Effect of selectivity of herbicides and plant growth regulators used in sugarcane crops on immature stages of Trichogramma galloi (Hymenoptera: Trichogrammatidae)

Abstract

-Herbicides and plant growth regulators are often used in sugarcane management. However, the use of non-selective pesticides can cause adverse effects on the efficiency of beneficial insects in integrated pest management. Within this context, this study aimed to evaluate the effect of such products on the immature stages of the parasitoid Trichogramma galloi. Eggs of Diatraea saccharalis containing the parasitoid at the egg-larva stage and at the prepupal and pupal stages were immersed in test solutions of the following pesticides (maximum recommended doses for sugarcane): herbicides clomazone and diuron + hexazinone, and plant growth regulators trinexapac-ethyl and sulfometuron-methyl. The biological properties evaluated were emergence (F 1 and F 2 ) and number of eggs parasitized by T. galloi (F 1 ). The products were classified according to percentage of reduction in emergence and parasitism: harmless (<30%), slightly harmful (30-79%), moderately harmful (80-99%) and harmful (>99%). The pesticides evaluated were considered to be harmless or slightly harmful to immature T. galloi and, thus, their use should be preferred for preserving this parasitoid species in sugarcane management programs.Keywords: Saccharum spp., egg parasitoid, Diatraea saccharalis, biological control, chemical control, toxicity. RESUMO -Herbicidas e reguladores de crescimento de plantas são frequentemente utilizados no manejo da cana-de-açúcar. Entretanto, o uso de compostos não seletivos pode prejudicar a eficiência de insetos benéficos no manejo integrado de pragas. Nesse contexto, avaliou-se o efeito desses produtos sobre as fases imaturas do parasitoide Trichogramma galloi. Ovos de Diatraea saccharalis contendo o parasitoide no período de ovo-larva e nas fases de pré-pupa e pupa foram imersos em caldas dos produtos avaliados (doses máximas recomendadas para a cana-de-açúcar)

Selectivity of mycoinsecticides and a pyrethroid to the egg parasitoid Cleruchoides noackae (Hymenoptera: Mymaridae)

“…The classification of B. bassiana as slightly harmful to C. noackae adults may be related to the production of secondary metabolites, such as organic acids involved in the infection process and linear and cyclic peptidic toxins such as beauvericin from the mycelium of this fungus 26,27 . The lack of Metarhizium anisopliae toxicity to C. noackae adults is similar to that reported with this fungus on Cotesia flavipes Cameron (Hymenoptera: Braconidae) 28 and Trichogramma galloi Zucchi (Hymenoptera: Trichogrammatidae) 29 . Metarhizium anisopliae is important for biological control because some isolates may be highly specific and others infect a wide host range 30 .…”

“…Means followed by the same lowercase letter per column do not differ according to the Tukey test (p ≤ 0.05). www.nature.com/scientificreports/ Trichogrammatidae) parasitism 29,39 . These differences may be due to the specificity of cyclic peptidic toxins, called destruxins, related to M. anisopliae pathogenicity 40 .…”

Toxicological and behavioral impacts of atrazine on Trichogrammatidae (Hymenoptera) in choice tests

“…No impact of atrazine on T. galloi and T. bennetti sex ratio may show, as explained before, host egg protection and detoxification capacity (Stefanello Júnior et al 2011;Oliveira et al 2014), but it needs to be better studied to understand the responses of both parasitoids to the herbicide. The emergence of Aedes (= Stegomyia) aegypti L., 1762 (Diptera: Culicidae) and Aedes (= Stegomyia) albopictus Skuse, 1894 (Diptera: Culicidae) were higher with atrazine than with glyphosate (herbicide, glycine chemical class) in a North American study.…”

“…The lack of impact of atrazine on the emergence of T. galloi and T. bennetti females may be due to its detoxification capacity (Stefanello Júnior et al 2011;Oliveira et al 2014). This indicates greater resistance of these parasitoid species to atrazine.…”

Selectivity of insecticides with two active ingredients on the parasitoid >i<Trichogramma pretiosum>/i< (Hymenoptera: Trichogrammatidae)

“…The best way to reduce their population to a noneconomic-injury level is through a combination of control methods, as in Integrated Pest Management (IPM). It is important to guarantee that the control methods, when used together, do not compromise the effectiveness of each other(Oliveira et al 2013, Torres and Bueno 2018, Feltrin- Campos et al 2019. Therefore, an important step for integrating biological and chemical control is the evaluation of the pesticide selectivity.…”