252 The Canadian Horticulturist. 



trees will Hot take up more than a certain percentage of this element from the 

 soil, even though it be very abundant there ; but spraying the trees with sul- 

 phate of iron in early spring has not only been highly recommended, but has 

 proved itself to be a valuable remedy for black knot. This substance is used in 

 the proportion of one pound to twenty-five gallons of water, and, although too 

 strong to be applied when the foliage has developed, it can be safely applied 

 while the trees are yet in bud, and will serve to destroy, not only a large 

 number of the spores of the black knot, but also of the scab, mildew, rust and 

 other fungi. 



LICE ON APPLE TREES. 



Sir, — My young apple trees are covered with young insects or lice, or whatever they 

 may be called. They seem larger than lice and are quite green. They cluster by the new 

 growth, and neither Paris green nor kerosene emulsion seem to do any good. The trees 

 are otherwise very healthy. 



E. B. E., Peterhoro\ Out. 



The insects which are troubling the trees referred to by our correspondent are 

 without doubt the apple tree aphides or plant lice, which, during a dry season, 

 are sometimes so abundant as to seriously interfere with the vigor of the 

 trees by sucking out all the juices of the young growth. Paris green has no 

 effect upon them whatever, as they do not eat the substance of the leaf, but 

 merely suck from the interior. The most effective remedy is kerosene emulsion, 

 and if the application made by our correspondent was not effective, it must 

 have been because the proportion of kerosene was not great enough. A formula 

 which would be sure to be effective in the most troublesome cases is the follow- 

 ing : " Soap, one-half pound, dissolved in one gallon of water, heated to a boil- 

 ing point, when two gallons of kerosene are added and the whole mixture stirred 

 rapidly until an emulsion is formed." This will keep for some length of time, 

 and when required for use should be diluted in the propartion of one part to 

 nine parts water. This emulsion is found to be very convenient for many pur- 

 poses, as for instance, brushing the wood work of the hennery, cleansing animals 

 affected with lice, and for the destruction of the squash bug. 



SUMMER PRUNING CURRANT BUSHES. 



SiK, — My currant bushes have thrown up wood very high. Should they be cut back, 

 and when ? 



Wm. McM. Niagara. 



The principal work of pruning the currant should be done in the autumn or 

 in the early spring, but, in order to produce large sized berries, some gardeners 

 pinch off the ends of the stronger growing shoots, about the middle of June, 

 with the object of causing the plant to expend its energies in developing large 

 sized berries. 



