Citrus Mealybug Advisory Issued

University of California Agriculture and Natural Resources (UCANR) recently issued an Extension advisory regarding citrus mealybug.

Citrus mealybug feeds on plant sap and is commonly found in protected areas of the tree, including under the calyx of fruit, in clusters of leaves and within dense canopy growth.

Mealybug infestations can reduce tree vigor, contaminate fruit with honeydew and sooty mold, and lead to fruit downgrading due to cosmetic damage and the presence of insects at harvest. In severe infestations, populations may interfere with harvest operations and increase management costs. 

Mealybug activity is increasing across several citrus blocks in the San Joaquin Valley. First-generation females are beginning to lay eggs, and crawler emergence is expected soon in many orchards. Second-generation male flight has started, and flight peak is expected soon. Early detection and timely intervention remain critical for successful management.

MONITORING

• Continue scouting known hotspot areas closely, especially along orchard edges, windbreaks and historically infested rows.
• Look for adult females with cottony egg sacs developing under the canopy, along the trunk and inner branches, inside fruit clusters if fruit is present, beneath calyxes and in protected areas of the tree.
• Watch carefully for crawler hatch. Crawlers are the most vulnerable stage and provide the best timing window for treatments.
• Monitor honeydew buildup, sooty mold development and ant activity, which are often early indicators of increasing populations.
• Evaluate biocontrol activity during scouting by checking for predators, parasitoid mummies and Cryptolaemus larvae/adults before making treatment decisions.

BIOLOGICAL CONTROL

• In orchards utilizing biocontrol programs, timely natural enemy releases can help suppress developing citrus mealybug populations before they spread.
• Consider releasing predators, lacewings or mealybug destroyers while eggs and early immatures are present and populations are building.
• Follow with Anagyrus parasitoid releases approximately two weeks later to target developing mealybug stages and support long-term suppression. Anagyrus does not affect first instars; it only parasitizes late second instars, third instars and adults.
• Preserve existing beneficial populations whenever possible by selecting softer chemistries and avoiding unnecessary broad-spectrum applications.

CHEMICAL MANAGEMENT

• Where treatments are necessary, combining an insect growth regulator (IGR) with a contact material may improve control, particularly when crawler emergence is underway.
• Coverage is critical. Most mealybug populations are protected deep inside the canopy, on interior fruit or within clusters. Ensure adequate water volume and spray penetration.
• If integrating pesticides with biological control programs, choose softer chemistries that are less disruptive to predators and parasitoids.
• Avoid using IGRs when planning Cryptolaemus releases, as these materials may interfere with beetle development and establishment.

ANT MANAGEMENT

• Ants protect mealybugs from natural enemies, move crawlers throughout the orchard and contribute to new infestations.
• Continue monitoring for ant trails and consider baiting or trunk barrier programs where pressure is high.
• Effective ant suppression significantly improves biological control performance.

As temperatures continue warming, mealybug populations can increase rapidly. Expect next-generation crawlers as early as mid-July, depending on temperature.

Source: UCANR