Progress 10/01/99 to 09/30/05
Outputs
During 2006, the focus of the Minnesota project included Objective C, Crop and Pest Management:Reduce environmental impacts of sweet corn production while maintaining or improving product quality. Work during this last year of the project also focused on insect pests, including the assessment of pyrethroid resistance in corn earworm (CEW), and the evaluation of transgenic sweet corn hybrids and reduced-risk insecticides for European corn borer (ECB) control. The Bt sweet corn hybrids all contained a modified gene from the bacterium, Bacillus thuringiensis (Bt-11 event). All three Bt hybrids tested, continued to provide 99-100% control of ECB in 2005, and approx. 90% control of CEW. The primary concern and project for 2005 was coordinating a multi-state effort to monitor for CEW resistance to the pyrethroid insecticides. For the processing industry, and many fresh-market growers, this is the primay option for control of CEW. Control of CEW with pyrethroid insecticides
continued to be very low in small-plot research trials, with mean percent control ranging from only 25-40%. In addition, using the Adult Vial Test (AVT), CEW moth survival ranged from 20-60% at either 5 or 10 micrograms/vial of cypermethrin. Results varied depending on location (MN, WI, IN, IL). However, these values are all quite high given that these discriminatory doses should provide 100% mortality if resistance was not present. Pyrethroid monitoring data will be continue to be collected in 2006, and plans are underway to expand the monitoring effort throughout the Midwest as well as Atlantic Coast states. In addition to these projects, an economic risk assessment of the Value of IPM for processing sweet corn was completed, in cooperation with economists at Minnesota and Wisconsin. This study, targeting the sweet corn period from first silk to harvest, confirmed the value of the first insecticide spray (application) for ECB control at 5-10% silk, with rapidly diminishing values
for subsequent sprays (2-4). On a per acre basis, the value of ECB sampling as part of an IPM program, on a per acre basis, was relatively low, ranging from $7 to 10/ac.
Impacts
We continue to monitor for, and document a low to moderate level of insecticide (pyrethroid) resistance in one of the most damaging sweet corn insects, the corn earworm. Resistant moths have been collected in MN, WI, IL, IN and Ontario, Canada. Sweet corn growers face a new significant challenge. Fresh market growers and processors are concerned about the presence of any larval contaminants in final product, as are most consumers. As most of the resistant moths migrate from the southern U.S. each summer, an Informal Conference was held in December 2005, at the National ESA meeting to bring Southern and Northern U.S. researchers and extension entomologists together to begin to develop new resistance management guidelines. Without viable alternatives for IPM, growers will likely increase insecticide use, which could have an increasing environmental impact.
Publications
- Foster, R.E., B. Flood & W.D. Hutchison. 2005. Sweet Corn (Ch. 2), pp. 19-40. In R.E. Foster and B. Flood [Eds.], Vegetable Insect Management. Meister Publishing Co., Willoughby, Ohio.
- Galvan, T., R.L. Koch, & W.D. Hutchison. 2005. Toxicity of commonly used insecticides in sweet corn and soybean to multicolored Asian lady beetle (Coleoptera: Coccinellidae). J. Econ. Entomol. 98: 780-789.
- Galvan, T., R.L. Koch, & W.D. Hutchison. 2005. Effects of spinosad and indoxacarb on survival, development, and reproduction of the multicolored Asian lady beetle (Coleoptera: Coccinellidae). J. Biol. Control. 34: 108-114.
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Progress 01/01/04 to 12/31/04
Outputs
Progress in 2004 focused on Objective C, "Crop and Pest Management: Reduce environmental impacts of sweet corn production while maintaining or improving product quality." Research at Waseca MN continued to focus on crop canopy manipulation as a management tool to minimize the impacts of weed competition in sweet corn production. These data, as part of a two-year study, continue to be analyzed; specifically, we plan to develop a light-base competitive index for processing varieties. A weed-competitive index is also being prepared for rapid distribution on the VegEdge web site (www.vegedge.umn.edu). Insect pest management studies focused on continued documentation of the spread of the Western bean cutworm (WBC) and Univoltine strain of European corn borer (ECB) into major sweet corn production regions of southern MN. The phenology of WBC, based on monitoring at 3 locations over 2 years, is limited to a single generation flight, with the timing occurring from late July
through August. Activity by both WBC and the univoltine ECB indicated no evidence of significant spread. In addition, the EPA-approved "reduced-risk" insecticide, SpinTor, and numerous synthetic pyrethroids were evaluated for ECB and corn earworm (CEW) control. SpinTor (spinosad) provides excellent control of ECB, but is more expensive than current materials. Control of CEW with pyrethroid insecticides continued to be low in research plots; as in 2003, extensive surveys were conducted to assess the potential for CEW resistance to selected pyrethroids. Assay data for 2004, thus far, confirms a moderate level of resistance; data were again collected in MN, WI, IL and Ontario, Canada. New transgenic sweet corn hybrids, expressing the Cry1Ab toxin (produced by the bacterium, Bacillus thuringiensis), provided good efficacy against CEW. All research updates were made available to the industry via seasonal articles in the MN Vegetable IPM Newsletter and the VegEdge WWW page.
Impacts
The new crop canopy and weed index will allow processors to allocate the most competitive lines to contract acres that pose the most serious weed challenges. We will determine the best, low-cost, low-labor input method which best characterizes competitiveness for light, to assay the larger population of current and future sweet corn hybrids. With the recent documentation of pyrethroid resistance in corn earworm, sweet corn growers and processors may experience major limitations for control alternatives. Processors may therefore incur increased costs of "processing out" larvae within the processing plant (husking, washing procedures). New IPM and Resistance Management Guidelines, and resistance monitoring procedures, will need to be developed to address these concerns in the near future. All research will aim to minimize the use of pesticides and environmental costs, while also maintaining profitable production.
Publications
- Hutchison, W.D., E.C. Burkness, Bryan Jensen, Roger Leonard, Tom L. Rabaey, R.L. Koch, R.A. Weinzierl, and J.L. Wedberg. 2004. Pyrethroid Resistance to Corn Earworm in Midwestern U.S. Sweet Corn. (Abstract). N. Central Branch, ESA Meeting, Kansas City, MO, March, 2004.
- ORourke, P.K. and W.D. Hutchison. 2004. Binomial sequential sampling plans for late instars of European corn borer (Lepidoptera: Crambidae) and corn earworm (Lepidoptera: Noctuidae), and damaged kernels in sweet corn ears. J. Econ. Entomol. 97: 1003-1008.
- Hutchison, W.D., J. Ciborowski and S. Wold-Burkness. 2004. Minnesota Fruit and Vegetable IPM Newsletter and Moth Trap Network; published weekly during growing season; hard copy and web versions available http://www.vegedge.umn.edu/
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Progress 01/01/03 to 12/31/03
Outputs
As in previous years, our work in 2003 focused on advancements within Objective C, "Crop and Pest Management: Reduce environmental impacts of sweet corn production while maintaining or improving product quality." Research at Waseca MN continued to focus on crop canopy manipulation as a management tool to minimize the impacts of weed competition in sweet corn production. Drought stress increased as the season progressed in 2003. The final stages of growth of planting date 2, and particularly in planting date 3, were impacted by moisture stress. Leaf firing occurred and varied among varieties. Leaf firing resulted in a premature opening of the canopy and some varieties suffered stalk lodging through scavenging of nutrients from the lower stalk area in response to drought. Succinct differences in light transmittance to the soil surface were observed in each planting date. Data are currently being analyzed with the intent to develop a light-base competitive index for
processing varieties; the weed competitive index is also being prepared for rapid distribution on the VegEdge web site (vegedge.umn.edu). Insect pest management studies focused on continued documentation of the spread of the Western bean cutworm and Univoltine strain of European corn borer (ECB) into major sweet corn production regions of southern MN, and western WI. Activity by both pests was limited in 2003, with no evidence of significant spread. In addition, the EPA-approved "reduced-risk" insecticide, SpinTor, and numerous synthetic pyrethroids were evaluated for ECB and corn earworm (CEW) control. SpinTor shows excellent control of ECB, but is much more expensive than current materials. Control of CEW with pyrethroids was surprisingly low (ca. 50% kill; 70-90% of ears infested) in both MN and WI trials. Initial assays, in collaboration with Louisiana State Univ., confirm moderate levels of resistance. MN also participated in the annual NE-124 regional seed treatment evaluations;
data have been summarized by ID colleagues. All research updates were made available to the industry via seasonal articles in the MN Vegetable IPM Newsletter.
Impacts
The new crop canopy and weed index will allow processors to allocate the most competitive lines to contract acres that pose the most serious weed challenges. We will determine the best, low-cost, low-labor input method which best characterizes competitiveness for light, to assay the larger population of current and future sweet corn hybrids. With expected documentation of pyrethroid resistance in corn earworm, sweet corn growers and processors may experience major limitations for control alternatives. Processors may therefore incur increased costs of "processing out" larvae within the processing plant (husking, washing procedures). New IPM and Resistance Management Guidelines, and resistance monitoring procedures, will need to be developed to address these concerns in 2004.
Publications
- Becker, R., V. Fritz, J. Hebel, D. Miller, B. Kinkaid. 2003. Sweet corn herbicide weed management trial, Waseca, MN. Proc. of the NC Weed Sci. Soc. Research Report. 5pp.
- Koch, R.L., W.D. Hutchison, R.C. Venette. 2003. Survival of monarch butterfly, Danaus plexipus, larvae on milkweed near Bt cornfields. J. Lepidop. Soc. 57:92-99.
- Koch, R.L., W.D. Hutchison. 2003. Phenology and blacklight trapping of the multicolored Asian lady beetle (Coleoptera: Coccinellidae) in a Minnesota agricultural landscape. J. Entomol. Sci. 38:477-480.
- Hutchison, W.D., E. Burkness, R. Koch. 2003. Corn earworm control in Minnesota sweet corn, 2003. MN Vegetable IPM Newsletter, Vol. 5(8). On-line: http://www.vegedge.umn.edu/mnvegnew/vol5/912cew.htm
- ORourke, P.K. & W.D. Hutchison. 2003. Sequential sampling plans for estimating European corn borer (Lepidoptera: Crambidae) and corn earworm (Lepidoptera: Noctuidae) larval density in sweet corn ears. Crop Prot. 22: 903-909.
- ORourke, P.K., W.D. Hutchison. 2004. Developmental delay and evidence for reduced cannibalism in corn earworm (Lepidoptera: Noctuidae) larvae feeding on transgenic Bt sweet corn. J. Entomol. Sci. 40:(in press).
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Progress 01/01/02 to 12/31/02
Outputs
We have continued our efforts in crop canopy manipulation as a management tool to minimize the impacts of weed competition in sweet corn production. An assessment is being made for the potential to manipulate crop canopy through sweet corn cultivar selection. A comparative weed competitiveness index for sweet corn varieties s being developed based on leaf area index and rate of leaf area accumulation. European corn borer (ECB) and corn earworm (CEW) infestation pressure was fairly typical (average) again this year in Minnesota and the Upper Midwest U.S. The univoltine (single generation/yr) strain of ECB continued to be present throughout southern Minn., though not as common as in 2001. Untreated check plots ranged from 20-40% of the ears infested with ECB and up to 40% with CEW. The expansion of the univoltine ECB strain, in addition to existing bivoltine activity creates significant management challenges for growers, with nearly constant pest pressure throughout the
year. The western bean cutworm (WBC) was also present in Minn., for the 4th consecutive year. However, the highest moth counts were limited to southwestern Minn., without much impact on sweet corn growing regions. Research updates for 2002 included: a) expansion of the trapping network for WBC, to develop a data-base of temporal activity in Minn., and how this will impact current IPM programs for ECB and CEW, b) field studies to assess the impact of univoltine ECB infestations in sweet corn were inconclusive due to low ECB pressure at the research site, c) annual assessment of foliar insecticides for ECB and CEW showed continued excellent control by the pyrethroids Warrior and Capture, as well as the reduced-risk d) 2nd year evaluations of Gaucho and Cruiser and Maxim/Apron seed treatments. Insect pressure was low; however, high disease pressure in the untreated plots, reduced stands by 75 and 5% for May 1st and May 15th planting dates, respectively, compared with the Maxim/Apron
treatment (provided maximum stand counts), e) Multi-colored Asian lady beetle, Harmonia axyridis, an exotic beetle introduced by USDA in 1970's was first detected in Minn. in 1994. Lady beetle activity was found to be highly correlated with sweet corn phenology (late whorl to silk), and to some extent, corn leaf aphid; a three-year study confirmed that light traps can be used as a reliable monitoring device for lady beetle adults, with adult trap catch highly correlated with subsequent larval activity in sweet corn. We again collaborated in the sweet corn seed treatment trial coordinated by Idaho Agricultural Experiment Station. Two varieties that received 14 different seed treatments each, were evaluated at Waseca, MN. Summary of work is reported in Idaho Agricultural Experiment Station report.
Impacts
We are one of few groups working to alter light quality via canopy architecture to improve competition of crops with weeds. This effort is strongly endorsed by the sweet corn processing industry, in part due to the foundation laid in our previous work on crop canopy architecture to manipulate weed pests. We have taken science to practice, providing the industry a means to reduce pesticide use through biology.
Publications
- Becker, R.L., V.A. Fritz, J.H. Hebel, D.W. Miller, and B.D. Kinkaid. 2002. Conventional and glufosinate tolerant sweet corn herbicide weed management trial at Waseca, MN - 2001. 2001 N. Cent. Weed Sci. Soc. Res. Report. 58:7-12.
- Hutchison, B. (ed.), R. Becker, D. Ragsdale, R. Jones, C. Rosen, and V. Fritz (Minnesota Contributors) (also faculty from Iowa State University and the Universities of Illinois, Missouri, and Purdue). 2002. 2002 Midwest vegetable Production guide for commercial growers. University of Minnesota Extension Service, St. Paul, Minnesota. BU-7094-S. 166 p.
- Venette, R.C., R.D. Moon and W.D. Hutchison. 2002. Strategies and statistics of sampling for rare individuals. Ann. Rev. Entomol. 47: 143-174.
- Bisikwa, J., R.L. Becker, V.A. Fritz, G.A. Johnson, F. Forcella. 2002. Influence of planting date and sweet corn genotype on growth and development of wild proso millet and giant foxtail. Proc. Weed Sci. Soc. Amer. 42:45 (abstract).
- Hutchison, B., E. Burkness, and P.K. O'Rourke. 2002. Regional Analysis of Pyrethroid Efficacy Against European Corn Borer and Corn Earworm. MN Vegetable IPM Newsletter, Vol. 3, No. 9. Department of Entomology, University of Minnesota, St. Paul, MN;
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Progress 01/01/01 to 12/31/01
Outputs
We completed the study on the effects of crop canopy architecture on competition by sweet corn with giant foxtail and wild proso millet. The work of our graduate student, Jennifer Bisikwa, has provided a framework for future research explorations to further delineate the mechanisms of competition between crop and weed species. We found that we could alter light quality through manipulation of crop canopy architecture. Incrementally decreasing the R:FR ratio of light significantly altered the competitiveness and mechanism of competition for giant foxtail and wild proso millet. These two weed species did not differ in their response to altered light quality however. We continue to develop herbicide management options for use on processing pea and processing sweet corn. Mesotrione (Callisto) is expected to be labeled on sweet corn for the 2002 season, based in part on University data. Mesotrione will provide another alternative to reduce atrazine use (for water resource
protection) and for cyanazine (phase out will be complete for sweet corn in 2002). During the past year, we completed the analysis and publication of two studies designed to assess the efficacy of new Bt sweet corn hybrids against European corn borer and corn earworm. The Minnesota study (Burkness et al. 2001) included some of the first hybrids developed by Rogers Seeds (Novartis). A three-state study was subsequently conducted in Minnesota, Wisconsin and Illinois during 1997-1998 (Burkness et al. 2002). All studies confirmed a very high level of control of European corn borer (99-100% ear protection), and a high to moderate level of corn earworm control (85-95%). No foliar insecticides were used in any of the studies. We collaborated in the sweet corn seed treatment trial coordinated by Idaho Agricultural Experiment Station. Two varieties that received 14 different seed treatments each, were evaluated at Waseca, MN. Summary of work is reported in Idaho Agricultural Experiment Station
report.
Impacts
We are one of few groups working to alter light quality via canopy architecture to improve competition of crops with weeds. Our work defines a mechanism by which competition can be altered. We are one of the leaders in the evolution of replacement series competition work in Weed Science. Our work has implications for herbicide use reduction, and improved crop performance. These results also indicate that Bt sweet corn can be used in the Midwestern U.S. with no foliar insecticide use for ECB. Typically, for late-season sweet corn, only one spray would be needed to control CEW. In either case, this would represent a significant savings in insecticide use.
Publications
- Burkness, E.C., W.D. Hutchison, P.C. Bolin, D.W. Bartels, D. Warnock and D.W. Davis. 2001. Field efficacy of sweet corn hybrids expressing a Bt toxin for management of Ostrinia nubilalis (Lepidoptera: Crambidae) and Helicoverpa zea (Lepidoptera: Noctuidae). J. Econ. Entomol. 94: 197-203.
- Burkness, E.C., W.D. Hutchison, R. Weinzierl, J.L. Wedberg, S.J. Wold & J.T. Shaw. 2002. Efficacy and risk efficiency of sweet corn hybrids expressing a Bacillus thuringiensis toxin for Lepidopteran pest management in the Midwestern U.S. Crop Protection (in press).
- Hutchison, W.D., E.C. Burkness, G. Pahl, T.M. Hurley, R. Weinzierl & J.L. Wedberg. 2001. Risk-based methods for assessing the value of IPM technology: examples for cabbage and sweet corn, pp. 35-42. In R.L. Hughes and B.A. Michaelis (Eds.). Proceedings, Midwest Food Processors Assoc. Vegetable Conference, La Crosse, WI. MFPA, Madison, WI.
- Hutchison, B. (ed.), R. Becker, D. Ragsdale, R. Jones, C. Rosen, and V. Fritz (Minnesota Contributors) (also faculty from Iowa State University and the Universities of Illinois, Missouri, and Purdue). 2001. 2001 Midwest vegetable Production guide for commercial growers. University of Minnesota Extension Service, St. Paul, Minnesota. BU-7094-S. 150 p.
- Becker, R.L., V.A. Fritz, J.H. Hebel, D.W. Miller, and B.D. Kinkaid. 2001. Conventional and glufosinate tolerant sweet corn herbicide weed management trial at Waseca, MN - 2000. Proc. 2001 Midwest Food Processors Assn. Processing Crops Confr. February 19-21. Ext. Serv. of the Universities of Wisc., Ill., and Minn. LaCrosse, WI. pp. 31-32, 253-256.
- Bisikwa, J., R.L. Becker, V.A. Fritz, G.A. Johnson, F. Forcella, and J.H. Hebel. 2001. Crop canopy architecture effects on growth and development of wild proso millet and giant foxtail. Proc. 2001 Midwest Food Processors Assn. Processing Crops Confr. February 19-21. Ext. Serv. of the Universities of Wisc., Ill., and Minn. LaCrosse, WI. LaCrosse, WI. pp. 97-102.
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Progress 01/01/00 to 12/31/00
Outputs
For the second year, sweet corn hybrids (35) were evaluated for emergence performance across three planting dates. Again, seedling emergence varied widely across hybrids due to soil temperatures at planting. These results paralleled the previous year's results. In addition, two hybrids treated with various seed treatments were evaluated for seedling emergence. This was part of the larger regional project that also involved other states. Best emergence (79%) was observed from seed treated with Maxim,Apron XL,Dividend,and Adage 150. Work is continuing on understanding the evolutionary history of common corn smut in North and South America. Smut on the two continents appears to have diverged based on RFLP and AFLP markers. Within North America, there is little local differentiation, however. Studies documenting the efficacy of Bt sweet corn against European corn borer and corn earworm were completed. These studies confirm, without the use of conventional insecticide, a
very high level of insect control (98-100% in MN, WI; >95% IL)and high levels, of marketability (usually > 90%) for processing sweet corn. A third project, showed minimal negative effects of Bt sweet corn on beneficial predator species. In addition, a new pest, the western bean cutworm was discovered in a Bt field and sweet corn.
Impacts
An understanding of relative hybrid vigor under a variety of environmental conditions contributes to selection decisions in both commercial production systems and breeding programs. Continued seed treatment evaluations will lead to improved seedling emergence potential and improve overall performance. Evaluation of Bt sweet corn for performance on both target and non-target species will help ensure sound environmental stewardship.
Publications
- Burkness, E.C., W.D. Hutchison, P.C. Bolin, D.W. Bartels, D. Warnock and D.W. Davis. 2001. Field efficacy of Bt sweet corn against European corn borer (Lepidoptera: Crambidae) and corn earworm (Lepidoptera: Noctuidae). J. Econ. Entomol. (in press).
- Wold, S., E.C. Burkness, W.D. Hutchison & R.C. Venette. 2001. In-field comparison of beneficial insect populations in transgenic sweet corn expressing a Bacillus thuringiensis toxin and in a non-Bt isoline. J. Entomol. Sci. (in press).
- O'Rourke, P.K. & W.D. Hutchison. 2000. First report of the western bean cutworm (Lepidoptera: Noctuidae) in Minnesota corn. J. Agric. and Urban Entomol. (in press).
- Venette, R.C., J. Luhman & W.D. Hutchison. 2000. Survivorship of field-collected European corn borer (Lepidoptera: Crambidae) larvae and its impact on estimates of resistance to Bacillus thuringiensis. J. Entomol. Sci. 35: 208-212.
- Venette, R.C., W.D. Hutchison & D.A. Andow. 2000. An in-field screen for early detection of insect resistance in transgenic crops: practical and statistical considerations. J. Econ. Entomol. (Forum) 93: 1055-1064.
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Progress 01/01/99 to 12/31/99
Outputs
Forty-five hybrids were evaluated for emergence performance across three planting dates. Planting dates corresponded to soil temperatures of 50, 55, and 60F at the 2 inch depth. One hundred seeds of each hybrid were planted for each planting date. The study was replicated twice. Seedling emergence varied widely across soil temperatures at planting and hybrids. In addition, specific hybrids had higher emergence rates when initial soil temperature at planting was 55F, compared to either 50 or 60F soil temperatures. One explanation for this type of performance in some hybrids might relate to the soil temperature during the critical period of 7-10 days after planting. Cumulative growing degree days (GDD) across three planting dates would suggest a natural progression of warming soil as the planting date becomes later. However, during the first 10 days following the initial planting in a soil temperature of 60F, soil temperatures plummeted abruptly during a lengthy cold
period. This probably led to imbibitional related injury and subsequent seed rot, resulting in poor seedling emergence. Time to initial emergence was also delayed by approximately 4 days in several hybrids when initial soil temperature at planting was 60F, compared to planting at either 50 or 55F. Variation in seed treatment was significant across hybrids. However, emergence performance did not correlate with seed treatment. The newer strobilurin chemistry was evaluated for control of common corn rust (P. sorghi) in the hybrid Jubilee. Quadris (azoxystrobin), Stratego (1/1 ratio of trifloxystrobin and propiconazole) and Tilt alone (propiconazole) were compared to traditional mancozeb treatment and a control. An additive control effect from the use of Stratego was observed on the leaf opposite and above the ear, however this did not translate into increased yield. Useable ears and cut corn recovery increased in all plots receiving fungicide treatment. However, useable ears increased
most over the control in the 0.163 lb.a.i./A rate of Stratego. Cut corn recovery was most improved over the control in the Quadrisr and mancozeb treatments. Over the years, our investigations have continued to show satisfactory control using the traditional EBDC chemistry when applied in a very timely fashion and with excellent foliar coverage. However, the systemic, rainfast, and residual properties of the newer chemistry offers an improvement in efficacy, particularly with aerial applications delivering only 4-5 gal./A.
Impacts
An understanding of relative hybrid vigor under a variety of environmental conditions contributes to selection decisions in both commercial production systems and breeding programs. Continued evaluation of new fungicide chemistry for relative performance in controlling common rust (P. sorghi) will result in improved management strategies that are sound environmentally and economically.
Publications
- No publications reported this period
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Progress 01/01/98 to 12/31/98
Outputs
Use of solid matrix priming and plastic mulch systems for improved earliness continued. Results were mixed. A study on sweet corn hybrid performance under narrow row configurations suggest a benefit in early spring plantings. This positive yield effect is lost in mid and late-season plantings. Three Bt sweet corn hybrids were evaluated for efficacy against both European corn borer and corn earworm. All three hybrids continued to perform well against all instars of ECB. For CEW, no late-instar larvae were found in any Bt ears. These results confirm previous observations that indicate a phenomenal level of insect control. Corn smut samples were collected from two fields of sweet corn to study its genetic variation. From each sample, we will obtain a single tetrad that will be characterized for several polymorphic AFLP markers and b mating type using conventional paring tests.
Impacts
(N/A)
Publications
- Reese, Curtis D., Vincent A. Fritz, and Francis L. Pfleger. 1998. Impact of pressure infusion of sh-2 sweet corn with Pseudomonas aureofaciens on seedling emergence. HortScience 33(1)24-27.
- Fritz, Vincent A., Carl J. Rosen, and Roger L. Becker. 1998. Impact of narrow row production on yield recovery, nitrogen use efficiency, and weed competition. HortScience 33(3):523 (abstract).
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Progress 01/01/96 to 12/30/96
Outputs
Interactive effects of host plant resistance and fungicide strategy were evaluated for effective mgmt of common rust (Puccini sorghi) in sweet corn. 3 varieties were chosen for the study which differed in their relative resistance to rust. They are in increasing level of resistance: Merit50% chance of being sexually compatible. Frequencies of observed heterozygosities in 5 commercial sweet corn fields will be compared with random-mating expectations. The pathogen may be widely dispersed and is therefore homogeneous, or local differentiation is occurring based on founder effects and selection. This info. may be useful in determining how best to use resistance sources or biological control strategies.
Impacts
(N/A)
Publications
- DAVIS, D.W., D.F. WARNOCK, J. ELIZONDO-B. and J. VASQUEZ. 1996. Further development of resistance to European corn borer and the combining of borer resistance with other disease and insect problems of sweet corn. IN: R.L Hughes and B.A. Mic WARNOCK, D.F. and D.W. DAVIS. 1996. Evaluation of two visual scales to estimate European corn borer ear feeding damage in sweet corn (Abstract). HortScience 31:613.
- WARNOCK, D. F., D.W. DAVIS and W.D. HUTCHISON. 1996. Initial screening of sweet corn tissues for allelochemicals that affect European corn borer larval development (Abstract). HortScience 31:622.
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Progress 01/01/95 to 12/30/95
Outputs
Under very high natural infestations (>7 egg masses/plant) U of M test hybrids were nearly free of ear damage from European corn borer, averaging <2.0 on a 1 to 9 scale. Key was resistance contribution by both inbred parents in the cross. Three-year generation mean analysis confirmed high degree of additive genetic variance. Initial results from investigating the role that sucrose and raffinose play in membrane stabilization during desiccation suggest that a raffinose:sucrose ratio of 0.3 in the embryo correlates to greater vigor in shrunken-2 sweet corn. Additional studies are currently under way whcih will follow the change in the embryo reffinose:sucrose ratio at various seed desiccation rates. Three su hybrids deffering in their relative susceptibility to common corn rust were produced under different disease management strategies to determine comparative disease severity and yield recovery. The variety Prime Pak (polygenic resistant variety) had less disease
pressure than either Jubilee or Merit. Mancozeb applies to Merit and Jubilee resulted in the highest cut corn recovery. In addition, cut corn recovery increased as rate and total number of applications of propiconazole were increased from .055 lb. a.i./A-7day interval until tasseling. Further understanding of the relative genetic resistance contribution to rust management among varieties may lead to improved management strategies that are both environmentally and economically sound.
Impacts
(N/A)
Publications
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Progress 01/01/94 to 12/30/94
Outputs
Commercial emphasis on the Rp1d gene for resistance to leaf rust (Puccinia sorghi) disease in sweet corn is risky because the fungus can mutate. In hybridizing parents possessing other, only partially effective, Rp genes to find out if the resistance of combinations would be higher, 23 genes were tested in 4 designs. Combinations Rp1k x Rp1g, Rp1k x Rp1l, Rp1i x Rp1f, and Rp1k x Rp3c were more resistant than either homozygote in field epidemics at 2 locations. Combinations may be a useful alternative to Rp1d used alone. Several single Rp genes permitting some infection produced rust-free heterozygotes. In other work the 11 most and 11 least resistant S1s of 268 random S1 sweet corn lines from an open pollinated stock were evaluated. Their partial (multigenic; genetically durable) resistance was stable across 2 locations and 3 years (r2 = 0.82). More resistant S1s were more stable across environments. Disease scoring of only a single (worst) leaf may have merit in
selection for greater partial resistance, thus accelerating breeding strategy at reduced cost. Breeders should select at various plant growth stages if epidemic levels are moderate to high, but accuracy will be greater at later stages. In other work, 3 su hybrids differing in susceptibility to leaf rust were grown under different disease management strategies. Two disease severity quantification methods were used. Visual assessment more closely tracked cut corn yield than did the leaf area meter method.
Impacts
(N/A)
Publications
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Progress 01/01/93 to 12/30/93
Outputs
In sweet corn, durable partial resistance to the leaf rust fungus (Puccinia sorghi) would be preferable to the strong, but genetically nondurable, hypersensitive-based resistance now used. Partial resistance could have several components, such as longer `latent period' (LP) (the duration between inoculation and symptom expression), but longer LP has never been found in field tests with common corn leaf rust. From a 2-year field study based on daily, rigorous, plant-by-plant disease incidence screening of 32 MN AES partial-resistant breeding lines, an extended LP of up to 7 days was discovered. Generation (P1, P2, F1, F2, BC1P1 and BC1P2) analysis, following hybridization of long x short LP parents, indicated a high degree of additive genetic control of longer LP. Thus, selection for longer LP, as a way of achieving greater partial resistance and, therefore, of delaying disease buildup and reducing reliance on the use of fungicides, is suggested as breeding strategy
which can be successful in small plot (< 25 plants/replication) field research--partial resistance to corn leaf rust is difficult to quantify in controlled-environment research. Evaluation of current commercial hybrids representing a range of partial resistance did not show LP differences. In related work a population improved for overall partial resistance, and typically scoring 1.5 to 2.5 on a 0 to 9 visual scoring scale, was released to public and commercial breeders as AS12.
Impacts
(N/A)
Publications
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Progress 01/01/92 to 12/30/92
Outputs
Progress of genetic selection for 3 generations (F2 to F5) to improve partial (nonhypersensitive-based) resistance to the leaf rust fungus (Puccinia sorghi) in sweet corn was evaluated in a final experiment. From remnant, stored seed most-resistant, self pollinated, single-plant selections made each generation were compared for 2 seasons in each of 2 locations. Across these 4 environments, resistance improved each generation. Area Under the Disease Progress Curve (the measure of the time course of disease development on the plants) by harvest declined from 2.79 at the F2 to 1.79 at the F5 across the 3 breeding populations (parentages) used. Realized heritability ranged from about 60 to 80%. Commercial hybrids in an adjacent test averaged from 2.8 (`Miracle'--has some resistance) to 4.2 (`Jubilee'--not resistant). This partial resistance is viewed as a genetically durable alternative to the mutable, single-gene, hypersensitive-based resistance now used commercially, and
thus will provide reduced vulnerability for growers, and less reliance on fungicides. In related work, field exposure of 24 alleles from 4 Rp loci conditioning race-specific resistance to P. sorghi surfaced only 2---R(subscript p1)(superscript d) and R(subscript p3)(superscript c)---which were totally effective; 4 others had only traces of rust. Two unknowns are under test to see if they are additions to the 24.
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Progress 01/01/91 to 12/30/91
Outputs
European corn borer (ECB) larvae on silking-stage corn plants may have abundant contact with pollen, especially as they pass through pollen-rich leaf axils in migrating from the leaf blades to leaf sheaths and stalks. Sweet corn produces pollen in great abundance. Does pollen as a food source contribute to larval success? In the lab, larval fed pollen from either ECB resistant or susceptible corn were able to develop equally well to adult stage. In the field, larval survival on ECB resistant plants with pollen added to leaf axils was about twice that on resistant plants without added pollen. Survival was highest on ECB susceptible plants with or without pollen. On the resistant corn larvae were most commonly found in the leaf axils when pollen was present and in the ear when it was not.
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Progress 01/01/90 to 12/30/90
Outputs
Behavior of European corn borer (ECB) larvae on resistant vs susceptible corn plants may lead to improved ways of breeding for resistance. Egg masses commonly are laid on the leaf undersurface, and larvae must migrate from the hatching site and become established. Plants of 4 corn stocks varying in resistance to leaf, sheath/collar, and ear damage were dissected 5 days after egg hatch following infestation at whorl, anthesis, and full-silk stages. Mortality was 30% higher on the most resistant stock at the whorl stage, and 97% of the survivors were found in the whorl leaves. In the most susceptible stock, surviving larvae were more evenly divided between the whorl leaves (47%) and the expanded leaves (53%). At the anthesis stage, 86% of surviving larvae on the most resistant stock had migrated from the leaf blade area and were found in the collar area vs 48% for the most susceptible stock. When plants were infested on the ear at the full-silk stage, only 28% of larvae
survived to the 5th day on the resistant stock vs 57% for the susceptible. Significantly fewer of the surviving larvae were found on resistant ears (71%) than on susceptible ears (86%). In general, ECB larvae do not survive as well and migrate more on resistant strains of corn. In breeding resistant varieties, evaluation of feeding pattern as well as total damage at various sites on the plant may be useful.
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Progress 01/01/89 to 12/30/89
Outputs
Tropical germplasm is of interest as a source of genes for insect, disease and environmental stress resistance and for broadening the germplasm base of temperate zone corn. Hence, the degree of conservation of tropical corn genes during introgression of tropical corn germplasm into temperate adapted sweet corn in a temperate environment is important. Hybridization between 17 tropical types and 11 U.S. sweet corn inbreds, and mechanical mixing of resulting seed to form a composite population was followed by 4 cycles of random mating without artificial selection, but with precautions to reduce assortative mating and natural selection. Horizontal starch gel electrophoretic analysis of 5 isozyme loci (Est 8, Glu 1, Got 1, Mdh 2 and Mdh 5) used as genetic markers of chromosome linked tropical alleles (as a sample of the genome) was made on remnant seed of the first 4 generatioons of the composite. No change was found in the 5 marked genomic regions (chromosomes) from
directional natural selection. Variations in the frequencies of only 2 of 9 tropical alleles were greater than could be attributable to genetic drift alone and only 1 of these had a significant linear decrease in frequency over cycles. Hence, tropical germplasmin temperate tropical corn composites can be maintained even when the composite is random mated in a temperate environment.
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Progress 01/01/88 to 12/30/88
Outputs
During two years of testing, 65 of 88 sweet corn selections were resistant to ear damage following infestation at the ear tip with two-egg mass equivalents of European corn borer. Ear resistance in sugary germplasm has not heretofore been reported. Fewer than 15% of the plants in the 9 best selections had kernel damage as compared to more than 90% for Jubilee, a typical commercial hybrid. Less than 5% of the ears on all commercial hybrids submitted (8) by Minnesota processors escaped kernel damage when artificially infested with borer larvae at the ear tip, indicating the high degree of susceptibility of industry varieties. Testcrosses utilizing the resistant selections will be evaluated to determine to what degree the resistance is transmitted to hybrids. The resistant selections were derived from 6 different parentages. In other ork, 15 years of introgression of tropical maize races/cultivars into temperate sweet corn to increase variation, combining ability
and heterosis were evaluated via derived random families and their testcrosses at 0, 5 & 10 cycles of stratified mass selection in a composite population. Tropical germplasm appeared to contribute to the combining ability of derived S1 families via greater early vigor, higher kernel rows and decreased stalk breakage in the testcrosses vs the check testcrosses. Cycle 10 testcrosses were at least equal to elite inbred (check) testcrosses for 8 of 11 traits. The first 5 cycles of selection were more effective than the 2nd 5.
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Progress 01/01/87 to 12/30/87
Outputs
Progeny evaluation culminating many years of full- & half-sib selection for resistance to ear & kernel feeding by European corn borer (ECB) (Ostrinia nubilalis) was made. From post-silking artificial infestation at the ear tip with about 25 larvae 226 S1 families were evaluated for ear, shank & stalk damage. On a 1-9 scale for ear & kernel damage observed on 24 plants ( 3 plants x 8 reps) for each S1 family, 20 families averaged 2.5 or less, while resistant, susceptible & highly susceptible checks averaged 3.4, 3.8 & 5.8, respectively. On the 1-9, 2 = husk and/or silk damage only, 3 = 1-5% of the tip kernels damaged, 4 = 6-10% of tip kernels damaged. Two sugary germplasm populations of half corn belt dent & half sweet corn heritage were released as breeding sources for vigor, yield, generalized pest resistance & other traits possessed by field corn & needed in sweet corn. As complementary populations designed to provide good combining inbreds, one population
9NE-HY-13A) is of Lancaster background & the other (NE-HY-13B) is of Stiff Stalk Synthetic background. Leaf rust evaluation of 84 S(1) families from cycles (years) 0, 5 and 10 in the domestication of a Latin x adapted sweet corn composite showed a progressive erosion of resistance. The population had been selected during the 10 cycles for many economic traits, but not for rust resistance. This behavior demonstrates one of the problems of germplasm preservation.
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Progress 01/01/86 to 12/30/86
Outputs
A sweet corn composite resistant to common leaf rust (Puccinia sorghi) and to maize dwarf mosaic (MDM) virus was approved for release to breeders and will be designated as ASII. A second composite, Minnesota 2400, also approved for release as rust and MDM resistant, will be retained for another one to two years in attempts to improve the level of its resistance to European corn borer (ECB). Sweet corn Population 22 was found to possess greater resistance to ear damage from ECB than six competing populations. In studies of the inheritance of ear length, additive genetic variance was found to be more important than dominance genetic variance in two of three pedigrees. Narrow sense heritability estimates for ear length were low to moderate (0.27 to 0.50). Ear length was negatively associated (r=0.50) with husk extension (tip coverage) and only weekly associated with tassel date, plant height, ear height, leaf number, shank length, tip blanking, ear diameter, kernel
length and kernel row number. Shank length showed a high degree of heterosis (averaging 20% longer than the long-shank parent), with a narrow sense heritability of 0.53. Long shank length was not strongly associated (r=0.35) with ear length. Hence it shoould be possible to develop longer eared types without unduly lengthening the shank. Narrow sense heritability of husk extension was 0.80. High negative heterosis for husk extension was found.
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Progress 01/01/85 to 12/30/85
Outputs
Reported herein are the results of investigation of the genetic association of the sugary (su) gene with various plant and ear traits of corn. This work was prompted by the desire to transfer a desirable level of expression of these traits from starchy (Su) (field corn) to sweet corn (su). Plant and ear traits contributing to yield and quality of sweet corn were measured on plants of known endosperm type from su of Stiff Stalk Synthetic Su heritage. S(0) plants were grown in three environments at each of 36905, 57407, and 73810 plants per ha with ear measurements taken at the milk stage. S(1) progenies were grown in two environments at 51668 plants per ha with fully mature dried ears used for measurements. Sugary S(0) segregates showed a greater tendency toward silking delay, failure to produce an ear, and lodging than starchy segregates. Reduced tip blanking and shortened ear length were associated with sugary endosperm in S(0) and S(1) plants. Plant and ear
heights were somewhat reduced on sugary S(1) plants than on their starchy counterparts. No association was detected between type of endosperm and the number of marketable ears or yield among S(0) segregates. S1 cob color, row number, ear diameter, taper, and curvature were also not associated with endosperm type. Associations generally were small but significant. It is not known if these associations are due to linkage or to pleiotropy; evidence for either alternative can be found in the literature.
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Progress 01/01/83 to 12/30/83
Outputs
This project emphasizes 1) disease & insect resistance, & 2) breeding strategy &germplasm development. Selected for reporting herein is the progress on breeding for resistance to common leaf rust caused by Puccinia sorghi. Of 94 adapted hybrids, varieties, & Plant Introductions during 2 years, 13 having some (detectable) "partial" resistance were composited with 20 new MN lines as a new gene source population. From a 2-year study of plot spatial designs those which increased the general rust level, as influenced by wind blown spore load, decreased the gradient in rust level between known resistant & susceptible types by up to 50%. Hence selection for resistance should not be made on a plant to plant basis in segregating families, but rather on advanced progeny lines. High (78%)narrow sense heritability estimates from resistant x susceptible crosses indicated a high degree of additivity & high expectation for genetic gain in resistance, while other parentages
showed epistasis or dominance to be of some importance. Considering these results, some form of reciprocal recurrent selection should be used to maximize progress for increasing resistance. However, in parental populations with less well known resistance levels, a 12-17% gain per cycle of selection was found during 2 cycles of phenotypic mass selection. Germplasm having resistance is available to sweet corn breeders.
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Progress 01/01/82 to 12/30/82
Outputs
Of the 5 phases of work under 21-035R parts of 2 are reported herein: In the first, experiments were conducted to determine progress made in breeding for resistance to ear damage in sweet corn by European corn borer, and permit at the same time additional selection for resistance. Twelve families still undergoing selection initiated in past years in Apache, a hybrid with low to moderate resistance, ranged from 2.8 to 8.1 on a '0' (no damage) to '9' (very high damage) scale, and averaged 6.5 as compared to 7.5 for Apache, 8.5 or more for other commercial hybrids, and 3.0 for Zapolote Chico, an unadapted tropical maize. In other experiments designed to backcross low but significant levels of ear damage resistance from field corn into edible sweet corn "more resistant" F(3) families, selected one year earlier from the first backcross, averaged 7.8 while "more susceptible" F(3)s averaged 7.3. Both of the above examples indicate first, that improvement will be a slow but
useful process, especially where high culinary quality is a concurrent emphasis, and second, that the backcross and pedigree approaches may be less viable than recurrent selections. However, to obtain quality plus resistance both approaches are suggested, and most likely should be used on an alternating basis.
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Progress 01/01/81 to 12/30/81
Outputs
Progress on 2 studies is reported. The objective was, for the first, to find out if damaged caused by European corn borer (ECB) differs for early vs. late sweet corn, or sweet corn maturing at different times, and, for the second, to determine optimum borer infestation level in breeding for resistance. Kernel damage and stalk tunneling caused by artificial infestation were measured on a series of sweet corn hybrids at several levels of maturity and three planting dates. Rate of increase in damage with maturity, magnitude or maximum damage and maturity at which maximum damage occurred varied by variety and planting date. There very likely is sufficient inconsistency of response on hybrids which silk on different dates so that some reduction in response to genetic selection could result. Differences caused by day length, daily mean temperature pattern, egg mass quality, predation or parasitism of the borer, and other factors may be responsible. Several varieties
differing in resistance were infested at the ear tip with 0, 2, 4, 8, 16, or 32 borer egg masses and evaluated for kernel damage. Kernel damage increased rapidly at first and then plateaued as infestation level increased. Based on the mathematical function generated, ability to separate varieties (based on genetic differences in resistance), was maximized at 9 egg masses per ear tip. Greatest accuracy at minimum dollar cost occurred at 6 replications of 2 plants per replication with 4 egg masses per ear tip.
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Progress 01/01/80 to 12/30/80
Outputs
Significant (P less than or equal to 5%) variation was observed among 16 F4 families of maize (Zea mays, L.) derived from 'I453' x B52' for ovipositional frequency by the European corn borer (Ostrinia nubilalis, Hubner) following natural infestation at 3 locations. A technique using oviposition cages was developed to remove lateral and horizontal gradients in paired evaluations of genotypes for relative ovipositional antixenosis (ROA) to the European corn borer. Partitioning of sums of squares for proportion of egg masses oviposited on experimental genotypes versus testers enabled extension of the concept of ROA to include general ROA, the variation in the average performance of genotypes over testers, and specific ROA, the variation due to deviations from general ROA. Evaluation was also made for absolute ovipositional antixenosis (AOA). No significant variation in ovipositional frequency was observed among these genotypes for general ROA, specific ROA, or AOA
although the presence of a lateral gradient was confirmed. These results should be conceptually useful in the breeding of maize for resistance to European corn borer.
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Progress 01/01/79 to 12/30/79
Outputs
Thirty-eight cultivars were evaluated in rep. trials for 1st and 2nd brood European corn borer (ECB) resistance (res.) via new artificial infestation techniques reported earlier yrs. Germplasm res. has been developed and is available to breeders as a su composite (1st brood res), and a su F(7) (2nd brood res) from the cross I453 x B52. Res of the F(7) as a) # of damaged kernels/ear and b) cm. of stalk tunneling was 4.6 and 4.3 compared to 57.3 and 35.0 for a susceptible control. In research on res. mechanisms kernel damage levels from artificial and natural infestation with 2nd brood ECB on 16 random S3 sugary and dent families from I453 x B52 were not highly related (R 2=.22-.35) in field tests. Multiple regression including # of egg masses oviposited on the families increased R 2 to .35. Morphology appears important, with silk length, length and firmness of silk channel, and length of flag leaves accounting for 42% of the variation in kernel damage. Husk, silk and
cob tissues were equally supportive of larvae in lab. feeding tests. Hence, ear morphology may be more important than chemistry in determining res. in this genetic material. A new procedure reducing environmental effects was developed to differentiate genotypes for absolute and relative ovipositional antixenosis in the field using caged gravid ECB moths.
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