Location: Crop Bioprotection Research
Project Number: 5010-22410-024-003-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Jun 1, 2023
End Date: Mar 30, 2025
Objective:
Determine the optimum method of administering (release of) the phoretic mites on avocado trees.
Approach:
Phoretic mites are naturally in constant contact with ambrosia beetles and other wood-boring pests. Therefore, they have the potential to serve as carriers of entomopathogens and fungal antagonists, such as Beauveria bassiana and Trichoderma harzianum, to the beetles’ galleries. An important matter is how to deliver the vectors into the system. Ideally, the field releasing method would allow mites to spread throughout the tree trunk and survive until microbial agent spores are successfully delivered to the beetle galleries. The best method for administering phoretic mites to avocado trees will be evaluated.
Avocado trees cv ‘Simmonds’ 10 years-old will be used in this experiment. Trees will be divided into four strata: (1) 0-20 cm; (2) 20-40 cm; (3) 40-60 cm, and (4) 60-80 cm. One artificial gallery (0.3 cm x 6 cm, diameter x length) will be created in each stratum using a drill. This experiment will use the phoretic mite species Histiogaster arborsignis. Stock colonies of these mites are kept by the collaborator. A red fluorescent pigment (Neon Red™, AX-12-5, DayGlo Color Corp.) will be incorporated into the mites’ diet, making them traceable and visible under UV light.
Three mite delivery methods will be evaluated. The first method is a commercial blower. The second method is an adaptation of commercially available slow-release sachets. A small bag (12 x 8 cm, height x length) with an opening, containing a mixture of mite-rearing substrate and all life stages of the mites will be stapled in the middle line of each tree trunk. The third release method consists of a V-shaped cardboard band hung around the tree trunk. A mixture of the mite-rearing substrate will be added to the device, which has a roof to protect mites and fungi from UV radiation and rain exposure.
Every day for a period of 10 days, the number of mites in each stratum of each tree will be recorded. The presence of mites in each artificial gallery will be recorded using a handheld UV flashlight. The delivery method that results in higher numbers of phoretic mites in the artificial galleries will be determined and utilized in future studies.
