<I>Trichogramma</I> (Hymenoptera: Trichogrammatidae) Ecology in a Tropical Bt Transgenic Cotton Cropping System: Sampling to Improve Seasonal Pest Impact Estimates in the Ord River Irrigation Area, Australia

Abstract

Trichogramma Westwood (Hymenoptera: Trichogrammatidae) cause high mortality rates in the potentially resistant pest species, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), and are considered integral to the resistance management plan for Bacillus thuringiensis transgenic cotton, Gossypium hirsutum L., production in the Ord River Irrigation Area (ORIA), Western Australia. Measured as percentage of parasitism, Trichogramma activity seems highly variable over time; yet, it contributes significantly to pest suppression at peak insect pest density. Environmental constraints on Trichogramma survival, especially insecticide applications, may limit their effectiveness. The decision to initiate insecticide applications in ORIA cotton crops is best delayed unless absolutely necessary to avoid disruption of Trichogramma impact on pests. Trichogramma disperse into young crops and display high intrinsic rates of increase effectively stifling Helicoverpa (Hardwick) population increase after initial egg lay during high-density years in the ORIA, and evidence suggests a possible preference for H. armigera host eggs.

Spatio-temporal variation in Helicoverpa egg parasitism by Trichogramma in a tropical Bt-transgenic cotton landscape

“…Spatial dynamics are rarely considered when testing ecological theories pertaining to predator–prey interaction. Arthropod populations generally demonstrate within‐field patchiness (Hughes, 1996), although the majority of spatial studies in agroecosystems examine correlation between predator and prey relative abundance over time generally at the whole‐field scale (Davies et al , 2009), neglecting spatial interaction at the within‐field and within‐plant scale. Such spatially explicit data can be combined with environmental and physical measurements to assess the ecological requirements of predators and their prey (Pearce & Zalucki, 2006).…”

“…If host patches proliferate beyond the dispersal capacity of parasitoids, their control potential is compromised. This is likely to occur during the initial host infestation of crops when parasitoids arrive, and after devastation of parasitoid populations by insecticide applications or adverse climatic conditions (Davies et al , 2009).…”

Parental genetic traits in offspring from inter-specific crosses between introduced and indigenous Diadegma Foerster (Hymenoptera: Ichneumonidae): Possible effects on conservation genetics

“…Given molecular evidence of hyrbidization presented herein, we suggest a similar field study to that of Yara et al (2007), and further laboratory studies of introgression beyond the F1 generation with reciprocal crosses, are warranted for these species'. Should introgression occur in the field, genetic "contamination" of indigenous D. fenestrale populations is a distinct possibility, perhaps leading to their displacement by D. semiclausum, as occurred with endemic Trichogramma species' in northern Australia following the introduction of Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) to control lepidopterous pests (Davies et al, 2006(Davies et al, , 2009Davies and Zalucki, 2008), although in this case displacement by competition rather than hybridization was implied but not proven. Possible localized extinction by introgression, as has occurred with native duck species following mating with introduced mallard ducks around the world (Rhymer and Simberloff, 1996), requires due consideration when exotic species, such as D. semiclausum in Japan, are introduced.…”

<b>Age and density of eggs of <i>Helicoverpa armigera</i> influence on <i>Trichogramma</i> pretiosum parasitism

“…In addition, this technology is used in pest control in other countries with the same occurrence of the pest, which in few years proved to be satisfactory (Öztemiz, 2008;Arain et al, 2014;Wang, He, Zhang, Lu, & Babendreier, 2014). Among the parasitoids, the Trichogramma Westwood (Hymenoptera: Trichogrammatidae) is the most studied and used throughout the world for its easiness and efficiency of propagation in the laboratory for later release in the field, especially in the control of the Lepidoptera pests (Davies, Pufke, & Zalucki, 2009;Davies & Zalucki, 2008). However, the biological changes of the pest may result in different answers regarding the use of the parasitoid.…”