Sustainable Management of Asian citrus psyllid (ACP) and Citrus Production

Sustainable Management of Asian citrus psyllid (ACP) and Citrus Production

Report Date: 10/17/2021
Project: 18-052C   Year: 2021
Category: ACP Vector
Author: Jawwad Qureshi
Sponsor: Citrus Research and Development Foundation

This project is focused on conducting research in four Integrated Pest Management (IPM) programs and biological control only program for ACP. The programs are listed below: 1.         conventional and organic insecticides plus biological control,2.         organic insecticides, and Horticultural Mineral Oil (HMO) plus biological control,3.         conventional insecticides plus biological control4.         HMO plus biological control.5.            biological control only.This report describes the activities from July to September 2021, which include monitoring the populations of ACP and beneficial insects in all programs as well as releases and evaluation of the parasitoid Tamarixia radiata and two commercially available predators (Ladybeetle Rhyzobius lophanthae and Brown lacewing Sympherobius barberi) against ACP. ACP populations remained well below our spray treatment threshold of 0.1 adults per tap sample and therefore no spray applications were required this quarter. Tamarixia radiata were released in all programs biweekly at the rate of 200 adults per plot for a total of 800 per program.  At least three shoots infested with ACP nymphs (4th and 5th instar) were checked per plot for a total of 12 samples per treatment to recover parasitoids. However, the nymphal populations were very low, and it was only in August when limited samples were available and the parasitism rates observed were between 2-3%. Rhyzobius lophanthae were released at the rate of 200 individuals per replicate (800/treatment) in July and 500 individuals per replicate (2,000/treatment) in September. Sympherobius barberi releases included 200 individuals per replicate (800/treatment) in July, 500 individuals per replicate (2,000/treatment) in August, and 300 individuals per replicate (1,200/treatment) in September. The potential of each predator to control ACP was also evaluated. In the laboratory conditions, ACP nymphs at six densities (1, 5, 10, 15, 20, and 40 nymphs) were offered to each predator (R. lophanthae or S. barberi) and the prey consumption was evaluated after 24 hours. The experimental unit was a citrus shoot infested with ACP nymphs with one predator inside a sleeve cage. Prey consumption by each predator increased with the increasing density of the prey, however, there was no significant difference in the consumption rate between the two highest densities (20 and 40 nymphs per shoots) for either species. The consumption rate averaged 12.70 ± 0.63 nymphs per R. lophanthae and 11.80 ± 0.95 nymphs per S. barberi. We also tested three release rates of both predators. In the field, citrus shoots infested with ACP nymphs were enclosed with 1, 3, or 5 individuals of R. lophanthae or S. barberi in the sleeve cages. The consumption rate increased with the increasing density of the predator averaging 28-64% for the R. lophanthae and 56-84% for the S. barberi. S. barberi were also captured in the yellow sticky traps that we installed to monitor their dispersal in the experimental area following releases. Findings on R. lophanthae or S. barberi suggest that both species are good predators of ACP nymphs. Among the naturally occurring predators in the field, we continue to see the predominance of lacewing particularly Ceraeochrysa cubana and spiders. It seems that the naturally occurring predators as well as releases of the two commercial predators and T. radiata were negatively impacting ACP populations which remained below the treatment threshold of 0.1 adults per tap sample during this quarter and therefore no spray applications were made in any programs.         


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