82 INSECTS AFFECTING VEGETATION 



Any method that will get rid of the old leaves on a strawberry 

 patch in late fall will serve to destroy the pupae ready there for 

 hibernation, and no old patch that is to be abandoned should be 

 allowed to remain on the ground over winter. Just as soon as such 

 a patch is no longer useful it should be turned under as thoroughly 

 as possible to destroy all the insects then feeding on the foliage. 



In bearing patches injury can be completely prevented by a 

 single, properly timed spraying with arsenate of lead, at the rate of 

 from four to five pounds per 100 gallons of water. The important 

 point is the time of application. It is quite obvious that any spray- 

 ing after the larvae have folded the leaves must be ineffective because 

 the material simply cannot reach the larvae in their concealed feed- 

 ing places. Applications made too early would permit the develop- 

 ment of foliage after the poisoning, and would leave uncovered 

 leaves to be injured by the larvae. Spraying should be done within 

 a week after the moths are noticed in the field, and just about the 

 time when they are becoming abundant. (Bui. 225, N. J. Agr. 

 Exp. Sta.) 



The Strawberry White-Fly. These white-flies are very small, 

 four-winged creatures, which, when at rest on the underside of the 

 leaf, look like miniature moths. This impression is heightened by 

 the white mealy powdering that covers the surface of the insect, and 

 is responsible for one of its common names. 



These flies occur at intervals throughout the summer from May 

 to September, and lay their small, shortly stalked eggs on the under- 

 sides of the leaves. They hatch in about ten days into active yellow- 

 ish larvae that very much resemble those of scale insects. As in the 

 case of scales, this active stage is short, and in a short time the little 

 creatures settle down and begin to suck the plant juices. 



Then their resemblance to the scale insects becomes yet more 

 marked for a time ; they lose antennae and legs and are as much fixed 

 to the plants as any scales. As they grow, this outside case or scale 

 becomes fringed with waxy filaments, and honey-dew is excreted. 

 When the insects are abundant this honey-dew dropping to leaves 

 below may form a sticky varnished surface, upon which a black 

 soot fungus develops. 



As a result the foliage loses vitality and dries up or decays, 

 seriously injuring or destroying the plants, especially if they be 

 young or small. The total period of development from egg to adult 

 is from thirty to thirty-five days under normal conditions, and there 

 may be three broods during the year. 



The insects are rarely abundant enough to do severe injury on 

 large plots, and usually it is only about midsummer that they are 

 abundant enough to attract even local attention. The normal 

 weather conditions are unfavorable to their development, and it is 

 only in droughty periods that they seem to become dangerous. 



In the active larval stages this white fly succumbs readily to any 

 of the contact insecticides at moderate strengths, and the adult is 

 not much more resistant, though this is harder to reach, because it 

 flies readily if not very strongly. As against the nymphs or scale- 



