From kstoner@caes.state.ct.us Tue Aug 3 12:30:21 1999 Date: Tue, 3 Aug 1999 11:14:15 -0400 From: Kimberly Stoner To: sanet-mg@amani.ces.ncsu.edu, Edna M Weigel Subject: Re: Corn root worm/cucumber beetle and jimson weed [ The following text is in the "iso-8859-1" character set. ] [ Your display is set for the "US-ASCII" character set. ] [ Some characters may be displayed incorrectly. ] Dear Edna and Sanet: When I took my first entomology course, the professor told me that it was important to be able to answer general entomology questions outside my specialty because once I identified myself as an entomologist, there would always be people in need of insect identification and advice. I think this is the best advice I ever received in my professional career. The confusion about different species of insects is pervasive. There are just not enough entomologists around for people to consult! Diatribe over. I think your post is about at least three different species of beetles. Assuming that you are in the east or midwest of the U.S. (There are different species on the west coast, and the whole species complex is different elsewhere in the world.), the most important beetle pest of cucurbits is the striped cucumber beetle, Acalymma vittatum. This beetle overwinters as an adult, typically appears soon after the plants germinate, lays its eggs at the base of cucurbit plants, where its larvae develop on the roots, and then the adults feed again on cucurbit leaves, flowers, and fruit. It also transmits bacterial wilt. There are several species of corn rootworms, one of which, Diabrotica undecimpunctata howardi, is known as both the southern corn rootworm and the spotted cucumber beetle. This beetle, like other corn rootworms, overwinters in the egg stage. The larvae develop on roots, but have a wider host range than other corn rootworm beetles or the striped cucumber beetle. I know they develop on corn roots, cucurbit roots, bean roots, and on a roots of some other grasses. Probably more than that. Because they overwinter as eggs, they appear on cucurbit plants later than the striped cucumber beetle. They feed on flowers, fruit, and leaves, and they can also transmit bacterial wilt disease. They are not as severe a pest on cucurbits in Connecticut as striped cucumber beetles, though. I suspect that the beetles on jimson weed were another beetle entirely. (Both of these beetles feed on pollen of many flowers, so they might have been feeding inside the flowers, but they wouldn't have been eating the leaves of jimson weed.) My guess would be that the beetles on jimson weed were the three-lined potato beetle, Lema trilineata. These beetles are striped in a pattern similar to the striped cucumber beetle. If you turn over the beetles and look at the body from the underside, three-lined potato beetles are reddish brown, while striped cucumber beetles are black. (The corn rootworm beetles, including the western corn rootworm, which is also often confused with striped cucumber beetles, have yellow abdomens.) Since corn rootworms spend the winter as eggs, crop rotation is an effective control. The larvae are believed to be able to travel 1 meter, at most, in the soil. There are various subtle problems with crop rotation that make it sometimes fail when corn and soybeans are grown in alternating years on a large scale, but in general, rotating corn with anything else should control rootworms to a substantial degree, as long as there are not too many grassy weeds that are also rootworm host plants. Kim Stoner -----Original Message----- From: Edna M Weigel To: sanet-mg@amani.ces.ncsu.edu Date: Monday, August 02, 1999 12:18 PM Subject: Corn root worm/cucumber beetle and jimson weed > I was startled recently to read that corn root worms grow up to >become cucumber beetles. I assume the reference was for either striped >cucumber beetle (genus Acalymma) or spotted cucumber beetle (genus >Diabrotica). This brings up a question about crop rotation. > Last year, I noticed jimson weed (Datura) was a "great" trap crop >for cucumber beetles (I think they were striped, but I'm not sure and I >can't find any to look at right now). I let one specimen grow in my >garden. By mid summer that jimson weed's leaves were riddled with holes >but it was taking over a lot more space than I intended. Still, I >enjoyed the lovely aromatic flowers and my cucurbits had not a beetle on >them. > This year, I planted corn and beans in that area and have been >grumbling about jimson weed ever since. Not only did I pull out jillions >of jimson weed seedlings, but I've been digging ever deeper into the corn >patch trying to get rid of the tuber that keeps putting up shoots. >Believe me, I'll limit jimson weed to the wild flower portion of the >property in the future. > Meanwhile, my corn (desert adapted--open pollinated) isn't >showing any signs of losing root growth. Some blew almost down, but that >was in a tremendous rain storm that even broke off lots of the native >wild flowers. > I conclude that it isn't a good idea to grow corn very close to >anything (jimson weed, wild gourds, cucumbers, etc.) that attracts >cucumber beetles, but I wonder how much distance and how long in the >rotation is appropriate. Or is corn root worm a problem only in large >mono cultures of hybrid corn that will be mechanically harvested? I'd be >interested in reactions from gardeners, corn growers, or entomologists. >Regards, Edna Weigel > >___________________________________________________________________ >Get the Internet just the way you want it. >Free software, free e-mail, and free Internet access for a month! >Try Juno Web: http://dl.www.juno.com/dynoget/tagj. > >To Unsubscribe: Email majordomo@ces.ncsu.edu with the command >"unsubscribe sanet-mg". If you receive the digest format, use the command >"unsubscribe sanet-mg-digest". >To Subscribe to Digest: Email majordomo@ces.ncsu.edu with the command >"subscribe sanet-mg-digest". > >All messages to sanet-mg are archived at: >http://www.sare.org/san/htdocs/hypermail > To Unsubscribe: Email majordomo@ces.ncsu.edu with the command "unsubscribe sanet-mg". If you receive the digest format, use the command "unsubscribe sanet-mg-digest". To Subscribe to Digest: Email majordomo@ces.ncsu.edu with the command "subscribe sanet-mg-digest". 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