As summer arrives, we notice interesting as well as annoying insect and disease problems in our gardens and landscapes. While many visiting insects are beneficial, some are not. Identifying and understanding these insect life cycles will help us to maintain a healthy and beautiful garden.

Bagworms

If you have needled evergreens, chances are you have encountered this nasty pest. Bagworms feed on needles and leaves and can be very damaging, especially to evergreens. Start looking now for bagworms on your evergreens, locusts, sycamores and oaks. These bags resemble cocoons hanging from branches of trees. They are 1 to 2 inch long "bags" made of silk, leaves and twigs attached to branches with a silken thread.

Scouting is especially important if you had bagworm damage last year. Many of these bags contained eggs that hatched at the end of May. At this time of year, the eggs have already hatched, so start scouting throughout June for the small (1/8-1/2") recently hatched caterpillars..

After this insect hatches, it crawls out of the bag and produces a tiny silken thread that will hang from the bag. This allows the tiny worm to be moved by the wind from plant to plant. It begins to feed and feed, and as it does so, builds the bag around itself. It continues to feed through August, at which point it pupates and turns into a moth around early September. The male will leave the bag and fly till it finds a female. The female remains in the bag until a male finds her. After mating, the male dies. The female will lay her eggs then die in the bag. The eggs will overwinter in those bags – perfect time to pick off and control next year’s population!

However, at this time of year chemical control is very effective. Bt (Bacillus thuringiensis), a naturally occurring microorganism that produces a toxin that paralyzes the insect’s digestive system, is successful at this stage. As the young caterpillars eat the leaves and ingest the Bt, they stop feeding and die several days later. Bt is selective. It kills just caterpillars. Other insects like beetles, bees or soft-bodied insects are not affected by this pesticide.

Other pesticides that are effective are Carbaryl, also known as Sevin, and Malathion, Unlike Bt, these pesticides are not selective in the insects that they kill. Beneficial insects as well as the bagworms will die from the application of these insecticides. As always, read the label before applying any pesticide.

Lacebugs on Broad-Leaved Evergreens

If you have azaleas or pieris, you have no doubt encountered these damaging insects. They insert their mouth parts into a leaf’s lower surface and suck out the plant juices, leaving many small white or yellow spots where the juices have been removed. In severe infestations the leaves will appear stippled and washed out. Scout for this insect by looking on the underside of the leaves. You may see black or dark red varnish-like spots made by their excrement or you may see the insects themselves, small, 1/16 to 1/8" nymphs or adults.

Prevention is often the best control for this pest. Most lacebugs seem to prefer sunny sites. If your shade loving azalea or rhododendron is in full sun and has recurrent lacebug problems, consider moving it to the shade. In the proper location it will be more pest free.

Using a hard, jet stream of water from a hose will dislodge young nymphs in mid May just after hatch. They have been living as eggs throughout the winter in the leaf tissue of the plant. At this time of year, however, you are limited to a more aggressive control.

Predators such as lacewings and assassin bugs help to naturally control lacebugs. You can conserve these allies by avoiding the use of broad-spectrum insecticides that kill a wide range of insects and linger on the plant. Begin looking for lacebugs in May and throughout the summer. Insecticidal soap is a useful tool, but you need to make sure you spray the underside of the leaves where the insects are feeding. You may need to make additional applications. At this point, getting the population under control early will prevent damage and avoid the need for more toxic chemicals. Keep scouting throughout summer to make sure plants don’t become re-infested. Other options of control are carbaryl (Sevin), or Malathion. As the summer progresses, these damaging insects can have as many as three generations, the second hatching in mid to late July.

Japanese Beetles

You’ve seen them, the metallic green beetles that show up on in your landscape every July. Later in summer you know them as white grubs that turn your lawn into a brown, rollup carpet. These are two of the stages of the Japanese beetle.

Knowing a little about your enemy helps in the battle. After skeletonizing your favorite plants last July the females laid eggs in the ground. These eggs hatched and the young grubs began feeding on plant roots. They fed and grew until they went deeper into the soil to overwinter. This April the grubs returned to the surface where they continued their development to the pupal stage. In late June, they will be back as those familiar metallic beetles.

When dealing with these colorful beetles, prevention is always better than reaching for the spray can. Keep in mind that though Japanese beetles feed on over 300 species of plants, 50 are preferred food. Adult beetles are attracted to plants in full sun, especially members of the rose family, which includes ornamental apples, cherries and plums. Norway and Japanese maples are also favorites. Minimizing these plants in your landscape will help reduce the beetles. The larvae (grubs), favor cool season grasses such as bluegrass, ryegrass and tall fescue. Replacing some lawn with tree, shrub and flower beds of less favored species may help.

This summer, when you see the first Japanese beetles emerging from the ground and landing on your plants, take action. Because beetles are pretty sluggish early in the morning, you can easily shake them off the plants into a bucket of soapy water. Not only will you prevent damage from this first wave, you will also keep them from using their pheremones to call in reinforcements. This hand-to-hand combat may seem yucky, but is has an added benefit over the standard treatment chemical sprays. Broad spectrum insecticides such as carbaryl (Sevin) and pyrethroids kill beneficial insects and may result in outbreaks of other pests.

This brings us to beetle traps. Though it may make you feel good to fill up bags with beetle carcasses, traps can draw beetles from all over your neighborhood and beyond. Research shows that only a fraction of them end up in the traps while the rest feed on your plants.

The other front on which you can attack Japanese beetles is the grub stage. Here are a couple of tips:

• Don’t water your lawn in mid/late summer. Moisture helps the survival of the eggs and young grubs.
• If you had grub damage last year, you may want to consider control in the problem areas. A non-chemical control is to introduce nematodes into the soil when the grubs are small.
• Chemical control for those problem areas include imidacloprid and halofenozide applied in June and early July.

And don’t be too quick to chase away the skunks that frequent your lawn in September. They work at night, do a great job eating the grubs, and the divots they leave behind are easily repaired.

Squash Borer

This common pest on cucurbits - melons, squash, pumpkins and cucumbers, can be a huge problem in our gardens. Causing wilting in the vine, the larvae of this borer will be feeding on the inside of the vine, where we can’t see it. When this symptom is found, there is no good control except to pull the plant and discard of it, getting rid of the damaging larvae.

The squash vine borer overwinters as a fully grown larva in cocoons in the soil. It pupates in the spring and the adult (a moth) emerges in June. Moths are active during the daytime and in the evening they rest on leaves. This is different than the behavior of most moths, which are active at night. The moths fly slowly in zig-zags around plants, and lay eggs singly on stems; eggs are usually found on the main stem near the base, but are also found on leafstalks or on the undersides of leaves. Moths are active for about one month.

Eggs hatch in 9 to 14 days. Larvae enter the stem at the plant base within a few hours after hatching from the eggs. Larvae feed inside the stem for 4 to 6 weeks. Fully grown larvae leave the stems and crawl into the soil to pupate. There is usually one generation per year, but a partial or complete second generation is possible.

Insecticides become almost impractical for the home garden, as timing is everything. An insecticide is effective only when applied at the time that eggs are hatching, which is very difficult to see or determine. A preventive treatment regime is to apply an insecticide, like Sevin or Malathion, when vines begin to run, and re-apply every 7 to 10 days for 3 to 5 weeks. The application should be directed to the base of plants, at crowns and runners. When it comes to the squash borer, often times it’s just better to harvest what you can salvage and discard the plant to get rid of the borer.

These common pests, while may be a detriment to our crops and plants, are not the end of our gardening career. Diversification of crops and plants will help reduce the amount of problems in our landscapes and gardens and proper management will lead to healthy gardens. Enjoy every minute of gardening, whether it’s pulling weeds, understanding the life cycle of an insect, or reaping the harvest of your hard work.

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