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Pest-damage relationships for Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) on vegetative soybean

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Rogers, D. J. and Brier, H. (2010) Pest-damage relationships for Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) on vegetative soybean. Crop Protection, 29 (1). pp. 39-46. ISSN 0261-2194

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Article Link: https://doi.org/10.1016/j.cropro.2009.08.016

Publisher URL: https://www.sciencedirect.com/science/article/pii/S0261219409002221


The response of vegetative soybean (Glycine max) to Helicoverpa armigera feeding was studied in irrigated field cages over three years in eastern Australia to determine the relationship between larval density and yield loss, and to develop economic injury levels. Rather than using artificial defoliation techniques, plants were infested with either eggs or larvae of H. armigera, and larvae allowed to feed until death or pupation. Larvae were counted and sized regularly and infestation intensity was calculated in Helicoverpa injury equivalent (HIE) units, where 1 HIE was the consumption of one larva from the start of the infestation period to pupation. In the two experiments where yield loss occurred, the upper threshold for zero yield loss was 7.51±0.21HIEs and 6.43±1.08HIEs respectively. In the third experiment, infestation intensity was lower and no loss of seed yield was detected up to 7.0HIEs. The rate of yield loss/HIE beyond the zero yield loss threshold varied between Experiments 1 and 2 (−9.44±0.80g and −23.17±3.18g, respectively). H. armigera infestation also affected plant height and various yield components (including pod and seed numbers and seeds/pod) but did not affect seed size in any experiment. Leaf area loss of plants averaged 841 and 1025cm2/larva in the two experiments compared to 214 and 302cm2/larva for cohort larvae feeding on detached leaves at the same time, making clear that artificial defoliation techniques are unsuitable for determining H. armigera economic injury levels on vegetative soybean. Analysis of canopy leaf area and pod profiles indicated that leaf and pod loss occurred from the top of the plant downwards. However, there was an increase in pod numbers closer to the ground at higher pest densities as the plant attempted to compensate for damage. Defoliation at the damage threshold was 18.6 and 28.0% in Experiments 1 and 2, indicating that yield loss from H. armigera feeding occurred at much lower levels of defoliation than previously indicated by artificial defoliation studies. Based on these results, the economic injury level for H. armigera on vegetative soybean is approximately 7.3HIEs/row-metre in 91cm rows or 8.0HIEs/m2.

Item Type:Article
Business groups:Crop and Food Science
Keywords:Cotton bollworm Economic injury level Economic threshold
Subjects:Science > Entomology
Plant culture > Food crops
Plant culture > Field crops
Plant pests and diseases
Plant pests and diseases > Economic entomology
Live Archive:30 Nov 2022 06:25
Last Modified:30 Nov 2022 06:25

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