At your local Cooperative Extension Service Office in Juneau we get daily inquiries about sick or insect-ridden plants. Most often the gardener wants to know what kind of spray or chemical is needed to treat the problem. It is all too easy for us to give the quick answer that the customer is looking for. Spray chemical X for insect Y, chemical Q for disease Z. Everything will be OK. All is right with the world. But is it?
In the 1960s, in response to environmental and health problems caused by indiscriminate use of pesticides in buildings, yards and on farms, scientists developed a concept known as Integrated Pest Management. Horticultural IPM stresses monitoring of insect problems, early detection of disease, horticultural practices and use of the least toxic chemical agents.
Consider the patient talking to the doctor. The patient is run-down, tired all the time, depressed. The patient wants the doctor to prescribe a pill to make him feel happier, vigorous and healthy. On further investigation the doctor finds out the patient lives on a diet of junk food, never exercises and only gets four hours of sleep a night. You might say the patient has an unhealthy lifestyle. He doesn't need a pill or a shot, he needs to change how he eats, drinks, exercises and rests.
So let's examine our plant's lifestyle issues. When we are called on to examine a plant that is having problems, we try to look at its lifestyle in terms of four environmental factors. All plants need the same things, the four elements of the ancient philosophers: Earth (soil), fire (sunlight), air, and water. Each plant needs a combination of these four factors in a proportion that best mimics the environment where it evolved to live. We want to look at the plant and consider the differences between the environment to which it is best adapted and the environment where we are trying to grow it. Most plants in our yards and gardens did not evolve in the North Pacific rain forest. Unless you stick to growing devils club and skunk cabbage there are going to be some differences between the plants' native environment and the environment where you are trying to grow them.
Questions to ask are: Where did the plant come from? What are the conditions in its native habitat? Where is it grown commercially? Then look at how local conditions vary from the native climate.
For instance, apples come from central Asia. They are adapted to a semi-arid climate with hot summers and cold winters. As a result they can handle our cold snaps, but the fruit does not "color up" as well because of the lack of ample sunshine in the summer.
The qualities of air we want to consider are temperature and humidity. Does the plant grow best in warm air or cold? Does it like humid or dry air?
Light is necessary to all plants. Too much light or lack of light for photosynthesis is rarely a problem. But sunshine does affect the amount of water in the soil or the amount of humidity in the air and these really can affect our plant's health.
When we look at soil we want to know if it is providing the plant with enough nutrients, air for the roots, and water. Healthy soil rarely lacks nutrients and holds enough water and air for optimal plant growth. Exceptions occur when nutrients are being removed from the soil faster than they can be regenerated. This happens when we harvest plants year after year - as occurs on a farm - or when nutrients are being leached out of the soil by water percolating through it. Soil pH or acidity also can affect nutrient availability.
Does the plant need a lot of water or does it like to stay on the dry side? Often a plant from a dry climate is susceptible to disease when it is grown in our moist, humid climate. Water - or, at least, the lack of it - would hardly seem like a problem in Southeast Alaska. But our soils can dry out quickly. On a recent walk on a sunny afternoon in downtown Juneau, I was quite surprised to see soil around some landscape trees completely dried out, even though that morning we had the usual clouds and drizzling rain. The soil had dried out in the space of just a few hours.
Another aspect of the plant's environment we look at is sanitation. Just as we try to keep our homes clean to avoid creating a breeding ground for disease, we want to clean up breeding grounds for plant problems. Get rid of brush piles and rotten wood. Do a fall cleanup, removing dead plants, crop residues and fallen leaves. Thin out dead branches from trees and shrubs to increase air circulation in the canopy.
Use a wide variety of plants in the landscape. Experimenting with new plants can be fun and educational. If one plant does well and another does not, we can treat it as a learning experience rather than becoming discouraged. Planting inexpensive small trees is preferable to buying large expensive ones. If planted in a good spot with proper care, the tree will grow more quickly than you might expect. If it doesn't, then at least you didn't spend a fortune on it. Look around the neighborhood to see what plants do well. If you see a plant growing well, look to see what the site characteristics are with respect to our four factors: light, soil, air, water.
In caring for the plant, the best thing to do is to put it in a situation where it feels comfortable and at home. Do this by researching the climate and conditions of the plant's native habitat, with attention to the basics of soil, air, light and water. Remember also the differences between a plant and an animal. An animal can move to a more comfortable location if it needs to. Unlike a pet or a child, a plant cannot come to us and complain about its food or living conditions. We must go to the plant and take a hard look at the lifestyle choices we have made for it and decide what is best for it. Do this, and the plant will better be able to fend for itself and fight off the pests and diseases on its own.
Just as a patient may need to use powerful prescription drugs to treat a severe illness, we sometimes do turn to chemical treatments to save our plants. Just as you should not take a prescription drug without a doctor's recommendation, you should get advice before using chemical pesticides. This advice, (unlike the doctor's!) is available free of charge from your local nursery, garden center and, of course, your Cooperative Extension Service.
Tom Heutte is a pest management technician with the University of Alaska Cooperative Extension Service.