Toxicidade dos inseticidas metamidofós, imidaclopride + beta- ciflutrina e extrato de neem (Azadirachta indica) ao predador Podisus nigrispinus (Heteroptera: Pentatomidae) em plantas de soja / Toxicity of methamidophos, imidacloprid + beta-cifluthrin and neem extract (Azadirachta indica) insecticides to the predator Podisus nigrispinus (Heteroptera: Pentatomidae) in soybean plants

Sheila Abreu Mourão

Exposition to the synthetic or fito-chemical insecticides in soybean crops may affect predators as the stinkbug Podisus nigrispinus (Dallas) (Heteroptera: Pentatomidae), through contact and feeding on treated plant surfaces or by topic action. The aim was to verify predator selectivity of insecticides on soybean plants on P. nigrispinus and evaluate its mortality and nymphal development, reproduction and fertility life table variables, after exposition of second instar nymphs to methamidophos, imidacloprid + beta-cifluthrin or neem extract (Azadirachta indica A. Juss) sprayed on soybean plants, at the doses recommended for Anticarsia gemmatalis Hubner (Lepidoptera: Noctuidae) control, as well as acute and chronic topic application toxicity of neem extract solution on P. nigrispinus third instar nymphs. P. nigrispinus second instar mortality through contact and feeding after exposition to insecticides on soybean plants was higher with imidacloprid + beta-cifluthrin and methamidophos than with the control, reaching 70% with this mixture. Methamidophos, at the concentrations of 0.125 and 0.250% c.p. had second instar nymph mortality levels of 43.25% and 61.25% respectively, while neem extract at the concentrations of 0.5 and 1.0% c.p., presented 21.25% toxicity. Net liquid reproduction (Ro), infinite (rm) and finite (λ) rates of P. nigrispinus population increase were similar to the control, 0.5% neem extract and 0.125% methamidophos, and lower for 1.0% neem extract, 0.357% imidacloprid + betacifluthrin and 0.250% methamidophos. P. nigrispinus presented greater population doubling period (D) with 0.250% methamidophos, 0.357% imidacloprid + betacifluthrin and 1.0% neem extract insecticides. P. nigrispinus highest generation time (T) with 0.5% neem extract sprayed soybean plants and lowest with 0,125% methamidophos. P. nigrispinus third instar nymph mortality rates after topic exposition to neem extract were 0.00, 15.38, 15.38, 19.23, 19.23, 28.46 and 34.61% at the concentrations of 0.0, 0.5, 1.0, 20.0, 25.0, 33.0 and 50.0% c.p. respectively, showing low acute toxicity. However, mortality of this predator increased in the fourth and fifth instars by chronic action of neem extract. P. nigrispinus adults topically exposed to neem extract at third instar presented wing and leg anomalies that may harm locomotion and reproduction of this predator, mainly with 33.0 and 50.0% c.p. concentrations. The insecticides 0.357% imidacloprid + beta-cifluthrin, 0.250% methamidophos and 1.0% neem extract showed contact and feed impact on P. nigrispinus second instar nymphs, by fertility and survival reduction on P. nigrispinus adults and therefore, may not be compatible with biological control programs with this predator on soybeen plants. However, the neem extract up to 25% concentration was selective to the nymphs of P. nigrispinus with topic action, but with higler toxicity by topic action that ingestion and contact.

AUTOR(ES)

DATA DE PUBLICAÇÃO

RESUMO

ASSUNTO(S)

ACESSO AO ARTIGO

Documentos Relacionados