How to Manage Pests

UC Pest Management Guidelines


June Beetles

Scientific name: Coenonycha testacea, Serica fimbriata, and Serica alternata.

(Reviewed 1/07, updated 8/08, pesticides updated 5/15)

In this Guideline:


June beetles (sometimes called Junebugs) and May beetles include various species in the family Scarabaeidae. Adult beetles fly into avocado from untilled fields and brushland during late spring or early summer. Adults chew tree foliage at night and when present night-after-night can completely defoliate a large number of young trees in a single grove. During the day, adults hide under litter or burrow into the upper 2 inches of soil, reappearing the following night to resume feeding.

Serica spp. are the most common and widely distributed scarabs in avocado. The adult Serica fimbriata is 0.6 inch long and velvety brown with faintly striated wing covers. Serica alternata and Coenonycha testacea adults are 0.4 inch long and uniformly shiny brown. Adult scarabs are robust beetles, although C. testacea is almost rectangular and is distinctly more narrow than the Serica spp. Scarab larvae are C-shaped, cream colored, soil-dwelling grubs. June beetles have one generation per year.


During spring they sometimes injure young, newly planted trees, typically near uncultivated land away from the coast. Chewing on mature trees with a well-developed canopy is generally of no economic importance.


Determine whether chewing is actually caused by June beetles and not other nocturnal pests, including earwigs, Fuller rose beetles, and snails. Caterpillars and grasshoppers also cause similar damage. June beetles can be detected, and perhaps controlled somewhat in small plantings, by deploying blacklight traps at night during late winter and spring. It may be best to deploy any blacklight traps somewhat away from the young or topworked trees. Placing traps in mature trees near new plantings and along grove edges bordering unmanaged vegetation reduces the risk that traps placed among susceptible hosts might attract adult beetles to those plants.

Common name Amount per acre R.E.I.‡ P.H.I.‡
(Example trade name)   (hours) (days)

Calculate impact of pesticide on air quality
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. Not all registered pesticides are listed. Always read the label of the product being used.
  (Malathion 8) 4.7 pt 48 7
  COMMENTS: Apply as a foliar spray at night when beetles are feeding in trees. Use of this material will disrupt biological control of other pests such as scales, thrips, mites, and whiteflies. Highly toxic to bees; do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging.
Restricted entry interval (R.E.I.) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (P.H.I.) 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.
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). For additional information, see their Web site at



[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Avocado
UC ANR Publication 3436


B. A. Faber, UC Cooperative Extension, Santa Barbara/Ventura counties
J. G. Morse, Entomology, UC Riverside
M. S. Hoddle, Entomology, UC Riverside

Acknowledgment for contributions to Invertebrates:
P. A. Phillips, UC IPM Program, UC Cooperative Extension, Ventura County
M. Blua, Entomology, UC Riverside
P. Oevering, UC Cooperative Extension, Ventura County
D. Machlitt, Consulting Entomology Services, Moorpark, CA
T. Roberts, Integrated Consulting Entomology, Ventura, CA
B. B. Westerdahl, Nematology, UC Davis

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