Rafael Antonio Pasini

Selectivity of herbicides registered for corn at the immature stages of Trichogramma pretio sum (Hymenoptera: Trichogrammatidae)

4 e SPAGNOL, D. 4 RESUMO - O controle quimico tem sido um dos metodos mais utilizados para o manejo de plantas daninhas na cultura do milho, no entanto o uso de herbicidas pode ocasionar efeitos adversos aos insetos beneficos, como os parasitoides de ovos. Nesse sentido, foi avaliada a seletividade de 12 herbicidas registrados para a cultura do milho para as fases imaturas de Trichogramma pretiosum em condicoes de laboratorio (temperatura de 25±1 oC, umidade relativa de 70±10% e fotofase de 14 horas). Os herbicidas foram diluidos em um volume proporcional a 200 L de agua por hectare e pulverizados sobre ovos de lepidoptero contendo formas imaturas do parasitoide em seu interior, nas fases de ovo-larva, pre-pupa e pupa. Avaliou-se, entao, a porcentagem de emergencia dos parasitoides e, em funcao da comparacao com a testemunha, classificaram-se os herbicidas em inocuo (classe 1, 99%). Os herbicidas Agrisato 480 SL, Finale, Glifos, Glifosato Nortox, Gliz 480 SL, Polaris, Roundup Original, Roundup Transorb, Roundup WG, Trop e Zapp Qi foram inocuos (classe 1) as diferentes fases imaturas de T. pretiosum e sao considerados seletivos ao parasitoide. Gramoxone 200, embora tenha sido inocuo para as fases de ovo-larva e pre-pupa, foi considerado levemente nocivo (classe 2) para a fase de pupa. Nesse sentido, para melhor compatibilizacao do manejo quimico das plantas daninhas e controle biologico de insetos, sugere-se que sejam utilizados, sempre que possivel, aqueles herbicidas que permitem maior sobrevivencia de T. pretiosum. Palavras-chave: controle biologico, controle quimico, efeitos colaterais, parasitoide de ovos, toxicidade, Zea mays. ABSTRACT - - Chemical control has been one of the most widely used methods for weed management in corn. However, the use of herbicides can cause adverse effects on beneficial insects, such as egg parasitoids. Thus, this work aimed to evaluate the selectivity of 12 herbicides registered for corn at the immature stages of Trichogramma pretiosum Riley, 1879 (Hymenoptera: Trichogrammatidae) under laboratory conditions (temperature 25±1 o C, relative humidity 70±10%; photoperiod 14 hours). The herbicides were diluted in a proportion of 200 L of water per hectare and sprayed on lepidopteran eggs containing immature forms of the parasitoids, at the egg-larva, prepupae and pupae stages. The emergence percentage of parasitoids was evaluated, and, when compared with the control, the herbicides were classified as harmless (class 1, 99%). The herbicides Agrisato 480 SL, Finale, Glifos, Glifosato Nortox, Gliz 480 SL, Polaris, Roundup Original, Roundup Transorb, Roundup WG, Trop and Zapp Qi were classified as harmless (class 1) at different immature stages of T. pretiosum, and considered selective to the parasitoid. Although harmless at the egg larva and prepupae stages, Gramoxone 200 was classified as slightly harmful (class 2) at the pupae stage. Accordingly, to better reconcile the chemical management of weeds with the biological control of insects, the use of herbicides allowing greater survival of T. pretiosum is suggested, whenever possible.

Persistência de agrotóxicos utilizados na cultura do milho ao parasitoide Trichogramma pretiosum Riley, 1879 (Hymenoptera: Trichogrammatidae)

The high yields in corn have been achieved due to various technical factors, being the pest control one of the most important. In this way, the objective was to evaluate the persistence of the pesticides used in corn field to the parasitoid Trichogramma pretiosum. It was evaluated the persistence of seven insecticides and three fungicides, which were separately diluted to 200L of water and sprayed on the vine leaves. These leaves were taken to the laboratory and used into cages at 3, 10, 17, 24 and 31 days, where remained confined the adults of the parasitoids to contamination. The adult mortality of T. pretiosum was measured according to the lower number of parasitized eggs of alternative host Anagasta kuehniella. The results were compared with the witness treatment and pesticides classified according to IOBC categorization. Four replicates for each treatment were used. The fungicides Opera, Priori Xtra and Folicur 200 EC were short life (class 1). The insecticides Match EC and Sumithion 500 CE were short life (class 1); Lorsban 480 BR and Safety were moderately persistent (class 3), and Engeo Pleno, Karate Zeon 50 CS and Tracer were persistent (class 4) to adults of T. pretiosum.

Toxicity of Pesticide Tank Mixtures from Rice Crops Against Telenomus podisi Ashmead (Hymenoptera: Platygastridae)

The use of insecticides, herbicides, and fungicides commonly occurs in mixtures in tanks in order to control phytosanitary problems in crops. However, there is no information regarding the effects of these mixtures on non-target organisms associated to the rice agroecosystem. The aim of this study was to know the toxicity of pesticide tank mixtures from rice crops against Telenomus podisi Ashmead (Hymenoptera: Platygastridae). Based on the methods adapted from the International Organisation for Biological and Integrated Control of Noxious Animals and Plants (IOBC), adults of T. podisi were exposed to residues of insecticides, herbicides, and fungicides, individually or in mixture commonly used by growers, in laboratory and on rice plants in a greenhouse. The mixture between fungicides tebuconazole, triclyclazole, and azoxystrobin and the mixture between herbicides cyhalofop-butyl, imazethapyr, imazapyr/imazapic, and penoxsulam are harmless to T. podisi and can be used in irrigated rice crops without harming the natural biological control. The insecticides cypermethin, thiamethoxam, and bifenthrin/carbosulfan increase the toxicity of the mixtures in tank with herbicides and fungicides, being more toxic to T. podisi and less preferred for use in phytosanitary treatments in the rice crop protection.

Side-effects of pesticides used in irrigated rice areas on Telenomus podisi Ashmead (Hymenoptera: Platygastridae)

Telenomus podisi Ashmead (Hymenoptera: Platygastridae) is an important agent for the biological control of stink bug eggs in irrigated rice areas and the best strategy for its preservation is the use of selective pesticides. The aim of this study was to know the side-effects of pesticides used in Brazilian irrigated rice areas on egg parasitoid T. podisi. We evaluated, under laboratory conditions, 13 insecticides, 11 fungicides, 11 herbicides, and a control (distilled water) in choice and no-choice tests. In the no-choice tests, the pesticides were sprayed at pre and post-parasitism stages (egg and larval stages of T. podisi). In the choice tests, sprays were conducted only at pre-parasitism stages. For all tests, we prepared cards with 25 eggs of the alternative host Euschistus heros (Fabricius) (Hemiptera: Pentatomidae) non-parasitized (pre-parasitism) and parasitized (post-parasitism), which were subjected to pesticide sprays. The parasitism and emergence rates of T. podisi were determined classifying the pesticides in terms of the reduction of parasitism or emergence rates compared to the control. The neurotoxic insecticide cypermethrin, lambda-cyhalothrin, zeta-cypermethrin, etofenprox, thiamethoxam, thiamethoxam + lambda-cyhalothrin, acetamiprid + alpha-cypermethrin, and bifenthrin + alpha-cypermethrin + carbosulfan were more harmful to T. podisi and, therefore, are less suitable for the integrated management of insect pests in irrigated rice areas.

Side effects of insecticides used in wheat crop on eggs and pupae of Chrysoperla externa and Eriopis connexa

In Brazil, chemical control is one of the main tools to manage insect pests in wheat. However, this kind of management can impair the biological control provided by the predators Chrysoperla externa and Eriopis connexa. The present study evaluated the side effects on C. externa and E. connexa of 15 insecticides registered for wheat. Insecticides were sprayed on eggs and pupae via Potter tower at the maximum recommended dose. We evaluated the viability of eggs and pupae as well as the sub-lethal effects on fecundity and fertility of the adults emerged from treated pupae. The insecticides were classified according to the scale of toxicity proposed by IOBC. Regarding the eggs, the insecticide etofenprox was classified as slightly harmful (class 2) to C. externa. Imidacloprid + beta-cyfluthrin, diflubenzuron WG, thiamethoxam + lambda-cyhalothrin A and B, gamma-cyhalothrin, and etofenprox were also classified as slightly harmful (class 2) to E. connexa, while methomyl was classified as moderately harmful (class 3) for the eggs of the predator. The insecticide imidacloprid + beta-cyfluthrin was considered slightly harmful (class 2) to pupae of C. externa, while imidacloprid + beta-cyfluthrin, thiamethoxam + lambda-cyhalothrin A and B, and lufenuron were classified as slightly harmful (class 2) to the pupae of E. connexa. The insecticides beta-cyfluthrin, diflubenzuron SC, lambda-cyhalothrin, permethrin, thiamethoxam, triflumuron, and zeta-cypermethrin were harmless to eggs and pupae of both predators and should therefore be prioritized in the control of insect pests in wheat, thus preserving the natural biological control provided by C. externa and E. connexa.

Toxicity of soybean-registered agrochemicals to Telenomus podisi and Trissolcus basalis immature stages

Biological control of phytophagous bugs in soybean crops is efficiently performed by egg parasitoids, such as Telenomus podisi and Trissolcus basalis. Based on this, the use of agrochemicals in these crops must be managed consciously, making use of pesticides that are selective to the egg of these parasitoids, in order to ensure a balanced ecosystem. The aim of this study was to assess the selectivity of 15 registered pesticides to the immature stages (pre and post-parasitism) of T. podisi and T. basalis, following the method proposed by the “International Organization for Biological and Integrated Control” (IOBC). Pesticides were classified as class 1 – harmless (RP < 30%); class 2 – slightly harmful (30% ≤ RP ≤ 79%); class 3 – moderately harmful (80% ≤ RP ≤ 99%); and class 4 – harmful (RP > 99%). During pre-parasitism, the insecticides imidacloprid+beta-cyfluthrin, deltamethrin, lambda-cyhalothrin+thiamethoxam, acephate, and fenitrothion reduced parasitism of both parasitoids. The others: flubendiamide, diflubenzuron, Bacillus thuringiensis, lufenuron, and the herbicide isopropylamine were selective, i.e. harmless (class 1), to both parasitoids, except for pyraclostrobin+metconazole, which significantly reduced T. basalis parasitism, being considered slightly harmful (class 2). In post parasitism, all the aforementioned pesticides were harmless to T. podisi and T. basalis. Moreover, in pre-parasitism, T. basalis was found to be more sensitive to the tested pesticides when compared to T. podisi. Still, more studies must be conducted to provide a better understanding of the impact of agrochemicals on these parasitoid species in semi-field conditions.