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THK AGKIOULTURAL NEWS. 



AuaosT -23, 1919. 



INSECT NOTES. 



BEAN AND PEA WEEVILS. 



Stored grains and cereal products are subject to attack.s 

 by several kinds of insects in the Tropics, to such an extent 

 as to interfere seriously with the growing of these crops. 

 The planter does not care to grow large quantities for 

 •torage because the loss from weevils is so great. 



As a safeguard against a certain amount of such loss 

 there have been established in Antigua and St. Vincent, 

 under Government control, drying machines in which 

 Indian corn has been conditioned. In St. Vincent in 

 particular, maize has been treated for the purpose uf drying' 

 ont excess moisture, and thereby preventing the growths of 

 moulds and mildews, and a'so for the purpose of killing the 

 insects in the grain. This, with proper arrangements for 

 storage in insect proof bins, constitutes a measure of pruluc- 

 tion against insects and fungi in sto'ed grains, an t it may 

 be applied to those species which infest peas and beans, 

 as well as the ' weevil ' and other pests in maize. The 

 trouble experienced in storing steJs and grains is not 

 confined to tropical regions. All temperate countries liave 

 the same trouble in greater or less degree. 



The United States Department of Agriculture recently 

 (September 1918) issued Farmers' Bulktin, No. 983, 

 entitled Bean and Pea Wee9ils, by Dr. E. A. Back and 

 Mr. A. B. Duckett, and the Department of Agriculture, 

 Union of South Africa, at the same time issued a similar 

 ptiblication, Bulletin No. 12, 1918, entitled Pea and Bean 

 Weevils, by .Mr. S. F. Skaife, B.A. 



Fu; 3. The FouR-SpoTTEn Bean Wekvil. («) adult; 



{b) larva, (c) pupa. All enlarged. 



(From U. S. Departnunt ni Agriculture^ 



It is sigtiificatit tliat at a time like the present, when 

 the demand for foodstuffs is pressing and the need for 

 oOBServation great that tlu^se two great agricultural 

 countries, one in the north temperate and the other in the 

 south temperate zone, should be dealing with the same 

 group of insect pests in order to help the growers and 

 others to save as much as possib'e of the valuable leguminous 

 grains. 



The weevils which attack beans and peas in the 

 We«t Indies appear to be of three species: the bean weevil 

 (Bruchui obl<ctui\ the cowpea weevil, (B. ckinensis), and 

 the fonr-spotted bean weevil (B- quadrimaculalus). The 

 injuries resulting tf> peas and beans in .storage from the at- 

 tacks of these insects is usually attributed to weevils, without 

 «li8tingui»hing between the several sp<^:cics. It would appear 

 likely, however, that the cowpea weevil is the most abundant 

 in the West Indies. The pea weevil {B. piiorum) is 

 sometimes to be found, but it probably is merely imported 



with peas from northern localities, and does not breed here. 

 Several other species of the genus liruchus are recorded as 

 occurring in the West Indies, but they do not seem to be 

 known as pests of cultivate^l peas and beans. 



The three species mentioned above as being of impor- 

 tance in connexion with the seed of cultivated leguminous 

 crops are all alike in the essential points of their life-history, 

 habits of feeding, and method of control. They all beain 

 their attack in the young developing pod in the field. The 

 insecLs in the seed at the time of harvesting continue breed- 

 ing in storage, and if left uncontrolled will, by successive 

 attacks, completely destroy the seeds. 



' Bean and pea weevils, like many other insect pests, 

 pass through several marked changes in form and habits 

 before reaching maturity. The adult weevil that is seen 

 crawling about among the seeds is the parent insect. Alany 

 of these fly from the storage room or house to the fields 

 where beans and peas are growing. As the bean and pea 

 pods develop, the mother weevil lays whitish eggs, either on 

 the outside or within the pods. These eggs are so small that 

 they are often not noticed, for they appear as mere white 

 specks upon the pods. From these eggs there hatch white 

 grubs that burrow their way through the pods into the soft 

 developing beans and peas. Because these grubs are so very 

 tiny, the holes through which they enter the seeds are too 

 small to be seen, unless one searches for them with a 

 microscope. Usually beans become infested first when they 

 are nearly full grown. As seeds expind and harden in the 

 final ripening process, the holes in the skin through which 

 the grubs entered become less and less ea.sy to find. The 

 wound in the skin either becomes entirely he.iled over or 

 remains similar in appearance to a pin prick. 



'Since beans and peas niiture much faster than tho 

 weevil grubs within them, it happens that the weevil grubs 

 are comparatively small or little developed in many instances 

 when the crop is harvested and placed in storage. Thus 

 many seeds that appear outwardly in excellent condition, in 

 reality have weevil grubs hidden away in their interior. 

 {Farmers' Bulletin, No. 983.) 



In this way the beans or peas become infested, and when 

 harvested they contain living insects which will shortly 

 emerge as adult beetles ; these will deposit eggs, and another 

 generation w.ll attack tLe beans or peas. The injury caused 

 by the first generation of the cowpea weevil and four spotted 

 bean weevil is not very great, but when the attacks are allo*- 

 ed to continue unrestricted durini: the whole time these seeds 

 are in storage they may be entirely destroyed. Although 

 cowpeas are the preferred food, most kinds of peas and beaoa 

 are attacked. The Farmers' Bulletin, No. '.tK3, menti"ii>d 

 above, gives the following list of food plants for the cowpea 

 weevil : - cowpea, common pea, pigeon pea, lentil, chick pea 

 inung bean, and common white bean In this list the mung 

 bean is the woolly pyrol of the West Indie.s. 

 a Nearly every one who has kept seed of legumiaoug 

 plants for any length of time in the West Indies know.s the 

 effect of tho work of these insects. From a monetary point 

 of view the loss i.s greater in those districts, particularly in 

 the temperate climates, where large areas are grown in legu- 

 minous crops for sale and shipment to the markets of (uties 

 and towns. The Bulletin (983), already mentioned, states 

 that 'One Province of Canada alone suffered from ravages of 

 the pea weevil to the extent of over -SI, 000,000 in a singlo 

 year. It was estimated in 1902 that the acreage of field 

 peas in Ontario would have been 1,000,000 instead of the 

 532,039 actually planted, had it not been for the (ear of the 

 |)ea weevil.' 



