48 EXPERIMENT STATION BULLETIN. 



GENERAL CONCLUSIONS 



DUSTING 



Apples. During the last three years* apple scab and chewing insects 

 have been controlled satisfactorily by the use of dusting materials. The 

 results have been equal to or better than where dilute lime-sulphur and 

 lead arsenate were used. 



No assurance is given that dusting will give satisfactory results in 

 seasons when weather conditions are more unfavorable than in 1917, 

 1918 and 1919. Weather conditions during 1917 were very favorable 

 to scab development but conditions were not so bad as in 1915 and 1916. 

 In many orchards in 1918 there was very little scab development even 

 on untreated trees. In 1919 conditions were favorable for scab develop- 

 ment early in the season and unfavorable later. 



The dusting method of application, however, is recommended at this 

 time as a supplement to spraying. Dusting is not a complete substi- 

 tute for spraying as no dusting material has been developed which can 

 be recommended for the complete control of scale insects. No recom- 

 mendation can be made covering aphis control because of the lack of 

 injury on check trees. 



Cherries. Sulphur dust failed to control shot-hole fungus on English 

 Morello cherries. It also failed to prevent the primary infection of 

 Coniothyrium which developed seriously on trees of this variety. Dilute 

 lime-sulphur controlled shot-hole fungus and prevented any development 

 of Coniothyrium. 



Plums. Dusting mixtures composed of sulphur, lead arsenate and 

 tobacco dust have caused no injury to plum foliage (Japanese varieties 

 included). 



Peaches. Dusting is not recommended for the control of leaf-curl. 

 No definite recommendation can be made regarding summer dusting of 

 peaches except that dusting materials have caused no foliage injury. 

 The indications, however, are that dusting will give satisfactory control 

 of peach scab, brown rot and curculio. Favorable results have been 

 reported from other states.** 



Currants. Sulphur dust and dilute lime-sulphur are not recommend- 

 ed for use on currants to control anthracnose because of foliage injury 

 during hot weather and their failure to control the disease satisfactor- 

 ily on all varieties. Bordeaux gave almost complete control of anthra- 

 nose and caused no foliage injury. It is recommended for use on cur- 

 rants where the leaf -spot diseases cause serious injury. It should be 

 used according to the schedule followed in the experiments reported in 

 this bulletin. 



*See Special Bulletin 87 for results of work in 1917. 



**Bul. 167, We-it Virginia Agricultural Experiment Station and Circular 21, Georgia State 

 Board of Entomology. 



