154 



THE AGKICULTUEAL NEWS. 



May G, 1916. 



INSECT NOTES. 



INSECTS ATTACKING ONIONS. 



The successful developnifiit of an onion industry has 

 Leen frequently referred to in the Department's publications 

 from time to time during the past two years, and in July 

 1915, a pamphlet, Xo. 76 of the Pamphlet series, on the 

 cultivation of onions, was issued. In the Agi {cultural Keivs 

 (Vol. XIII, No. 3U, p. 1.57) for May 9, 1914, a short article 

 appeared on the control of the .onion thrips in the United 

 States. 



This article was a summary of a portion of a paper 

 which was published in the \'ear-book of the United States 

 Department of Agricultuie, 1912, entitled Insects Injurious 

 to the Onion Crop, by F. H. Chittenden, D.Sc. 



The notes on the onion thrips and its control given below 

 are reproduced from the issue of the Agricultural News, as 

 noted above. Dr. Chittenden's article is drawn upon for 

 further statements regarding the onion and certain of its pests 

 in the United States, and with iliis is given information with 

 regard to pests in the West Indies. 



The onion crop is a valuable one in many place.s, and the 

 experience of planters in the West Indies during the past few 

 years goes to show that in these islands, onions when properly 

 grown, cured, packed and shipped form a secondarj- crop 

 which is capable of yielding substantial profits. 



Fortunately this crop is attacked only by a few different 

 kinds of insect pests, of which the onion thrips is the most 

 serious in the I'nited States, and perhaps akso in the West 

 Indies: although in Antigua the grubs of the brown hard 

 back have been known to cause very serious losses. 



It is stated that in one distiiet in Indiana a few years ago 

 the losses in one year resulting fiom the deiiredations of the 

 onion thrips over an area of 1,500 acres, amounted to 

 $54,000 — an average toll of ^3(y per acre. In .spite of this 

 loss the profits were sufficiently satisfactory, so that in that 

 district the area planted in onions in the following year was 

 doubled, when it is satisfactory to note, the thrips were not 

 SO numerous. 



Fic. 8. Onion Thrips. a .Ulult, c and d immature thrips. 

 Knlarged. {U. i^. Dept. of Agriculture.) 



An interesting instance of the destructiveness of the 

 onion thrips in the West Indies has just come to the notice 

 of this Department. 



A planter in Antigua had 10 acres of onions which grew 

 most lu.xuriantly and gave promise of an unusuidly heavy 

 yield. The season had been one of abundait rainfall, and as 

 a result, onions in common with other crops grew unusually 

 well. These onions were attacked by thrips, and in about 

 three weeks from the time when the attack was first noticed, 

 the crop was ruined. Instead of the estimated 1,400 crates, 

 the 10 acres gave a return of less than 300 crates. 



The Onion Tiirii's (T/it-ijis tnhitci, Lind.). 



•Of the insect enemies of the onion, the onion thrips 

 [Thrips tabnci) is the most important. It causes injury to 



the onion crop practically throughout the country, producing 

 a condition somewhat generally known as 'white blast', 

 'white blight', and 'silver top'. It is also the cause of 

 'scullions' or 'thick neck'— terms used for the undeveloped and 

 unmarketable bulbs. This thrips is now found in practically 

 all cultivated fields in the United States, as well as in many 

 uncultivated areas, so that there is always danger of infesta- 

 tion to onions and other susceptible crops, whether grown in 

 new or in old land. Observations tend to demonstrate that 

 in some localities, at least, it makes little difference as to 

 the previous crop. 



'The life cycle has been found to require, under the most 

 favourable conditions, about three weeks. Thus a dozen or 

 more generations might be produced during a season. 'Besides 

 onions and related plants, this thrips attacks cabbage, 

 cauliflower, parsley, cucumber, melon, pumpkin, .squash^ 

 kale, turnip, tomato, seed beets, blackberry and strawberry! 

 Of ornamental plants, it does much injury to carnations and 

 roses, and more or less injury to aster, blanket flower 

 (Gaillardia), honeysuckle (Lonicera), daisies, nasturtium, 

 narcissus, mignonette, candytuft (Iberis), four o'clock 

 (Mirabilis), and cone flower or golden glow (Rudbeckia). 

 Yery serious injury is fre<iuently committed to cucumbers 

 and carnations in greenhouses, the damiige sometimes amount- 

 ing to the destruction of entire plantings. 



'Kerosene emulsion, whale-oil or fish-oil soaps, and 

 tobacco or nicotin extracts are recommended for use, their 

 application being commenced early in the season. The 

 importance of cleaq methods of field management, including 

 the destruction by burning of culls, tops, and injuied plants 

 after the crop is gathered, is emphasized. Investigations in 

 Texas and Indiana have shown the following formulas to 

 give the most successful re.sults; (1) Nicotin sulphate 3-2 oz., 

 cresol soap o pints, and water 50 gallons: (2) nicotin sulphate 

 43 oz., whale-oil .soap 41b., and water 50 gallons. Whea 

 spraying is once begun it should be continued at intervals of 

 from seven to ten days, in case there is no heavy rainfall 

 during this period, and no surrounding breeding host for the 

 species. The spraying .should, as a rule, be continued up- 

 to three or four weeks of harvest time. In spraying for- 

 thrips, the nozzles should be held well down upon the plants 

 acd the spray applied with as much force as possible. 



'Where setts are used considerable injury may be pre- 

 vented by dipping them about a week before planting in 

 nicotin -sulphate at about the same strength as used for 

 spraying, and then giving two dippings in the same insecti- 

 cide at planting time, or in almost any other of the solutions 

 mentioned, including kerosene emulsion Since this thrips 

 displays preference toward cabbage and cauliflower, neither 

 of these two crops .should be grown contiguous to onions." 



The nicotin sulphate may be obtained in convenient 

 form for use in the preparation known a.s Black Leaf 40 

 prepared and sold by ihe Kentucky Tobacco Products Co.! 

 Louisville, Kentucky, U.S.A. 



NATURAL CONTKOL. 



It is well known that rain, especially when falling in 

 heavy showers, destroys great numbers of this insect. 



There are also many insect enemies of the onion thrip.a 

 known in the Cnited States, one of which, the spotted 

 lady-bird (Miyilln Afaculata), occurs in the West Indies. 

 It is likely that further study of this pest will reveal the 

 presence in these islands of other predaceous and parasitic 

 insects which exert .some measure of control on this pest. 



This article on insects attacking onions will be continued 

 in the next numb(>r of this Journal. 



H.A.B, 



