elm leaf beetle. 815 



The Greenhouse White-Fly. 

 Aleyrodes vaporariorum Westw. 



Cucurbits growing under glass or out of doors near green- 

 houses are often attacked and considerably injured by this white- 

 fly. The insect is found on the under sides of the leaves, where 

 the eggs are laid and where the nymphs attach themselves to the 

 leaves. They are very light green, almost white, oval, and resem- 

 ble scale insects. The empty pupa skins remain on the leaf, and 

 these are silvery white. Adults are pure white and mealy in 

 appearance, resembling tiny moths. They rest upon the under 

 surface of the leaf, where they lay eggs, but fly about when 

 disturbed. 



Descriptions and figures of this insect will be found in the 

 Reports of this station for 1902, p. 148, and for 1906, p. 275. 



Frequent spraying of the under surface of the leaves with 

 soap and water (one pound in eight gallons) will kill the adults 

 and larvffi and keep the pest in check. Fumigating greenhouses 

 with hydrocyanic acid gas, using one-half ounce of cyanide for 

 each one thousand cubic feet of space, with an exposure of three 

 hours, is perhaps the most effective remedy under glass, but 

 this must be repeated frequently, because the eggs are not all 

 killed by a single treatment, while if more cyanide be used or a 

 longer exposure given, there is danger of injuring the plants. 



THE ELM LEAF BEETLE. 



Galerucella luteola Miill. 



During the past summer (1908) the elm trees of Connecticut 

 have been injured more seriously by the elm leaf beetle than for 

 several years. Many persons thought that the pest had run its 

 course, and that never again would it do much damage to the 

 shade trees of this part of the country. But they were mistaken. 

 In some parts of the state, and especially along the coast, the elm 

 trees were partially defoliated by canker worms in May, with 

 more or less feeding, of course, by the adult elm leaf beetles. 

 The canker worms disappeared about June ist, and were followed 

 immediately by the newly hatched larvse of the elm leaf beetle, 

 which devoured the green substance of the under side of the 

 leaves, in many cases completing the defoliation of the trees. 



