24 MONTANA EXPERIMENT STATION BULLETIN 408 



actually taken in Montana, when a mixed collection of this species 

 and the plum gouger was received from Miles City. 



The plum curculio is a "broad-shouldered" snout beetle about a 

 sixth of an inch long, brown or black in color with lighter mark- 

 ings and with rough-looking wing covers. It is primarily a pest of 

 stone fruits, but may cause considerable injury to apples. Feed- 

 ing punctures are quite similar to those of the plum gouger. The 

 egg punctures are characteristic of the species. After the egg has 

 been placed beneath the skin, the female turns around and makes 

 a crescent-shaped slit partially around and beneath the egg cavity. 

 This type of wound is not made by the plum gouger and will serve 

 to indicate whether or not the plum curculio is present. 



The larvae burrow into the fruit and lie next to the pit, and the 

 fruit often drops prematurely. Pupation is in the soil and in about 

 a month the new generation of beetles appears above the ground. 

 They may feed for some time in the fall, after which they hibernate 

 in protected places. 



Injury caused by this pest can be greatly reduced by spraying 

 the trees with lead arsenate. The first application should be made 

 just after the petals have fallen and a second, ten days later. 



seed-corn maggot.— This pest (Hylemia cilicrura Rond.) was 

 especially abundant in the Yellowstone Valley during the spring 

 of 1942, more so than in many years. The spring was very wet and 

 cool, and the growth of crops retarded, a combination of factors 

 which would be expected to bring on an infestation of these insects. 

 As a usual thing this injury is limited to crops in soils rather rich 

 in humus, but during the last spring conditions were such that 

 bean plantings on light sandy soils showed from 10 to 30 per cent 

 loss by the middle of June. Injury reported or observed included an 

 area from Bozeman east and north to Froid, and seemed to center 

 in the Yellowstone Valley near Billings, and up the Clark's Fork of 

 the Yellowstone to a point well beyond Bridger. 



Corn and peas were attacked to some extent, but by far the 

 greatest damage was suffered by beans (figure 7) . It was neces- 

 sary to replant many of these fields. Usually eggs are laid in moist 

 soil where there is plenty of decaying vegetation. The larvae may 

 feed as scavengers on this material, but when succulent sprouting 

 plants or large soft seeds are present they make their way into 

 these. The larvae are typical fly maggots, cylindrical, pointed at 

 the front end, and dirty white in color. When the infested area 

 around Billings was visited on June 18, 1942, the adult flies were 

 emerging from the soil in large numbers. These flies are smaller 

 and more fragile looking than a house fly, and more grayish-brown 

 in color. 



Thorough mixing of the vegetable matter in the soil, and any 

 cultural procedure which will tend to dry out the surface of the 

 ground will assist in reducing the damage caused by this pest. 



