Cucurbit insects strike

By John Fulton         

[June 25, 2007]  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. In the first group of insects are the cucumber beetles. These can be green, black and yellow-striped, or black and yellow-spotted. These are also called corn rootworm beetles when they are in cornfields. When these insects are in cucurbits, they are usually called cucumber beetles.

The importance of the beetles is not that they eat small holes in the leaves, but that the striped and spotted 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 parenthesis: 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 clearwing 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. Sevin will work on the smaller-sized 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.

Other items of note

Several diseases are found in lawns at this time. Brown patch, dollar spot and helminthosporium are some of them. It is not recommended to treat lawns for diseases, since it a never-ending proposition. Sprays are generally applied every 10-14 days forever. It is recommended to let diseases run their course and reseed in the early fall if needed.

Evergreens are not looking the best. Most evergreens don't do well for long periods of time in central Illinois. Scotch, red and Austrian pines get several needle diseases. White pines have weather and environment-related problems that can lead to sudden death. Spruces have needle diseases, spruce spider mites and canker diseases. Spider mites and bagworms can be treated, but we may have to look at the other problems. Most evergreens don't like the Illinois extremes for moisture and temperature. Many are even found as understory trees in natural settings, rather than specimen trees. Take care when selecting evergreens for landscape use.

On the Web

The Logan County Extension online site has information and updates on horticulture and other topics. Check it out at www.extension.uiuc.edu/logan/.

[Text from file received from John Fulton, University of Illinois Extension, Logan County Unit]