Laboratory and field evaluation of integrated insecticide-fungicide treatments for controlling Euwallacea interjectus and its symbiotic Fusarium fungi.

Abstract

As an emerging forestry pest characterized by rapid spread, wide distribution, and significant damage, Euwallacea interjectus necessitates comprehensive and scientifically validated chemical control measures. Currently, there is a lack of large-scale and precise experimental data on the efficacy of insecticides and fungicides for chemical control. Even for closely related ambrosia beetles, existing chemical control methods have unresolved aspects. Given the high dependency of E. interjectus life cycle on its symbiotic fungi, this study employed fungicides as a pivotal control strategy. Additionally, to mitigate potential secondary environmental hazards associated with broad-spectrum insecticides, detailed toxicity tests were conducted in laboratory settings, followed by field spray experiments. An organosilicon compound was utilized to examine the synergistic effects of insecticides, and liquid chromatography was employed to quantify insecticide residues in the xylem of host trees. In the laboratory, beta-cyfluthrin exhibited the lowest LC50 value (8.989 mg/L), achieving an 80.6% reduction in beetle infestations after 30 d. The addition of adjuvants increased residue levels by 2.5%, thereby enhancing control efficacy. Among the tested fungicides, a 4:1 mixture of fludioxonil and prochloraz-manganese chloride complex demonstrated the highest efficacy, with an EC50 value of 2.669 mg/L. In field experiments, spraying at a concentration of 2000 mg/L resulted in a 58.7% reduction in beetle infestations after 60 d. The findings provide a scientific basis for the control of E. interjectus and the judicious application of chemical pesticides, offering technical support for the management of wood-boring pests in forestry production.