16 BULLETIN 812, TJ. S. DEPAKTMEITT OF AGRICULTURE. 



Any plants carelessly cut, so that some stems remain standing, and 

 allowed to develop seed in advance of the regular seed crop, offer 

 favorable conditions for the multiplication of the chalcis-fiies. All 

 pocket gophers should be poisoned or trapped and their mounds, as 

 well as other irregularities in the surface of the field, should be 

 leveled so as to make clean cutting possible. 



PASTURING BEFORE GROWING SEED. 



After removing the first crop of alfalfa for hay, and preparing to 

 grow a seed crop, it is frequently possible to secure a herd of live 

 stock, which may be turned into the field for two or three days. If a 

 sufficient number of horses, cattle, or sheep can be secured they 

 will render a valuable service by destroying the clusters of plants 

 which frequently escape the mower, develop early seed pods, and 

 form favorable breeding places for the development of the chalcis- 

 fly before the regular seed crop has become sufficiently advanced. 



ALLOWING THE SEED CROP TO STAND TOO LONG. 



The development of seed pods in the alfalfa seed fields is to a great 

 extent periodical. That is to say, the first set of pods will have been 

 formed when a new set of blossoms appears, or the first set of pods 

 will be reaching maturity when the second set of pods is soft and 

 green. This condition is most noticeable in fields receiving frequent 

 irrigation. The tendency on the. part of the farmer is to allow the 

 seed crop to remain on the field too long, while waiting for a third 

 or even a fourth set of pods to develop. It has frequently been ob- 

 served that the chalcis-fly passes a complete generation in the earlier 

 pods, and, in much greater numbers, infests the later pods forming 

 on the same plants. Consequently, all seed fields should be handled, 

 as much as possible, so that a heavy setting of pods will be secured 

 with the first bloom and the crop removed from the field as early as 

 possible. This will avoid a greater percentage of infested seeds as 

 well as loss of time and will make room for the growing of subse- 

 quent crops for hay. 



SECOND CROP OF SEED. 



In the Southwest, where there is little danger of early frost, seed 

 growers occasionally attempt to grow two crops of alfalfa seed in a 

 single season. The results of such instances are usually very disap- 

 2)ointing, on account of the usual severe infestation common to the 

 second crop. This is frequently so great that the crop does not pay 

 the harvesting expenses. 



An attempt to grow a second crop of alfalfa seed in a single sea- 

 ;Son will meet with almost certain failure as a result of the increased 

 abundance of the chalcis-flies late in the summer. 



