AGRICULTURAL RESEARCH IN NEW HAMPSHIRE 45 



the mean ripe yields, total yields, and dry weights of the plants in the 

 treatments were compared with the check plants at the end of, the season. 

 In general, the fruit quality decreased rapidly after the plants showed about 

 80 per cent defoliation. When the marketable fruits produced by the check 

 plants were compared with those obtained from the treated plants — up to 

 the time when the plants showed 80 per cent defoliation — it was found that 

 a significant increase in yields had been obtained as a result of the 

 treatment. 



On the basis of the data taken this year, it is believed that when toma- 

 toes of the determinate type are grown, a fairly accurate interpretation of 

 the values of spray treatments may be obtained by comparing cumulative 

 yields up to the 80 per cent defoliation level rather than waiting -until the 

 end of the season to compare green fruit yields, ripe fruit yields, or total 

 fruit production. 



II. Testing Tomato Varieties for Resistance to Late Blight 



In searching for a tomato variety resistant to the late blight pathogen 

 Phytophthora injcstans, a great many commercial varieties, selections, and 

 species of the genus Lycoperscion have been tested. Selections in the spe- 

 cies L. csculcutuin, L. p'unpincUijoUnm, L. chilense, L. pcrinnanitni have 

 proved very susceptible. A few selections in L. hirsutuni have shown some 

 resistance to P. injcstans with potato tubers as the source of the inoculum. 



III. Factors Affecting the Development of Early Blight on Tomatoes 



Differences in defoliation from Early Blight among varieties of toma- 

 toes have been observed and studies have been made to determine the fac- 

 tors causing such differences. The relationship between fruit load (the ra- 

 tio of fruit to leaves) and defoliation was investigated. Sixteen varieties 

 were chosen to represent extremes in tomato types. Ten plants were used 

 from each variety and replicated in a randomized block. The plants were 

 harvested about midseason and the percentage defoliation and fruit-to-leaf 

 ratio was calculated. The results show the fruit-to-leaf ratio is significant- 

 ly related (at the 1 per cent level) to percentage defoliation regardless of 

 variety. In a second experiment the onset of fruit load in four varieties — 

 Early Chatham. Earliana, New Hampshire \Tctor, and Marglobe — with 

 respect to defoliation was investigated. Fifty plants from each variety 

 were used and 10 plants from each were sampled weekly. Defoliation was 

 recorded and the fruit-to-leaf ratio calculated. A curvilinear relationship 

 was found to exist between fruit load and defoliation for each variety. The 

 time of fruit yield and the fruit load were found to affect the physiol- 

 ogical maturity of the tomato plant. The maturity brought about largely 

 by these two factors vitally affects the time and rate of defoliation of the 

 tomato plant from Early Blight. 



]\I. C. Richards. R. W. Barratt 



Spraying for Apple Scab 



Spray tests on ^Iclntosh trees were conducted at the University Hor- 

 ticultural Farm. Seven spray applications were made as follows : pink, 

 bloom, calyx, and four cover sprays. Fermate (1^-100) and Mike sul- 

 phur (6.6-100) were compared. In a third treatment. Bordeaux mixture 



