March 29, 2007 at 7:28 a.m.
During the summer they were doing what they do best, that was eating aphids in the fields and gardens. During the winter they were just crawling into our coffee cups.
The second bug of concern is the boxelder bug. We all remember how the walls and sidewalks were full of them last fall. As the weather turned cold they marched right through the foundations of old houses, such as mine. NOW, as the weather turns warmer they are everywhere. All we can do is vacuum them up and hope they will soon move outdoors.
A bug of much greater concern is the squash bug. I realize that writing about the squash bug at this time is not the proper time to do so. However, I have several gardeners who said that the squash bug destroyed their gardens last summer. I remember several gardeners coming to the plant clinic at the Extension Office last summer. They were all very frustrated at the damage done by the squash bug.
This bug is common throughout the United States. This bug will attack all members of the cucurbit family but are most common on pumpkins and squash. Their piercing, sucking mouthparts feed primarily on plant foliage. However, late in the season, squash bugs may also feed on fruit. The associated damage symptoms include wilting of leaves and ultimately result in leaves that appear black or dried out.
The squash bug can be misidentified as a stinkbug. Both insects look similar and have a distinct odor when crushed. However, the stinkbug is not a pest on cucurbits. The squash bug adults are about 5/8-inch long and about 1/3- inch wide. They are usually grey to black with the edge of abdomen having orange and brown stripes.
The young nymphs have a red head and legs with a green abdomen. However, as the nymphs age the red color will turn black. Eggs are 1/16 inches long and have a yellowish brown to brick red color. The eggs are laid individually in groups of about twelve on the underside of leaves. Each cluster is laid under leaves from spring to midsummer and will take one to two weeks to hatch.
Unmated adults over-winter and find shelter during the early fall. They emerge in the spring and fly into fields when plants begin to grow. Mating begins early in the spring and the females lay eggs until midsummer. It takes from 4 to 6 weeks for them to develop into adults.
Both the adults and the nymphs cause damage by sucking the nutrients from the leaves and disrupting the flow of water and nutrients, which causes the wilting. Before the wilting, yellow specks will develop on the foliage that eventually turns brown. It is important to determine what is causing the wilting. The striped cucumber beetle can spread bacterial wilt and if that is the reason for the wilt, the infected plant will continue to decline and die. By contrast, plants affected by the squash bug can recover if bugs are removed.
The squash bugs will also feed on the fruit, not just the foliage. The adult bug is very difficult to kill, so it's important to control them in a nymph stage. The threshold is reached when the average number of egg masses is greater than one egg mass per plant. Seedlings, new transplants, and flowering plants are the most critical growth stages to monitor. When plants look wilted, check under the leaves for the squash bug and eggs. If the threshold is exceeded, organic methods may need to be abandoned and insecticides considered.
While doing research for this article, I came across a recommended insecticide list from 1990, there were eight on the list but five of them were marked as restricted use. Since that list was developed, thioden has been taken off the shelves. This leaves only methoxycholor and carbaryl.
Our spring class series 'Garden Fever' has begun! Brochures are available on the website at www.extension.umn.edu/county/chisago or you can call the Extension office at 651-674-4417 to have one mailed to you. Many of the topics from our cancelled Gardening Bonanza are included in this series.
The class scheduled May 8 will cover the use of some common garden chemicals, as well as a discussion of the effectiveness of some often recommended 'home remedies' by Jeff Gillman from the University of MN.
A cutback in staffing has made it necessary for the Extension Office to limit hours of operation. As of the beginning of April, the office will be open Tuesdays and Thursdays. We would suggest that you call ahead to verify that the office is open before you stop by.