Summer brings both good things and bad. The arrival of several creepy-crawlers in your yard and garden definitely indicates the latter. Bag Worms, Sawflies and Japanese Beetle larvae are hatching, eating and growing this month, potentially wreaking havoc on plants and trees on your property.

These bugs have something in common: they’re more vulnerable but more voracious when they’re young. Take preventative measures to control newly hatched larvae and you will avoid a world of trouble in the garden.

Bag Worms

• Characterized by their ambitious appetite for both deciduous and evergreen trees, they resemble hanging pinecones and can easily disguise themselves by using material from their host to create a well-camouflaged bag. Look for leaves with small brown spots and holes to indicate the presence of larvae.

• Prevention: The easiest and quickest way to eliminate these pests is simply pick the bags off of your tree and squish them. Remember, their bag is extremely hardy, so make sure you have disposed of them completely so they don’t crawl away back to your tree. Immature larvae can be destroyed using an insecticidal spray containing Bacillus thuringiensis (BT), but as they grow larger they become less sensitive. Act fast. Another preventative measure is to grow Shasta daisies or other plants which attract ichneumonid wasps. These tiny wasps are natural predators of the bagworm but do not harm humans.

Sawflies

• Also known as “stingless wasps,” sawflies are virtually harmless once they reach adulthood, but hungry larvae can cause extreme damage to your flora. Sawfly larvae can be identified by their tendency to rise up on their hind legs when approached (see picture). They eat in clusters, typically side-by-side, eating along the leaf margins.

• Prevention: Natural insecticides like spinosad work well against sawfly larvae. However, though sawflies resemble caterpillars, insecticides created for caterpillars like BT will not harm them.

Japanese Beetles

• These pests are a major concern for landscapers everywhere. Larvae hatch and grow under the turf of your lawn, eating holes in the grass as they go. Adults damage plants and trees.

• Prevention: Adults begin to emerge in late June and, if spotted early enough, can be picked off the plants by hand and dropped in soapy water. Adult beetles release a pheromone that attracts other beetles to mate, increasing the population dramatically. Beetle traps have been found to be largely ineffective against Japanese Beetles. Larvae will rise to the surface of the soil in late July and August, so this is the best time to apply pesticides to your lawn.

For more advice on preventing these and other pests, stop by and talk with one of our staff. See you in the greenhouse!

MVG - Growing sustainably since 1984