eral use for this purpose and for fodder is the susceptibility of cowpea seed to weevil attack. The cowpea weevils are the worst pests of cowpea seed. They are a big factor in maintaining, in years of normal production, the high cost of seed, and in the consequent cur tailment of the use of this plant as a soil builder. These weevils, also, because of the rapidity with which they destroy cowpeas grown for human consumption, have caused seedsmen and merchants to view with suspicion cowpeas grown in certain sections of the South, and this attitude has had a depressing effect upon the production of cowpeas for food. Yet the South is a veritable Eldorado for the production of leguminous crops. for food once weevils are con trolled. It is evident, therefore, that bean and pea weevils should be charged not only with the damage they cause leguminous foods actually produced, but also with the indirect losses to the country due to the reduction in the areas planted to beans, peas, and cowpeas. LOSSES OFTEN DISCOVERED Injury to edible legumes usually is observed first after the crop has been in storage for several months. Many believe that once the crop has been harvested it needs no further attention. Seeds put away at time of harvest are sometimes not examined again until the following planting season, when they are found "buggy "buggy" or "weevily" and badly damaged. The town or city gardener has proudly put away for winter consumption beans grown during the previous summer, only to find them worthless as food and full of holes and honeycombed by grubs when later he opens the jar or sack in which they have been stored. Wonder is often expressed that seeds apparently sound when put away for the winter, and FIG. 1.-Navy beans showing the emergence holes of weevils. Each of these holes is made by a weevil as it matures in the seed and leaves by cutting out a piece of the skin. All except the five small beans at the bot tom have been injured by the common bean weevil. The five small beans were grown in Central America, and are infested by the Mexican bean weevil. About natural size overed, should be found later injured by weevils. nd holes (see title-page and fig. 1) and weevils ds seemingly perfect when harvested, a belief is ny that bean and pea weevils develop spontanem of the seed. That there is no foundation for wn by the facts following. BEANS AND PEAS BECOME INFESTED eevils, like many other insect pests, pass through nges in form and habits before reaching maturity. opment is shown in Figure 3. The weevil that is at among the seeds is the parent insect. Many of storage room or house to the fields where beans bloom. Adult pea weevils begin laying their eggs on the young It should be remembered that the bean and pea weevils begin their while the crop is developing in the field. Photo by Vinal are growing. As the bean and pea pods develop, 1 lays whitish eggs, either on the outside or within eggs are so small that they are often not noticed, as mere white specks upon the pods. From these white grubs that burrow their way through the pod eloping beans or peas. Because these grubs are so oles through which they enter the seeds are too unless one searches for them with a microscope. ecome infested first when they are nearly or quite seeds expand and harden in the final ripening procthe skin through which the grubs entered become sy to find. The wound in the skin either becomes over or remains similar in appearance to a small FIG. 3.-Life cycle of a cowpea weevil: 1, Cross section of seed showing embryo or germ at a, and on upper left side an eggshell and the small burrow made by the newly hatched grub from the underside of egg into the seed; 2, 3, and 4, larva or grub in different periods of growth, the larva of 4 being full grown; 5, pupa or resting stage, which is intermediate between the larva and the adult; 6, side view of beetle within the pupal cocoon and ready to gnaw the round hole in the seed coat so it can crawl out of the seed; 7, beetle has eaten a circular hole in the seed coat and is crawling out (note that this emergence hole is some way from the point of entry); 8, female beetle laying eggs upon the seed peas mature much faster than the weevil grubs opens that the weevil grubs are comparatively oped, in many instances, when the crop is harplaced in storage. Thus many seeds that appear ent condition in reality have weevil grubs hidden or, as shown in Figure 3. WEEVILS IN STORAGE COME FROM rubs developing from eggs laid on or in the pods e devoured very little of the seed contents, but if d in a warm place, or in a climate where the ly warm, they continue to feed and become well grown they have eaten out of the seed contents a rger than themselves and extending outward to, the skin of the bean. (Fig. 5.) The grub then of field peas brought to mill to be threshed. Remember that the d-bean weevil, and the lentil weevil are the only weevils menin that can not breed in dried seeds in storage. For this reason hese weevils occurs only in the field while the crop is maturing; ubs are in the seeds at the time they are harvested, shelled, or treatment at that time, if done thoroughly, will prevent the s in seeds resulting from the emergence of adult weevils orms into the pupa (fig. 10, c; fig. 12, c) and later This adult has a pair of sharp jaws which it uses ssors to cut out a circular flap (fig. 6) in the bean the small round hole which is, to most gardeners, that insects are in their beans. Through these lts crawl out and by their presence in sealed jars ers cause much concern. STRUCTION CONTINUES IN STORAGE ption of the pea weevil that attacks the different the broad or Windsor bean weevil, and the lentil Is attacking beans and cowpeas continue to produce generation after generation in dried seeds in storage. (Fig. 7.) The pea and the broad-bean weevils will die in storage and can not reproduce unless they can find growing plants in which to lay eggs. But the ordinary bean and cowpea weevils lay eggs for successive generations as readily upon dried seeds in storage as upon the growing plants in the field. As each generation of weevils reduces the value of seeds FIG. 5.-Beans in which the common bean-weevil grubs have become full grown and have eaten out from the interior of the bean to, but not puncturing, the skin. As they transform to adult, each insect darkens and this dark color shows through the thin skin and makes the dark, sometimes bluish, trans lucent spots in beans. Such spots indicate that seeds are infested. It should be remembered that while the grubs are still growing they are white, and seeds do not indicate their presence by any such dark spots as shown above. Three times natural size for planting and for food, steps should be taken to kill, at harvest time, such grubs as may be in the seeds and thus prevent further losses. If this is not done the seeds become honeycombed by the feeding of generations of grubs and may be reduced to a powder. (Fig. 8.) Because bean and cowpea weevils can breed in dried seeds it is important not to store uninfested seeds near seeds that are infested, for the weevils spread rapidly and will soon infest the newer seeds. THERE ARE DIFFERENT Injury to leguminous crops is caused by more than one insect. Those considered in this bulletin are the pea weevil. the common bean weevil, the southern cowpea weevil, the cowpea weevil, the broad-bean weevil, the lentil weevil." and the Mexican bean weevil. These are all found in supplies of beans, peas, cowpeas, or lentils in this country. Other bruchid weevils are sometimes found in imported seeds, but will not be discussed here. GENERAL DESCRIPTIVE FACTS The bean and pea weevils of the United States are all very small. None of them is longer than one-eighth to one-fifth of an inch. They are dull-colored with markings of white or black. For the 1 Bruchus pisorum Linnaeus. 2 B. obtectus Say. B. quadrimaculatus Fabricius. 4 B. chinensis Linnaeus. 5 B. rufimanus Boheman. B. lentis Boheman. Spermophagus pectoralis Say. |