Progress 02/01/03 to 09/30/07
Outputs
OUTPUTS: A. Field studies were conducted to develop application methods of thymol as a preplant soil fumigant for controlling bacterial wilt and root-knot nematodes on tomato. In addition, acibenzolar-S-methyl (ASM), was applied in conjunction with thymol to evaluate if disease suppression could be enhanced. The test sites were artificially infested with Ralstonia solanacearum and Meloidogyne javanica, and thymol was applied through drip irrigation lines under polyethylene mulch at a rate of 73 kg/ha. ASM was applied foliarly at a concentration of 25 mg/liter. Application of thymol significantly reduced bacterial wilt on tomato. In thymol-treated plots only 26.2% and 22.6% of plants wilted in the two trials, respectively, while in untreated plots more than 90% of plants wilted. Integrated use of thymol and ASM significantly reduced bacterial wilt incidence in both years. Nematode galling on roots was reduced in the field plots treated with thymol, and combined use of thymol and ASM provided the greatest reduction of root galling among the treatments. B: Host suitability studies of 22 weed species, commonly found in Florida, to five root-knot nematode species (Meloidogyne arenaria race 1, M. floridensis, M. incognita race 4, M. javanica and M. mayaguensis) were conducted under greenhouse conditions. Root-galling, egg mass indices, and eggs per gram of root were recorded at plant harvest in the four experiments. Reproduction factor (Rf = final population /initial population) was calculated to determine the host status for each plant species. Ten weeds species (Abutilon theophrasti, Amaranthus retroflexus, A. spinosus, Cnidoscolus stimulosus, Cucumis anguria, Dichondra repens, Ipomea. violacea, I. tribola, Leonotis nepetaefolia, and Phytolacca americana) were good hosts (Rf ≥ 1) to the five root-nematodes evaluated, with average gall indices ranging from 4.2-8.0 and egg mass indices ranging from 2.8-5.0. The non-hosts of the Meloidogyne spp. were Cassia occidentalis, Crotolaria spectabilis, Dactyloctenium aegyptium, Desmodium purpureum, Digitaria sanguinalis, Panicum dichotomiflorum, Oenothera biennis, Setaria pumila, and Sorghum halepense. In these tests, 12 out of 22 weed species were hosts of at least one of the five nematode species evaluated. C: Microwave radiation of 2450 MHz frequency was used to irradiate sandy loam soil placed in 12 cm high and 10 cm dia columns as function of exposure time of 30, 45, 60, and 120 seconds to evaluate effect of radiation on highest soil temperature attained and subsequent temperature patterns in relation to time. Soil columns were packed to field bulk density of about 1.4 g / cm3, and treatments consisted of moist soil, dry soil, and layers of moist and dry soil of different thicknesses. An exposure time of 45 seconds was the most efficient in yielding soil temperature high enough to kill plant-parasitic nematodes. Irradiation of soil infested with Rotylenchulus reniform for 45 seconds resulted in a 99% kill in all treatments. Greatest of radiation depth penetration occurred when 6.0 cm dry soil was placed over 6.0 cm moist soil layer. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Tomato Growers, Extension Specialists and Agents, Consultants PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
A: Results indicated that thymol applied through drip irrigation lines is highly effective in controlling bacterial wilt caused by Ralstonia solanacearum but only moderately effective to manage root-knot nematodes caused by Meloidogyne javanica. The integrated use of thymol and ASM was shown to be feasible for managing these diseases and increasing tomato yield in tomato production. B: Our results confirmed the broad host range of the major root knot nematodes used in the study and gave new information regarding weed host range of M. floridensis and M. mayaguensis. The knowledge of host status of these nematodes provides information useful for establishing nematode management strategies in infested agricultural fields. C: Microwaves kill nematodes in soil through heating of soil water. However, the practical application of microwaves to manage neamtodes will depend upon further development of cost effective treatment methods.
Publications
- Ji, P., T. M. Momol,J. R. Rich, S.M. Olson, and J. B. Jones. 2007. Development of an Integrated Approach for Managing Bacterial Wilt and Root-Knot on Tomato Under Field Conditions.Plant Disease 91:1321-1326.
- Kaur, R., J. A. Brito, and J. R. Rich. 2007. Host Status of Selected Weeds to Five Meloidogyne spp. Nematropica 37:107-120.
- Rahi, G.S., and J. R. Rich. 2007. Use of Microwaves to Control Plant-Parasitic Nematodes. Journal of Microwave Power and Electromagnetic Energy 42:1-5.
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Progress 10/01/05 to 09/30/06
Outputs
Weed enable plant-parasitic nematodes to survive in the presence or absence of a crop, providing a source of nematode inoculum for the following season. Host suitability studies of 22 weed species commonly found in Florida, USA to five root-knot nematode species (Meloidogyne arenaria race 1, M. floridensis, M. incognita race 4, M. javanica race 1and M. mayaguensis) were conducted under greenhouse conditions. Root-galling, egg mass indices and eggs per g of root were recorded at plant harvest. Reproduction factor (Rf = final population/initial population) was calculated to determine the host status for each plant species. Nine weed species (Abutilon theophrasti, Amaranthus retroflexus, A. spinosus, Cnidoscolus stimulosus, Cucumis anguria, Dichondra repens, Ipomoea triloba, Leonotis nepetaefolia, and Phytolacca americana) were good hosts (Rf=1) to the five root-knot nematode species evaluated, with average gall indices ranging from 4.2-8.0, and egg mass indices ranging
from 2.8-5.0. Of these good hosts, Abutilon theophrasti sustained the highest number of nematode eggs (M. javanica) per g of root (102,560). The non-hosts of the five Meloidogyne spp. were Cassia occidentalis, Crotolaria spectabilis, Dactyloctenium aegyptium, Desmodium purpureum, Digitaria sanguinalis, Panicum dichotomiflorum, Oenothera biennis, Setaria pumila, and Sorghum halepense. Echinochloa muricata was a poor host (0.1< Rf <1.0) for M. arenaria and M. incognita, and non-host (Rf ≤ 0.1) for M. floridensis, M. javanica and M. mayaguensis. Senna obtusifolia was a good host for M. mayaguensis (Rf = 37), but a poor host for M. floridensis (Rf = 0.3), M. incognita (Rf = 0.4) and M. javanica (Rf = 0.7), and a non-host for M. arenaria (Rf = 0). Current studies indicate that 12 out of 22 weed species tested are good hosts of at least one of the five nematode species evaluated.
Impacts
In many cases in the agronomic cropping systems of the southern U.S., rotation systems are adequeate for nematode management. In these systems, weed management during the cropping system is usually very good, however, weed mangement between cropping systems is generally neglected. These tests show the need for greater weed management, particularly before and after production of a crop. By doing so, losses to nematodes can be reduced and fewer nematicide applications made in agronomic production systems.
Publications
- R. Kaur*, J. A. Brito, and J. R. Rich. 2007. Host suitability of selected weed species to five Meloidogyne spp. Nematropica 37:(In Press).
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Progress 10/01/04 to 09/30/05
Outputs
Survey: In Florida, cotton and peanut are produced on greater than 38,000 and 59,000 hectares, respectively, each year. Key nematode species include Meloidogyne arenaria and Pratylenchus brachyurus on peanut and M. incognita and Rotylenchulus reniformis on cotton. Past surveys of nematode problems and presence in Florida agronomic crops have been limited and were taken 15-30 years ago. Significant cropping pattern shifts have since occurred including considerable monoculture. A survey was conducted in late summer and fall of 2004 in six counties in north Florida. Samples were taken from randomly selected cotton and peanut fields to provide unbiased nematode assay results. A total of 83 fields in the six counties were sampled, and within these fields, 115 soil samples were collected. Results showed that nearly 50% of the soil samples had nematode population densities capable of crop damage. Additionally, an emerging P. brachyurus problem was identified in peanut and a
greatly increased R. reniformis presence was found in cotton. Survey results indicate that changes in Florida field crop production patterns have led to increased nematode population densities and increased distribution frequencies in Florida peanut and cotton production. Weeds: The role of weeds as hosts for plant-parasitic nematodes and as factors in nematode-induced crop losses has been little studied. A review of the literature indicated that out of hundreds of weeds known worldwide, approximately 74 have been identified as hosts for Meliodogyne spp. In the southern United States, over 120 troublesome weed species are found, but only 27 have been reported as hosts for one or more root-knot nematode speciess. Some of these weeds include Amaranthus spp., Artemisia vulgaris, Biden pilosa, Eleusine indica, Portulaca oleracea, and Torulimum odoratum. Even fewer weeds are known to be hosts to specific Meloidogyne spp. including the four most commonly occurring M. incognita (25), M.
javanica (13) M. arenaria (2), and M. hapla (12). Since, many weed species serve as reservoirs of nematode inoculum, the recognition and control of such weed species are important for nematode management. Currently, we are studying potential interactions involving five Meloidogyne spp. (M. arenaria, M. floridensis, M. incognita, M. javanica, and M. mayaguensis) with common weeds associated with agronomic crops in the southern United States, to advise growers to follow weed management strategies for their fields infested with root-knot nematodes.
Impacts
Survey: The survey showed large and damaging populations of plant-parasitic nematodes in north Florida agronomic crops, primarily peanut and cotton. Since the last surveys some 15 or more years ago, nematode populations and potential damage has increased and as importantly, dramatic changes in nematode species distribution were found. Cotton and peanut nematode management recommendations were updated to meet current challenges growers face with economic losses from nematodes. Also, the increased and widespread occurrence of reniform and lesion nematodes must be dealt with quite aggressively, including more emphasis on county extension agent involvement and use of on-farm grower demonstrations. Weeds: Weed hosts of commonly occurring root-knot nematodes have been updated to provide extension agents information for use by growers in managing nematode problems before and after crop harvest.
Publications
- J.R. Rich and T.W. Katsvairo. 2005. Nematode presence and problems in Florida cotton and peanut production. Nematropica 35: (in press).
- R. Kaur1, J.A. Brito and J.R. Rich. 2005. Weed hosts of Meloidogyne spp.: A review. Nematropica 35: (in press).
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Progress 10/01/03 to 09/30/04
Outputs
Two field trials were conducted to determine the effects of using combinations of Mi-gene resistant tomatoes and methyl bromide chemical alternatives on root galling and yield of a succeeding cantaloupe crop. The sites were on loamy sand soils in northern Florida U.S.A infested with Meloidogyne javanica. Chemical treatments served as main plots, each replicated six times, and Mi-gene resistant and susceptible tomato cultivars served as subplots. Soil fumigants applied in the tests were 1,3-D, 1,3-D + 17% chloropicrin, 1,3-D + 35% chloropicrin, and a standard methyl bromide + 33% chloropicrin treatment. The tomato and the succeeding cantaloupe crops were grown on polyethylene mulch and irrigated through drip tubing. In both tests, chemical treatments and use of Mi-gene resistant tomato cultivars reduced root galling on the tomato crop. Root galling on the subsequent cantaloupe crops were not affected by chemical treatment of the previous tomato crop, but cantaloupe
yield was increased. Root galling on cantaloupe grown after resistant tomato cultivars was significantly reduced, and use of first crop Mi-resistant tomato increased cantaloupe yield and fruit number. Reduced root galling and increased yield of cantaloupe was generally found when using chemical soil treatment and Mi-gene resistance in a first tomato crop.
Impacts
The impending loss of methly bromide as a broad spectrum soil biocide in vegetable production has created a strong need to identify chemical replacements and other alternatives to this fumigant. Field trials reported herein have demonstrated nematicidal efficacy efficacy of 1,3-dichloropropene-chloropicrin mixtures that are comparable to methyl bromide to manage nematodes in vegetable production systems. Growers can now confidently use these products as replacements to methyl bromide.
Publications
- Rich, J. R., and S. M. Olson. 2003. Influence of first crop Mi-gene tomatoes and methyl bromide alternatives on root-galling and yield in a succeeding cantaloupe crop. Nematropica 34:103-108.
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Progress 10/01/02 to 10/01/03
Outputs
Four field trials were conducted on loamy fine sand soils in northern Florida U.S.A. to determine efficacy of soil fumigant alternatives to methyl bromide for control of root-knot (Meloidogyne spp.) and reniform (Rotylenchulus reniformis) nematodes in tomato. Tests were conducted with commercially available fumigants and arranged in randomized complete block designs containing five or six replications. Fumigants and combinations varied but generally included 1,3-dichloropropene (1,3-D), methyl bromide (Mbr), and chloropicrin (Pic). Chemicals were applied on 0.91-cm-wide raised beds formed in 1.8-m-wide rows. Black polyethylene mulch, drip irrigation, and trellising were used in the tomato production system. Data collection in these tests included fruit yield, root gall indices, and reniform nematode soil population densities. Mbr and Mbr + Pic generally resulted in greatest reduction in root galling and reniform nematode populations in these tests. The 1,3-D + Pic and
Pic alone treatments, however, approximated Mbr treatments in yield but varied somewhat in nematode control. These data indicated that soil treatments with 1,3-D + Pic or Pic may be used as chemical alternatives to Mbr, but appropriate rates of these materials should be further explored.
Impacts
The impending loss of methly bromide as a broad spectrum soil biocide in vegetable production has created a strong need to identify chemical replacements and other alternatives to this fumigant. Field trials reported herein have demonstrated nematicidal efficacy efficacy of 1,3-dichloropropene-chloropicrin mixtures that are comparable to methyl bromide to manage nematodes in vegetable production systems. Growers can now confidently use these products as replacements to methyl bromide.
Publications
- Rich, J.R., S.M. Olson, and J.W. Noling. 2003. Management of root-knot nematodes and nutsedge with fumigant alternatives to methyl bromide in north Florida tomato production. Nematologia Mediterraneae 31:163-168.
- Rich, J.R., and S.M. Olson. 2003. Fumigant alternatives to methyl bromide in north Florida tomato production. Nematropica 33:(In press).
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