78 
Treatments were made in April, May, July, and September 1941. 
Treated and duplicate untreated divisions were planted in field 
plots for comparing their recovery. 
The results from these investigations indicate that no significant 
differences in average height of plants, mortality, or flowering 
capacity exist between plants fumigated with methyl bromide at 
the 24% or 3 Ibs. rates, or between them and the untreated plants 
for any one treatment period. In general, the treated and un- 
treated plants in the April and May sets showed better recovery, 
larger and more vigorous clumps, lower mortality, and better 
This behavior, however, seems to be directly corre- 
flowering. 
le time of year at which the iris were treated and 
lated with tl 
planted. 
The demonstrated tolerance of the various iris to methyl bromide, 
le importance. In- 
according to the methods used, is of considerab 
1 bromide 
fested iris plants now can be safely treated with methy 
for the eradication of the iris thrips. Furthermore, such treated 
plants would adequately satisfy the recommended requirements for 
eliminating Japanese beetle larvae from stock intended for ship- 
—— 
ment outside of the quarantine areas, 
CHESTNUT BREEDING Work IN 1942 
By ArtHuR HARMOUNT GRAVES 
This project has been explained in previous annual reports. 
Hybrids of 1942—TIn 1942 most of our second generation 
Japanese-American hybrids, back crosses and intererosses, bloomed, 
being then 5 years old; and, selecting the tallest and most blight 
resistant of these, we crossed them with each other and also with 
blight resistant pure Japanese. In all, 21 different crosses were 
made, using first and second generation hybrids and_ resistant 
Japanese. As in previous years, relative disease resistance was 
determined by inoculations from pure cultures of Endothia. At 
the same time, check inoculations were made on native chestnut 
sprouts, large numbers of which grow naturally in the woods sur- 
rounding the plantations at Hamden, Conn. In almost every case 
the growth of the fungus was rapid in these native chestnuts. 
