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MONTANA EXPERIMENT STATION BULLETIN 408 



days showed temperature maxima above 90° F. Fields planted 

 after June 1 remained rather uniformly free from psyllids and the 

 psyllid yellows disease. 



Vines infected by psyllid yellows were seen in potato plantings 

 in Jefferson, Gallatin, Carbon, and Big Horn counties, in addition 

 to the Yellowstone Valley plantings from Laurel to Glendive. 



red humped apple caterpillar. During the past few years 

 requests for information on the control of the red humped apple 

 caterpillar {Schizura concinna S. and A.) have been received in 

 increasing numbers. Although these caterpillars are striking and 

 conspicuous, they are of but minor importance and only locally 

 are of sufficient abundance to warrant control measures. 



When fully developed, the larvae have a reddish-yellow ap- 

 pearance due to the alternating stripes of these colors on the body. 

 These stripes are more conspicuous on the sides. Slender, dark, 

 pointed processes occur along the back, and are most conspicuous 

 on the segments just behind the head. One of the segments toward 

 the head is enlarged and red, and from this structure the insect 

 gets its common name. When irritated the rear end of the body is 

 raised considerably above the surface upon which the larvae is 

 standing. Because they are voracious eaters, feeding openly on 

 leaf tissue, they can be controlled without difficulty by the usual 

 lead arsenate sprays. 



All of our Montana records are from the western third of 

 the State, Big Fork, Deer Lodge, Dixon, Heron, Kalispell, Ronan. 

 and Troy, and all observations were for the month of August but 

 one, in September. 



diamond back moth.— The larva of this little moth (Plutella 

 maculipennis (Curt.) attacks cabbages, mustard, and related plants. 

 While it is widespread in Montana, its attack on garden crops is 

 usually so slight as to be 

 hardly noticeable, and only 

 occasionally does it become 

 so abundant as to require 

 control. 



Recently, however, it be- 

 came abundant in large 

 plantings of commercial 

 mustard in the north-cen- 

 tral part of the State, and 

 during the summer of 1941 

 it damaged acreages of this 

 crop by boring into the 

 pods and destroying the 

 seeds. It was very abun- 

 dant that season also on 

 several species of wild 

 mustard, notably tumbling mustard (Sisymbrium altissimum) 



Figure 5. Diamond-back moth, larva 

 above, cocoon below. Greatly enlarged. 



