Stress Encourages Pest Problems
It is generally true that when cucumber beetles attack a plant in sufficient numbers for you to begin to see damage, then it is very likely that the plant was experiencing some degree of stress BEFORE the beetles appeared. Pest insects prefer to go after weakened plants that are struggling and lack vigor for some reason. Researchers are examining the effects on insects of glutathione, a chemical produced by stressed plants, and they have found that glutathione is actually beneficial for certain harmful insects - It aids their reproduction, growth, and may even bolster their ability to resist pesticides.
Some Causes Of Plant Stress
After you deal with the immediate beetle problem, try to figure out what might be causing the affected plant to be vulnerable to pest attack. Some causes of plant stress include:
· Lack of sufficient sunlight or water (or, too much water causing soggy soil)
· Inappropriate plants for the climate or local conditions
· Excessive use of nitrogen-rich fertilizer, which encourages too much leafy plant growth--perfect beetle food!
· Natural aging (senescence) and deterioration of the plant
· Drastic pruning of trees or shrubs, which encourages growth of succulent suckers (side shoots)
· Shock resulting from transplanting, which makes plants vulnerable to beetles for a few days to a week
· A temporary springtime superabundance of cucumber beetles that later levels off when natural enemies catch up.
In the end, you may never figure out what caused the plant’s stress, but it’s always good to think about it when cucumber beetles show up. If you eliminate the stress in the plant, the beetles are hardly ever expected to come back!
Other Conditions That Foster Cucumber Beetles
Cucumber beetle populations normally are controlled by various kinds of birds and beneficial insects living in healthy home landscapes that host a diversity of plants and wildlife. However, where there has been frequent use of broad-spectrum insecticides which kill insects indiscriminately, nature’s first line of defense--the beneficial insects--is eliminated along with the pest insects. Because pest populations rebound faster than those of their natural enemies, the beetles can reestablish themselves unmolested.