Fall treatment of four applications of methyl parathion at 0.5 pound per 
acre at 10-day intervals was made between September 27 and October 27 at 
Quebec. This treatment reduced the percentage of boll weevils in diapause to 
some extent, but results indicated that a shorter interval treatment would be 
necessary to reduce or to eliminate diapausing weevils. There were five 
times as many weevils in hibernation in the untreated as in the treated area, 
but hibernating populations were not eliminated. 
In the spring of 1962, weevil populations in ground trash in the untreated 
community were almost four times those in the treated community. Differences 
in field populations were similar. Four spray applications of Guthion at 0.25 
pound per acre at weekly intervals in the fall-treated community resulted in a 
very low weevil infestation for a 6-week period, during which a high percentage 
of the crop was set. Bollworm control was needed during this period. 
Results of these studies indicate that fall treatment followed by early 
treatment in the spring would reduce weevil populations to low enough levels 
in the main boll weevil belt to make feasible the release of sterile males to 
eliminate populations. 
Summary 
Results of experiments conducted in 1960, 1961, and 1962 indicated that 
fall applications of methyl parathion were effective in reducing hibernating 
boll weevil populations. However, a 7-day application interval would probably 
be more effective than a 10-day interval. Although control of overwintered 
boll weevils with Guthion required a minimum of late-season treatment, the best 
control was obtained when fall treatment with methyl parathion was followed 
with Guthion for overwintered boll weevil control. This procedure would be 
much more effective in reducing overwintered boll weevil populations in the 
boll weevil belt than fall treatment or early-spring treatment alone. 
Sais 
