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.
From: Edna M Weigel <email@example.com>
To: firstname.lastname@example.org <email@example.com>
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
> 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
> 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
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