Insect Pests of Blackberries
Among the most commonly observed insect pests of blackberries are the Spotted Winged Drosophila, Japanese Beetle, and the Blackberry Psyllid. Read on to learn more about how to control these pests to optimize your blackberry yield.
Spotted winged Drosophila male.
Spotted Winged Drosophila (Drosophila suzukii)
Adults look similar to a common fruit fly/vinegar fly. Males have a large black spot on each wing. Females cannot be differentiated from other species of fruit fly without the use of a microscope. The best way to identify an infestation is by looking for larvae. Larvae look like tiny white worms and can be found inside the fruit. Fruit can be tested for the presence of larvae by soaking it in a warm saltwater solution. If larvae are present inside the fruit, they will emerge and float to the top of the water within half an hour.
Spotted winged Drosophila larvae.
Adult flies will lay their eggs in unripe, ripe, or overripe fruit, leaving a tiny scar. The developing larvae will eat the fruit from the inside. The fruit will eventually collapse and rot.
Insecticides should be applied once the pest is detected. This can be done by setting up a trap made of any small container. Add apple cider vinegar to attract the flies, and a drop of dish soap that will break the surface tension and cause the flies that enter the trap to drown. Check the trap periodically by straining out caught insects and inspecting them. If even a single adult spotted wing drosophila is found, begin insecticide treatment. Non-chemical: Harvest all fruit as soon as it is ripe and keep it refrigerated to prevent larval development. Do not leave overripe or fallen fruit on or around the plant. Keep the area around the plant clear of other debris. Do not compost any disposed fruit.
Japanese beetle adults skeletonize leaves and eat ripe fruit!
Japanese Beetle (Popillia japonica)
Adult beetles are approximately ½ and inch in length. They have copper wings and metallic green bodies. Their abdomens are spotted with distinctive white hairs. Adults typically emerge in June.
Adult beetles will eat leaves, buds, and fruit. Damaged leaves will have the tissue between the veins eaten, but not the veins themselves.
Insecticides may be applied at several different times throughout the year depending on the chemical used. The Ohioline factsheet on Japanese beetles (https://ohioline.osu.edu/factsheet/ENT-46) provides information on some of these chemicals. Many insecticides are preventative and are therefore only effective on the grubs, so they should be applied to the soil/turf rather than directly to the blackberry plant. Non-Chemical: Japanese beetles may be diverted from blackberries by planting more appealing plants nearby, such as linden trees and geraniums. Alternatively, companion plants such as garlic, tansy, and rue may deter the beetles. Beetles are attracted to plants that have already sustained damage, so it is important to prevent damage early in the season. This can be done by handpicking beetles off the plant or protecting the plant with a row cover. Parasitic wasps, milky spore disease, and parasitic nematodes can be used as a biological control, but this is expensive and will not prevent adult beetles from flying onto the blackberries from a neighbor’s yard.
Blackberry psyllid adults that have recently emerged from the nymphal forms.
Blackberry Psyllid (Trioza tripunctata)
Psyllids are small, winged insects similar to aphids. This species is best identified by the reddish-brown stripes on the wings, but this can be difficult to see due to their small size. They will jump when disturbed.
Blackberry psyllid damage shows up as curled leaves.
Adults feed on leaves and may leave behind a white, silky substance. Leaves that are severely affected will begin to curl.
If a large number of leaves become visibly damaged and psyllids can be seen on the plant, insecticide treatment may be considered. However, psyllids will not threaten the fruit and rarely threaten the overall health of the plant, so insecticides are not truly necessary. Non-chemical: Because psyllids overwinter in pine trees, the best control method is to simply not plant blackberries near conifers.
Buckeye Yard and Garden Line – Spotted Winged Drosophila
Ohio State University Extension – Japanese Beetle Factsheet
The Midwestern Home Fruit Guide is a regional bulletin that covers all the fruits that a home gardener may wish to grow. It is a “for sale” bulletin, but well worth the $24!! Click on the title to go to a web page for ordering this guide. This bulletin covers cultural and chemical control of diseases and insects that attack fruits.
(We wish to thank Dr. Celeste Welty & Dr. Gary Gao for consultations!)