Blueberry Bud Mites

You may not be able to see blueberry bud mites, but they can be devastating to your blueberry and huckleberry plants.

Symptoms of blueberry bud mite infestation (Jerry A. Payne, USDA ARS, Bugwood.org) CC BY-SA 3.0

Blueberry bushes start producing next year’s fruiting buds as soon as the harvest is over. This is when blueberry bud mites (Acalitus vaccinii) begin causing problems in some blueberry varieties. Bushes that ripen early in the season are the most likely to develop blueberry bud mite infestations.
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Blueberry bud mite damage

Poor growth and low fruit set are the first signs of a blueberry bud mite infestation. This damage is first seen around the tops of plants. If you look closely, you may be able to see blistering on bud scales. This blistering is caused by mite feeding. Later in the growing season, deformed flowers, smaller leaves and fruit, and fewer berries per cluster may also be seen. Berries may also be deformed or appear roughened.

Blueberry bud mite identification

If you have a microscope, you can see that these tiny mites are white. Unlike most other arthropods, which tend to have four pairs of front legs, blueberry mud mites have only two. Eggs are clear and spherical. Since these pests are so small, you are probably better off bringing shoot samples to your local Master Gardeners or County Extension Office for identification.

Blueberry bud mite control

Because these pests are so small and tend to stay hidden, they can be difficult to manage. Eggs are laid within the buds, and the nymphs feed on their host buds once they hatch. As buds open, those nymphs crawl up stems where they feed on young shoots.

Blueberry bud cluster infested with bud mites (Jerry A. Payne, USDA ARS, Bugwood.org) CC BY-SA 3.0

Commercial growers apply miticides directly after harvesting when blueberry bud mites are detected. Once buds have formed completely, the mites are safe from chemical treatments. Many of the miticides used against blueberry bud mites are not available to home growers. Those that are available require careful timing. Other options include pruning infested shoots and tossing those shoots in the garbage. Predatory mites and predatory thrips provide a little protection, so avoid using broad-spectrum pesticides and plant a few insectaries near your blueberries.

Blueberry bud mites are currently only found east of the Rocky Mountains, but that can always change as more people grow blueberries and huckleberries on the West Coast.