16 BULLETIN 812, U. S. DEPARTMENT 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-flies. 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- 
j^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. 
