PBGM galls on branch of pluot tree

Photo: Kyle Beucke, California Department of Food and Agriculture

The Plum Bud Gall Mite (Acalitus phloeocoptes) is a new pest that has recently been found in Santa Clara County. The San Mateo County Agricultural Commissioner’s office, with the California Department of Food and Agriculture (CDFA) is currently surveying fruit trees to assess the present range of this pest in California.

Plum Bud Gall Mites (PBGM) has been 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

What should you do if 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 and a county Biologist will visit to inspect the suspected tree(s) and collect a small sample of the bud galls for confirmation. 

What will happen if Plum Bud Gall Mites are found on your fruit trees?

At this time, we need to know if PBGM exists within San Mateo County so we can determine how widespread this pest is within California. If PBGM is found on fruit trees, we will ask that infested budwood and propagative material 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. 

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