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Funded Project |
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Funding Program:
Regional IPM Grants (S-RIPM) |
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Project Title:
Management of Twospotted Spider Mite on Vegetables in a Multicrop Agroecosystem |
Project Directors (PDs):
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Lead State: NC Lead Organization: North Carolina State University |
| Research Funding: $67,912 |
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Start Date: Aug-01-2004 End Date: Jul-31-2007 |
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Pests Involved: twospotted spider mite |
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Summary:
In recent years, the twospotted spider mite (TSSM) has developed into a key pest of vegetables in the piedmont and mountain regions of the southeastern US. Studies during 2002 and 2003 suggest that in vegetable-producing regions, certain vegetables (primarily tomato and pepper) have replaced corn as a key summer host of TSSM. Factors contributing to this occurrence include a reduction in both corn acreage and use of the soil insecticide turbufos, which greatly accelerates mite population increases on corn, and vegetable cultural and pest management practices that serve to enhance TSSM reproduction and minimize the potential for biological control. Not all mite-susceptible vegetable fields become infested with TSSM, with the previous years' crop, time of harvest (if mite infested), and distance from mite overwintering sites appearing to be important in dictating the potential for infestation. The high value of vegetable crops and lack of basic information related to mite management on these crops has led to frequent and unnecessary acaricide applications. This has contributed to the development of acaricide-resistant TSSM populations, and, in the absence of management guidelines, will likely lead to resistance to new acaricides entering the market. The goal of this project is to better understand the area-wide population dynamics of TSSM so as to identify risk factors for mite infestations in individual fields, and to development strategies for minimizing acaricides use on vegetable crops. Specific objectives include: 1) identify factors contributing to the susceptibility of vegetable fields to infestation by TSSM; 2) determine the effect of late-season weed control in the border of tomato fields on overwintering populations of TSSM; 3) develop a sampling plan for estimating mite populations on tomato and pepper; and 4) determine the mite density-yield relationship on sequential plantings of tomato and pepper. Analysis of the temporal distribution of mites in different habitats and correlation with previous cropping history, planting date, field disking date, distance of vegetable crop from various habitats and weed abundance, will enable us to identify those factors most important in predicting TSSM infestations. This information, together with the development of mite ` sampling plans and an assessment of the economic impact of mites on tomato and pepper, will form the basis of a management program for TSSM on vegetables.
Objectives: 1. Identify factors contributing to the susceptibility of vegetable fields to infestation by twospotted spider mite. 2. Determine the effect of late-season weed control in the border of tomato fields on overwintering populations of TSSM. 3. Determine the mite density-yield relationship on sequential plantings of tomato. |
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Final Report: |
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Results PROGRESS: 2004/08 TO 2007/07 OUTPUTS: The twospotted spider mite (TSSM) is a key pest of vegetables in western and central North Carolina. Infestations are particularly problematic on tomatoes, where growers spend as much as $100 per acre to manage this pest. Little was known about the population dynamics of TSSM in relation to vegetables in this region of the state. The goal of this project was to better understand the area-wide population dynamics of TSSM so as to identify risk factors for mite infestations in individual fields, and to development strategies for minimizing acaricides use on vegetable crops. Specific objectives include: 1) identify factors contributing to the susceptibility of vegetable fields to infestation by TSSM; 2) determine the effect of late-season weed control in the border of tomato fields on overwintering populations of TSSM; 3) determine the mite density-yield relationship on sequential plantings of tomato. To accomplish these objectives, more than 100 field locations were sampled over a three year period to determine mite phenology in tomato fields and surrounding crop (soybean, corn, strawberry, pepper, cucurbits) and non-crop (weeds) habitats. These data, along with tomato production practices associated with individual tomato fields (location, planting date, rotation, and pesticides applied) were subjected to multiple regression to identify factors important in predicting mite infestations on tomatoes. To more clearly understand the movement TSSM populations into and out of tomato fields, field studies were conducted to determine the distance of mite migration from tomatoes in the autumn. Finally, to examine the impact of mite infestations on the yield, quality and economics of early and late-planted tomatoes, economic threshold studies were conducted in field trials. PARTICIPANTS: Individuals: James F. Walgenbach - principal investigator responsible for all aspects of project. George G. Kennedy - co-PI. David W. Monks - co-PI Elijah Meck - M.S and PhD student conducted research as part of thesis. Hourly employees - Tom Hoyt, Jason Livingston, Anna Hinshaw. Training development: Project providing training in IPM to one graduate student and three undergraduate students during summer months. Training of vegetable extension agents and producers occurred at field days. TARGET AUDIENCES: Extension Agents, vegetable growers, pest control industry, agrochemical industry, and general public. IMPACT: 2004/08 TO 2007/07 A number of different factors were associated with high mite densities in tomato fields, including previous crop, acaricide use, insecticide use, and mite intensity in weeds surrounding fields. Acaricide use and mite intensity in the weeds were important factors associated with the maximum mite intensity in tomatoes. Year, location, planting date, and acaricide use were all important factors associated with the time it took for tomato fields to reach their maximum density. Upon further analysis, it was found that none of the dependent variables (year, location, previous crop, adjacent crop, planting date, acaricide use, insecticide use) were associated with seasonal mite intensity in weeds or mite intensity in weeds on the last two sample dates. However, previous crop and insecticide use were significant factors associated with mite intensity in weeds on the first two sample dates. Furthermore, seasonal mite intensity in weeds was significantly correlated with seasonal and maximum mite intensity in tomato fields. While previous crop, current season insecticide use, and mite intensity in weeds were factors associated with mite intensities in the field, high overwintering mortality appeared to negate the effects of these factors; consequently it was not possible to predict in advance fields that were most susceptible to high mite infestations. Acaricides will likely remain a key management strategy in the near future, and the use of thresholds will be important to use these materials in a judicious manner so as to avoid resistance development. Two vegetation management techniques (herbicide and cultivation) plus an untreated control plot were established around senescing tomato plants. Twospotted spider mite dispersal was monitored by planting chickweed trap plants at 2, 6, and 12 m from the tomatoes. Sampling took place in the fall of 2004 & 2005 and the spring of 2005 & 2006. Only a small number of mites were collected in the 2004-2005 sampling period, making it difficult to draw conclusions. The 2005-2006 sampling period showed that herbicide-treated soil facilitated mite dispersal in the fall, while there were no differences in mite populations among treatments in the spring, suggesting a high rate of overwintering mortality. Finally, TSSM threshold studies on tomatoes in 2006 and 2007 showed that mite populations built to higher densities on early vs. later planted tomatoes, and mite-induced fruit quality effects included reduced total yields and increased levels of gold flecking disorder. On early and late-planted tomatoes, total yields in the controls were reduced by as much as 31.1 and 15.7% compared to the low threshold treatment. In addition, net profits in the early planting were reduced from $14,663 in the low threshold treatment to $2,158/acre in the control. A provisional economic threshold level for twospotted spider mite on tomatoes is 3 mites per terminal leaflet. PUBLICATIONS (not previously reported): 2004/08 TO 2007/07 No publications reported this period |
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Outcomes N/A |
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Impacts From report submitted by the PI to USDA CRIS report system A number of different factors were associated with high mite densities in tomato fields, including previous crop, acaricide use, insecticide use, and mite intensity in weeds surrounding fields. Acaricide use and mite intensity in the weeds were important factors associated with the maximum mite intensity in tomatoes. Year, location, planting date, and acaricide use were all important factors associated with the time it took for tomato fields to reach their maximum density. Upon further analysis, it was found that none of the dependent variables (year, location, previous crop, adjacent crop, planting date, acaricide use, insecticide use) were associated with seasonal mite intensity in weeds or mite intensity in weeds on the last two sample dates. However, previous crop and insecticide use were significant factors associated with mite intensity in weeds on the first two sample dates. Furthermore, seasonal mite intensity in weeds was significantly correlated with seasonal and maximum mite intensity in tomato fields. While previous crop, current season insecticide use, and mite intensity in weeds were factors associated with mite intensities in the field, high overwintering mortality appeared to negate the effects of these factors; consequently it was not possible to predict in advance fields that were most susceptible to high mite infestations. Acaricides will likely remain a key management strategy in the near future, and the use of thresholds will be important to use these materials in a judicious manner so as to avoid resistance development. Two vegetation management techniques (herbicide and cultivation) plus an untreated control plot were established around senescing tomato plants. Twospotted spider mite dispersal was monitored by planting chickweed trap plants at 2, 6, and 12 m from the tomatoes. Sampling took place in the fall of 2004 & 2005 and the spring of 2005 & 2006. Only a small number of mites were collected in the 2004-2005 sampling period, making it difficult to draw conclusions. The 2005-2006 sampling period showed that herbicide-treated soil facilitated mite dispersal in the fall, while there were no differences in mite populations among treatments in the spring, suggesting a high rate of overwintering mortality. Finally, TSSM threshold studies on tomatoes in 2006 and 2007 showed that mite populations built to higher densities on early vs. later planted tomatoes, and mite-induced fruit quality effects included reduced total yields and increased levels of gold flecking disorder. On early and late-planted tomatoes, total yields in the controls were reduced by as much as 31.1 and 15.7% compared to the low threshold treatment. In addition, net profits in the early planting were reduced from $14,663 in the low threshold treatment to $2,158/acre in the control. A provisional economic threshold level for twospotted spider mite on tomatoes is 3 mites per terminal leaflet. |
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