Effect of plant protection products on Rhynchophorus palmarum L. (Coleoptera: Curculionidae) larvae in laboratory

Abstract

With the aim of developing tools for simultaneously managing Rhynchophorus palmarum and the coconut stem bleeding disease, we evaluated the effects of the insecticide thiamethoxam and the fungicide cyproconazole on R. palmarum larvae under laboratory conditions. Early-instar and intermediate-instar larvae were fed on an artificial diet containing 0.1% concentration of insecticide, fungicide or a mixture of both. Larval mortality was assessed daily during the 48 hours after the application of the treatments. Mean mortality values were subjected to analysis of variance and compared by Tukey’s test (p ≤ 0.05). Thiamethoxam caused mortality of 100% of early-instar and 90% of intermediate-instar larvae. In contrast, mortality was significantly lower in the cyproconazole treatment (60% for early-instar and 0% for intermediate-instar larvae) and the control (0% mortality for both treatments). The insecticide/fungicide mixture was equally effective (100% for early-instar and 86.67% for intermediate-instar larvae) to the insecticide only treatment. Differences in mortality between early-instar and intermediate-instar larvae were significant only for the thiamethoxam and cyproconazole treatments. These results indicate that, for the doses used here, thiamethoxam is toxic to both early-instar and intermediate-instar larvae, while cyproconazole is toxic just to early-instar larvae. Moreover, cyproconazole does not increase the toxicity of thiamethoxam. Early-instar larvae are more sensitive to thiamethoxam and cyproconazole than intermediate-instar larvae. We conclude that thiamethoxam + cyproconazole mixture may be effective for managing R. palmarum and associated fungal diseases on coconut palms.

Local Agricultural Management Filters Morphological Traits of the South American Palm Weevil (Rhynchophorus palmarum L.; Coleoptera: Curculionidae) in Ornamental Palm Plantations

“…In this sense, exposure time to synthetic insecticides is likely shorter in individuals with wider pronotum. In accordance with this, some studies have reported that this pest can prevail in agricultural areas with high intensity of insecticide use [75]. This is related to the prediction that agricultural intensification can create insect pests from herbivores, which illustrates that frequent insecticide use provides conditions permissive or conducive to the emergence and spread of pests [3,8].…”

Topical effect of thiamethoxam on adults of Rhynchophorus palmarum L. (Coleoptera: Curculionidae) in laboratory

“…Em estudo similar, Chihaoui-Meridja et al (2019) observaram que adultos de Rhynchophorus ferrugineus (Olivier) (Coleoptera: Curculionidae) alimentados com dieta natural (maçã) tratada com o produto à base de tiametoxam (Renova 250 ® WG) na dose equivalente a 0,2 mL do p.c./inseto, tiveram mortalidade de 50% após 5 dias de exposição ao produto. Avaliando a mortalidade das larvas de R. palmarum alimentadas com dieta artificial contendo tiametoxam incorporado, Santos et al (2018) constataram que, na menor concentração (0,1% de i.a., equivalente a 1.000 ppm), o inseticida causou 100% de mortalidade nas larvas pequenas e 90% em larvas de tamanho intermediário, as quais apresentaram os mesmos sintomas verificados nos adultos do presente trabalho, após 48 horas. Ao compararmos ambos os estudos, fica evidenciado que as doses avaliadas por Santos et al (2018) estão além do espectro de letalidade capaz de determinar com maior precisão as doses letais (CL 50 e CL 90 ), como observado para adultos desta praga, observados no presente estudo.…”

“…Avaliando a mortalidade das larvas de R. palmarum alimentadas com dieta artificial contendo tiametoxam incorporado, Santos et al (2018) constataram que, na menor concentração (0,1% de i.a., equivalente a 1.000 ppm), o inseticida causou 100% de mortalidade nas larvas pequenas e 90% em larvas de tamanho intermediário, as quais apresentaram os mesmos sintomas verificados nos adultos do presente trabalho, após 48 horas. Ao compararmos ambos os estudos, fica evidenciado que as doses avaliadas por Santos et al (2018) estão além do espectro de letalidade capaz de determinar com maior precisão as doses letais (CL 50 e CL 90 ), como observado para adultos desta praga, observados no presente estudo. Assim, estudos futuros para determinação das doses letais para larvas desta praga são essenciais para melhor dimensionamento da aplicação deste inseticida a fim de otimizar o uso deste método de controle em possíveis aplicações em campo.…”

EFFICACY AND COST EFFICIENCY OF TRAPS FOR MASS CAPTURE OF Rhynchophorus palmarum L. IN A MEXICAN Cocos nucifera L. ORCHARD

“…Chemical control of APW with carbaryl, carbofuran, imidacloprid, abamectin, deltamethrin, fipronil, spinosad and phenylpyrazole often is not fruitful (Al-Dosary et al, 2013;Dos Santos et al, 2018;Martinez et al, 2019). The application of entomopathogenic fungi, such as Metarhizium anisopliae (Metschn.)…”