By Lauren Diepenbrock
While scale and mealybug pests commonly found in citrus have historically been controlled by predators and parasites, management advice for this group of insects is often requested. There are likely several underlying factors to these insects becoming more frequently encountered. This includes changes in insecticide management practices, changes in nutritional management, and increased scouting due to the appearance of the recently established lebbeck mealybug pest. Whatever the cause, knowing how to scout for activity and having some basic identification tools at hand can help growers make informed management decisions.
Scales and mealybugs are generally present and not problematic throughout the year. Most species produce offspring in the spring through mid-summer months. Because these insects have piercing-sucking mouthparts, like Asian citrus psyllid (ACP), many of the systemic materials used for ACP control have efficacy on them as well. Historically, these groups of pests have largely been kept under control by a combination of biological controls (predators and parasites) and well-timed insecticide and/or oil applications.
Crawler activity in open groves and citrus under protective screen systems can be monitored using double-sided sticky tape wrapped around branches placed throughout the grove and checked weekly. In young plantings in individual protective covers, sooty mold development on bags may be an indicator of scale establishment. These trees should be checked periodically as management for pests which establish in these protected environments can be challenging to get under control.
While there are no established economic thresholds for scales or mealybugs in citrus, growers can use this activity information to decide when to treat or even if they should treat.
While crawlers are challenging to identify from one another, identification information for adult scales found in citrus is available from the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) Electronic Data Information Source (EDIS) here. Crawlers are often located near adult scales, enabling identification.
Some scale and mealybugs are more of a concern than others based on what species they are or what the intended market is for the crop. For example, a scale that causes fruit blemishes but does not impact fruit quality is a concern for fruit intended for the fresh market but less of a concern for fruit sold for juice.
Information in both the EDIS document listed above and in the Florida Citrus Production Guide chapter on soft-bodied insects attacking foliage and fruit can help growers decide if treatment is needed and what products can be used to manage pest scales and mealybugs of concern.
Lauren Diepenbrock is an assistant professor at the UF/IFAS Citrus Research and Education Center in Lake Alfred.