How to Manage Pests
UC Pest Management Guidelines
Mealybugs are soft, oval, flat, distinctly segmented, and covered with a white, mealy wax that extends into spines (filaments) along the body margin and the posterior end. The species differ mainly in the thickness and length of the waxy filaments. Citrus mealybug, the most common species, has a pinkish body that is visible through the powdery wax. The filaments around its margins are not appreciably longer at the posterior end. The Comstock mealybug primarily occurs on lemons in the San Joaquin Valley and has a thicker wax cover than the citrus mealybug. In addition, it has two spines at the posterior end, about one-quarter the length of the body. The other two mealybug species are usually not a problem in citrus because their numbers are kept at low by parasites.
Female mealybugs lay several hundred eggs on the leaves, fruit, or twigs; eggs for some of the species are laid in cottony egg sacs. Newly hatched nymphs are light yellow and free of wax, but soon start to excrete a waxy cover. There are two to three overlapping generation a year.
Mealybugs are often found between clusters of grapefruit, especially in groves tended by ants. Due to their habit of hiding in crevices, light infestations are easily overlooked.
Mealybugs extract plant sap, reducing tree vigor, and excrete honeydew, which gets on plant surfaces and provides a surface upon which sooty mold grows. If a cluster of mealybugs feeds along a fruit stem, fruit drop can occur.
Oranges develop hard lumps as a result of mealybugs feeding, resulting in discolored and poor quality fruit. Development of sooty mold on the fruit leads to commercially unacceptable appearance of fruits and requires vigorous scrubbing before packing the fruits. If not removed from the fruit after harvest, the remaining mealybugs continue to breed, causing loss during transit and storage. Damage is most severe in spring and fall.
Manage mealybugs by conserving their natural enemies and reducing ant numbers and dust problems. Insecticide application is rarely required.
Parasites provide good control of the citrophilus, longtailed, and Comstock mealybugs if they are not destroyed by insecticide applications for other pests. Native predators include lady beetles, lacewings, and syrphid flies. An introduced predator of the citrus mealybug, the mealybug destroyer, Cryptolaemus montrouzieri, is a voracious feeder of the pest in both the larval and adultsstages. Its larvae resemble a mealybug but are about twice as large as the adult citrus mealybug females. The adult is a small beetle with dark brown wing covers and a light brown head and prothoracic shield. Because Cryptolaemus does not survive the winter well, it can be purchased from commercial insectaries in early spring and released in orchards where citrus mealybugs were a problem the previous year. Release about 500 Cryptolaemus per acre.
Use biological control, including the release of Cryptolaemus montrouzieri, in organically managed citrus groves.
Spirotetramat is relatively nontoxic to Cryptolaemus.
|Common name||Amount to use||REI‡||PHI‡|
|(Example trade name)||(type of coverage)**||(hours)||(days)|
|Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least harmful to natural enemies, honey bees, and the environment are at the top of the table. When choosing a pesticide, consider information relating to air and water quality, resistance management, and the pesticide's properties and application timing. Always read the label of the product being used.|
|RANGE OF ACTIVITY: Pests: narrow (mealybugs); Natural enemies: none|
|PERSISTENCE: Pests: intermediate, does not survive winters well; Natural enemies: none|
|COMMENTS: Release in early spring in orchards where citrus mealybugs were a problem the previous year.|
|(Movento)||10 oz/acre (See comments)||24||1|
|RANGE OF ACTIVITY: Pests: broad (mites, thrips, leafminers, aphids, armored scales); Natural enemies: predatory mites|
|PERSISTENCE: Pests: long; Natural enemies: short|
|MODE-OF-ACTION GROUP NUMBER1: 23|
|. . . PLUS . . .|
|NARROW RANGE OIL|
|(415)||1.2–1.4%||See label||See label|
|RANGE OF ACTIVITY: Pests: broad (unprotected stages of insects and mites); Natural enemies: most|
|PERSISTENCE: Pests: short; Natural enemies: short|
|MODE OF ACTION: Contact including smothering; also improves uptake.|
|COMMENTS: For use on all varieties. Allow 1 to 2 weeks for systemic movement through the plant. Must be applied with an adjuvant to improve penetration. Do not apply before bloom, during bloom, or 10 days after petal fall. Toxic to predatory mites but nontoxic to Aphytis or vedalia beetles.|
|**||TC - Thorough coverage uses 750 to 2000 gal/acre.|
|‡||Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest.|
|#||Acceptable for use on organically grown produce.|
|1||Rotate chemicals with a different mode-of-action group number, and do not use products with the same mode-of-action group number more than twice per season to help prevent the development of resistance. For example, the organophosphates have a group number of 1B; chemicals with a 1B group number should be alternated with chemicals that have a group number other than 1B. Mode-of-action group numbers are assigned by IRAC (Insecticide Resistance Action Committee).|
UC IPM Pest Management Guidelines:
UC ANR Publication 3441