327 



can only be used against tlie adults, since the other stages of the 

 insect are protected by the epidermis of the plant. Control of the 

 adult is useless, unless it can be killed before the eggs are deposited. 

 Since the female frequently lays eggs on the day of emergence, fumi- 

 gation is necessary every night from October to April. Experiments 

 have been conducted to find a material for fumigation that vnW kill 

 or prevent oviposition by the insect and yet can be used every night 

 mthout injury to the plant. Pyrethrum and nicofume were tried, 

 but were not strong enough ; one sheet of nicofume in 600 cub. ft. 

 of space did not prevent oviposition, and it is doubtful whether the 

 plants would stand a stronger dose on 180 consecutive nights. Hydro- 

 cyanic acid gas is considered too dangerous for such frequent exposure 

 in the moist atmosphere of an orchid house. Further investigation 

 with fumigants is necessary. Spraying also would reach only the 

 adult, and as it must be applied with, the same strength and frequency 

 as fumigation it is not thought to be practicable. At present, there- 

 fore, neither of these methods is recommended. Injections of ether, 

 chloroform, carbon bisulphide, nicotine solution and pure air have 

 all been tried in infested growths. The first three named killed both 

 insect and infested part of the plant. Nicotine solution is satisfactory 

 when put into the cavity with the insects, but will not permeate the 

 plant tissues. Simple piercing of the shoot, that is, the injection of 

 pure air into the cavity, kills the insects. Piercing the swollen portion 

 would therefore be satisfactory if it were possible to discover all 

 infestations and pierce them properly. The destruction of infested 

 parts is the oldest and surest method of control known, but has the 

 disadvantage that the infestations are not all discovered. It is best 

 to examine all growths less than 18 months old at least once a week 

 unless the grower has not imported orchids or has had no infestations 

 for a year or longer. All the infested portions should be removed 

 and burned. New importations should be carefully kept in a separate 

 house until they have been known to be free from 7. orchidearum 

 for at least a year. If a very valuable plant becomes infested and 

 it is not desirable to remove the infested growth, the plant should 

 be quarantined. 



RoBSON (R.). The Shortage of Clover Seed in Essex in 1917.— JL Bd. 



Agric, London, xxv, no. 2, May 1918, pp. 176-179. 



The shortage of clover seed in Essex in 1917 was in part due to 

 the absence of bees to pollinate the flowers, the Isle of Wight disease 

 having killed off the majority of these, and in part to the destruction 

 of the seed by insects. In 1917, beans, peas and clover were all muck 

 eaten by beetles of the genus Sitones, which eat the leaves. A more 

 serious pest was the weevil, Ajpion apricans, Hbst. This weevil 

 oviposits in the flowers, and when the clover is cut the young weevils 

 in the larval stage are stacked with it, and these in a few days give 

 rise to adult weex'ils that issue from the stacks and eat up the first 

 clover plants they encounter and then pass on into the field to lay 

 eggs for the next generation. The heads of clover in which these 

 eggs are laid produce few or no seeds. Cloth bands coated with 

 coal-tar and pitch, placed round the stacks, catch a great many weevils, 

 and a trench with water and tar would undoubtedly trap the majority. 



