For Release April 9, 2002

AGRI-VIEWS
by Chuck Otte, Geary County Extension Agent

Diseases are a difficult concept to understand. Many people barely understand diseases in themselves. When they don’t feel well, they go to their doctor who will sometimes prescribe some medication and then the patient gets better and all is well. Unfortunately, life isn’t so simple for plant diseases. When you get sick, you feel bad, you have symptoms and hopefully you get over the affliction and then you feel better. In essence, you are healed. When a plant gets a disease, it never really becomes healed. And that seems to be a difficult concept for many homeowners to grasp.

Let’s take an apple tree. It is springtime, the blossoms are open and a spring shower causes the Cedar Apple Rust spores to release from the galls on the cedar trees. One of these spores lands on a wet apple leaf and within a few hours the spore has infected that particular apple leaf. Eventually the infection on the leaf will grow to a spot about a half inch across. It won’t spread throughout the apple plant, it’ll just affect the spot on the leaf that was infected. If several infection periods occur a tree could end up with five or six disease spots on every leaf.

At that point of time, a few hours after the spore landed on the leaf, there is nothing that the plant, or you the homeowner can do. That infection has occurred and it will run its cycle. You can not spray anything on the plant to kill the disease. The only way to prevent the infection is to plant a resistant apple variety or apply a fungicide prior to an infection event to protect the leaf. You are essentially attempting to vaccinate each leaf to protect it.

There are probably twenty to thirty plant diseases that I will encounter in the yard and garden every year, and another dozen or so in crop plants. Many of the lawn and garden diseases are a nuisance or an annoyance. They seldom do serious damage to the plant or vegetable/fruit. A disease may diminish the appearance of a lawn or ornamental plant, but it is seldom fatal, with a few noted exceptions.

The most important step in disease prevention is proper management of the plant and its environment. If you select the right plant for your location and then keep it in a healthy state, you will have fewer disease and insect problems. Many homeowners contact me for a recommendation of a fungicide to "cure" a disease. The problem is that the disease is the symptom of a management problem.

Now the two "biggies": brown patch in yards and septoria leaf blight in tomatoes. Once either of these diseases get started on your plants, it is going to be very difficult to control with a fungicide. You may feel better, but it won’t change much. The disease will run its course, the plant will not die, but it won’t be pretty for a while either!

The first step is to keep the leaves as dry as possible. With lawns, water early in the morning. With tomatoes, don’t use a sprinkler. Lawns need to be planted to a brown patch resistant variety, then mowed high, regularly and keep the stand vigorous.

Tomatoes need to planted far enough apart to allow good air movement. If you are serious about having blight free leaves, you need to start spraying before the disease shows up and then remove, immediately, any leaves showing infection. This will help slow the spread.

Plants aren’t people. You don’t cure their diseases. You try to keep the disease from getting started or limit the spread of the disease if it starts. And when it is all said and done, you can probably do far more good with improved management than you can with an arsenal full of fungicide!

-30-

Return to Agri-Views Home Page

Return to Ag Home Page