Dryberry Mites

Are your raspberries dry and crumbly, instead of sweet and juicy? It may be dryberry mites.

Dryberry mites attack raspberries, blackberries, Loganberries, and boysenberries. They are so small that you may not realize you have a problem until it is time to enjoy the fruits of your labor. If your cane fruits are dry and crumbly, there are steps you can take to protect future crops.

Dryberry mite description

Dryberry mites (Phyllocoptes gracilis) are not what you would expect from the Arachnids. If you could see them, these tiny pests look more like worms than spiders, with yellow to brown sausage-shaped bodies and only two pairs of stubby legs. (If you’ve ever seen a sea cucumber, you have the basic idea.) Dryberry mites are only 0.1 mm long, so you cannot see them without a microscope or a 15X hand lens. This particular group of Arachnids are called eriophyid mites and they are parasitizing plants all around the world.

Dryberry mite lifecycle

Dryberry mites are found in the nooks and crannies of your caneberries, around buds, nodes, and fruit. Dryberry mites begin life as transparent, round eggs, deposited in leaf buds. Colonies of 50 to 200 mites may overwinter together in the crevices of last year’s growth. As temperatures begin to rise in spring, the mites move to areas of new growth, feeding on primocane leaves and developing fruit, and laying more eggs. There are multiple generations present during summer and fall.

Damage caused by dryberry mites

Yellow blotching on leaves and reduced leaf size are caused by dryberry mites feeding on the underside of the leaf. Damaged leaves mean less sugar production through photosynthesis. Less sugar means less fruit and plants that are more susceptible to other problems. Young fruit may turn brown just as the flower petals fall, never reaching full size. Loganberries, boysenberries, and the earliest fruits of other caneberries to form are the most vulnerable to dryberry mite feeding. Raspberries may look sunburned and many of the little spheres of deliciousness that make up a raspberry fruit, called drupelets, will be white or tan.

Dryberry mite management

Natural predators are your best defense against dryberry mites, so avoid using broad spectrum pesticides. This means you have to be willing to tolerate a certain amount of fruit loss, but the biodiversity will work in your favor in the long run. If infestations were particularly bad during the previous year, apply sulfur just before buds open. You can also apply horticultural oils to green fruit every 2 or 3 weeks. Just be sure that you do not use both oil and sulfur. These treatments should never be used within one month of each other, to avoid chemical reactions that can damage your plants. Cutting back old growth and disposing of the old canes may interrupt the mite lifecycle.

Other causes of dry berries

Mites are not the only cause of dry berries. If dry berries are happening, take a look at which plants are affected and where they are affected. Physical damage will only occur at the point of impact, while exposure to too much sun or cold will show up more on outer fruit and leaves than on those protected on the interior or closer to a fence or wall. Consider these possibilities:

• Poor pollination due to extreme weather conditions, Colony Collapse Disorder, or a habitat that lacks biodiversity may appear on different areas of the plant
• Vascular injury caused by physical damage or severe cold can block the flow of water and nutrients to specific fruit-bearing canes
• Viruses, such as bushy dwarf, leaf curl, mosaic, or tomato ringspot can also cause crumbly fruit throughout an entire plant

Growing caneberries is an investment of time. These perennial members of your foodscape deserve your attention and care. Who else is going to give you sun-warmed sweetness the way a raspberry plant can?