REPORT OF THE CRANBERRY SUBSTATION. 131 



All these tests were tried in sunny weather. Judging by their results, 

 the 1 to 400 Black-Leaf 40 spray kills the worms in their early stages, 

 but is of no use when they are nearly full-grown. One part to 800 parts 

 of water is too weak at any time. Further experiments may show that 

 a medium strength, such as 1 part to 600, will kill the very young cater- 

 pillars. 



These conclusions are of special interest in relation to the recent de- 

 velopments in the control of the black-head fireworm. 



The Black-Head Fireworm (Rhopobota vaciniana (Pack.)). 



This pest was well controlled in several 1917 tests where Black-Leaf 

 40 was used at the rate of 1 part to 400 parts of water, with 2 pounds of 

 resin fish-oil soap to 50 gallons added. After this treatment the infesta- 

 tion always was greatly reduced and the worms were found dead among 

 the sewed-up vines in great numbers. The plots treated with the 1 to 

 800 Black-Leaf 40 spray were not well located to show results, the in- 

 festation in no case proving great enough to hurt the vines around them 

 much. 



This insecticide must be tried more thoroughly before we can tell 

 what strength to use under all conditions, but it certainly has displaced 

 arsenate of lead as a control for this insect. It is expensive, costing about 

 $7 per acre per application when used at the rate oi 1 part to 400 of water. 

 The number of applications advisable depends on how severe the infesta- 

 tion is and how well it can be curbed by refiowing. While this spray 

 checks either brood, it can as a rule be used more profitably against the 

 first than against the second. 



Control of the gypsy moth and the fireworm with the same appHcation 

 is feasible, as the time for the first treatment of the fii'st brood of the 

 fireworm is usually not too late for spraying the gj^psy. When both 

 insects are treated, the Black-Leaf 40 must be used as strong as 1 part 

 to 600 of water, and 1 to 400 probably will pay better. Treatment of the 

 spittle insect, the gypsy moth and the first brood of the fireworm with 

 the same application of Black-Leaf 40 is practicable on bogs that are 

 winter flowed but not reflowed. 



The use of arsenate of lead with the Black-Leaf 40 in spraymg for the 

 fireworm and the gypsy moth is probably advisable, for the arsenate 

 whitens the spray and so marks where it is appUed, thus reducing the 

 liabihty of leaving areas unsprayed. It also adds to the insecticidal value 

 of the spray, and, as shown elsewhere in this report, gives it a fungicidal 

 value when it is used on Early Black vines. Whale-oil soap is preferable 

 to resin fish-oil soap for use with Black-Leaf 40, especially if arsenate of 

 lead is added, for the arsenate and the resin soap make a burning combi- 

 nation. 



Several fireworm-infested bogs on the Cape had then- winter flowage 

 held until the 10th of July, 1918. While this greatly reduced the infesta- 

 tion, there was a considerable hatch in every case after the water was let 



