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Thresholds for vector control and compatibility with beneficial fauna in citrus with high incidence of Huanglongbing

Monzo, Cesar, Stansly, Philip A.
Acta horticulturae 2015 no.1065 pp. 1137-1143
Citrus, Diaphorina citri, Psyllidae, beneficial arthropods, biological control, disease incidence, economic threshold, experimental design, fauna, fruit yield, greening disease, insecticides, juices, leafminers, mites, pesticide application, prices, vector control
Huanglongbing (HLB) or citrus greening disease is vectored by the Asian citrus psyllid (ACP), Diaphorina citri Kuwayama. Vector control is considered a basic component of HLB management even in a high disease incidence scenario. Such control is mostly chemically oriented. However, overuse of insecticides would increase costs and be incompatible with biological control. Establishment of economic thresholds for psyllid control under different price scenarios would optimize returns on investment. A 3-year experiment is being conducted in a commercial orange block with high HLB incidence. Experimental design is RCB with 4 treatments and 4 replicates: (1) calendar applications, (2) insecticide applications according to a threshold of 0.2 psyllids/stem tap sample, (3) applications according to a 0.7 threshold and (4) no insecticide. Vector populations are monitored biweekly by tap sampling. Differences in vector abundance among treatments are being correlated to fruit yields. Consequences of each vector control strategy on beneficial arthropod fauna are also being evaluated, as well as potential negative impacts on biological control. After two years, a significant yield increase was observed with the calendar treatment, but so far, justification for the additional costs would require higher than actual juice prices scenarios. ACP management strategies based on nominal thresholds are so far more profitable. Negative impacts of calendar sprays on biological control of mites and leafminers have been observed.