Entomologist Lauren Diepenbrock discussed control of three pests — lebbeck mealybug, Bulimulus sporadicus snails and diaprepes root weevils — at the recent Citrus & Specialty Crop Expo. The University of Florida Institute of Food and Agricultural Sciences researcher described the mealybug and snails as “new pest challenges” and diaprepes as the resurgence of an old pest.
Lebbeck mealybug was found in Florida in 2019 and is now spread through Central and South Florida. Diepenbrock said early infestation leads to fruit drop, while infestation later in fruit development can cause distorted fruit. Infestation once fruit is fully expanded won’t distort fruit, but the fruit will be unmarketable.
Diepenbrock offered suggestions and information to minimize loss:
- Target developing populations.
- Systemic materials will reduce offspring by killing females.
- Systemics have fewer impacts on mealybug predators.
She suggested that growers include predators in their management plans. Growers can help keep predators in groves by minimizing the use of broad-spectrum materials when predators are active, performing knockdown in winter when there is less predator activity, and by controlling fire ants. She explained that more mealybug predators are present when fire ant colonies are reduced. Baits work best for fire ants, she reported.
The first Florida find of Bulimulus sporadicus snails was in Duval County in 2009. In citrus groves, the snails impact irrigation, feed on young trees inside individual protective covers and add to existing damage such as freeze damage to trunks.
Bulimulus snails are present year-round and are attracted to moisture as well as to dead, damaged and decaying plant material.
Diepenbrock said the snails can’t be killed with insecticides. But she said some growers have had short-term success with Deadline GT molluscicide, which contains metaldehyde active ingredient and an attractive odor. She added this is not a long-term option and suggested that growers limit spread of the snails by people and equipment.
Diepenbrock said grower efforts to control HLB-spreading Asian citrus psyllids likely kept diaprepes populations in check for several years. But with recent reductions in psyllid sprays, diaprepes is “now becoming problematic again in some regions,” she reported.
Her best management suggestions for those with high diaprepes pressure included control of larvae and reduction of the adult population. Larvae can be controlled by preventing access to roots with barrier insecticide or with tightly woven ground cloth. Nematodes can also be used to control larvae. Diepenbrock said several broad-spectrum materials have efficacy against adult diaprepes.
See Diepenbrock’s full Citrus & Specialty Crop Expo PDF presentation here.
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