A number of legumes are susceptible to serious damage by insects, especially when grown in quantity as crops. Examples of insects harmful to leguminous crops are the blister beetles; alfalfa weevil; Mexican bean beetle; velvetbean caterpillar, which also attacks kudzu and peanuts; clover seed chalcid; clover seed midge; clover root borer; and locust borer, which causes much damage to black locust grown on infertile sites. Some insects, such as the pea aphid, may winter on alfalfa, clover, or other perennial plants, but in the spring and again in the fall they may be found largely on peas. Such insects might be favored by strip-cropping systems in which alfalfa, clover, and peas are severally the components of the strips. The pea weevil may be encouraged where alfalfa-grass strips, planted to control erosion on critical slopes, are adjacent to peas, as they are in the Palouse country of the Northwest.

Similarly, in the Southeast, cotton strip-planted with cowpeas may increase populations of and subsequent damage by the cowpea aphid. When the soil conservationist recommends strip cropping and other soil conservation practices employing new patterns of vegetation, he must weigh the consequences of a change in the composition of insect populations against the gain in erosion control. An unbiased statement of this general problem has been lucidly presented by Bishopp. Legumes may harbor the cotton root aphid and cotton leaf aphid, and leguminous crops such as peanuts and velvetbeans encourage the white-fringed beetle. There is much yet to learn about the proper use of legumes compatible with cultural control of injurious insects, and the problem must be considered by all who operate on agricultural lands.

The wildlife manager may need to consider arguments for clean cultivation against his support of scattered cover and vegetated fence rows. Although patches of vegetative cover headquarter insects it must be remembered that many of these are themselves predacious upon injurious insect species. Fence rows also harbor many birds that aid in the control of insect pests that attack legumes. For instance, red-winged blackbirds, English sparrows, and chickadees are natural enemies of the pea aphid. Beal, McAtee, and Kalmbach state that in the Southeast—

Clover is attacked by a number of insect pests, including the imbricated-snout beetle and the various clover weevils. The first named is eaten by 20 kinds of birds. The common or large clover-leaf weevil is the prey of 25 species of birds. The smaller clover weevils are eaten by 74 species of southeastern birds.

Early publications of the Bureau of Biological Survey are replete with examples of the value of birds in the control of destructive insects.

A number of plant diseases attack legumes. Examples of these diseases are the bacterial wilts of peas, clovers, and alfalfa; virus diseases such as alfalfa, clover, bean, and cowpea mosaics, the last transmitted by the bean leaf beetle; the brooming disease of black locust; peanut rosette and sweetclover ring spot; diseases due to downy mildews and their fungus allies, such as root rot of peas, damping-off, and stem rot, and the downy mildews of lima beans, peas, alfalfa and clover the crownwort of alfalfa, caused by primitive fungi called chytrids; spot diseases like the alfalfa leaf spot, caused by a cup fungus; root rot of peas and beans, caused by a powdery mildew, and the powdery mildew of peas and clover; black spot of clover, ascochyta blight of peas, and the leaf spots of alfalfa and clover, due to sphere fungi and their allies; bean anthracnose, caused by one of the fungi imperfecti; and clover rusts, due to rust fungi.

Legumes are also attacked by nematodes or eelworms, such as the stern nematodes of clover and alfalfa and those that cause the root knot or root gall of alfalfa, clover, cowpea, vetch, sweetpea, bean, and garden pea. These organisms may cause serious damage to nursery stock. Large quantities of black locust seedlings, for example, have been rendered worthless when propagated in soil heavily populated with root-infecting nematodes.

While legumes, like other plants, are subject to serious damage by insects and fungi, it is significant that very few legumes act as alternate hosts of critically destructive insects, like the chinch bug and Hessian fly, or damaging fungi, like the white pine blister rust, apple rust, and wheat stem rust. Consequently, so far as planting for wildlife and erosion control is concerned, there are scarcely any legumes that need be rejected on this score.

Jason Ladock

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