ENTOMOLOGY 383 



mite of the peach, and in California Mr. Clark has shown that it la 

 an entirely satisfactory remedy for the peach twig borer. 



In addition to this range of usefulness against insect pests this 

 wash has shown itself to be a valuable fungicide, notably for the 

 peach leaf curl, sprayed trees being practically immune from this 

 disease, so that the cost of treatment in the case of the peach is often 

 more than made good by the fungicidaJ benefit alone. Later ex- 

 perience indicates its usefulness also as a winter application for apple 

 scab and possibly for other plant diseases. 



Time to Spray for Sucking Insects. For the larger plant-bugs 

 and the aphides, or active plant-lice, and all other sucking insects 

 which are present on the plants injuriously for comparatively brief 

 periods, or at most during summer only, the treatment should be 

 immediate, and if in the form of spray on the plants, at a strength 

 which will not injure growing vegetation. 



For scale insects and some others, as the pear Psylla, which hi- 

 bernate on the* plants, two or more strengths are advised with most 

 of the liquid insecticides recommended, the weaker for summer 

 applications and the more concentrated as winter washes. The 

 summer washes for scale insects are most effective against the young, 

 and treatment should begin with the first appearance of the Iarva3 in 

 the spring or any of the later broods, and should be followed at in- 

 tervals of seven days with two or three additional applications. The 

 first brood, for the majority of species in temperate regions, will 

 appear during the first three weeks in May. Examination from 

 time to time with a hand lens will enable one to determine when 

 the young of any brood appear. 



The winter washes may be used whenever summer treatment 

 can not be successfully carried out, and are particularly advantageous 

 in the case of deciduous plants with dense foliage which renders a 

 thorough wetting difficult in summer, or with scale insects which 

 are so irregular in the time of disclosing their young that many 

 summer treatments would be necessary to secure anywhere near com- 

 plete extermination. In the winter also, with deciduous trees, very 

 much less liquid is required, and the spraying may be much more 

 expeditiously and thoroughly done. In the case of badly infested 

 trees, a vigorous pruning is advisable as a preliminary to treatment. 



DUSTING AND SPRAYING APPARATUS.* 



Powder Distributers. For the application of powders the dust- 

 ing bags already described are very satisfactory for field work. 

 Much more expensive and more rapid machine distributers have been 

 devised, but these are rarely used. For garden work some of the 

 small powder bellows and blowers are excellent. These cost from $2 

 to $8. 



Liquid Sprayers. For the application of poisons in liquid 

 form the prime essential is an apparatus which will break up the 

 liquid into a fine mist-like spray that will coat every leaf and every 

 other part of the plant as lightly as is compatible with thoroughness. 

 The essential features of such an apparatus are the force pump, 

 suitable hose, and nozzles or spray tips. The leading pump manu- 



*For illustrations, see pages 141, 159, 231, 249, 384, 458. 



