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WICHE: Learn to describe plant problems accurately

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By Jeneen Wiche

We all seek advice from experts and describing what ails us or our plants it key in determining what’s really going on; and not everyone understands the nomenclature of symptoms caused by insect and disease problems.

“I’ve got this thing on my whatcha-ma-call-it” won’t get you very far. We need to know how to describe the “things” that we find on our plant material so a proper diagnosis and treatment can follow. Knowing a plants history and environment helps, too.

There are several different scenarios that can threaten our plants. Non-living, non-infectious diseases or “disorders” are linked to environmental circumstances. A late spring freeze, flood, drought or excessive heat are all factors in causing non-infectious disorders that effect plants adversely.

There’s a ripple effect with some of these things because these disorders can lead to infectious diseases or insect infestation once a plant is in a weakened state. A frost crack in the cambium layer of a tree because of a late spring freeze, for example, allows for the fire-blight to spread quickly; or dead wood from an ice storm last year invites borers this year.

Living or infectious diseases involve parasitic plants, bacteria, fungi, viruses or nematodes.

For example, white pine root decline is a living, infectious disease caused by nematodes in the soil that slowly attack the root system. You will notice a white film at the base of the pine’s trunk when it is suffering from white pine root decline.

There is also a condition called white pine decline (note that root is omitted here) which is a non-living, non-infectious disorder caused by environmental circumstances that weaken the tree overall and cause eventual death. 

The white pine example illustrates how paying attention to the details of the problem make a difference in how one should proceed.

In one circumstance you could replace the declining white pine (and improve the environmental conditions). In the case of white pine root decline, the soil is infected, so it is likely that a second white pine in the same location would see the same demise.

Karen Rane and Peggy Sellers, plant disease and pest diagnosticians at Purdue University, define the following common symptoms that plague our landscape plants. Hopefully understanding some of the following terms will help us better describe some of the disappointments we’ll likely face in the New Year.

Recognizing symptoms early on also help us stop the spread of infectious diseases and allow us to treat our plants in a more timely fashion.

Their list:

§       Leaf spots are small discolored areas on the plant’s foliage. Rosarians are quite familiar with leaf spot on their roses.

§       Blight causes larger, dead areas on leaves, shoots or flowers of a plant. Stunting is the abnormally small growth of a plant or plant part.

§       Chlorosis is when normally green tissues appear yellowish-green in color.

§       Marginal necrosis is a symptom where the edges, or margins, of a plant’s leaves turn brown due to dead tissue. Houseplants suffer from this during the winter months because of the low humidity in our homes.

§       Distortion is the twisting or abnormal formation of leaves and new shoots. Aphids, mites and thrips cause this to happen to new daylily growth if the plant is infected, for example.

§       Wilt, of course, is a flaccid, limp condition of leaves or non-woody shoots. Wilt generally occurs from insufficient water, but can also be brought on by too much water or living diseases. The dreaded clematis wilt is caused by nematodes.

§       Cankers are localized, often sunken, dead areas on a twig branch or stem, with ooze sometimes associated!

§       Gall is an abnormal swelling of a portion of a branch, root, or bud.

§       Witches’ broom is the symptom where twig growth appears distorted and stunted forming a broom-like mass of twigs. Once witches’ broom has appeared it is likely to stick around in the vascular system of the plant.