50 



A series of experiments with various chemicals used as insecticides 

 against P. rosae is described, and the results are shown in tables. On 

 carrots sown in March, the first application was made about the third 

 week in Ma}^, and continued five times at intervals of three or four 

 weeks. Many of the substances tested proved useless ; the most 

 effective was green tar oil, which gave 89 per cent, clean carrots and 

 is recommended at a strength of 1 part to 99 parts precipitated chalk 

 scattered between the rows. Other chemicals recommended are 

 heavy creosote and heavy cresylic acid, applied in a similar manner, 

 and crude naphthaline and soap (the last, used at the rate of 1 oz. per 

 sq. yard in equal proportions, gave 71 per cent, clean roots). Carrots 

 sown in May showed much greater promise, the flies of the first 

 generation having finished oviposition by the time they were of appre- 

 ciable size, and they were practically free from attack until mid- 

 August, when the second generation of flies was ready for oviposition. 

 On these, I oz. of derris powder [1 oz. in table], mixed with double 

 the quantity of soot, used over each square yard, gave the best results. 

 Recommendations, therefore, include late sowing (in the second half 

 of May) and the application of one of the above insecticides. 



Hylemyia antiqua generally appears in early May and begins to 

 oviposit about 7th June ; from that date until September or later 

 the maggots are always present, the flies breeding continuously and the 

 generations overlapping. The eggs are laid in clusters, usually upon 

 the onion, where they can easily be found and crushed by hand. The 

 young larvae descend to the base of the onion and bore upwards into 

 the bulb. Pupation takes place in the soil surrounding the onion. 

 Leeks are also occasionally attacked. From 20 to 30 maggots may 

 be found in one onion, infested plants showing wilting and discolora- 

 tion, and finally lying prone on the ground. A Hymenopterous parasite, 

 Aphaereta cephalotes, helped to reduce the second generation ; this 

 insect also parasitises P. rosae, though to a less extent. 



In testing various insecticides none of the chemicals used gave a 

 very high degree of immunity, though it is pointed out that the in- 

 festation of 1920, when the trials were made, was the worst experienced 

 for man 3^ years ; 68 per cent, immunity was obtained by the use 

 of nicotine, 1 oz. in 5 gals, water, applied with a watering can ; 60 

 per cent, with 2 parts soot and 1 part derris, 1 oz. of the mixture per 

 square yard (soot alone, however, proved useless) ; 55 per cent with 

 1 oz. potassium permanganate in 2 gals, water, applied like the nicotine ; 

 54 per cent, with carbolic acid, 1 pint, with 1 lb. hard soap in 1 gal. 

 water, 1 part to 35 gals, water ; and 51 per cent, with 1 oz. resin 

 soap in 2 gals, water with \ oz. sodium carbonate, applied with a 

 watering can. Tar oils killed many of the plants, but used with another 

 medium than sand might give better results. 



While the time of sowing does not afford much help in control, some 

 advantage might be gained by sowing under glass in January and 

 planting out in the open in April. 



BucKHURST (A. S.). The Codlin Moth {Cydia pomonella, Linn.). 

 Its Life-history in England. — Fruit-Grower, Fruiterer, Florist & 

 Mkt. Gdnr., London, lii, nos. 1352, 27th October 1921, pp. 642- 

 643; 1353, 3rd November 1921, pp. 717-720; 1354, 10th 

 November 1921, p. 753, 27 figs. 



Cydia pomonella (codling moth) has been present in Great Britain 

 probably since the time of the Roman invasion, its food-plants being 



