-83- 
on adhesives for cryolite suspensions. Derrisol, O.S cc. to 1 gm. of syn- 
thetic cryolite (in water suspension), was unsatisfactory as an adhesive, 
but it increased the adhesiveness of oil-cryolite suspensions about 16 per- 
cent. 
The Southern Rhodesia Department of Agriculture (382) in 1929 reported 
that some experiments in top-dressing maize against the borer were carried 
out with 2 proprietary insecticides and derris powder. AH gave a satis- 
factory hill, but only derris failed to scorch the plants. 
Chorley (_72_) in 1932 stated that Derrisol showed a 91-percent kill of 
the young larvae in a trap crop of small maize plants. Further tests showed 
treated rows to be infested to the extent of 16 percent with an average of 
0.25 larva per plant, while untreated plants were 97 percent infested, with 
an average of 5.38 larvae per plant. 
t 
The Kenya Colony Department of Agriculture (235) in 1931 stated that 
experiments had been conducted with Derrisol during the preceding season. 
At a dilution of 1:1,000 Derrisol had been recommended in South Africa. It 
was found necessary to use a strength of 1:600 before complete success was 
attained. Maize growers suffering losses from this pest are strongly 
recommended to use Derrisol as a top dressing. 
Andries ( 15) in 1932 wrote that this product is the most efficient 
top-dressing against the borer in maize. At least 24 hours after applica- 
tion must be allowed before the maximum killing results can bo observed. 
Haines ( 178 ) in 1933 reported that in South Africa top-dressing is 
one of the effective and practical control methods. Top-dressing means 
applying an insecticide to the top or crown of the maize plant for the 
purpose of destroying the young larvae, or grubs . 
Lefevre ( 249 ) in 1935 referred to experiments in South Africa. The 
control measures recommended included top-dressing with Derrisol (1:150) 
at the rate of 10 cc. per plant. 
Du Plessis (103) in 1936 stated that in South Africa the average 
annual loss caused by this insect, the most serious pest with which the 
maize farmer has to contend, is about $1,500,000. Under intensive systems 
of farming, top-dressing with Derrisol and the cutting out of infested 
plants are very effective methods of control. 
The Kenya Colony Department of Agriculture (236) in 1936 reported 
that complete control was obtained by the application of Derrisol. 
Calogramma f estiva (Donov. ) 
A derris dust containing 0.5 percent of rotenone gave complete control 
of the larvae. — Van der Vecht (454) in 1936. 
