Environmental Entomology (1988) 17, 470-475
H.R. Gross (1988)
Effect of temperature, relative humidity, and free water on the number and normalcy of Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) emerging from eggs of Heliothis zea (Boddie) (Lepidoptera: Noctuidae)
Environmental Entomology 17 (3), 470-475
Abstract: The effect of selected temperatures, relative humidities, and levels of free water at time of eclosion, and the effect of selected temperatures and relative humidity during development, were measured on the number of adult Trichogramma pretiosum Riley emerging from parasitized eggs of Heliothis zea (Boddie), and on the frequency of abnormal (brachypterous) wings among emerged adults. At time of eclosion, highest mean rates of emergence occurred at 32 ± 1°C and 60 and 80% RH. Significant declines in adult emergence occurred above 80% and below 40% RH at all temperatures evaluated. Temperatures of 38 and 43 ± 1°C lowered mean rates of adult eclosion by >70%under optimum relative humidity. T. pretiosum adults that emerged at 27 and 32 ± 1°C and 40, 60, and 80% RH generally had fully developed wings, whereas adults that emerged at higher and lower relative humidity and adults that emerged at 35, 38, and 43 ± 1°C (all RH) had significantly higher mean frequencies of brachypterous wings than did the control. Brachypterous wings among adult T. pretiosum emerging at 38 and 43 ± 1°C generally exceeded 50%. Eclosion responses of T. pretiosum reared at day temperatures of 27, 32, and 35 ± 1°C (21 ± 1°C night) and a range of relative humidity from 10 to 100% generally paralleled those of T. pretiosum exposed to similar ambient conditions only at time of eclosion. Largest mean numbers of T. pretiosum per host emerged from host eggs held for development and eclosion at 27 and 32 ± 1°C and 80% RH. Only when reared at day temperatures of 32 and 35 ± 1°C and 40, 60, and 80% RH was the mean number of T. pretiosum emerged with brachypterous wings the same as that of the control. Eclosion of T. pretiosum from eggs of H. zea held on filter paper substrates was statistically lowered when levels of free water reached or exceeded saturation. If augmented Trichogramma are ever to perform as expected; requisites for their successful eclosion and ambient conditions in which they are expected to emerge and perform must be identified and carefully aligned.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Research topic(s) for pests/diseases/weeds:
biocontrol - natural enemies
Research topic(s) for beneficials or antagonists:
general biology - morphology - evolution
environment/habitat manipulation
Pest and/or beneficial records:
| Beneficial | Pest/Disease/Weed | Crop/Product | Country | Quarant.
|
|---|---|---|---|---|
| Helicoverpa zea | ||||
| Trichogramma pretiosum (parasitoid) | Helicoverpa zea | Mexico |
