934 Summary of Agricultural Experiments, [feb., 



neighbouring plants. The presence of dodder seeds in seed used for leys 

 is obviously dangerous, and the suggestion that seed containing dodder 

 may safely be used in pasture is incorrect. 



Thrips on Peas (Jour, of Roy. Agric. Soc, vol. 69, 1908). — A 

 number of cases of thrips on garden peas came under the observation 

 of the Zoologist in 1908. The first seat of attack was not known, but 

 after a number of dissections, the eggs were always found buried 

 beneath the surface of the stamen sheaths. From there the larvae 

 emerge, and suck the sap of the adjacent pod. It is not known where 

 the insect passes the winter, and preventive measures cannot, conse- 

 quently, be adopted. Some treatment is, therefore, needed which will 

 check the pest when it first begins to attack the peas. Various washes 

 were tried on the already infested plants, but with very slight success. 

 Paraffin emulsions did not reach any large proportion of the insects, 

 which were too well hidden. Arsenic washes were hardly indicated 

 in the case of sucking insects, but they were tried, with no very bene- 

 ficial result. Distinct improvement, however, resulted from topping 

 the plants, just as beans are topped when suffering- from aphis. The 

 topmost shoots seemed to be the main seat of the attack, and the 

 pest was certainly mitigated by their removal. In some cases, badly 

 infested plants so treated put forth a late crop of perfectly clean pods. 



Leather Jackets (Jour. Roy. Agric. Soc, vol. 69, 1908.) — Ex- 

 periments were undertaken (a) to determine if any treatment would kill 

 the grubs without injuring the grass; (b) to see if by any means the 

 grubs could be induced to come to the surface, so that they might be 

 collected and killed. Carbon bisulphide vapour and solutions of 

 formalin, ammonia, carbolic acid, toluene and other substances were 

 tried, but none of them were found capable of destroying the grubs 

 without greatly injuring the grass. Hydrocyanic acid vapour did not 

 diffuse through the soil. Covering the ground at night, and copious 

 waterings with insecticides with the object of bringing the grubs to the 

 surface gave no consistent results. 



The effect of the above substances on the grubs was tested in the 

 laboratory, and showed that the grubs were remarkably difficult to 

 kill, and that it is highly improbable that any substance will be found 

 capable of destroying them in the ground without greatly injuring 

 the grass. 



The grubs frequently come to the surface, particularly in the early 

 morning, and rolling at such times cannot fail to be useful. Steps 

 should also be taken when the flies are about to emerge. The grubs 

 come up to the surface to pupate, and constant rolling- would be bound 

 to kill a great number. 



Spraying for Apple Sucker (Worcester C.C. Reports, by Kenneth G< 

 Furley). — In the winter of 1906-7, a number of washes were tried on 

 seven plantations in Worcestershire, against the eggs of the Apple 

 Sucker, Psylla malt. The principal washes used were : — Lime and 

 salt wash ; strong paraffin emulsion ; lime, sulphur, and caustic soda 

 wash. In addition, six other washes were used, including medium 

 and weak strengths of paraffin emulsion, Mr. Spencer U. Pickering's 

 paraffin and soda wash, and a lime and paraffin wash. It was also 

 thought advisable to try the ordinary caustic alkali wash, which was 

 at one time thought to have an injurious effect on the eggs, in order 



