MONTANA INSECT PESTS, 1949 AND 1950 19 



WIREWORMS (See General Feeders) 

 ALFALFA AND CLOVER 



ALFALFA SEED CHALCID (Bruchophagus gihhus) 



The alfalfa seed chalcid is known to occur throughout most 

 of the state. The worm-like larvae of this insect burrow into the 

 alfalfa seed, hollowing it out and leaving only the shell. The only 

 economic damage to alfalfa seed reported during the past two 

 years was in the Camus Prairie area in 1949. No damage to clover 

 seed by this insect was reported. 



ALFALFA WEEVIL (Hypera postica) 



The area known to be infested by the alfalfa weevil covers 

 all or parts of Wheatland, Sweetgrass, Stillwater, Carbon, Mussel- 

 shell, Yellowstone, Big Horn, Treasure, Rosebud, Prairie, Custer, 

 Powder River, and Fergus counties. Alfalfa weevil populations 

 and damage to alfalfa appeared to be less in 1949 than in 1947 

 and 1948. In 1950 the populations were high and the damage was 

 severe in the infested areas where control measures were not 

 conducted. The recently developed control measure of spraying 

 the alfalfa in the early spring with dieldrin makes it possible to 

 successfuUv and economically combat this serious insect pest of 

 alfalfa. 



LYGUS BUGS (Lygus sp.) 



Several species of Lygus bugs are common throughout the 

 state. These bugs are particularly destructive to alfalfa and clover 

 seed crops. They suck the plant juices from the stem below the 

 blossom and the blossom dries up without forming seed. Economic 

 populations are generally considered to be five or more Lygus 

 bugs per sweep with the standard 15-inch insect net. Lygus bugs 

 are readily controlled with the proper application of DDT, toxa- 

 phene, or benzene hexachloride. 



SWEET CLOVER WEEVIL (Sitona cyliyidricollis) 



The sweet clover weevil appears to be present throughout most 

 of the state, and caused considerable defoliation of sweet clover in 

 most areas where large acreages of sweet clover were grown in 

 1949. This beetle was not observed or reported west of the Con- 

 tinental Divide in Montana during the past two years. In 1950 

 sweet clover weevil damage apparently was not as severe as in 

 1949. Two cases of alfalfa defoliation by adult sweet clover weevils 

 were observed in 1950. 



CLOVER HEAD APHID (Anuraphis hakeri) 



Practically all of western Montana and Carbon County in 

 southern Montana are known to be infested with clover head 

 aphids. Populations in these areas in both 1949 and 1950 were 

 extremely high. Considerable reduction to seed production occur- 



