46 
to dig them up, separate them, and reset them. In the past the 
plantations at the Brooklyn 
— 
Jotamie Garden have been compara- 
tively free from this serious disease of the iris. In fact, it has been 
noted only during the last three years, and this past season was the 
first one in which serious damage occurred. 
Tris thrips control 
The Beardless iris, especially the Japanese varieties, have been 
severely infested with thrips in plantings at the Brooklyn Botanic 
Garden. ‘The invasion goes back several vears. Frequently very 
serious Injury to the flowers of the Japanese varieties is produced. 
The insect occurs in large numbers on the vellow flag of Europe 
(/ris pscudacorus) and on our native blue flag (/. versicolor). 
On these species, however, very little flower injury occurs. The 
foliage injury, however, may be severe on these as well as on the 
Japanese varieties. The insect also occurs on the Southern and 
other beardless types, but apparently is quite rare on the Bearded 
varieties. During the past few years extensive experiments on 
the control of these insects have been undertaken in cooperation 
with Dr. C. A. Weigel and Dr. lloyd Ff. Smith of the Division of 
Truck Crop and Garden Insect Investigations, Bureau of [nto- 
mology and Plant Quarantine, Washington, D.C. A method of 
treating the iris with hot water has been devised which has proved 
to 
—H 
be very successful. These experiments involve the use o 
varieties belonging to the various groups of the iris. 
In April many additional treatments were made and further 
series in late July and October. Nearly all of the treated iris 
were taken out to the pro 
— 
agation section on the grounds of the 
State Institute of Apphed Agriculture on Long Island at larm- 
~ 
ingdale, where the necessary land 1s available, through the courtesy 
of the officials of the Institute. 
The hot water treatments, of course, involve digging the plants 
and resetting them after treatment. A series of preliminary ex- 
periments was carried out to determine whether thrips could be 
kept in control by the use of suitable sprays. 
