MONTANA INSECT PESTS, 1949 AND 1950 21 



SUGAR BEET WEBWORM (Loxostege sticticalis) 



Late outbreaks (August) of sugar beet webworm occurred in 

 the Conrad and Sidney areas in 1949. These late outbreaks have 

 been attributed by some to second generation webworms, but they 

 may be late first generation webworms, and further studies must 

 be made before this point is established. In 1950, relatively small 

 localized outbreaks occurred in Carbon and Richland counties. 



It was discovered in the cases of later outbreaks, when the 

 beet foliage is relatively larger, usually closing in the rows, that 

 it is necessary to increase the rate of application of toxaphene 

 from IV2 pounds per acre to 2 pounds per acre. Also, in the case 

 of airplane application, it is necessary to increase the total spray 

 volume per acre (water) from 2-3 gallons to 4-5 gallons. 



FLEA BEETLES (See General Feeders) 



SPINACH CARRION BEETLE (Silpha hituberosa) 



Moderate to light damage to sugar beets by the larvae of 

 spinach carrion beetle, a leaf-chewing insect, occurred in Ravalli 

 County in 1949. This insect was not reported or found in 1950. 



PEAS AND BEANS 



PEA APHID (Macrosiphum pisi) 



On the average, the pea aphid is of probably greater economic 

 importance in alfalfa in Montana than it is in peas. The damage 

 lendered to alfalfa, particularly seed alfalfa, by pea aphids has 

 never been fully studied; however, pea aphids are nearly always 

 present in alfalfa and occasionally present in extremely large 

 populations. Such large populations occurred in the Fromberg 

 area in 1949. and in several areas, particularly Chouteau, Yellow- 

 stone, and Cascade counties, in 1950. 



Pea aphids were not reported or found in large numbers in 

 peas in 1949, and were only reported in economic numbers in a 

 small acreage of canning peas in Carbon County in 1950. 



PEA WEEVIL (Bruchus pisorum) 



During the past two years pea weevil infestations have not 

 been of economic importance in field peas. Pre-bloom sweeps in 

 canning peas indicated the presence of adult weevils in western 

 Montana. Wherever adult weevils were found in canning peas, 

 the fields were dusted. One percent rotenone dust applied at rates 

 of from 20 to 30 pounds per acre has satisfactorily controlled this 

 insect. 



LATERAL LEAF HOPPER ( Oncometopius lateralis) • 



The lateral leaf hopper was reported to be present in beans 

 in the Billings area in 1949. In 1950 a survey was conducted in 

 the above area, and no leaf hoppers were found. 



