RESEARCHES AT WISLEY. 



167 



suggests that they are only quite at home when within a bud, and do not 

 promiscuously take a walk on a twig for the sake of an airing. As it is 

 practically impossible to destroy the mites when in a bud, it follows that 

 they can only be destroyed when migrating from old to new buds, or by 

 preventing their escape from the old buds. 



Experiment III. — Strips of black paper coated with a thin layer of 

 vaseline were tied round the main stem and branches at various points of 

 a badly infected bush. Judging from the relative number of captures on 

 the difierent traps, it was obvious that the mites knew exactly what to do 

 when they left the old buds. What they did was to ascend the shoots in 

 the direction of the new, healthy buds, the terminal bud being specially 

 favoured by their presence. A band of vaseline paper fixed round the 

 stem two inches above the ground line did not capture a single mite, 

 proving that the mites showed no desire to voluntarily leave the bush. 



The above experiments appeared to indicate a satisfactory solution of 

 the problem I had attempted to solve ; in fact, like most laboratory 

 experiments, where every possible care is taken that all details necessary 

 to ensure success are religiously carried out, they left nothing to be 

 desired. However, knowing from past experience that successful labora- 

 tory experiments do not necessarily mean success when widened out to 

 the extent of practical field work, it was considered necessary to test the 

 idea that mites could be prevented from reaching healthy buds by the use 

 of a sticky substance, by some method that could be practised on a large 

 scale and at a moderate cost. 



Having enlisted the practical sympathy of some friends, I merely 

 suggested that grease or a sticky substance of some kind, not easily 

 washed off by rain, should be brushed over the branches, leaving the 

 choice of materials to themselves. 



The substances used by these experimenters were cart grease, " palm 

 oil " or the material used for lubricating the wheels of railway carriages ; 

 dripping. One person covered the diseased buds with thinned gas-tar. In 

 my own experiments vaseline was used. 



In every instance the method employed proved a success ; a good crop 

 of fruit was produced, and the greatest number of "big-buds " found on 

 any one bush after one year's treatment was seven, not a single diseased 

 bud being met with after the second year's treatment. All the treated 

 bushes are perfectly healthy and ^igorous. 



For practical purposes vaseline would be too expensive, although it 

 stands rain better than any other substance I have tried. The choice lies 

 between cart grease and " palm oil," as defined above, which should be 

 applied by means of an ordinary paint brush of the size known as a sash 

 brush. The branch to be treated is held by the tip, and the brush, loaded 

 with grease, is rubbed up one side, down the other, taking care to hit 

 " big-buds," which need not be removed. This treatment should be 

 applied early in the season, before the young buds begin to expand. 

 If I had infested bushes, to make certain of permanent results I should 

 make two applications of grease during the season, one about the middle 

 of February and another the last week in April. However, as stated 

 above, one application during the second week in March proved very 

 satisfactory. 



