Enhanced uptake ofdrip-appliedflonicamid by arbuscular mycorrhizal fungi and improved control of cotton aphid

BACKGROUND Drip application of insecticides has been used for controlling crop pests, but the application doses are usually higher than those used for foliar spray. Arbuscular mycorrhizal fungi (AMF) have been reported to improve root absorption of nutrients from soil, which may also enhance the uptake of drip-applied insecticides, reducing application doses. In this study, greenhouse and field experiments were carried out to determine if AMF could colonize cotton roots, if the colonization could enhance the absorption of drip-applied flonicamid, and if the enhanced uptake could reduce flonicamid application dose, while maintaining control efficacy against cotton aphid. RESULTS The applied AMF effectively colonized cotton roots and significantly promoted root growth. Fresh weights of cotton roots inoculated with multiple AMF were 28% greater than those of uninoculated plants. Multiple AMF colonization significantly increased flonicamid concentrations in leaves, which were 44.5-139.7% higher than for non AMF-colonized roots, corresponding to 3.7-31.8% increases in corrected mortalities of cotton aphid compared with uninoculated plants. AMF colonization reduced the application rate of flonicamid and the residue level of flonicamid in soil. CONCLUSION Drip application of flonicamid to cotton roots inoculated with AMF represents a new approach to insecticide application. AMF colonization increased flonicamid uptake, improved aphid control efficacy and reduced flonicamid application rates.