February, '17] REEVES: ALFALFA WEEVIL 129 



kind of drag, and the cost is about $1 per acre. This is only nominally 

 a cultural method, since in order to start the growth of the second crop, 

 it must be followed by irrigation, which compacts the soil and this 

 counteracts the cultivation. It is nevertheless a valuable method, 

 and great credit is due the Utah Experiment Station for the principal 

 share in developing it. 



Parasites 



Several species of parasites have been imported from Europe, and 

 one is known to have become acclimated in Utah. This Ichneumonid, 

 a species of Bathyplectes, was liberated in an alfalfa field near Salt 

 Lake in 1912 and several secondary colonies have been started in 

 neighboring localities. As high as 30 per cent of the larvae present in 

 midsummer were found to be parasitized, and it is possible to collect 

 parasite cocoons for wider distribution without difficulty. Outside 

 of the artificial colonies the parasite has spread spontaneously almost 

 as widely, and it now occurs in this way throughout the Weber Valley, 

 which is approximately parallel to Salt Lake Valley and from ten to 

 thirty miles distant from it. It is still too early to say how valuable 

 the parasites will be as a means of control, but a certain amount of 

 usefulness is demonstrated beyond doubt, and there are great possi- 

 bilities. In this connection the rapid reproduction of the weevil is a 

 consideration. Although there is but one annual generation, one half 

 of the beetles are females, and since the number of eggs produced by 

 each is not far below one thousand, natural causes must destroy nearly 

 99.8 per cent in order merely to prevent the actual increase of the 

 species. 



Several parasites which are undoubtedly native American have been 

 reared from the alfalfa weevil, and there is a possibility that they may 

 sometime be useful. However useful they and the imported parasites 

 may become, the alfalfa grower must take steps to protect his crops 

 from the pest by one of the methods which have been described. 



Spread of the Weevil 



The alfalfa weevil investigation must devise new processes and adapt 

 old ones for the control of the pest in new territory as fast as it spreads, 

 and this necessitates a close watch of the boundaries of the infested 

 district. It has been impossible to search the entire frontier every 

 year, but the survey has been completed every second year, warnings 

 have been given to the farmers and state authorities who were con- 

 cerned, and preparations have been made for meeting new conditions. 

 The weevil has now been found in three states and has entered the 

 Pacific Slope. Scouting is the most expensive and least productive of 



