Persistent Link:
http://hdl.handle.net/10150/197949
Title:
Making Late Season Decisions to Terminate Insecticide Use Against Lygus
Author:
Ellsworth, Peter C.; Barkley, Virginia
Affiliation:
Department of Entomology & Maricopa Agricultural Center
Issue Date:
May-2003
Publisher:
College of Agriculture, University of Arizona (Tucson, AZ)
Journal:
Cotton: A College of Agriculture and Life Sciences Report
Abstract:
The focus of our 2002 field study was to answer a fundamental question in insect control. Once spraying has begun for a particular pest, when should it stop? In this case, we are faced with the question of when to discontinue sprays for Lygus hesperus in cotton. Cotton is susceptible to Lygus any time there are productive squares on the plant. This study developed a series of worst-case scenarios in which to provide information on timing of the latest possible sprays of economic benefit. By late planting (30 May) varieties from three different maturity groups, we were able to examine Lygus control dynamics just prior to, at, and after cutout — initiation of cut-out was defined as NAWF = 5. We found large differences in yield among the four Lygus chemical termination (LT) treatments. The earliest termination (LT1, 2 weeks prior to cut-out) suffered the largest losses to Lygus, ca. 20–50% of the maximum yield. Conversely, extending Lygus chemical control 1–3 weeks after cut-out (LT3 & LT4) provided no yield benefit whatsoever, regardless of the variety examined. Maximum yields and maximum profits were gained in the LT2, where Lygus controls were continued up to 1 week prior to cutout. Given that there was only 1 week separating the LT1 and LT2 timings, it is clear that timing is absolutely critical. The timing used in this study corresponds with previously established threshold guidelines; treat when there are at least 15 total Lygus with at least 4 nymphs per 100 sweeps. Levels far exceeded this threshold late in the season, yet additional chemical controls after cut-out provided no additional yield or control benefits. Further, we have confirmed that nymphs are the life stage of major concern with, by far, the most capacity to reduce yields. Nymphal reductions were well-correlated with yield enhancement. The best timing (LT2) achieved ca. 93% reduction in nymphal densities during the critical 3- week period around cut-out. In contrast, adult numbers were reduced by only 16% during the same period. These results establish an upper bound for treatment of Lygus, no later than 1 week prior to cut-out; however, more work is necessary to identify if earlier cessation is possible under more normal planting conditions.
Keywords:
Agriculture -- Arizona; Cotton -- Arizona; Insect investigations
Series/Report no.:
AZ1312; Series P-134

Full metadata record

DC FieldValue Language
dc.titleMaking Late Season Decisions to Terminate Insecticide Use Against Lygusen_US
dc.contributor.authorEllsworth, Peter C.en_US
dc.contributor.authorBarkley, Virginiaen_US
dc.contributor.departmentDepartment of Entomology & Maricopa Agricultural Centeren_US
dc.date.issued2003-05-
dc.publisherCollege of Agriculture, University of Arizona (Tucson, AZ)en_US
dc.identifier.journalCotton: A College of Agriculture and Life Sciences Reporten_US
dc.description.abstractThe focus of our 2002 field study was to answer a fundamental question in insect control. Once spraying has begun for a particular pest, when should it stop? In this case, we are faced with the question of when to discontinue sprays for Lygus hesperus in cotton. Cotton is susceptible to Lygus any time there are productive squares on the plant. This study developed a series of worst-case scenarios in which to provide information on timing of the latest possible sprays of economic benefit. By late planting (30 May) varieties from three different maturity groups, we were able to examine Lygus control dynamics just prior to, at, and after cutout — initiation of cut-out was defined as NAWF = 5. We found large differences in yield among the four Lygus chemical termination (LT) treatments. The earliest termination (LT1, 2 weeks prior to cut-out) suffered the largest losses to Lygus, ca. 20–50% of the maximum yield. Conversely, extending Lygus chemical control 1–3 weeks after cut-out (LT3 & LT4) provided no yield benefit whatsoever, regardless of the variety examined. Maximum yields and maximum profits were gained in the LT2, where Lygus controls were continued up to 1 week prior to cutout. Given that there was only 1 week separating the LT1 and LT2 timings, it is clear that timing is absolutely critical. The timing used in this study corresponds with previously established threshold guidelines; treat when there are at least 15 total Lygus with at least 4 nymphs per 100 sweeps. Levels far exceeded this threshold late in the season, yet additional chemical controls after cut-out provided no additional yield or control benefits. Further, we have confirmed that nymphs are the life stage of major concern with, by far, the most capacity to reduce yields. Nymphal reductions were well-correlated with yield enhancement. The best timing (LT2) achieved ca. 93% reduction in nymphal densities during the critical 3- week period around cut-out. In contrast, adult numbers were reduced by only 16% during the same period. These results establish an upper bound for treatment of Lygus, no later than 1 week prior to cut-out; however, more work is necessary to identify if earlier cessation is possible under more normal planting conditions.en_US
dc.subjectAgriculture -- Arizonaen_US
dc.subjectCotton -- Arizonaen_US
dc.subjectInsect investigationsen_US
dc.identifier.urihttp://hdl.handle.net/10150/197949-
dc.relation.ispartofseriesAZ1312en_US
dc.relation.ispartofseriesSeries P-134en_US
All Items in UA Campus Repository are protected by copyright, with all rights reserved, unless otherwise indicated.