Cucurbit insects, bagworms and pruning evergreens

By John Fulton

[June 30, 2009]  Cucurbits are basically everything in the squash and melon families. There are several potential insect problems with them, and today's column attempts to help minimize or prevent these problems.

The first group of insects is the cucumber beetles. These can be green, black and yellow striped, or black and yellow spotted. The importance of the beetles is not that they eat small holes in the leaves, but that the beetles can transmit a bacterial wilt to the plants as they eat. The first thing you see is you have a plant that suddenly wilts on various runners, or the entire plant.

The best means of controlling this disease is a good beetle control program. Current homeowner recommendations would include these products, with the days-to-harvest restrictions in parentheses: carbaryl (zero), bifenthrin (three days) or rotenone (one day).

Of course, Japanese beetles love cucurbits as well. Their damage is direct leaf feeding. Remember they feed in groups, so once they get started you will have a battle on your hands. The carbaryl and bifenthrin are both good control measures.

Squash bugs are the next problem to discuss. Squash bugs are usually dark gray to black in color and like a long stink bug. Their eggs usually hatch mid-June to mid-July. Best control timing is when the eggs first hatch. Nonrestricted products are sabadilla (one day), which is an organic product that might be a little hard to find, and bifenthrin (three days to harvest).

One last note: If the squash bugs get past their early growth stages, then physically removing them is about the only control method available.

The last insect problem on cucurbits is squash vine borers. These borers usually drill into the new runner areas and kill off individual runners one at a time. The adults of these larvae are red and black clearwinged moths. Scout your plants and look for the adults, as well as entrance holes and the chewed-up plant material. Treat as soon as early damage occurs and use one of the following homeowner products: carbaryl, bifenthrin or rotenone. Days-to-harvest restrictions have already been covered (and these would also apply to pumpkin blossoms).

Bagworm check

If you haven't checked for bagworms yet, now would be a good time. Small bags have been noticed in the county for the last few weeks. Re-treatment may be necessary in some cases. Carbaryl (Sevin) will work on the smaller bagworms, while the Bt products may be required for the larger ones.

Remember, bagworms frequently start in the tops of trees. Bagworms are the larvae of clearwing moths that don't fly too well. If you control the bagworms well, you may not have high populations for a few years.

Pruning evergreens

This is the time of year to wrap up pruning chores on evergreens. This includes both needle-type and broadleaf evergreens. If you're wondering what a broadleaf evergreen is, that includes holly, rhododendron and azalea. The logic behind pruning your yews at this time is to allow sufficient time for regrowth to become hardened off before winter, and to keep new growth from becoming too rank before the winter months.

Pruning evergreens is part art and part science, but mostly art. A few simple rules to follow make the job results much more pleasing. Upright growing evergreens, such as pines and spruces, should not have the main leader cut off. This will destroy the natural shape and will make the resulting growth more susceptible to breaking off. If individual branches are being cut off, they should be cut back to a bud. This will allow the bud to become the new main branch. You can also control growth direction of branches in this way. If you are growing trees for cut Christmas trees, all bets are off, as you are only dealing with trees through the first seven years or so of their life.

Make sure you use the proper equipment. Individual pruning cuts are best done with bypass loppers or pruning shears. These make clean cuts without much damage to the remaining wood. The old anvil-type shears and loppers cut to a point, then crush the remaining wood. For yews, junipers and arborvitae that are trained to a certain size or shape, you will want to use hedge shears (electric or manual) that are sharp and properly tightened. Most of these types of shears can cut up to about a quarter of an inch in size.

When pruning evergreens, remember the dead zone. This is the area toward the center of the plant that doesn't receive much light. It also has few needles or active buds. Cutting into the dead zone will cause many years (or forever) of little green growth. Also remember to prune so that the base of plants is wider than the top. This allows sunlight to hit the bottom area as well and keeps the bottom from dying up.

[By JOHN FULTON, University of Illinois Extension, Logan County]