June, ’23 
WEIGEL AND DOUCETTE: STRAWBERRY ROOTWORM 
287 
succeeded in locating only five or six adults, and this condition pre¬ 
vailed throughout the year. 
What do these commercial tests show? They have demonstrated 
that tearing-out the plants was of considerable importance in the re¬ 
duction of all infestations; that fumigation with hydrocyanic-acid gas 
at the rate of 2 ounces of sodium cyanid per 1,000 cubic feet was used 
successfully during the drying-off period to kill the adults above the 
ground; that a persistent campaign of handpicking aided materially in 
getting rid of many beetles; that the regular use of an arsenical dust 
to keep the plants coated during the whole time when the adults were 
present was of prime importance in controlling them; that a dry mixture 
consisting of 10 or 15 pounds of either arsenate of lead or calcium arsen¬ 
ate, and 90 or 85 pounds of sulphur gave effective results; and that some 
of the other measures, such as scraping the soil surface, spraying the cut¬ 
back plants and applying tobacco dust and wood ashes on the soil to 
help combat the larvae and pupae, also have their places in an effective 
control program. 
The following recommendations for control are based on the life 
history of the insect, and are applicable with the regular cultural 
practices. During the summer months the paramount consideration is 
to protect the plants from immediate as well as future injury. This 
may be accomplished by fumigation during the drying-off period to kill 
as many adults as possible, by scraping the surface soil from the bed 
when the plants are cut-back, and then spraying them with arsenate of 
lead or calcium arsenate using 4 pounds to 50 gallons of water to protect 
the swelling “eyes” from the further depredations of the beetles. During 
September, October, and November, eradication should be the florists’ 
aim, because the beetles are still emerging and feed voraciously for some 
time. Every effort should therefore be directed toward ridding the 
houses of as many beetles as possible in order to prevent a recurrence of 
an infestation the following spring. During this period dusting must be 
very thorough and continuous in order to keep the foliage coated with 
the poison. Hydrocyanic-acid gas, however, cannot be used at this 
time at a killing strength without causing severe injury to the plants. 
Two or more treatments by filming the surface water of the bed with 
kerosene nicotine oleate may then be most effectively used to kill many 
of the adults. Beginning about the middle of February the plants must 
be kept coated with dust to poison any adults which may come out of 
hiding to resume feeding, and the soil in the beds should be kept covered 
with tobacco dust until “drying-off” time with occasional applications 
