Cucumber Beetles

This week I had a conversation with a newcomer to Williamson County who was interested in plant recommendations for our area and lawncare guidelines.  I have those conversations fairly often, and usually some of the questions are focused on the weather and how different it is in Texas.  Lately, I have to laugh and say that it has been a weird few years, even for Texas!

The weather already feels like spring, and we are just in the beginning of March.  I love warm weather, and I am already enjoying nice days in the garden.  I did get a dose of reality this weekend when I came across three spotted cucumber beetles crawling around the garden.  I’m not ready to see bugs in the garden, but the warm weather is bringing them early!

The spotted cucumber beetle that I found in the garden is the very same pest as the Southern corn rootworm.  As an adult, the spotted cucumber beetle is ¼ inch long and yellow-green with 12 black spots, a black head and antennae.  The larva (rootworm) is cream colored and three-quarters of an inch long.  It has a brown head capsule and three pairs of short legs.

Adult beetles overwinter and emerge in the spring to feed on grass and weeds.  They are a serious pest to corn and sorghum because they get into the fields soon after plants emerge and lay their eggs in the soil.  Eggs hatch after five to 11 days and begin to feed on the roots of corn or sorghum.  Sometimes they tunnel directly into the stalk and stunt the growth of the plant or kill it.

Larvae go through three stages in 10 to 15 days before pupating.  They emerge as adults after 5 to 12 days.  Adult cucumber beetles feed on the leaves and flowers of many ornamentals and vegetable plants, particularly cucurbits and beans.

Spotted cucumber beetles cause minimal damage unless the population numbers get high.  They can spread diseases such as bacterial wilt and squash mosaic virus.  Two ways to prevent damage in the garden is to use trellises to get plants off the ground and mulch heavily around plants.  Purchase squash plants that are resistant to mosaic virus.

In case of a pest outbreak, treatment options are available.  Hot pepper wax or neem are examples of a least-toxic repellants or insecticides.  Products containing bifenthrin would also treat the beetles.

I am hoping for a beautiful spring with just the right amount of rain and very few pesky bugs.  Who am I kidding, this is Texas! For more lawn and garden information, contact Kate Whitney-Hajda, Horticulturist at the Williamson County AgriLife Extension Office, at 512-943-3300.

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