Managing insects and mites in bramble plantings is challenging because the plants are perennial, allowing populations of insects to build up over time, and because there are relatively few pesticides labeled for use on these crops. Therefore, preventing insect pests from ever getting established in a planting is a critical part of a pest management program. In order to reduce local pest pressure, growers should eliminate all wild brambles within 600 feet of the planting. Wild brambles act as hosts and harbors for pest species. Weeds may also act as hosts for insect pests, so good weed management is essential. Good sanitation in and around the planting, such as removing dead or injured canes promptly and destroying all canes that are pruned out, will also reduce pest problems. Finally, encourage populations of natural enemies of pests in your planting, such as predatory mites, lacewings and lady beetles, by using pesticides only when absolutely necessary, and by using compounds that are least injurious to natural enemies whenever possible.
Aphids are small, green, soft-bodied insects that suck plant sap with straw-like mouthparts. These insects transmit viruses from infected plants to healthy ones as they feed. Removal of wild brambles from the area around your planting will reduce the source of virus infections. Clear all wild brambles from within 600 feet of the planting. Keep weeds under control, because these may also act as hosts for viruses. If virus symptoms appear on your plants, dig up the infected canes, including the roots, and destroy them. Insecticides may be applied to control aphids when these insects appear. Some varieties of brambles (e.g. Royalty, Titan) are immune to aphid feeding, and thus are less susceptible to virus problems.
Two-spotted spider mites are very small (1/50 inch), insect-like creatures with oval, translucent bodies and two dark spots on their backs. They feed on raspberry foliage, sucking out plant juices and causing a white or bronze stippling on the leaves. If the plants are heavily infested, fine webbing may be seen on the leaves, which eventually turn brown and die. Mites may also move onto the fruit. There are no effective miticides available to manage two-spotted spider mites on brambles at this time. Soaking, high-pressure water sprays may temporarily suppress mite populations. Predatory mites such as Amblysejus fallacis may be released into an infested field and can provide significant control of spider mites, although the results are not immediate. To encourage natural predator populations, avoid the use of pesticides, such as benomyl, which are highly toxic to predatory mites.
Raspberry cane borer is one of the most common insects that infest raspberries. The adult form is a half-inch-long, narrow-bodied black beetle with long antennae and an orange band just below the head. The beetle chews two rings about 1/2 inch apart and three to six inches below the tip of a young cane, and inserts an egg in between them. The egg hatches and the larva, or grub, feeds inside the cane. The girdling rings made by the adult causes the cane tip to wilt, blacken and fall off. Cut off all wilted tips as soon as they are noticed just below the lowest girdle mark and remove them from the planting. Destroy any wild brambles in the area, which act as hosts for this pest. These two practices should bring this insect under control. An insecticide spray just prior to bloom may offer some control of the adults.
Red-necked Cane Borer is a ¼ inch long, slender, black beetle with short antennae and a reddish-orange band just below the head. The female beetle inserts an egg into young bramble primocanes near the base. As the larvae develop, a round swelling appears on the cane that may vary in length from 1/2 inch to nearly three inches. Infested canes become weakened from the larval feeding. During pruning in the early spring, remove all canes that show swellings. Eliminate any wild brambles nearby that act as alternate hosts for this insect. Insecticide sprays may be applied just prior to bloom to control the adults, but regular removal of infested canes and destruction of wild brambles often provides adequate control.
Raspberry Crown Borer is a clear-winged moth that resembles a yellow-jacket. The moths lay eggs on the undersides of raspberry leaves during late July and August. The larvae overwinter in the soil and the following spring they bore into the base of the raspberry canes to feed. Infested canes become weak and spindly. The leaves may brown along the margins and wilt. Eventually, the plants may die. Scout for the adult moths in late July and August. If moths are found, or canes with larval feeding symptoms have been noticed, insecticide drenches applied in the fall or early spring may provide control of the larvae. Elimination of all wild brambles in the area may also reduce local populations of this pest.
Japanese Beetles and Rose Chafers are relatively large insects that feed upon raspberry foliage. Japanese beetles are about 1/2 inch long, robust, shiny and copper-colored with green markings. Rose chafers are also about 1/2 inch long, but are slimmer, dull, and buff-colored. The feeding habit of the two insects is similar, chewing holes between the veins of the leaves, resulting in a skeletonized appearance. The beetles may also feed on flowers and fruit. The larvae of both species live in the soil and are considered turf pests. When beetles are observed feeding in a raspberry planting they can be controlled with appropriate insecticide sprays applied to the foliage. Pheromone and scent traps are available to control Japanese beetles, but these have not proven effective in commercial settings. Place traps near, but not within, the planting to prevent increased injury from beetles which are attracted to, but do not fall into, the traps.
Raspberry fruitworm is a small (1/8 inch), brown beetle that feeds on raspberry flower buds in the spring. The female beetles chew a small hole in the side of a flower bud and insert an egg into it. The small, white grubs feed within the ripening berries and often end up in the harvested fruit. Check flower buds for small holes chewed in the sides, or look for the 1/2 inch long, translucent grubs when picking or sorting fruit. Pesticide sprays should be applied as soon as flower buds emerge in the spring or when the damage is first noticed. Do not apply insecticides during bloom. Remove any wild brambles from the area, which act as hosts for this insect. There is some evidence that this insect is more of a problem in weedy fields.
Tarnished plant bug is a small (¼ inch) bronze insect that feeds on the flowers and developing fruit of raspberries. The immature stage, or nymphs, are bright green and resemble aphids, but are much more active. The feeding results in fruit that are poorly developed, and may crumble or fall apart when harvested. Controlling weeds in and around the raspberry planting will help reduce populations of this insect, but insecticide sprays may be necessary. Sprays should be applied pre-bloom, and repeated after petal fall. Do not apply insecticides during bloom.
Strawberry bud weevil or "clipper" is a serious pest of strawberries, but it will also attack raspberries. This insect is a very small (1/8 inch) beetle with a copper colored body and a black head with a long snout. The female weevil lays eggs in raspberry flower buds and then girdles the buds, causing them to dry up and eventually fall off the stem. If clipped flower buds are noticed in the spring, pre-bloom control measures can be applied.
Wasps such as yellow-jackets and bald-faced hornets can become serious pests of raspberries, especially during dry seasons, when they feed on ripe fruit and become a hazard to pickers. These insects are attracted to moisture and sugar, and are very difficult to discourage once they have discovered a good source. To prevent wasps from becoming a problem, harvest frequently and thoroughly. Do not allow over-ripe or injured berries to remain on the plants. Rotting or fermenting fruit is very attractive to wasps. If wasps start to become a problem, try to find the insects' nest and destroy it. Wasps build nests underground, in hollow or rotten logs, in trees and in or on houses. Follow all precautions for using wasp-destroying compounds. If the nest cannot be found, several types of wasp traps are available which may offer some relief. The keys to successfully using traps are to determine the appropriate bait for the type of wasp, placing the traps out early, i.e. before the wasps become a problem, and deploying them around the perimeter of the entire field. Applying insecticides to the raspberries is not an effective method of controlling the wasps, because they generally attack when the fruit are ripe and thus spraying would create a residue problem.
David T. Handley, University of Maine Cooperative Extension, Highmoor Farm, P.O. Box 179, Moninouth, ME 04259-0179, (207) 933-2100
Originally published: Proceedings. 1999. New England Vegetable & Berry Growers Conference and Trade Show, Sturdbridge, MA., p.80-82.
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