564 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 
Mottling, Composition of Citrus Leaves at Various Stages of. By C. A. 
Jensen {Jour. Agr. Res. ix. pp. 157-166 ; May 1917)- — An examination of the 
chemical composition of mottled orange leaves, leading to the conclusion that the 
mottling is not due to deficiency in any of the chemical elements usually required 
by plants. (See also • Citrus.') — F. J. C. 
Myzus ribis (Linn.), The Migratory Habits of. By C. P. Gilette and L. C. 
Bragg {Jour. Econ. Entom. x., pp. 338-340 ; June 1917). — This is one of the 
best- known aphides. It occurs on various species of Ribes, more especially the 
common red currant. It has long been known that many of the aphides leave 
the currant bushes during the summer ; and the authors state that they have 
repeatedly successfully transferred migrants from Ribes to Stachys and Leonurus, 
and the autumn migrants from these plants to the currant. They feel safe, there- 
fore, in announcing these two genera, at least, as summer hosts of Myzus ribis. 
G. W. G. 
Nicotine Sulphate, a Neglected Factor in the Use of. By W. Moore and S. A. 
Graham {Jour. Agr. Res. x. pp. 47-50, July 1917). — The authors report illness 
due to eating of lettuce sprayed twelve days before with a nicotine wash. 
Nicotine itself is very volatile and no harm will follow the use of plants sprayed 
with it twenty-four hours before, but nicotine sulphate is non-volatile and should 
not be used in spraying greenhouse plants which are to be eaten later. The 
lime, &c, in hard waters indirectly brings about the volatilization of nicotine 
from nicotine sulphate, and the authors recommend that washes containing 
nicotine sulphate should be made alkaline with soap, &c, before use. — F. J. C. 
Nicotine Sulphate as a Poison for Insects. By A. L. Lovett {Jour. Econ. 
Entom. x., pp. 333-337 ; June 191 7). — An account is given of some experiments 
with nicotine sulphate as a stomach poison for insects. Tent caterpillars 
{Malacosoma pluvialis) were placed on foliage sprayed with " Black Leaf, 40" 
1-1200, after the leaves had dried. In this as in the other experiments the 
spray had an extremely nauseating effect on the caterpillars causing many of 
the larvae to fall from the foliage and lie as dead for some hours, eventually 
recovering and crawling away. Where any feeding took place the larvae were 
killed. The general conclusions reached are : — 
1. Nicotine sulphate is a very powerful repellent to caterpillars. 
2. Caterpillars will not ordinarily feed from choice on foliage sprayed with 
comparatively weak solutions ; but when they do so, even small portions of 
leaves are sufficient to kill. 
Nicotine sulphate as a contact insecticide is usually considered a very 
efficient but expensive spray. It is pointed out that, in view of the possibility 
of its wider insecticidal properties, this conception may yet be considerably 
modified. — G. W. G. 
Onion. By A. F. Pearson {Irish Gard. xiii., Feb. 1918, pp. 29-30). — A 
useful cultural article. — E. T. E. 
Onion Fly, Poisoned Bait Spray against. By H. H. P. Severin and H. C. 
Severin {Jour. Econ. Entom., 8, pp. 342-350 ; June 1915)- — The life-history of the 
well-known onion fly {Phorbia cepetorum) is detailed and an account given of its 
ravages. It is stated that seventy methods of control have been proposed, but 
that a poisoned bait spray has not been used. The authors experimented with 
a spray to be applied before the fly lays its eggs, composed of molasses £ pint, 
sodium arsenite (dissolved in boiling water) J oz., water 1 gallon. They found 
the flies were attracted by this spray, which need therefore not be applied so as 
to cover the whole plant, but there is considerable danger of the material being 
washed off by spring rains and also of the foliage being burned, while invasions 
from neighbouring gardens would render the frequent repetition of the spraying 
necessary. — F. J. C. 
Onion-growing. Is it worth while ? By Douglas Newton {Jour- Bd. Agr. 
vol. xxix. No. 12 ; March 191 8). — A five-page article giving facts and figures 
in connexion with onion-growing on a commercial scale. Figures given for 
1915 crop show a loss but in 1916 andigi7, owing to high pr ces of the crop, sub- 
stantial profits were made, notwithstanding the high costs of cultivation. Brief 
notes on soil, previous crop, seed, labour, manuring, and storage are given, and 
the author concludes that owing to exigencies of shipping situation home-grown 
onions will pay for some years to come, as we^are faced by a shortage of some 
millions of bushels of onions. — G. C. G. 
