74 ANNtWL BSPOBTS OF DEPARTMENT OF AGRICULTURE, 1940 
Mack nightshade (Solatium nigrum L.). Of these, tobacco and potato 
appear to he of greatest importance as a source for t lie early-season 
breeding of the beetle. 
Intensive studies were conducted in North Carolina to determine 
the relative importance of tobacco plant beds and of potato fields as 
breeding places of the flea beetle. An average of 250.8 beetles per 
square foot of tobacco plant bed and 91.5 beetles per square foot of 
potato row emerged during May and June from plants that had been 
natural I v infested by beetles. In the cages containing artificially in- 
fected plants there was a positive relationship between the numbers 
of beetles emerging and the numbers introduced initially. These data 
show that both tobacco in plant beds and early potatoes are of great 
importance as breeding hosts of the beetle during the early part of 
the season. Considering the total areas devoted to each of these crops, 
however, tobacco plant beds are undoubtedly of much greater im- 
portance as breeding grounds of the beetle than early potatoes. The 
beetles emerging in plant beds soon left the beds and moved to the 
fields of newly set tobacco. 
In the spring of 1940 further experiments were conducted to deter- 
mine the effectiveness of several treatments designed to eliminate or 
reduce the importance of the tobacco plant bed as a breeding ground 
of the beetle. These studies corroborate those of 1939 as to the impor- 
tance of the plant bed as a breeding source during the early pari of 
the year, and they also indicated several promising possibilities for 
reducing its importance. For example, during June an average of 
432.6 beetles per square foot emerged from an open plant bed to 
which no control measures against the beetle had been applied. By 
destroying the tobacco plants remaining in the bed after all trans- 
planting was complete, and before emergence of the beetles began, 
the numbers of beetles to emerge was reduced TO percent. Other 
valuable means of reducing the beetle productivity of the plant beds 
included the application of insecticides at regular intervals during 
the plant-bed season and the use of beds constructed and covered so 
as to exclude beetles during the early part of the plant-bed season. 
SVVEETPOTATO WEEVIL CONTROL AM) ERADICATION 
Cooperating Federal-State control and eradication activities 
against the sweetpotato weevil were continued during the year in 
an as of commercial production where wild host plants do not persist 
throughout the year, in the States of Alabama. Georgia, Mississippi, 
and Texas. The activities, which were supplemented by State-spon- 
sored W. l\ A. projects in Alabama, Georgia, and Mississippi, con- 
sisted of the destruction of infested seedbeds throughout the control 
areas, and of volunteer sweetpotato plants Oil infested and adjacent 
properties. Storage place- were cleaned of hosl materials. During 
tlic year four count ies were released from quarantine, all infestations 
having been eliminated. These counties were Gregg and Shelby in 
Texas and Lawrence and JefT Davis in Mississippi. The regula- 
tions of the standardized State quarantines were strictly enforced 
and the States otherwise materially assisted in the conduct of con- 
trol ana eradication operations. Twenty-two counties in the four 
States mentioned were inspected during the year. Initial SUTVeVS 
in north centra] Texas and southern Arkansas resulted in finding no 
Weevils in t bese areas. 
