Garden Enemies

When you are dealing with living things such as plants, the problem of combating insects and diseases is inescapable. Evergreens are no exception to the rule. However, on the bright side of the picture the gardener can now approach this phase of upkeep with real encouragement, because of the more efficacious sprays and dusts which modern research has made available.

INSECTICIDES AND FUNGICIDES

introduction of all-purpose sprays and dusts has greatly simplified the task of controlling many of the troubles that attack plants. These also come in the form of aerosols. Besides eliminating the necessity of mixing the materials oneself, the question of combining chemicals that are com­patible is also taken care of. One of the several good all-purpose mixtures on the market contains malathion, ferbam or captan, and methoxychlor.

Regular applications of sprays or dusts will do much to hold in check the usual pests. Since the majority of the chemical preparations can be dangerous, it is important to keep them out of the reach of children and pets. In all instances the manufacturer's directions must be followed exactly, otherwise harm rather than good may result. Another important point to observe is to give the plant a thorough treatment. The undersides of the leaves, which are so often overlooked, require the same coverage as do the other parts of the plants. After spraying, discard any mixture that is left over, as it is likely to deteriorate rapidly after being diluted with water; next clean the sprayer thoroughly and promptly after each use. On the other hand, if a dust gun is used it requires no special after care, and the gun can be kept filled with the mixture in readiness for the next applica­tion. Dusting is an easy method of applying insecticides and fungicides; however, in most instances spraying gives better results. No matter which chemical is used, be sure to check on the temperature at which it is safe to apply without causing burning of the foliage. Phaltan, captan, and ferbam can be used even when the temperature is in the nineties. Except in special summer preparations, oil sprays should be applied only when the temper­ature is between 40 and 65° F. They are much more likely to damage evergreens than deciduous shrubs; therefore be sure that directions are followed precisely. Sulfur is also apt to burn the plants if it is used when the temperature is above 80° F.

When a spray is used it is a satisfaction to know that almost every modern spray material has a compound in it that has sticker-spreader properties; this will help to give protection against the loss of spray material during rainfalls; therefore one need not feel too much concern if a shower comes along soon after spraying. Ordinarily the coarser particles of the chemicals are washed off by the rain, but microscopic examinations have shown that a film of the finer particles still remains on the leaves. If the plants to be sprayed have exceedingly waxy leaves, then it is advisable to further increase the sticker quality by adding to the spray a few drops of one of the sticker-spreader preparations on the market.

Space limitation does not permit a thorough discussion of insects and diseases. A short list of some of the best insecticides and fungicides is given here. If a disease or insect infestation is not controllable by the usual means, it is then best to contact your County Agricultural Agent, or to write to the Department of Plant Pathology, or the Department of Ento­mology at your State Agricultural College for specific diagnosis and con­trol measures. There are several excellent books on plant troubles, some of which are: "Tree Maintenance," by P. P. Pirone; "The Plant Doctor," by Cynthia Westcott; and "The Gardener's A B C of Pest and Disease," by A. W. Dimock.

It should be borne in mind that there are numerous trade names for the same kind of material, consequently it is important to read the ingredients of a given preparation to make certain it contains the material you re­quire to combat the specific trouble. There is a group of official generic names for these chemicals, and it is these and not the trade names that are used when the state extension service gives recommendations. For example, ferbam is the generic name for ferric dimethyl dithiocarbamate; trade names of sprays containing this material include Fermate (Du Pont), Coromate (Corona), Ferberk (Berk), Karbam Black (Sherwin-Williams), etc.

Nicotine is a splendid preparation; it is extremely toxic, but effective for use against aphids, lace bugs, and in fact most insects that suck the juices out of the leaves. This kind of insect does not eat holes in the leaves but discolors them by removing the green coloring matter. Aphids can also cause serious galls on some evergreens. Nicotine activity depends a great deal on temperature, and an important shortcoming is its limited residual activity.

Chlordane is an excellent insecticide which is aimed against pests that live in the ground, such as the black vine weevil which causes severe injury especially to Yews, Hemlocks, Laurels, Rhododendrons, and Azaleas. This weevil can sometimes be detected by the crescent-shaped holes that it makes on the leaf or the margins of the needles, but a good deal of its damage is to the roots where the larvae feed. Chlordane is also efficacious in com­bating the strawberry root weevil and the rough strawberry weevil. In applying this insecticide it is dusted on the soil and then watered in, the lower branches should also be thoroughly covered with the dust. Other in­secticides that are used against weevils are Dieldrin, Aldrin, Heptachlor, and DDT.

DDT is one of the good insecticides in general use; it is efficacious in combating various beetles, caterpillars, White Pine weevil, Juniper web-worm, and Pine sawflies. The name of the latter is misleading, as they re­semble caterpillars—they are about 1 inch long and are usually yellow with black spots. The drawback to DDT is that it increases mites and some aphids, by killing some of their predatory enemies. This insecticide in combination with malathion will combat various leaf-eating insects.

Kelthane is highly useful for controlling mites. Of the various mites that attack plants, the spider mites are the most numerous. Some of these are the Box mite, Pacific mite, European red mite, Spruce mite, and red spider mite. Mites are among the enemies that suck out the chlorophyll (green coloring matter) from the foliage, causing the leaves to turn a sickly green, then yellow, and later brown. There are other kinds of mites which cause galls to form on the stems and the foliage. In addition to kelthane and malathion, other chemicals for controlling mites are Ovex, Aramite, and Dimite.

Lindane and malathion are effective sprays for use against lace bugs, leaf miners, aphids, and other pests. Leaf-miners are detected by the tracks they make by mining their way between the leaf surfaces.

Malathion is excellent in combating aphids, leaf miners, lace bugs, mites, and white flies, as well as other pests that draw out the green color from the foliage, leaving in their wake discolored marks. It is also efficacious as a summer spray for scales, those numerous motionless insects that adhere to the trunk and branches.

Bagworms are a menace and should be hand-picked and burned. They can be checked with malathion applied late in June before the bags have become large.

Methoxychlor is similar to DDT, but it has the advantage of being less toxic to mammals. In common with DDT it is directed particularly against leaf-eating insects.

Oil sprays, such as Volck, are used for scales, both the hard-shelled and soft-scale types (such as mealybugs). Oil should be used only as a dormant spray, and when the temperature is between 40 and 65° F. As previously mentioned, malathion can safely be applied during the growing season, but the plant coverage must be very thorough.

Rotenone attacks sucking insects, and it helps to control some of the leaf-eating pests. Rotenone and dusting Sulfur can be purchased already mixed. These make a relatively nontoxic combination, and serve the double purpose of an insecticide and a fungicide. Sulfur also has insecti-cidal properties.

PLANT DISEASES

When the weather is rainy, foggy, or if the dew is heavy and lasts for several hours, diseases are very apt to make an appearance, since they develop rapidly during periods of moisture. An ounce of prevention is worth a pound of cure in fighting diseases, therefore it is wise to use a fungicide as a preventive measure rather than as a cure.

In combating diseases some of the best fungicides to use are Cap tan, Ferbam, Zineb, and Karathane. The latter is splendid for the control of powdery mildew, but it should not be applied if the temperature is over 85° F. It is more effective if it is used with one of the sticker-spreader preparations.

An interesting fungicide now making its appearance on the market is Phaltan, an introduction of the California Spray-Chemical Corporation, Richmond, Calif. This product is nontoxic and can be used at any temper­ature. Laboratory experiments have already proved its value in combating such baffling rose diseases as black spot and mildew. Further experiments are now under way to test its efficacy on various ornamentals. Gardeners will do well to follow the development of these experiments as new uses unfold for this promising fungicide. In common with captan, phaltan is compatible with most pesticides. Either of these materials combined with malathion will make an excellent insecticide-fungicide mixture.

It is also important to keep in touch with the progress being made with antibiotics, as new avenues are opening for their use in the field of plant pathology.

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