27 



During a jea,r of greater bollworm abundance the number of eggs 

 that would be deposited on corn would doubtless far exceed the num- 

 bers here given. The number of eggs occurring on an acre of trap 

 corn at one time, as based on the above figures, is surprisingly great. 

 Taking the average number of eggs per plant on Juh^ 28-, as given in 

 the table, the protection afforded by the phmts on a single acre ma}' be 

 calculated in a theoretical way. Assuming the corn rows to be 6 feet 

 apart and the plants li feet apart in the row, there would be on an 

 acre 4, 8-10 plants. On the average of 338.4 eggs per plant, as found 

 above, there would be 1,637,856 eggs distributed over the acre of corn. 

 B}^ a series of observations it has been determined that a single boll- 

 worm feeding freely on cotton will destroy on an average 8 squares, 1 

 flower, and 1| bolls during the course of its growth. Assuming that 

 all of the fruit destroyed would have eventually matured, there would 

 be a total destruction of 17,470,464: bolls. On an average of 70 bolls 

 to the pound of seed cotton, this would mean a destruction of 249,578 

 pounds of cotton in the seed, or at the rate of 1,500 pounds seed cotton 

 to the bale, 166 bales. 



It must be remembered, however, that in the above calculations it 

 was assumed that from every egg a mature larva would develop. 

 This would be far from the case in reality. In fact it has been 

 observed that on an average but one larva reaches maturity from 

 about 50 eggs deposited on corn. It was further assumed that all of 

 the squares and flowers injured would have otherwise reached maturity, 

 which in fact would not be the case, as many squares and young bolls 

 are shed by the plants on account of unfavorable weather or other con- 

 ditions. However, after making due allowance for all of these condi- 

 tions, the benefits to be derived from a proper use of corn as a trap 

 crop are seen to be very great. 



It might appear at first sight that the practice of furnishing the 

 bollworm with an abundance of its preferred food would simply result 

 in its greater increase and consequent destructiveness. This, however, 

 does not result, for when the eggs are concentrated on the corn plants, 

 as on the silks, they are very largely destroyed by a certain parasite 

 and by predaceous enemies, and the larvje hatching from these eggs are 

 largely killed by the cannibalistic habits of the bollworms themselves. 

 Out of some 15 to 30 3'oung larvffi which ma}' usually be found in a 

 recently silked ear of corn, but one or two bollworms will eventually 

 reach maturity. 



Numerous instances have come under the observation of the writers 

 where planters, in attempting to make use of trap crops, have made 

 the mistake of planting the corn at the usual time in the spring. The 

 result has been, that the cotton has suffered greater injury than would 

 otherwise have occurred. The success of the trap crop idea as here 



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