BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE 45 
Physiological Resistance to Wheat Stem Sawfly Apparent in One 
Wheat Variety 
Entomologists studying a large number of wheat varieties for their 
resistance to the wheat stem sawfly have at last found a completely 
hollow -stemmed wheat, P. I. 170924, that appears to possess a physi- 
ologic al type of resistance. All other resistant varieties observed 
have solid stems. Resistant varieties are used by plant breeders in 
the wheat-improvement program. The work was done in coopera- 
tion with the Bureau of Plant Industry, Soils, and Agricultural 
Engineering, and the Montana and North Dakota Agricultural Ex- 
periment Stations. Rescue, a Canadian, solid-stemmed, resistant 
spring wheat, was used as a resistant check in all tests. 
TRUCK-CROP AND GARDEN INSECTS 
Potato Psyllids Traced to Southern Breeding Grounds 
Eight years of ecological studies have at last tracked down the 
breeding grounds of the potato psyllid. This species is the cause of 
the destructive psyllid yellows disease of potatoes and tomatoes. 
Heavy infestations of this insect in the Rocky Mountain States have 
been traced to psyllids that overwinter and breed in the spring in 
southern New Mexico and southwestern Texas. These studies have 
shown that psyllid outbreaks in the potato- and tomato-growing areas 
in Colorado, Wyoming, and Nebraska depend on the spring develop- 
ment of huge numbers of psyllids in southwestern Texas and Xew 
Mexico and favorable weather during their northward migration. 
In years when spring populations in the southern States were light, 
outbreaks did not occur in the northern potato-growing areas. When 
spring populations in the south were high, outbreaks occurred in the 
northern areas if weather conditions were favorable during May 
and June. 
Sweetpotato Weevil Control 
By the end of 1952 the sweetpotato weevil had apparently been 
eradicated from 14,928 farm property units, including 45 entire 
counties in the 7 southeastern States of Alabama, Florida, Georgia, 
Louisiana, Mississippi, South Carolina, and Texas. Weevil infesta- 
tions of 26 percent in commercial producing acreages in Louisiana have 
been reduced to 2 percent and losses reduced from approximately $3 
million in 1946 to an estimated $228 thousand in 1952. 
Owing to the effectiveness of the 1952 program, planting restric- 
tions were removed from 1,595 farm units formerly infested. Four 
formerly infested counties were declared free from infestation. The 
number of infested properties in 54 counties of the 6 States com- 
prising the eradication area was reduced from 3,522 to 3,191. 
During the year cooperating States contributed about 70 percent 
of the total cost of the control program. In addition, sweetpotato 
growers, processors, and shippers in the control area purchased and 
applied insecticides and fumigants in the amount of $50,000. 
