CONTROL OF BOLL WEEVIL IN MISSISSIPPI DELTA. 39 



From this it is seen that a total of eight pickings was distributed 

 over the period from July 1 to August 27. The weevils per picking 

 ranged from 40 to 2,445, and a total of 8,608 were collected during 

 the experimental period. As the plat consisted of 1.53 acres, the 

 weevils collected per acre thus ranged from 26 to 1,600 at the different 

 pickings, with a total per acre of 5,626. During this same time 

 2,274 infested bolls and 11,475 infested squares were collected in the 

 pans with the weevils. During the first three pickings a record was 

 kept of the number of uninjured forms knocked off by the machine, 

 and this was found to total 22 bolls and 488 squares. After that time 

 the forms collected were so highly infested that they were considered 

 as all injured. The time required for covering the plat ranged from 

 45 minutes to 1 hour and 10 minutes. This would make the average 

 time in the neighborhood of 40 minutes to the acre. However, this 

 did not include the time spent in emptying the pans. Studies on 

 the operation of this machine over larger areas have shown that it 

 may be expected to cover an average of 10 to 12 acres per day when 

 operated on a plantation basis. 



BROKEN PLANTS. 



The greatest difficulty which was found in the operation of this 

 machine was the breakage of plants. It was found that if the 

 machine was adjusted so that the plants were not broken it failed to 

 catch an appreciable number of weevils, while if it was adjusted so 

 that it collected a considerable number of weevils the plant breakage 

 was very high. Consequently, in adjusting the machine, an attempt 

 was made to strike a happy medium between these two extremes. 



Following each picking, the plat was gone over and the number of 

 broken plants counted. It was found that the number per picking 

 ranged from 37 plants to 704 plants. The number decreased rapidly 

 as the season progressed, owing to the fact that nearly all of the 

 larger plants had already been broken down. During the course of 

 the eight pickings a total of 1,827 plants were broken in the plat. 



FALLEN FORM COLLECTIONS. 



In order to determine whether or not the forms collected in the 

 picking machine decreased the number reaching the ground to 

 any appreciable extent two collections of fallen forms were made. 

 For this purpose an area 3 rows wide and 20 feet long was selected 

 at each end and the middle of each plat. This made a total of about 

 750 square feet for each plat. Care was taken to locate these points 

 where the stand was as nearly perfect as possible and where the plant 

 growth represented about the average of that portion of the plat. 

 The results of these collections are shown in Table 34. 



