July 15, 1920] 



NATURE 



629 



perature is very marked. The downward percolation 

 of warm or cold rain from the surface to the 4-in. 

 depth causes rapid changes in temperature, especially 

 in sandy soils, when percolation is rapid. After 

 drainage has ceased a rise in temperature may enable 

 it to begin again, owing to the diminishing viscosity 

 of water with increasing temperature. The formation 



of a dry surface-mulch reduces the value of (^") 



owing to the low conductivity of dry soil. But the 

 actual temperature at the 4-in. depth is not greatly 

 reduced by the poor conductivity of the dry soil. This 

 is attributed to the dry surface layers reaching a 

 higher temperature owing to their lessened specific 

 heat, and this counteracts the effect of decreased con- 

 ductivity. It is shown that a strong dry wind causes 

 the temperature of the surface soil to fall considerably 

 below that of the air. The effect of frost is examined 

 and a formula given for depth of soil frozen in 

 terms of mean surface temperature and duration of 

 frost. A very close relation holds between the date 

 of flowering of coltsfoot and the number of frosts for 

 the two months previous to the date of flowering on 

 open soil not covered with deep snow. It is shown 

 also that strong warm west winds — associated with 

 cyclonic depressions — rapidly raise the temperature of 

 the underground layers of soil in spring. B. A. K. 



Control of Insect Pests. 



ENGLISH tomato-growers in the Lea Valley are 

 threatened with an annual loss of from 5L-10/. 

 per acre unless special remedial measures are adopted 

 against the glasshouse tomato moth, Polia (Hadena) 

 oleracea. L. Lloyd (Monthly Circular of the 

 Lea Valley and District Nurserymen's and 

 Growers' Association, Ltd.) finds that spraying 

 with lead arsenate for the destruction of the pest 

 must be supplemented by trapping the caterpillars 

 and moths and by destruction of the pupae. The cater- 

 pillars can be trapped in old sacks, and ultimately 

 killed by boiling water, while the moths are attracted 

 to wide-mouthed jars containing brown treacle and 

 ale mixed with i per cent, of sodium fluoride. Emphasis 

 is laid on the necessity for ascertaining that each 

 control measure is effective. 



Several papers have recently been published dealing 

 with the control of various "borers" that infest crop 

 trees. Attempts have been made to control the peach- 

 borer by means of toxic gases derived from poisonous 

 substances distributed on the soil round the base of 

 the trees, E. B. Blakeslee (Bull. 796, U.S.A. Depart. 

 Agric.) finds that the more usual toxic agents, viz. 

 carbon bisulphide, carbon tetrachloride, sodium 

 cyanide, and naphthalene, are all unsuitable for 

 various reasons, but that para-dichlorobenzene offers 

 distinct possibilities for the purpose. The surface 

 crust about the collar of the tree is broken, the 

 required dose of poison (about i oz. per tree from 

 6-15 years old) distributed evenly about the trunk 

 in a band 1-2 in. wide, and a covering of earth 

 applied and moulded up. It is claimed that by this 

 method 94 per cent, of the larvae can be destroyed. 



Much damage is wrought in the United States by 

 the apple-tree borer, which usually takes two or three 

 years to pass through its life-cycle. It is difficult to 

 attack the larvae by means of poisonous sprays, and 

 mechanical devices are necessarilv resorted to. F. S. 

 Brooks (Farmers' Bull. 67.C;. U.S.A. Depart. Agric.) 

 maintains that the most effective method of control 

 is the old-fashioned practice of "worming" with a 

 knife and a piece of wire, but recommends the use 

 of carbon bisulphide when the burrows are obstructed 

 NO. 2646, VOL. 105] 



and the larvae cannot be reached by the wire. Egg- 

 laying can be prevented by a thick coat of paint 

 applied to the bark of the tree, or by means of wrap- 

 pings of cloth or newspapers applied close enough to 

 exclude the adult female from the bark. The beetle 

 can be killed by spraying the trees with arsenate of 

 lead, as by this means their food is poisoned, but it 

 is doubtful if this is profitable as a general rule. 



A most comprehensive account of the toon shoot 

 and fruit borer (Hypsipyla robusta, Moore) is given 

 by C. F. C. Beeson in the Indian Forest Records 

 (vol, vii., part vii.). The stages of the insect, its life- 

 history and habits, and studies of its seasonal history 

 are fully described, and from the information thus 

 gained the best methods of control are elucidated. 

 The toon borer passes through five generations in the 

 year; the first is spent in the flower, the second in 

 the developing fruits, and the last three in the young 

 shoots of the current season. The effect of this habit 

 is that the first and second broods cause great injury 

 to the seed crop, and in bad years may hinder seed- 

 formation entirely, whilst the three later broo(^ mav 

 completely nullify the season's growth in young trees, 

 and, in any case, they cause great delay in the 

 development of the saplings. It is often of little use 

 to make young plantations in the neighbourhood of 

 old toon trees which are infested with the borer. 

 The young trees are subject to attack frpm their 

 second or third year onward, but may be somewhat 

 protected by banding the trees breast-high with 

 sacking, and removing and destroying at intervals 

 all the larvae and cocoons found inside the sack-bands. 

 After the fruits are ripe it is advisable to cut out and 

 burn all shoots that are attacked, and in bad cases a 

 second pruning should be made during the cold 

 weather. 



Scientific and Systematic Pomology.^ 



T T may be taken as a sign of the development of 

 -»- research in fruit culture in this country, and of 

 the interest which has been aroused in connection 

 therewith among growers of fruit and progressive 

 horticulturists generally, that the well-known firm of 

 nurserymen, Messrs. George Bunyard and Co., Ltd., 

 of Maidstone, has considered the time ripe for the 

 issue of a new quarterly journal devoted exclusively 

 to pomology. The editor, Mr. E. A. Bunyard, a 

 member of the firrn named, is recognised both as a 

 practical grower of wide experience and as one 

 of the foremost authorities on systematic pomology 

 and pomological literature. Under his guidance the 

 Journal of Pomology should without difficulty estab- 

 lish itself as a publication of scientific value, meeting 

 the needs of a branch of horticulture which has ad- 

 vanced with rapid strides in its importance for the 

 country economically and physiologically since the day 

 when the late Mr. W. E. Gladstone advised farmers 

 to grow fruit for jam production as a remedy for 

 agricultural depression, and is at present none too 

 well catered for in this res|>ect. 



The contents of the first two numbers may appear 

 to suggest that there is scarcely occasion yet for a 

 periodical intended primarily to serve for scientific 

 and svstematic pomology in this country, some of the 

 more important articles being reprints or abridgments 

 of papers previously published in other journals. Such 

 articles, however, as those by Miss Sutton on self- 

 sterility in plums, cherries, and apples, and by 

 Brooks and Bailey on silver-leaf disease, are of a 



» T/ie Journal of Pomology. Edittd by Edward A. Bunyard. Vol. i. 

 Nos. I and 2. (Maidstone : Geo. Bunyard and Co., Ltd.) Published 

 Quarterly, Single N*s. y. 6d. ; Anaual Subscription los. 



