Insecticides Combined with a Wood Vinegar-Based Product (SDFender Citrus™) for the Control of Psyllid (Diaphorina citri) in Orange Crops

Huanglongbing (HLB), or citrus greening, causes extensive damage to global citrus cultivation and severe economic impacts, yet no effective curative treatment exists. The primary measure to mitigate losses is the suppression of vectors such as the Asian citrus psyllid (ACP), which has shown resistance to conventional synthetic insecticides—the standard control method. The present study’s innovative hypothesis is that adding a wood vinegar-based product (SDFender Citrus™) to the spray solution can improve the performance of insecticides currently used to control of psyllid (Diaphorina citri) in orange trees. Therefore, two experiments compared the individual effects of three insecticides currently in use with the effects of adding SDFender to the spray mixture, specifically regarding ACP control efficacy, plant phytotoxicity, and orange crop productivity. To this end, we performed two foliar applications—using the insecticides alone and in combination with pyroligneous acid extract—spaced 14 days apart. These were followed by counts of D. citri nymphs and adults on the leaves, determination of control efficacy, visual assessment of product phytotoxicity, and estimation of fruit yield. We analyzed data using a linear mixed model for repeated measures, with blocks and plots within blocks as random effects. Mixing pyroligneous extract into the spray solution resulted in average reductions of 16.8% (95% CI: 5.3–27.0) in D. citri adults in EXP1, 21.3% (11.2–30.3) in nymphs in EXP1, and 17.5% (0.4–31.7) in adults in EXP2 when combined with commercial insecticides containing cyantraniliprole, spinetoram, or a thiamethoxam/lambda-cyhalothrin mixture (in evaluations conducted up to 21 days after the second application in the first experiment) and with spinetoram alone (in the second experiment). These treatments did not cause phytotoxicity or affect fruit production. Therefore, the addition of SDFender to the spray solution of the tested insecticides proved technically promising for the population control of D. citri in orange crops.