Managing These Cool Conditions

In reference to a newspaper article last week, I would say the weatherman must have seen his shadow. By the sounds of it, we’re in for six more weeks of bad weather. Is this deja vu? Haven’t we been here before? Weren’t the spring and summer of 1997 cool, wet and downright uncooperative?

Before we get too discouraged, there are some positives to wet, cool conditions. Because the rain has been steady and not too hard, the soil has been able to absorb it slowly and deeply. Trees and shrubs are already responding to this excess moisture with lots of new growth and an abundance of healthy leaves. When the hot, dry summer arrives (hopefully this isn’t making assumptions), their roots will be able to draw from the extra reserves.

Cool weather is very favorable to flowers, as long as the rain doesn’t beat them down. Flowers seem to be lasting for weeks, whereas in hot weather they can be gone in a few days.

Everything is green and lush, including the pasture in our front yard we used to call a lawn.

The water bill is down, the air conditioner is off and we’ve experienced some of the most glorious rainbows.

However, these conditions definitely have their downsides. Plants such as tomatoes, peppers, squash and corn are just sitting. They didn’t bargain for this kind of treatment. And, like Randy Johnson, until the terms are met on their contract, they aren’t budging. If possible, cover these heat lovers with clear plastic during the day. What heat is collected under the plastic will keep plants warmer during the cold night hours.

The cold ground causes problems throughout the yard. In order for nitrogen to be activated, the soil temperature should be 45 degrees or above. Some soils are pushing the bottom number, especially the heavier, denser soils such as clay and clay-loam. Plants are suffering from lack of nitrogen as seen by their yellowing leaves.

Cool, wet days bring more than cool air and cold ground. Along with a herd of insects, we may be seeing a plethora of diseases. Note, the operative word here is MAY be seeing. Keep an eye out for these culprits: powdery mildew, fungus spots and bacterial blights.

Powdery mildew is recognized by the white to gray felt on leaves, buds or flowers. It usually develops when the days are warm and the nights cool. It flourishes in low areas where it’s damp, with little or no air circulation.

Once mildew gets its foot in the door, it’s very difficult to eradicate. There are fungicides on the market containing the active ingredient of either sulfur or daconil which do a fair job. In the case of powdery mildew, prevention is always preferable to eradication. You might try spraying a solution of soda and water mix 1 tablespoon baking soda to 1 gallon of water along with 1 teaspoon fine horticultural oil. Or try spraying susceptible plants with an antitranspirant such as Wilt-Pruf. There has been some research using this material and it seems to show promise in preventing mildew.

Fungus leaf spots are obvious spots with distinctive margins. You get a group of them together and they may form one large irregular area referred to as a blotch or blight. You may have encountered a few of these villains in the past - late blight on tomatoes, blackspot on roses, anthrancnose on dogwoods and a host of others.

Leaf spots are the most common of the diseases, favored by wet weather, high humidity and splashing rain.

There are many fungicides that do an adequate job of controlling most leaf spots. However, good sanitation practices are the best means of getting a handle on these diseases. Always rake up or remove infected leaves from the plants in the fall. Rotate crops whenever possible.

Plant disease-resistant plants. Always use clean seed.

Good cultural practices also help control leaf spot. Try to keep plants healthy by planting them in the right place (sun, shade, rich soil, moist soil etc.), fertilize only when necessary (fertilizing too often can be just as harmful as fertilizing too little) and know the plant’s water requirements. Try not to water in the late evening. Are you listening, Mother Nature?

Fireblight seems to prefer members of the rose family - apple, pear, rose, etc. This disease is easily recognized. The tips of young shoots often bend to form “shepherd crooks.” Leaves turn brown, wilt and hang from twigs that look like they have been burned. The bacteria overwinters in cankers on the branches and trunks as well as on the buds. It is spread by rain, birds, insects and pruning tools.

The only method for controlling this disease is by pruning it out. Pruning tools must be sterilized between each cut. After removing an infected branch or twig, dip the shears in a solution of bleach (1 part bleach to 9 parts water). Try to cut back into at least 4 inches of clean, disease-free wood. This may not always seem possible, but if any bacteria is left, the disease will recur. Once fireblight enters the trunk, the plant is as good as gone.

Before rushing out with an arsenal of sprays, always determine what you are dealing with first. If you aren’t familiar with diseases (they can be difficult to diagnose, even for the professional), please seek help.

Take a sample of your problem to the WSU Master Gardeners at 222 N. Havana, Monday through Thursday from 8 a.m.-1 p.m., or to a knowledgeable nursery.

Your sample has to be a twig that includes healthy leaves as well as diseased leaves. The disease can’t be diagnosed solely within the dead material. And as a reminder, if you are taking samples into nurseries, please place your sample in a baggy of some sort. You don’t want to take a chance of infecting nursery stock. Thanks.