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

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

Report Date: 07/15/2020
Project: 18-052C   Year: 2020
Category: ACP Vector
Author: Jawwad Qureshi
Sponsor: Citrus Research and Development Foundation

This project evaluates four Integrated Pest Management (IPM) programs for ACP, including 1) conventional and organic insecticides plus biological control, 2) organic insecticides and Horticultural Mineral Oil (HMO) plus biological control, 3) conventional insecticides plus biological control, and 4) HMO plus biological control. Program 5 is biological control only. During this quarter, project activities were significantly impacted due to COVID-19. We had to stop all sampling and applications between March and May. When we sampled in the middle of May, ACP numbers were well above our treatment threshold of 0.1 adults per tap sample in all programs. Therefore, sprays were conducted immediately in programs 1-4. Program 1 plots were sprayed with Microthiol, program 3 with Voliam Flexi, while, program 2 and 4 plots were sprayed with 2% 435 oil. All these treatments provided some level of suppression during the next 2-3 weeks, but only Voliam Flexi treatment was able to bring the ACP populations down to 0.1 adults per tap sample for about two weeks. The next treatments warranted in all programs were delayed due to the continuing situation with COVID-19, and sprays were not applied until the last week of June. At that time, Program 1 and 3 plots were sprayed with Delegate, Program 2 with Entrust, and Program 4 with 2% 435 oil. We were able to measure the direct contact effect of all these treatments on ACP by caging the adults on the trees in the respective treatments. At 24 h after treatment application, 98-100% caged adults were dead in programs 1-3 and 85% in program 4. We started rereleasing the parasitoid Tamarixia in the second quarter of May at the biweekly rate of 800 adults per program. In June, we conducted exclusion experiments to observe the effect of natural mortality factors on ACP populations in all programs. The developing colonies of ACP nymphs were protected with the sleeve cages or left exposed to the natural mortality factors. The natural mortality factors impacted the nymphal populations of ACP, which was reflected in the less adult emergence in the uncaged colonies compared with caged colonies in all programs. Adult emergence from nymphs in the programs 1, 2, 3, 4, and 5, averaged 19%, 33%, 15%, 38% and 41%, respectively, in the uncaged colonies, and 92%, 80%, 62%, 80% and 76%, respectively, in the caged colonies. We were expecting less impact of natural mortality factors such as predators in programs 1 and 3 due to the negative impact of conventional insecticides on their populations; however, that was not the case. It seems that disruption in sprays between March and May diluted the previous effects of program-specific sprays on the populations of beneficial organisms, and they were able to spread across all programs. Spiders and the lacewing, particularly Ceraeochrysa cubana, were the most abundant predators and common in all programs.      


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