RESE/'.RCH ON ORCH/iRD DISEASES 

 at the 



¥Altha;i field station 



Orchard disease research has been a part of the overall activity of the 

 ViTaltham Field Station almost from the beginning of its establishiiient as the ilarket 

 Garden Field Station in Lexingtoft in 1917. The v;ork vras done by members of the 

 staff of the Botany Department ot the University, originally by v/ebster S. Krout 

 (1920-22), then William L, Doran (1923-2?), and from 1928 by the writer. The 

 work Mia3 related to disease control, spray injury, dust vs. spray and laboratory 

 and service work, 



Krout 's work ell owed that Bordeaux mixture v/as as good as lime sulfur in the 

 pre-blossom sprays. Lime sulfur ?:as advised for the rest of the schedule (/ass. 

 Sta. Bui. 21i;, 1923). Doran showed that there was nothing gained from copper 

 sprays or dusts before bloom. Preference was given to lime sulfur and sulfur dusts. 

 Omitting copper materials significantly lessened fruit russet. Lime sulfur and 

 lead arsenate caused foliage injury, but a dry mix of sulfur, lime and casein 

 (New Jersey Dry ilix) did not. 



This vras the beginning of the trend tovrard vrettable, insoluble sulfurs. 

 The fineness of sulfur particles \vas emphasized, and eventually perfection was 

 reached with sulfurs with particles in a range of 1-3 microns in diameter. In 

 this respect the paste sulfurs were unique. This viras a vast improvement over 

 75-100 micron sulfur used in the first dry mix sulfurs in the period 1922-2^ and 

 coincidentally in better control of scab. Lime sulfur became less and less worthy 

 and then in 19U3 it was omitted altogether from our official schedule of applications. 



Yifith improvements in fine particle size came multiple X sprays, concentrates 

 and mist blovrers, air borne machines and improvements in dusting to improve dis- 

 tribution and coverage, and less dependence on virater as a carrier. 



The introduction and success of ferbam was sensational. The substitution of 

 ferbam for sulfur eliminated fruit russet on Delicious. It improved foliage color 

 and yields by supplying nitrogen directly through the leaves. It gave better 

 control of apple rust than sulfur. The circumstances led to exhaustive search for 

 more and better dithiocarbamate fungicides, Ferbam was follov/ed by ziram, zineb, 

 maneb, for vegetable disease control, replacing the traditional copper fungicides, 

 and by thiram and the new iron and manganese carbamates. 



The phenyl mercury fungicides were introduced in the early forties, and what 

 an immense help they have been in serious scab situations. They replaced lime 

 sulfur for eradicating scab. They gave back-action control of scab three to four 

 days from the beginning of the rain- infection period. Scab control with back- 

 action fungicides exploded the idea of protection in advance of infection rains as 

 the one and only method of controlling scab, Coincidentally, in-the-rain spraying 

 and dusting became a feature of the grovier's practice. 



In the progress with organic fungicides we have also seen the trend away from 

 lead arsenate in the apple schedule and its elimination altogether from the peach 

 schedule. These circumstances have given the fungicide schedules a greater measure 

 of safety. 



