T) were variable and appeared not related to rootstock susceptibility. Finite rates of increase (Lambda) were less than 1.0 on resistant varieties, 1.06 and 1.10 on suceptible varieties. Phylloxera on Cabernet Sauvignon tuberosities had higher GRR, R(o) and T-values than on nodosities. However, (Lambda)-values were nearly equal, 1.05 and 1.07 on tuberosities and nodosities, respectively. Above life table results are
applicable to problem of phylloxera resistance screening in new rootstocks. Eleven numbered rootstock lines were evaluated for phylloxera resistance.
Impacts
(N/A)
Publications
|
|