GENERAL PRACTICE EXEMIES. 259 



hatching appears to be solely influenced by weather after a certain period, and full 

 grown u lice " may often be found infesting the unfolding buds. The fecundity of 

 aphides is very great ; their increase is astounding. One aphis, according to Reaumur, 

 may give origin to 5,904,900,000 forms in five generations by the viviparous mode of 

 reproduction, and in a single year twenty generations may possibly be produced. 



Salt has long been known as a preserver of eggs whilst destructive of their " basis 

 of life." Spraying trees whilst dormant with a strong brine of common salt, and 

 brushing the stems as advised for lichen and moss (page 251), destroys the vitality of 

 aphis eggs, and has a beneficial effect upon the trees. Salt, however, dries and 

 crystallises, and in a dry winter is not so effectual as the caustic soda and potash 

 solution, named at page 251, for spraying trees to destroy lichen and moss as well as 

 insects or their eggs. This we advise for all fruit trees that have been infested with 

 aphides namely, spray them in winter before the buds commence swelling, with the 

 caustic soda and potash solution. 



Tobacco is one of the oldest and best remedies for aphis. Fumigation with good 

 tobacco paper or rag destroys all aphides infesting fruit trees grown under glass (see 

 " Fumigation "). Tobacco powder causes no smell, and if dusted over aphides effects their 

 destruction. If first attacks are met with a dredging of the powder, large trees may 

 be saved from complete infestation, and small trees, whether under glass or outdoors, 

 can be readily freed of aphides by its early and persistent use. It is best applied in 

 the evening, syringing off the following morning. Tobacco water, made by pouring 

 3 gallons of boiling water on 1 pound of the strongest tobacco, is, when strained and 

 cool, very effective used as a spray. If for syringing (a wasteful process), dilute to 

 6 gallons. Apply in either case in the evening and syringe with clear water the 

 following morning. Infested shoots or wood of cherries, and peaches or nectarines, 

 should be dipped in the tobacco water, and whilst immersed be rubbed with the 

 fingers. This unseats the black or brown aphis on the points of the shoots or under 

 side of the leaves, and they are then effectively assailed. A good syringing the 

 following evening with soapsuds thoroughly frees the trees of aphides. The tobacco 

 juice of manufacturers is efficacious and cheaper than tobacco decoction. It may be 

 diluted with six times its bulk of water for spraying purposes, and proportionately 

 more for syringing, but the strength varies considerably, so that no definite propor- 

 tions can be given. Tobacco water need not, as a rule, be so strong for trees under 

 glass as for those outdoors, because the narcotic vapour rises ; hence, spraying extra 



L L 2 



