-5- 



betvveen the last usual cover spray and harvest time. Based upon artificial 

 infection experiments, using ivlclntosh apples in Now York State several years ago, 

 pathologists found that wet periods of at least 40 to 45 hours are necessary for 

 Scab infection during the first half of August, v/hile the fruit must remain wot 

 for 3 to 4 days to allow infection during late August and early September, 



This means that there still is time to head off an infection of unprotected 

 fruits if an application of sulfur dust or wettable sulfur spray is made (1) after 

 a wet period in the first half of August has progressed to the 30 to 35 hour period 

 and promises to extend still further, or (2) after a 2- to 3-day v;et period in 

 late August or early September, 



Although no definite information is available on length of wetting period 

 required for late season leaf infection, observations indicate that the upper 

 surface of v/ell matured loaves may require nearly as long a period as the fruits. 

 The under surface of leaves is much more readily infectod during August and 

 September than, the upper surface. 



In considering standard spray materials possessing the longest protective 

 properties for late season Scab control, the sulfurs rank first. Full strength 

 Formate in the late cover applications coinmonly allows considerable under-surface 

 leaf infection during August and September, whereas good protection may be main- 

 tained from its use duriiig the same period on tho apples. Spray residues of 

 wettable sulfur, or sulfur plus Formate, outlast Formate alone for leaf protection 

 -- find probably also for fruit protection, 



— 0. C. Boyd 



FRUIT INSECTS IN MIDSUMi\./[ER — 1948 



Fruit insect pests have made this an interesting season for the entomologist -- 

 perhaps a hectic one for the grower. Or, should I say that insect pests are 

 making this a tough season -- because they are not through yet. Of that unfor- 

 tunate fact, wo can. be sure. 



Let's review a few of tho outstanding developments, note our mistakes and 

 make plans to correct them before we forget v;hat they vrorc rjid how im.portant they 

 became as the season progressed, 



PEACh'ES - The BHC-DDT coiibination appears to have done an excellent job for 

 peach growers and has not caused injury. In a few cases those late Curculios did 

 some damage after the final application had lost its effectiveness but the 

 Oriental Fruit Moth never got started in the tenriinals where the three applications 

 of DDT were applied at weekly intervals. Injury by Tarnished Plant Bug was also 

 reduced, but an early — real early — petal-fall application of DDT would improve 

 the control of this post. There uro too many peach trees being weakened or 

 destroyed by the Peach Tree Eoror, It is now so practicable to control that insect 

 with DDT that I hope growers really do a good job and thus lengthen the productive 

 life of their trees, 



PEARS - Some excellent reduction in Pear Psylla early broods have been 

 obtained with dormant oils applied before many eggs had been laid, DN materials 

 including the novt DN-289 were good ovicides, but many eggs were laid after they 

 could no longer be applied safely. Nicotine sulphate alone and with simraer oil 

 have been effective against the nymphs of summer broods. 



