Many citrus growers in Florida’s panhandle were experiencing high populations of scales early this year, particularly Florida red scale and false Florida red scale, Jefferson County Extension agent Danielle Sprague announced in a recent issue of the Cold Hardy Citrus Connection newsletter. The newsletter is a University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) Extension publication.
Sprague pointed out that most citrus grown in the region is marketed as fresh fruit, and the presence of scale on fruit reduces its marketability.
In the newsletter, Sprague and UF/IFAS entomologist Xavier Martini provided information about scouting and control of scales. That information is summarized below.
In the past, Florida red scale was very well controlled by natural enemies, including ladybeetle predators and other parasitoids. One possible contributor to the increase in scales this year is repeated applications of broad-spectrum insecticides during periods when natural enemies are active. Because of that, the first action might be to eliminate any unnecessary insecticide applications.
Control of armored scale is particularly difficult as the pest spends most of its life protected by the scale cover. It is only the earliest nymph instar that is mobile and unprotected. Since this stage is mobile, the moving nymphs are referred to as crawlers. This stage is the most susceptible to insecticides. Therefore, it is important to monitor for crawlers in the early spring to target insecticide applications to this life cycle stage.
When scales are in the crawler stage, most insecticide labeled for scales will be effective in controlling the population; however, buprofezin and spirotetramat are the best options. Thorough coverage is important.
Insecticide applications targeted for scales are only recommended if the population is at a high density and causing significant damage to trees or fruit.
When monitoring for scales, base management decisions on the population levels of living scales. It is not uncommon to mistake scale bodies from previous generations and/or parasitized scales for living scales.
To monitor for scale crawlers, use double-sided sticky tape wrapped around a citrus branch near scale adults and check weekly. In the adult stage, Florida red scale will be more difficult to control. When in this stage, the best option for control is horticultural mineral oil at 2%.
Source: University of Florida Institute of Food and Agricultural Sciences
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