Highlands County Extension agent Lourdes Pérez Cordero recently offered scouting and management suggestions for citrus leafminers (CLM), Asian citrus psyllids (ACP) and rust mites. The suggestions were part of an article in the January issue of Citrus from the Ridge to the Valley, the Central Florida citrus Extension newsletter.
Photo by E. Grafton-Cardwell, University of California Cooperative Extension
CITRUS LEAFMINERS
The emergence of spring and summer flush benefits CLM, increasing their population. The larvae of these insects make tunnels on the surface of leaves that can become entryways to the canker pathogen, especially during the rainy season. Therefore, soil systemic insecticides on young non-bearing trees should begin two weeks before leaf expansion. Only foliar applications are available for the management of bearing trees. These target emerging larvae and should be applied at least two weeks after budbreak.
ASIAN CITRUS PSYLLIDS
The population of ACP also increases when trees begin to flush. Compared to mature leaves, adults prefer the younger flushes because they are more suitable for egg-laying. However, adult psyllids will feed on mature leaves if flush is not available. Managing overwintering psyllid adults with a dormant spray prior to bloom on bearing trees can help suppress their population and reduce the need for spraying later during the year. On young non-bearing trees, systemic insecticides applied as soil drenches are the only option of chemical protection. Rotating the modes of action is critical in preventing pesticide resistance.
RUST MITES
Rust mite populations begin increasing in early May and peak around mid-July. However, they can peak again between mid-October and November. When scouting in a 10- to 40-acre block, select 20 trees randomly and mentally divide each one in four quadrants. Select one fruit at random per quadrant between the interior and the exterior of the canopy of each tree. Record the number of rust mites per cm2 and average them for 10 acres. For processed fruit, an average of six rust mites per cm2 means that management may be needed between 10 to 14 days, while 10 mites per cm2 means that management is needed as soon as possible. For fresh fruit, the action threshold is two rust mites per cm2 to avoid damage to the peel and reducing the quality of the fruit.
Source: University of Florida Institute of Food and Agricultural Sciences
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