Cucumber beetles are one of the most common garden pests in North America. They cause damage to plants by feeding on fruits and vegetables, causing wilting or browning of leaves and stems, stunted growth, loss of fruit production and other problems. These insects can be controlled with pesticides but they pose a major problem when there is no natural predator present to control them.
The striped cucumber beetle (Dendroctonus ponderosae) is a serious pest of cucurbits. It causes severe damage to cucurbit crops such as cantaloupes, eggplants, zucchini and watermelons.
There have been several reports of these beetles attacking commercial varieties of cucumbers in California and Florida. The striped cucumber beetle is not native to the United States. It was introduced into the U.S. in the late 1800’s and it has spread rapidly throughout the country since then.
In addition to its destructive nature, striped cucumber beetles can transmit diseases to susceptible cucurbits if they feed upon infected plants. One of these plant diseases known as bacterial wilt is caused by a species of the genus Erwinia.
This disease is most serious in cantaloupes but it has also been found on cucumbers, watermelons and other cucurbits.
WHAT SPRAYS AND POWDERS KILL CUCUMBER BEETLES?
Sevin dust can be used to kill cucumber beetles but it must be applied directly onto the insect to be effective. Dust should be applied to the outer surface of the plant and then the beetles will ingest it when they feed on the plant. Since the dust can also be poisonous to humans, it is recommended that you wear gloves when applying it.
A much safer (and more effective) way to kill cucumber beetles is to spray infested plants with a ready-to-use insecticide such as Cyonara (which contains cyfluthrin).
As mentioned earlier, natural predators can play an important role in controlling the population of cucumber beetles. Since no such natural predators exist in most areas of the United States, gardeners should seek other means of controlling the pest population.
Sevin dust applied to the outer surface of plants is a good start but it is not nearly as effective as using a pesticide such as Cyonara.
READY-TO-USE SPRAY INSECTS
Many home gardeners choose to use pest repellents rather than pesticides. These products are generally less effective than pesticides but they are much safer for humans and pets.
Unfortunately, some pests (such as the striped cucumber beetle) do not respond very well to most repellents.
Some of the most popular and effective repellents are those that contain the active ingredient of oil of lemon eucalyptus. Products such as these can be sprayed directly on to plants to repel a variety of common pests including striped cucumber beetles.
Most of these products should be reapplied every 7-10 days in order to sustain their effectiveness.
In addition to repellents, many gardeners also choose to plant “companion plants” in their gardens. Companion plants help to protect plants from pests by acting as a physical barrier (most of the time) or by releasing natural toxins that deters the insects from landing on them in the first place.
Here are a few examples of common companion plants and the pests that they are known to repel:
Catnip: flea beetles, cabbage looper, tomato hornworm
Lavender: spider mites
Chives: aphids, thrips, spider mites
Marigold: various insects
Bee balm: thrips, whiteflies
Rosemary: carrot fly, spider mites
Nasturtium: potato beetle, aphids
Roses: Japanese beetles
This is by no means an extensive list. There are many, many more.
Be creative! Many gardeners have had success planting garlic around their tomato plants to keep the dreaded tomato hornworm from laying eggs on the plants. It’s also important to remember that companion plants only repel or kill pests, they don’t kill them. If you have a serious pest problem you will still need to use pesticides (in addition to companion plants) in order to achieve control.
WHAT ABOUT INSECTICIDES?
Insecticides are chemicals used to kill insects. There are many different kinds of insecticides that are used to kill a wide variety of pests. It is beyond the scope of this article to discuss all of the different types of insecticides available (there are over 2,200 registered for use in the U.S. by the EPA). When using any type of pesticide, you must always follow the label instructions. Failure to do so can result in harm to the plant you are attempting to protect and even harm to yourself or other animals.
Most of the insecticides that you will find at your local big box store (Home Depot, Lowes, etc.) fall into the broad category of pesticides called “organophosphates”.
Most of these products contain derivatives of nerve gas which is why they kill insects so quickly. Most of these products cause paralysis or death in insects within minutes of contact.
Sources & references used in this article:
Affinity of spotted cucumber beetle (Coleoptera: Chrysomelidae) larvae to cucurbitacins by CJ Deheer, DW Tallamy – Environmental entomology, 1991 – academic.oup.com
Comparison of insecticide use programs for managing the striped cucumber beetle (Coleoptera: Chrysomelidae) in muskmelon by GE Brust, RE Foster, WG Buhler – Journal of economic …, 1996 – academic.oup.com
Effects of two triterpenoids from neem on feeding by cucumber beetles (Coleoptera: Chrysomelidae) by DK Reed, JD Warthen Jr, EC Uebel… – Journal of Economic …, 1982 – academic.oup.com
Cucumber beetle antifeedants: laboratory screening of natural products by DK Reed – 1981 – books.google.com
Effects of a black plastic mulch on the soil and plant dispersal of cucumber beetles, Acalymma vittatum (F.) and Diabrotica undecimpunctata howardi Barber … by S Necibi, BA Barrett, JW Johnson – J. Agric. Entomol, 1992 – scentsoc.org
Effect of buckwheat as a flowering border on populations of cucumber beetles and their natural enemies in cucumber and squash by JO Platt, JS Caldwell, LT Kok – Crop Protection, 1999 – Elsevier
Organic management of cucumber beetles in watermelon and muskmelon production by GR Cline, JD Sedlacek, SL Hillman, SK Parker… – …, 2008 – journals.ashs.org
Development of summer squash seedlings damaged by striped and spotted cucumber beetles (Coleoptera: Chrysomelidae) by MJ Brewer, RN Story, VL Wright – Journal of economic …, 1987 – academic.oup.com
Cucurbitacins and predation of the spotted cucumber beetle, Diabrotica undecimpunctata howardi by F Gould, A Massey – Entomologia experimentalis et applicata, 1984 – Wiley Online Library