Opening up your raspberry patch to find leaves riddled with holes, skeletonized or otherwise damaged can be disheartening. However, identifying the culprit pest is the first step in protecting your crop Raspberries are vulnerable to a range of insects that can quickly defoliate plants when infestations get out of control. Here are some of the most likely suspects eating and damaging raspberry leaves
Japanese Beetles
The adult Japanese beetle (Popillia japonica) is one of the most notorious raspberry pests in many regions. These 1⁄2 inch long metallic green and copper beetles skeletonize leaves, leaving only the major veins behind. Heavy feeding can stunt plants and reduce yields. Japanese beetles also feed on ripening fruit.
Raspberry Fruitworms
The raspberry fruitworm (Byturus unicolor) is a small beetle that feeds on leaves and lays eggs in buds and fruits. Adults chew irregular holes between leaf veins causing a skeletonized appearance. Larvae bore into fruits making them unmarketable. They prefer red and purple raspberry varieties.
Raspberry Sawflies
Raspberry sawfly larvae (Monophadnoides geniculatus) devour leaf tissue voraciously, sometimes removing all but the main leaf veins. Heavy feeding can completely defoliate plants. The greenish caterpillars reach about 1⁄2 inch long when fully grown. Sawflies prefer wild blackberries but also attack cultivated red and black raspberries.
Leafminers
Leafmining larvae of insects like the raspberry leafminer (Metallus rubi) feed between the top and bottom leaf surfaces, creating winding tunnels or blotch mines. Damage is visible when leaves are held up to the light. Leafminers mainly affect blackberries but also raspberries at times.
Spider Mites
Spider mites (Tetranychus spp.) are tiny pests that puncture plant cells and suck out contents. Feeding causes stippling, bronzing and drying of leaves. Webbing may cover severely infested foliage. Hot, dry conditions encourage mite outbreaks.
Aphids
Several aphid species feed on raspberries. Their piercing-sucking mouthparts drain sap, causing curled, stunted leaves. Aphids also spread debilitating viruses. Colonies tend to develop on the undersides of leaves.
Thrips
Thrips are tiny insects that rasp plant tissues and siphon out the juices. Damaged areas appear silvery before browning. Leaves may be distorted, stunted or dried out from thrips injuries. These pests are especially problematic in hot, dry weather.
Keeping a close eye on raspberry plants and quickly identifying leaf damage can allow you to take prompt action against infestations before they escalate. Compare symptoms to pest feeding patterns to determine which are affecting your crop. Employ cultural, biological and least-toxic chemical controls as needed to keep these insects in check and foliage protected. With smart integrated pest management, your raspberry leaves will remain lush, healthy and undamaged.
CANE MIDGE, SPUR BLIGHT AND CANE BLIGHT
Different kinds of Raspberry Blight and the Cane Midge are grouped together because, even though they are all very different, a Cane Midge attack always does a lot of damage. Cane Midge grubs spend the winter in the ground and first appear as tiny flies in late spring to early summer, depending on the weather. The female fly lays her eggs in splits on the surface of raspberry canes. The grubs eat the canes and then fall to the ground, where they will grow into more flies later in the season. Up to four generations of Cane Midge can occur within a growing season.
The raspberry canes have small brown spots that are caused by the Cane Midge. These spots are only on young canes and are up to 30 cm (1ft) high. The reason is that Cane Midge cannot fly well and tend to lay eggs just above soil level.
Cane midges don’t do much damage to raspberry canes by themselves, but they do damage that lets different kinds of fungus get into the canes. These fungi are generally referred to as Spur Blight and Cane Blight. It is these fungi which cause significant damage. The canes are infected and then grow irregularly producing a very poor raspberry crop. Cane and spur blight are both marked by brown sores on the canes that show up all over the canes, not just at the base.
There is no cure for Cane Midge nor for Spur Blight and Cane Blight. Pesticides that work are quickly running out even for commercial growers, and home gardeners can’t get any of them. Infected canes should be dug up and burnt.
Many smart articles have been written about these pests, but none of them seem to have answered the question of how Cane Midge first attack a raspberry crop. It seems likely that the Cane Midges are introduced by planting already infected canes. So, carefully check the health of the new raspberry canes and burn any that look like they might have an infection.
It’s not very well known how to get rid of a cane midge infestation because it’s almost impossible to do so in a business setting. But from the point of view of a beginner gardener, there is still the matter of whether to remove and burn an infected crop and then plant again on the same ground.
The little solid evidence that exists shows that if the raspberry plants are removed in spring and then new crops are planted in autumn, the new plants will be considerably healthier. However, there is no evidence that the midges will be eradicated completely. This is based on trials held in Sweden where new raspberry shoots were removed entirely, leaving only one year old shoots.
This resulted in a vastly reduced incidence of cane midges but not a total eradication. After reading all the available research, it seems that planting again in the same spot where an attack happened should not happen for 18 months. There is no proof that the midges can still be in the soil after two years have passed.
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FAQ
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