Effect Of Five Insecticides On Bradysia Difformis And Safety Evaluation Of Their Application On Oyster Mushroom

Bradysia difformis is one of the important pests in mushroom production, it can seriously reduce the mushroom yield and quality, and threatens the development of mushroom industry. In this study, the insecticidal activities of 5 insecticides against B. difformis were determined. The sensitivity of 6 different species of mushroom to the pesticides was also determined by growing on pesticide-amended medium (substrate) or by spraying treatment. The effective pesticides for applying in the mushroom production were selected, and the residual quantity of the selected insecticide in the substrate and rruitbody was tested. The main results are as follows:1. Toxicity and efficacy of insecticides on B. difformisThe Beta-cypermethrin showed the highest insecticidal activity on the second instar larvae of B. difformis with 7.15 mg/L of LC50 value among of the tested insecticides. All insecticides at the test maximum concentration, Diflubenzuron showed the best effeciency of 82.23% when mixed with the substrate, but Beta-cypermethrin presented the best effeciency of 80.97% occurring in the 3 days after spraying..2. Sensibility of edible fungi to the insecticidesThe mycelium growth rate method is applied to determine the sensibility of edible fungi to Bti. It shows that mycelium of Pleurotus pulmonarius and Lentinus edodes are most sensitive which EC50 value were 68.37 mg/L and 137.08 mg/L, respectively. The mycelium growth rate method and dry weight method are respectively used to determine the sensibility of edible fungi to the rest four insecticides. Azadirachtin had the most strong effect on the growth inhibition of tested mushroom which EC50 value lower than 26.554 mg/L. Beta-cypermethrin, Diflubenzuron and Cyromazine had less growth inhibition, their EC50 values were higher than 17.327 mg/L.3. Influence of insecticides on the yield and agronomic trait of fruiting bodies of oyster mushroomAzadirachtin showed the greatest influence on sporocarp yield and trait of oyster mushroom by mixing substrate. Even the minimal concentration could result in deformities. Compared with the control, Bti has most significant influence on the sporocarp trait and yield of oyster mushroom after spraying. Other insecticides showed no significant differences from the controlled group.4. Residues of Beta-cypermethrin in substrate and fruitbody of oyster mushroomThe residual quantity of Beta-cypermethrin in the fruitbody was 0.019 mg/kg and lower than MRL after 5 d spraying treatment on young fruiting bodies. The first flush of fruiting bodies and subatrate were collected after 42 d of mixing pesticides,the highest residual quantity of Beta-cypermethrin was 6.72 mg/kg in substrate, but residues not detected in the fruit body.In summary, Beta-cypermethrin showed good control effect, small influence on oyster mushroom, and low residue. Therefore, it is suggested to be applied in oyster mushroom production to control the B. difformis.