Lethal and sublethal effects of spiromesifen,spirotetramat and spirodiclofen on Tetranychus urticae Koch (Acari: Tetranychidae)

Lethal and sublethal effects of spirotetramat, spiromesifen and spirodiclofen were assessed on Tetranychus urticae Koch. Leaf disc bioassay was used in all experiments. In this study, toxicity of these compounds was tested on T. urticae eggs and adults. Ovicidal activity was observed in all of the compounds tested, but only spirodiclofen was considerably effective against adult mites. Up to 24?h-old adult females were placed on leaf discs treated with sublethal concentrations (LC₁₀ or LC₂₅). Twenty-four hours after exposure to treated discs, 20 females showing no visible symptoms of poisoning were transferred to untreated leaf discs. The leaf discs were changed daily for up to five days. The number of eggs laid during this period was recorded. The survival rate, total number of laid eggs per female and egg hatching rate were calculated. All above-mentioned parameters were slightly lower in treated females compared with controls.     

Selectivity of acaricide exposure on Galendromus occidentalis reproductive potential

The effects of fenpyroximate (Fujimite®), acequinocyl (Kanemite®), etoxazole (Zeal®), spiromesifen (Oberon®) and bifenezate (Acramite®) on adult female Galendromus occidentalis (Nesbitt) (Acari: Phytoseiidae) survival, fecundity and fertility were assessed following exposure to leaf surface residue and direct contact. Exposure to leaf surface residues of either bifenezate or acequinocyl did not affect fecundity or egg hatch, while spiromesifen decreased fecundity and etoxazole reduced egg hatch. Treating adult females with bifenezate, acequinocyl or spiromesifen reduced fecundity but did not reduce egg hatch, while etoxazole reduced both fertility and fecundity. Fenpyroximate killed all of the females by either method of exposure. Total effects on female G. occidentalis varied among chemicals. Knowledge of specific effects of these acaricides on spider mite predators may facilitate their use in integrated pest management programs.     

Enhanced mortality of Bemisia tabaci nymphs by Isaria javanica combined with sublethal doses of chemical insecticides

The aim of this current study was to evaluate the mortality of Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) nymphs by the combination between the entomopathogenic fungus Isaria javanica (Friedrichs & Bally) Samson & Hywel‐Jones and synthetic chemical insecticides. The bioefficacy of I. javanica and the insect growth regulators named spiromesifen and buprofezin was tested alone and in combination against B. tabaci nymphs under screenhouse conditions. The in vitro compatibility between these two control agents was previously assessed under laboratory conditions. The sublethal concentration (LC₂₅) of these insecticides towards second‐instar nymphs was determined and then mixed with the fungal treatments to investigate the type of interaction. All I. javanica isolates at 5 × 10⁷ conidia/ml inflicted nymphal mortality by up to 62.4%. The insecticides did not influence the germination and mycelial growth of the selected I. javanica isolate CG1282. In general, the insecticide–fungus combinations increased nymphal mortalities in comparison with their single counterparts. Combinations with the fungus and buprofezin or spiromesifen augmented nymphal mortality by 10% and 24%, respectively, in comparison with the fungus alone. Additive interaction was found with the combination of the I. javanica CG1282 at 1 × 10⁶ conidia/ml and spiromesifen at 1.56 ppm, and additive and synergistic interactions were achieved with the fungus at 5 × 10⁶ conidia/ml and spiromesifen at 3.12, 6.25 and 12.5 ppm. Additive interactions were also observed from mixtures of fungus at 5 × 10⁶ and buprofezin at 3.12 and 6.25 ppm. Only combinations of I. javanica with spiromesifen reduced to some extent the mycosis on dead nymphs. The joint action of I. javanica with sublethal doses of these insecticides may be a promising tool to assist in the integrated management system for B. tabaci.