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serious infestations of the -pest developed. Apparently DDT remains effec- 
tive against the predators and parasites longer than against the aphid 
itself. Thus the aphid becomes established and builds up a large popula- 
tion before being subjected to its natural enemies. The results of this 
investigation indicate that more work is needed before any recommendations 
can be made for the use of DDT as an insecticide on walnuts,— Mi chelbacher 
£t al. (260) . 
Eriosoma lanigerum (Hausm.), the woolly apple aphid 
In the fall of 1944 at Vinoennes, Ind., aerial colonies of this 
species were common on trees treated with lead arsenate, but absent from 
trees treated with DDT or nicotine. At Yakima, Wash., it was noted 
that woolly aphids had become much more common in some apple trees spray- 
ed with DDT (1 part plus 2 parts of pyrophyllite) than in adjaoent trees 
sprayed with lead arsenate. Tests made on this species in October with 
DDT resulted in almost no control whatever. It was only by dissolving 
the DDT in a petroleum oil derivative, and using an emulsion of this so- 
lution with a wetting agent, that anything approaching satisfactory con- 
trol of this aphid was obtained. — Baker and Porter (81 ) • 
When DDT was used on a block of apple trees it gave sensationally 
good control of the apple worms but killed off the small parasitic wasps 
introduced 10 years ago to check the woolly aphid. As soon as these 
aphids are freed of their natural enemies they increase immediately to 
dangerous numbers.— Burtner (98). 
DDT failed to kill the woolly apple aphids, whereas it practically 
eliminated all the beneficial insects that act as predators or parasites 
of this plant louse, including at least two species of syrphid flies, 
lace wings, lady beetles and the very important internal parasite 
Aphellnus mail Hald. which, after its introduction into the Hood River 
area in"T928," so reduced the aphid population that this pest has been of 
minor importance sinoe that time* In the mid-Columbia apple-growing 
districts, a biological upset of this character is of major importance, 
sinoe the woolly apple aphid is associated with the spread of a serious 
canker disease known as perennial canker, Gleosporium perennans , which 
attacks both trees and fruit. Following the introduction of Aphelinus 
mall and its establishment throughout the district, aphid populations 
were so reduced that canker likewise became of minor importance. Any 
spray practice that would tend to build up the aphid population would 
likewise lead to a serious increase of canker disease with disastrous 
results.— Childs and Robinson (111 ) . 
Macrosiphonlella sanbornl (Gill.), the black chrysanthemum aphid 
DDT at 1 ounoe per 100 imperial gallons of water gave 100 percent 
control. The DDT was emulsified by adding to water a solution of 20 grams 
