INSECTS INJURIOUS TO GLOBE ARTICHOKE. 3 



become distorted in such a manner that the aphids can be reached 

 only with difficulty with a contact insecticide. (See PI, II, figs. 1 

 and 2.) 



CONTROL OF THE APHIDS ATTACKING ARTICHOKE. 



During 1917 Myzus braggii and Aphis rumicis were controlled sat- 

 isfactorily at Baton Rouge by spraying with 1 part, by weight, of 

 nicotine solution (containing 40 per cent of nicotine as sulphate) to 

 1,000 parts of water, with laundry soap (standard, noncaustic type) 

 added at the rate of 1 pound to 25 gallons of water. (See PL I, fig. 2, 

 and PL III. ) Because the plants in some rows in the field where the 

 experiments were conducted were never sprayed, these plants served 

 as a constant source of infestation for the sprayed plants, especially 

 those near the untreated plants. The Argentine ant apparently was 

 responsible in part for the spread of the aphids. More frequent 

 sprayings were necessarj^, therefore, than would have been the case 

 had all the plants in the field been sprayed. The plants were sprayed 

 seven times, January 31, March 2, March 14, March 29, April 19, 

 April 26, and May 26, respectively. The material was applied with a 

 compressed-air sprayer holding about 3 gallons. The first picking of 

 edible heads from the sprayed and unsprayed rows was made on May 

 11 and at frequent intervals thereafter until June 29. From 65 

 plants in the sprayed rows 310 heads or burrs were obtained and 

 from 39 plants in the unsprayed rows 39 heads, an average of nearly 

 5 heads from each sprayed plant and an average of 1 from each un- 

 sprayed plant. The difference in growth made by the sprayed and 

 unsprayed plants was very noticeable and if the weather had not been 

 dry there is little doubt that the increase in the crop from the 

 sprayed plants would have been still greater than that from the un- 

 sprayed plants. 



It is especially advisable to begin spraying globe artichokes when 

 the aphids first appear on the plants, which is usually when they 

 are small. One reason for this is that after Aphis rumicis has be- 

 come abundant the leaves are so badly distorted as a result of feeding 

 that it is very difficult to reach them with the spray. Another reason 

 for timely spraying is that if delayed until the aphids have reached 

 their maximum abundance, much of the injury for which they are 

 responsible already has been done, and as the period of maximum 

 abundance under such conditions often comes when the plants have 

 developed a heavy growth of leaves, a larger amount of spray mate- 

 rial and more time for its application are required than when the 

 spraying is done early. Some growers who spray for the control of 

 the aphids, but who do not begin until the plants are large and 

 heavily infested, find it advisable first to cut off and destroy the older 

 and badly distorted leaves. 



