Parasitism of cotton leafworm Alabama argillacea eggs by Trichogramma pretiosum in commercial cotton fields

Abstract

Release of natural enemies in commercial fields is challenging and has been inconsistent in the results achieved. This work discusses the augmentative releases of Trichogramma pretiosum to control the cotton leafworm (CLW) Alabama argillacea and also examines the parasitoid–host interaction under grower field conditions. The treatments consisted of fields with and without releases of T. pretiosum set up in Primavera do Leste and Campo Verde Counties, MT, Brazil, during three different seasons (2003 and 2004 dry and 2004 regular summer seasons). Trichogramma wasps were weekly released in the treated fields throughout the entire sampling period (14–15 week period) at a rate of 100 000 wasps per hectare. One‐way repeated measures analysis of variance was performed for the number of parasitized eggs, followed by a meta‐analysis procedure to determine the contribution of T. pretiosum release on overall parasitism. In addition, regression analysis was conducted with each season’s data sets to study the relationship of the host density and parasitism response by T. pretiosum. The overall results of Trichogramma augmentative releases did not result in significant increase of CLW egg parasitism beyond the natural parasitism in the areas studied. However, based on Cohen’s d effect sizes from the meta‐analysis, the parasitism rate was greater in fields under T. pretiosum releases during four out of 15 weeks surveyed. The parasitism of CLW eggs by T. pretiosum exhibited host density‐dependence only in one out of three seasons surveyed. These findings are encouraging as they are evidence that T. pretiosum is able to maintain a considerable level of parasitism under commercial field conditions, highlighting their potential value in large‐scale commercial areas of cotton as previously found at the small and diverse farming scale. Future studies should address the potential of early‐season, low density releases of the parasitoid.

Assessing the impact of arthropod natural enemies on crop pests at the field scale

“…The interaction between host and parasitoid is thought to be strongly influenced by density dependence (Pareja et al ., ). However, density dependence, or increasing levels of parasitism with increasing host density, is not universally detectable in the field, which suggests its importance has been overrated (Walter & Zalucki, ; Bastos et al ., ; Rand, ). Asynchronous development alone does not explain, in terms of density dependence, cases of Trichogramma inoculation that achieve high parasitism levels concurrent with high pest abundance that ultimately result in limited control and unacceptable crop damage (see Twine & Lloyd, ).…”

REPRODUCTIVE PERFORMANCE OF Trichogramma pretiosum RILEY ON Trichoplusia ni HÜBNER UNDER DIFFERENT THERMAL CONDITIONS

“…Among alternatives, biological agents represent an important tool to reduce the indiscriminate use of insecticides for pest control (PRATISSOLI et al, 2008). The use of parasitoids in brassica crops and commercial cotton plantations may promote regulation of the insect pest population below the economic injury level (GODIN; BOIVIN, 1998;BASTOS et al, 2010).…”

Estimativa Da Exportação De Nutrientes Pelos Frutos Do Maracujazeiro Doce Em Função Da Aplicação De Ureia E De Esterco Bovino

“…Among alternatives, biological agents represent an important tool to reduce the indiscriminate use of insecticides for pest control (PRATISSOLI et al, 2008). The use of parasitoids in brassica crops and commercial cotton plantations may promote regulation of the insect pest population below the economic injury level (GODIN;BOIVIN, 1998;BASTOS et al, 2010).…”