57 
these sprays also proved highly effective. When the same sprays 
were applied 4 times at weekly intervals during the early part of 
the season, the control of thrips was not entirely satisfactory 
Four applications of the same materials during June, however, 
gave excellent results. Sprays with reduced derris and nicotine 
content also gave promising control. Liquid extracts of pyre- 
thrum (Pyrethrol 20), with the Grasselli-spreader-sticker, and 
derris (5 per cent. rotenone) were first tested during the year. 
The former gave good control, but below that of the standard 
derris and nicotine sprays, while the latter proved equally effec- 
tive. It is proposed to carry out tests with nicotine, pyrethrum, 
and derris dusts during the coming year. 
The southern United States iris plants growing in the green- 
house during the winter were heavily infested with the tulip 
aphids, and experiments were carried out in order to control them. 
Fumigations for one hour with calcium cyanide, used at the rate 
of 3 ounces to 1,500 cubic feet, gave fairly complete control. This 
concentration, however, 1s too high for some kinds of plants, al- 
though the iris seemed to be uninjured. Frequent spraying with 
40 per cent. nicotine sulphate (1-400) and Grasselli-spreader- 
sticker (1-1,000) also gave marked reduction in the number of 
the aphids. 
Soft Rot of the Iris Rhizome 
Soft rot of the bearded iris continued to be destructive. The 
damage appeared somewhat later than last year, but toward the 
end of the summer large numbers of plants and some varieties 
had been completely destroyed. ‘Treating the soil with bichloride 
of mercury, formalin, semesan, and ethyl mercury iodide during 
the preceding fall did not prevent the infection of the iris. Dip- 
ping the iris rhizomes in solutions of bichloride of mercury, forma- 
lin, potassium permanganate, carbolic acid, copper sulphate and 
semesan, or dusting with cupro jabonite, copper carbonate, and 
sulphur, before planting, proved ineffective. No difference in 
control was noted between such treated iris when planted in treated 
or non-treated soil. 
