Photo: Kyle Beucke, California Department of Food and Agriculture
The Plum Bud Gall Mite (Acalitus phloeocoptes) was first found in San Mateo County in 2019. The pest is now widespread throughout Santa Clara and San Mateo Counties.
Plum Bud Gall Mites (PBGM) can be found on branches and twigs of stone fruit trees such as plum, peach, and apricot, as well as almonds. The mites are tiny (0.15 mm) and difficult to see, but they produce visible galls when feeding on nearby buds on fruit trees. The galls cause damage to buds and fruit spurs, but do not cause significant damage directly to fruit. PBGM infestation can cause weakened trees which may eventually cause tree fatality, but other trees have been found to recover.
Do you think you have found Plum Bud Gall Mites on your fruit tree?
Please contact the County of San Mateo Department of Agriculture at (650) 363-4700. Samples can be submitted to our office duty biologist for identification.
Due to the widespread distribution of the pest, control or abatement of PGBM is not feasible in San Mateo County. If PBGM is found on fruit trees, infested budwood and propagative material should not be removed from the property to prevent further spread of the pest.
Fruit movement is not restricted (although we recommend fruit be thoroughly cleaned before transportation), and tree treatments or pest management is not required.