170 



THE AGRICULTURAL NEWS. 



May 20, 1916. 



INSECT NOTES. 



INSECT ATTACKING ONIONS. 



(C'lurludcd.) 

 THK iii;()\VN iiAKi) BAi.'K {Lachnosterna .sp.). 



The grubs of the brown hard back have come to be 

 recognized in Antigua as causing serious injury to certain 

 crops. Sugar-cane, Indian corn, onions and sweet potatoes 

 are all attaclied. These grubs feed upon the young tender 

 roots of growing plants, and they also devour the young 

 developing bulbs of the onion, eat into the cut ends and 

 buds of cane cuttings used as plants, and eat intfj the potato 

 roots. 



In one instance in Antigua, hard back grubs attacked 

 and completely destroyed a field of 7 acres of onions, at 

 a time when the bulbs were just forming. 



The remedies to be employed for the control of the hard 

 back grub have frequently been mentioned in recent numbers 

 of the Agricultural Netns. They consist in hand-picking, 

 the use of trap crops, and improved cultivation. As onions 

 are grown as a .secondary crop in Antigua, the improved 

 cultivation would be carried out as a part of the routine work 

 in connexion with the sugar cane. 



In considering the cour.se to pursue in preparing land 

 for onions, the following points should be borne in mind; 

 (1) land known to be badly infested with grubs should not 

 be planted in onions; (2) preparation of the soil should be 

 thorough, and any grubs lound should be carefully collected 

 and destroyed; and (.3) a trap crop of corn might be planted 

 after the "land has been prepared. This could be pulled 

 up when the time came for transplanting the onions, and the 

 .soil about the roots carefully searched for grubs. }!y attention 

 t« these points it ought to be possible to escape serious injury 

 to onions by this pest. 



rilK ONION CATEUI'ILLAR (Procletli't .Sp.). 



Onions arc attacked at times in the West Indies by one 

 or more kinds of caterpillar or cut-worm. They are the 

 larvae of moths of the genus Prodenia They live in the 

 ground and often cut oft' young seedlings at the surface of 

 the t'round. In the case of onions,' the caterpillars climb up 

 at night and feed upon the leaves, sometimes eating through 

 and hiding inside the hollow leaf. If these insects are sus- 

 pected of being in the soil before the onions are planted out, 

 ' they may be ett'ectually checked by the use of a poison bait 

 made of bran or pollard, Paris green and molasses and 

 water. The bran and Paris green are thoroughly mi.xed while 

 dry at the rate of -50 B). bran and IB). Paris green, and stirred 

 to a thick mash with water to which a small amount of 

 molasses has been added. This should be scattered about 

 on the surface of the soil a few days before the plants are 

 set out. Applications of poison bait are best made in the 

 late afternoon. 



If the caterpillars attack the onions after they have 

 become established, they may be collcctc<l and destroyed. 

 They will be found during the day in the .soil near the 

 base of the plant, or, as already mentioned, they are sometimes 

 to be found within the liollow leaf of the onion plant. 



If the caterpillars were attacking onions when it was 

 necessary to spray for thrips, the addition of Paris green or 

 arsenate of lead to the thrips spray mi.xturc would probably 

 provide a remedy. Exiieriments might well be tried as to the 

 effect of mixing arsenicals with tlie Nicotine Sulphate com- 

 bination, and of their effect on the onion leaves. 



KOOT .MAGGOT.S. 



In the United States a very considerable amount of 

 injury to the growing "onions, and even to the stored product, 

 has been experienced from time to time, as the result of the 

 attacks of root maggots, which are the larvae of several species 

 of flies. 



These tlies, of wliich four species are described by 

 Dr. Chittenden, are mo.stly to be found in northern 

 localities, but one at least is said to occur as far south as 

 Cuba and B.ermuda. 



The seed-corn maggot (Pegomyia fasciceps) attacks the 

 roots and underground portions of plants of maize, onion.s, 

 leaves, cabbage, turnip, radish, peas, beets, potatoes, and many 

 others. The imported onion m3.ggot (f'egomi/ia cef^etorinu) 

 is similar to the preceding insect; they both have a general 

 resemblance ti) the ordinary house fly. The larvae attack the 

 roots and bulbs of the onion, the injury to the latter often 

 causing decay in the harvested bulbs. 



The black onion tly {Ti yoro fle.ni) differs from the 

 preceding somewhat in appearance, principally in being 

 darker in colour, and in the presence of three light bands 

 extending across each wins. The larvae differ in their habit 

 of continuing to live in the stored bulbs. 



The barred-wing onion Hr {Cltnetopni^ aenea) attacks 

 living plant tissue, and is able to live and develop in decay- 

 ing vegetable matter. This insect is often found attacking 

 plants wliich have been injured by other pests, as for 

 instance, following the attack of the sugar-cane beetle 

 {Ligyrus rwgicepx) in sugar-cane and Indian corn. It is 

 stated that one onion grower composted 700 bushels of 

 onions which were attacked !>}• this pest, and as a result, his 

 whole crop, in the next season, of 2,000 bushels was 

 destro3'ed, and he was obliged to abandon onion growing for 

 a time. 



The eggs are laid just under the margins of the leaf- 

 .sheath: the larvae live and feed under the leaf sheath, where 

 also the pupal stage is passed. 



The following is copied from the paper by Dr. Chit- 

 tenden, already referred to: — 



1;EMEDIES i'Ol; EOOT .MAfiOOTS. 



'Owing to the difficulty of destroying root maggots and 

 other subterranean pests and the cost of chemicals for the 

 purpose, growers depend largely upon methods of prevention. 

 To bo thoroughly effective these methods .should be employed 

 hcforc the ftp's egga are laid. 



'A common method for deterring the parent flies from 

 depositing eggs consists in placing sand soaked in kerosene — 

 a cupful {G fluid ounces) to a bucket of dry sand — at the 

 base of the plants, along the rows. This mixture will also 

 kill young maggots attempting to work through it. 



'For all forms of root maggots which we arc considering 

 a carbolized form of kerosene emulsion is effective. This is 

 prepared by adding to 1 pound of soap, boiled in 1 gallon of 

 water, one-half gallon of crude carbolic acid, and diluting the 

 whole with from .'5-5 to 50 parts of water. This mixture is 

 apjjlied about the stalks of the plants affected. It is best to 

 use it a day or twoafier the plants are up, or are transplanted, 

 and to repeat every week or ten days until about the third 

 week in May, in the north. Farther south these applications 

 must be made earlier in the &cison. 



'Mineral fertilizers are useful as deterrents, particularly 

 when employed just before or after a shower has thoroughly 

 wet the ground. The principal fertilizers for this purpose are 

 kainit, nitrate of soda, and sulphate or chlorid of potash. 

 They may be used as top dressings before planting, or if not 



