g6 AGRICULTURAL RESEARCH AND THE FARMER : 



White Fly. — {Asterochiton vaporariorum) . — This is one of the 

 worst pests of greenhouses. Breeding freely on a variety of plants 

 outside, the adult insect constantly gains access to the houses, 

 in which it is able to pass the winter. Considerable financial loss 

 is caused to tomatoes, beans and potatoes grown under glass. 

 If infection takes place when the plants are young, and no 

 treatment is resorted to, frequently more than half the crop is 

 lost. As the result of an extensive investigation at the Cheshunt 

 Station, it has been demonstrated that successful control measures 

 are attained through fumigation with hydrocyanic acid gas, 

 which is generated with the following chemicals : sodium 

 cyanide, i oz. ; sulphuric acid (specific gravity i'8) i^ fluid 

 ounces ; water, 3 fluid ounces. For houses in good repair, or 

 in blocks, i oz. sodium cyanide is required for every 1,000 

 cubic feet. To prevent damage to the foliage, water must be 

 withheld from the tomato plant before fumigation, and the jars 

 for generating the gas should be placed at equal distances from 

 one another, a maximum of i oz. sodium cyanide being used 

 in each jar for houses 20 feet wide, and | oz. for those 14 feet 

 wide. Fumigation must begin at dusk, and the ventilators be 

 opened again at dawn ; the temperatue should not exceed 6o°F. 

 during the operation. As the eggs of the fly are not killed by 

 the gas, a second fumigation is necessary from 14 to 25 days after 

 the first according to temperature. 



East Anglian Institute of Agriculture, Chelmsford. 



Eelworm in Tomatoes. — Experiments to control this glasshouse 

 pest have been in progress for several years. As a preliminary, 

 it was necessary to test numerous chemicals and proprietary 

 articles, and it was found that the most effective was sodium 

 cyanide appHed in heavy doses to the affected soil. The more 

 recent glasshouse experiments have been undertaken to discover 

 the minimum dressing of cyanide, and it has been found that if 

 applied at the rate of 10 cwt. per acre per i foot depth, this will 

 clear the soil of eelworms without adversely affecting the tomato 

 plants. The tomato grower in whose glasshouses the experiments 

 have been carried out has become enthusiastic of the method. 

 He estimates that a moderate attack of eelworm disease would 

 reduce a crop by 25 per cent. Assuming a low average price of 6d. 

 per lb. for the tomatoes throughout the season, this loss would be 

 equivalent to at least £600 per acre. The cost of treatment with 

 sodium cyanide, even at present high prices, would not be more 

 than £100 per acre. 



