This year is proving to be another memorable year in the garden. With all of these pop-up showers, it has caused problems for me and for many of my gardening friends. My garden spots on level ground have had problems with all of the rain. Those that drain well seem to be thriving in these conditions. In addition to the rain, insects have been plentiful this year. I've talked about a couple of them in previous columns and I have information on yet another.
If you find that the stems of your seedlings are being eaten off, leaves are yellowing and wilting and holes are appearing, you may have a striped or spotted cucumber beetle problem. Striped cucumber beetles are specialists on cucurbits such as cucumbers, squash, pumpkin, watermelons, while spotted cucumber beetles feed on other plants as well.
Often, the beetles leave their hibernating sites early in the season mid-April to early June, and feed on seedlings right as they are emerging, usually killing them. Then, their larvae feed on the roots of the host plants. As they grow into adults by mid-July to September, the beetles will once again feed on the leaves, vines and fruit of plants that survive, leaving deep marks in the rind.
Cucumber beetles hold another threat too. They can carry bacterial diseases and viruses from plant to plant, such as bacterial wilt. Adult striped cucumber beetles are about ¼ inch long and have a yellow-and-black striped abdomen and a dark-colored head and antennae. Spotted cucumber beetles are the same length but have 12 black spots on a yellow abdomen. The larvae are worm-like, white, dark-headed, and have three pairs of legs on the thorax.
While cucumber beetle larvae feed on cucurbit roots, adult feeding is more damaging to the crop. Adults feed on leaves and can stunt plant growth. Look for holes and yellowing and wilting leaves. Feeding on flowers can reduce fruit production and direct feeding on fruits cause unattractive scars and pock marks on the fruit, too. Often, the cucumber beetles alone will not kill the plants or cause major damage, but the spread of disease will. Feeding by adult cucumber beetles can spread bacterial wilt disease among cucurbit plants, even when population density is low. Adult cucumber beetles overwinter in weeds, garden debris and woody areas. The diseases they carry can also overwinter internally, and can be passed onto plants the next spring through fecal matter.
What you need to do is inspect newly planted cucurbit plants for the presence of this beetle and be watchful when plants are seedlings. This year, I have used yellow sticky traps to catch cucumber beetles. Few insecticides can be used on cucurbit plants because they are very sensitive. They would need to be used when plants are just beginning to emerge through the soil. Please contact the University of Kentucky Extension office for a list of approved insecticides for your area. Folklore published in The 1963 Old Farmer's Almanac suggests that nasturtiums and wood ashes are effective against cucumber beetles.
For the future, there are some things you can do. If you till your garden in the late fall, you will expose cucumber beetles hiding there to harsh winter conditions and reduce their populations next year. Remove all debris after fall harvest to reduce overwintering habitat. Rotate crops so cucurbit crops are not planted directly into soils containing overwintering populations. Transplanting young plants rather than direct seeding can protect vulnerable seedlings from damage. Natural predators include beneficial insect like braconid wasps, some nematodes and soldier beetles. This year I have learned about some beneficial insects that has helped. I have watched the beneficial insects and have been satisfied. Happy Gardening!!