WSU Tree Fruit Research & Extension Center

Little Cherry Disease

Wednesday, January 16, 2019

Challenges controlling mealybugs

Apple mealybug on trunk
 Apple mealybug on trunk (E. Beers)

Certain aspects of a mealybug’s life cycle make them notoriously difficult to manage. For example, mealybugs tend to live in protected areas of trees, such as bark cracks and crevices, and the undersides of leaves, and the eggs are protected by waxy filamentous secretions of the ovisac, making them extremely difficult to reach with insecticides. Newly hatched crawlers are the most susceptible stage; however, mealybug crawlers gradually emerge from nests over a period of months, making their control difficult. Lastly, visual detection and control are made challenging in some orchards because mealybugs are often only in the tops of trees, and can only be found by climbing a ladder in mature orchard.

Recommendations for mealybug control

Mealybugs are most susceptible to pesticides in the crawler stage (see above life cycle information for crawler emergence), due to their small size, and because they are most exposed on twigs and leaves making them vulnerable to foliar sprays. Delayed dormant sprays targeting the overwintering stage are also recommended. Excellent coverage is necessary at this time since mealybugs are tucked away in crevices and under bark, making them difficult to reach with foliar sprays. The effectiveness of the delayed dormant sprays require high-volume applications (400 gpa) to ensure good coverage.

Grape mealybug control product recommendations can be found in the WSU tree fruit crop protection guide These recommendations are for pear; therefore labels should be checked and timings adjusted for use on cherries.

The British Columbia Ministry of Agriculture has some recommendations for products and timing for controlling apple mealybug on cherry:

 Apple mealybug nymphs Apple mealybug crawlers
 Apple mealybug crawler stage (E. Beers) Apple mealybug crawlers in nest (E. Beers) 
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