The apple twig which you send is infested with the eggs of the leaf aphis or leaf louse.  These eggs are very difficult to kill.  A good thorough spraying with lime-sulphur might, however, get rid of many of them and would be good for the trees otherwise — diluting according to condition of tree growth.  The chief campaign against the leaf aphis, however, must be made early in the growing season, just as these pests are beginning to hatch out and to accumulate under the leaves of the new growth.  They should then be attacked with properly made kerosene emulsion or tobacco extract with a nozzle suited to land the spray on the under side of the leaves.  Unless these pests are attacked early in the season and repeated if necessary, your apples on bearing trees will be ruined so far as they attack them, being small, misshaped and worthless.  On young trees the destruction of the foliage is fatal to good growth.

Woolly Aphis.

Will you kindly inform me what you consider the best treatment for apple trees affected by woolly aphis?

The best way to kill the woolly aphis on the roots is to remove the earth from around the tree to a distance of one or two feet, according to the size of the tree, digging away a few inches of the surface soil, Then soak the soil around the tree with kerosene emulsion, properly made, of 15 per cent strength, and replace the earth.  Be sure you get a good emulsion, for free oil is dangerous.  For the insects above ground on the twigs, a good spraying while the tree is out of leaf will kill many, but some will survive for summer spraying, and for this a tobacco spray may be most convenient.

Blister Mite on Walnuts.

I am sending you some walnut leaves with some swellings an them.  They are very plentiful on some trees here.  Is the trouble serious and will it spread?

This is merely Erinose, or Blister Mite, which is a very common trouble on walnuts, but does not do enough damage to call for methods of control.  These swellings are caused by numerous, very small insects which live within the blisters on the under side of the leaf amongst a felt-like, heavy growth which develops there.  While this effect is very common, it produces no appreciable injury and needs no treatment for its control.

Scale on Apricots.

I would like to know how to check the scale on apricot trees.

The most common scale on apricots, the brown apricot scale, is usually held in check by the comys fusca, which is as widely distributed as the scale itself.  If it gets beyond the parasite, you should spray in winter with crude oil emulsion.  If some scales are punctured or have a black spot on top, the comys fusca is busy and you probably will be safe enough without doing anything.

Fumigating for Black Scale.

I would like to know the best method of eradicating the black scale from my orange trees, whether by spraying or fumigation?