An adjustable action threshold using larval parasitism of Helicoverpa armigera (Lepidoptera: Noctuidae) in IPM for processing tomatoes
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Published source details
Walker G.P., Herman T.J.B., Kale A.J. & Wallace A.R. (2010) An adjustable action threshold using larval parasitism of Helicoverpa armigera (Lepidoptera: Noctuidae) in IPM for processing tomatoes. Biological Control, 52, 30-36.
Published source details Walker G.P., Herman T.J.B., Kale A.J. & Wallace A.R. (2010) An adjustable action threshold using larval parasitism of Helicoverpa armigera (Lepidoptera: Noctuidae) in IPM for processing tomatoes. Biological Control, 52, 30-36.
Actions
This study is summarised as evidence for the following.
Action | Category | |
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Incorporate parasitism rates when setting thresholds for insecticide use Action Link |
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Use pesticides only when pests or crop damage reach threshold levels Action Link |
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Incorporate parasitism rates when setting thresholds for insecticide use
A controlled study in 2000-2002 in Hawke’s Bay, New Zealand (Walker et al. 2010) found that tomato Solanum lycopersicum damage from cotton bollworm Helicoverpa armigera larvae did not exceed the commercially acceptable level of 5% on 16 of 17 occasions when treatment decisions were based on parasitism-adjusted pest thresholds. Only 1.2-5.5% of tomatoes were damaged in 11 fields where decisions to not spray crops used thresholds accounting for parasitism (damage exceeded the acceptable 5% level in only one field), and 3.0-3.4% were damaged in two sprayed fields where conventional thresholds (using pest but not parasitism levels) were used. Tomato damage averaged 3.9-7.1% in three unsprayed fields where cotton bollworm numbers exceeded parasitism-adjusted threshold levels. Treatment decisions were made for 22 fields which met or exceeded a conventional threshold of one cotton bollworm larvae/plant, suggesting spraying was necessary. However, in 16 fields and one half-field, crops were only sprayed if bollworm numbers exceeded thresholds adjusted for site-specific parasitism rates (ranging 1-8.3 larvae/plant). Controls included two fields sprayed when only the conventional pest threshold was exceeded, and three fields and one half-field left unsprayed despite exceeding all thresholds. Insecticides included spinosad and Bacillus thuringiensis pesticidal bacteria. Fruit damage was assessed for 40 random plants/field.
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Use pesticides only when pests or crop damage reach threshold levels
A trial in 2000-2002 in Hawke’s Bay, New Zealand (Walker et al. 2010) found that tomato Solanum lycopersicum damage did not exceed the commercially acceptable level of 5% at harvest on 16 of 17 occasions when decisions to spray were made using thresholds of cotton bollworm Helicoverpa armigera larvae abundance. On average, 0.8-5.5% of tomatoes were damaged in treated fields compared with 3.9-7.1% in unsprayed fields (where thresholds were also exceeded). The decision to not treat crops while maintaining < 5% damage was correct 10 out of 11 times. Treatment decisions were made for 22 fields which all met or exceeded a conventional threshold of one larvae/plant. However, in 16 fields and one half-field, spraying only took place if larvae numbers exceeded an adjustable threshold accounting for site-specific parasitism rates (see 'Incorporate parasitism rates when setting thresholds for insecticide use'). Thresholds varied from 1-8.3 larvae/plant. Insecticides included spinosad or Bacillus thuringiensis pesticidal bacteria. Fruit damage was assessed for 40 random plants/field. Three fields and one half-field were left unsprayed to assess crop damage without treatment, but the effects of spraying with and without a pest threshold approach were not compared. Effects on natural enemies were not presented.
Output references
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