A Greener View by Jeff Rugg

Q: I was told by a neighbor that we were going to have lots more insects in our yards this year and that he was applying a preventative and that I should do it, too. He didn't say how he knew there would be lots more insects. I am wondering what you think about applying a preventative for the potential insects.

A: No matter where you live, there is someone predicting that some kind of a pest is going to wreak havoc on your lawn, trees or crops. As a general rule, it makes better headlines to say there is some kind of problem or disaster about to happen rather than saying nothing much is about to happen. Another general rule is that the way to sell many garden products is to have them fill the need of preventing or curing an impending problem. No problem, no sales.

A final general rule that helps support the other two rules is that every year, all of our insects and diseases will be around your property at some population level. It doesn't matter if they occur at an average to low level; you will notice more of them if there were a previous headline announcing their presence. And at the same time, if anyone used a preventative treatment, they will assume it worked, even when it had no influence whatsoever.

How successful is the prediction of high levels of insects or diseases? About as successful as long-term predictions of the weather. We know in general terms that the weather will be warm in the summer, but predicting the number of days over a specific temperature is more difficult. The insects will be around this summer, but how many is hard to predict in advance. Just like rainfall totals vary widely within a short distance, insect populations can also vary within a short distance.

The weather actually has a lot to do with the population levels of most insects and diseases and the health of plants. It influences the ability of these problems to grow and it influences the plant's ability to resist the problems.

If you live in a year-round warm climate, the insects, insect predators, plant diseases and the plants themselves will all grow year round and keep one another in balance. In warm climates, most insect populations only change small amounts over time as predators, diseases and other factors keep them in check.

On the other hand, if you live in a climate that has frozen winters, everything is dormant for a while. In these climates, insect populations typically start as eggs or over-wintering larvae in the spring. Often, these kinds of insects have a starting temperature of around 50 degrees. Below the starting temperature, there is no growth. For each hour of the day that is above their preferred temperature, they grow. A few warm days in a row and they will grow rapidly, and if it is cool, they slow down.

Most cold-climate plants have a starting temperature in the upper 30s or 40s. If it is a cool spring, both the insects and plants will have slower growth and come out late. For instance, this coincidental timing keeps the insects that need flowers coming out around the time the plants are in bloom.

The timing is not exact, which helps both plant and insect populations stay in balance. A cool spring allows plants to grow faster than the insects so that the plants do better and there are fewer insect problems. In warmer springs, the insects are out in droves before the plants so that the insects can keep the plant populations in check and insecticide sales high.

Other factors enter into the population balance equation, such as rainy weather that promotes fungal diseases that can harm plants and kill insects. Dry weather harms plants and desiccates insects. If your area is too wet or too dry, the insect populations will be lower and you may not need to spray.

Let's start from the viewpoint that last year, your insect population level was high. That probably means that the predator population grew. It probably also means that more people used some kind of treatment to control the insects last year, thus reducing the population. Was there enough cold weather for a long enough period to reduce the population last winter? Animal populations always go up and down, so a high level one year is not a predictor of high levels the next year, even without man's intervention.

Every location has some pest problems that rear their ugly heads every year and some pests that have a regular pattern of showing up every few years. Some of these pests are native, and some have been introduced. Other introduced pests are in nearby areas and are headed our way. Just because an insect is around every year doesn't mean it needs to be controlled in any year.

What should you do? In the vast majority of cases, all you should do is monitor your plants. Make it a habit to walk around your whole property every week. Get to know your landscape. Look at the trees, shrubs and flowers. Stop to smell the roses. The more familiar you are with your plants, the better you will know when one of them doesn't look right.

When you see a plant that looks different, start the diagnosis process. Think about the past week or two and try to figure out what has changed. Does the plant need water, or has it received too much water? Look for insect or disease signs and symptoms. A sign is actually seeing the pest or maybe something it left behind. A symptom is the plant's reaction to the problem. Compare the healthy plant parts to the sick or damaged plant parts.

Is there enough damage to be concerned about? Is the damage happening slowly or quickly? If you can't figure it out, get help because if you can't make the correct diagnosis, you cannot safely or properly treat the problem. Bring one healthy and one sick sample into your local help desk at the Extension Office and have a Master Gardener take a look at it.

Every pest has a pattern of damage that it will cause. Sometimes, the pest only develops on a few kinds of plants or only one family of plants, while occasionally a pest will infest or infect many plants. If you have a plant susceptible to a particular problem, then you need to monitor at the proper times to see if the population level of the pest increases to a point where it is in the best interest of the plant to spend the money on a treatment.

In a few cases where the problem occurs every year at a treatable level, a pre-emptive treatment may be the best solution, but this is usually not the case.

E-mail questions to Jeff Rugg, Kendall County unit educator, University of Illinois Extension at jrugg@uiuc.edu. To find out more about Jeff Rugg and read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate website at www.creators.com.

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