What’s Eating My Raspberry Leaves? Identifying and Preventing Raspberry Leaf Damage

Raspberry leaves are delicate and susceptible to damage from various pests. As a raspberry grower, seeing ragged, chewed or mined leaves on your plants can be concerning. However, don’t panic! With some detective work, you can identify the culprit and take steps to protect your raspberries.

Common Raspberry Leaf Pests

Several insects are attracted to the tender foliage of raspberry plants Here are some of the main offenders to look out for

Japanese Beetles

Japanese beetles are a very common pest of raspberries in most regions. The adult beetles are metallic green and copper colored, around 1⁄2 inch long, and tend to congregate in large numbers on leaves which they voraciously devour. This leaves behind characteristic skeletonized or lacy looking leaves with just the veins remaining.

Raspberry Fruitworms

The raspberry fruitworm is a small green beetle that feeds on leaves and other tender plant tissues. Adults nibble holes between the leaf veins, while the larvae bore into buds and fruits. Close inspection will reveal the adult beetles and larvae, as well as the tell-tale round holes in developing leaves.

Raspberry Sawflies

Sawfly larvae look like caterpillars, but they are actually the young of a different kind of wasp. Raspberry sawfly larvae feed on the edges of leaves and can completely remove leaves from canes if there are a lot of them. Look for up to 3⁄4-inch long yellowish-green larvae on leaves that aren’t being used.

Leafminers

These tiny flies lay eggs inside of leaves. The larvae then feed and develop between the upper and lower leaf surfaces, creating meandering tunnels or ‘mines’. Damaged leaves will appear dried or brownish when held up to the light. Different leafminer species target specific plants so infestations usually indicate the presence of raspberry-specific leafminers.

When Do They Feed?

Timing and weather patterns influence when each pest is active:

• Japanese beetles emerge as early as late May and are active through summer into fall. They are especially problematic during hot, dry midsummer weather.

• Cranberry fruitworms do the most damage in the spring and early summer, when the adults eat the new leaves and the young ones bore into the fruit. Monitor for them starting from budbreak onward.

• The young raspberry sawfly bugs show up in the spring, soon after the first leaves come out. They eat for four to six weeks before laying their eggs in the ground.

• Leafminers produce 2-4 generations per year starting in early summer. The most people are there in the middle of summer, but damage can happen at any time from May to October.

Preventing Raspberry Leaf Damage

While some nibbling is inevitable, you can reduce serious defoliation with integrated pest management:

• Encourage natural predators like birds, beneficial insects, spiders etc. Avoid broad-spectrum insecticides which kill these allies.

• Use row covers as a physical barrier to insects in spring and early summer when leaves are most vulnerable.

• Hand pick Japanese beetles and larvae of other pests to reduce populations.

• Apply insecticidal soaps or oils to suffocate soft-bodied insects like sawfly larvae. Avoid pollinator-toxic neonicotinoids.

• Use pheromone traps to capture adult pests like raspberry fruitworms before they can breed and lay eggs.

• Improve plant vigor with regular watering and pruning. Healthy canes can better withstand some leaf loss.

• Clean up thoroughly after harvest. Remove old canes and debris where insects can overwinter.

When to Worry

Minor leaf damage is no cause for concern. But if pests defoliate entire canes or damage is severe over multiple seasons, yields may drop. Seek expert help to identify the exact pest and consider stronger chemical control if required. Always follow label directions exactly.

With some basic monitoring and prevention, you can keep most leaf pests in check. And if you do see leaves getting eaten, use the clues above to identify which culprit is munching on your raspberries so you can take targeted action to stop them. Vigilance and quick response will help ensure your plants can keep growing and producing berries.