Agricultural Research in New Hampshire 45 



roll spread by aphids late in the season. It is conceivable that improved 

 equipment for the application of DDT, which will enable the grower to 

 obtain a more complete coverage of the lower leaves of the potato plant, 

 may prove helpful. 



DDT in the form of 3 per cent dust, applied to Alarglobe tomato 

 transplants the day after setting in the field and again 16 days later, gave 

 excellent control of flea beetles and caused no apparent plant injury. 



In the spring of 1945, DDT at the rate of two pounds per acre, com- 

 bined with Yigoro fertilizer at the rate of 1000 pounds per acre, applied 

 by means of a mechanical spreader to approximately one acre of lawn 

 heavily infested with Japanese beetle grubs, reduced the grub population 

 approximately 90 per cent. At the peak of beetle flight later in the sea- 

 son the treated area was relatively free of adult beetles. 



J. G. CONKXIN 



Plant Disease Investigations 



Three varieties of raspberries, Taylor, Latham, and Viking, were 

 sprayed April 9, when the plants were in the late delayed dormant stage, 

 with 1 per cent Elgetol. Some injury to the exposed leaves occurred at 

 this concentration, but no permanent injury was evident. Periodic inspec- 

 tion of the fruiting bodies of spur blight pathogen showed that spore de- 

 velopment within the fruiting bodies ceased if the canes were covered by 

 the spray material. No further spray applications were made during the 

 growing season. On October 29, 1945, data taken showed the presence 

 of spur blight lesions on each of the three varieties as follows: Taylor 96 

 per cent, Latham 96 per cent, and Viking 80 per cent. Average number 

 of lesions per cane were: Taylor 3.3, Latham 3.5, and Viking 1.4. Win- 

 ter injury on the above varieties, as observed in May, 1946, was greatest 

 on Viking which showed the least amount of spur blight both as to the 

 number of canes infected and the number of lesions per cane. The test 

 this year indicates that one Elgetol spray in the spring of the year is not 

 sufficient to control spur blight, and that winter injury is not directly 

 correlated with spur blight. 



M. C. Richards, R. C. Jones 



The Control of Tomato Diseases 



In former tests it was found that tomato varieties having a heavy 

 fruit-to-leaf ratio defoliated earlier than those with a high leaf-to-fruit 

 ratio. The leaves appeared to become susceptible to attack by the patho- 

 gen as the nutrients were drained from the leaves by the rapidly develop- 

 ing fruits. In 1944, and again in 1945, attempts were made to supply the 

 roots of the test plants with an excess of N. P, and K so that a higher 

 level of these nutrients could be maintained in the leaves during the fruit- 

 ing period. The New Hampshire Victor tomato variety was used, as it 

 fruits abundantly and defoliates severely. Inorganic nutrients of N, P, 

 and K were added to the soil at the base of each plant, about six inches 

 deep, when the plants were set in the field from three-inch pots. The 

 tests were arranged in randomized blocks with five replications per treat- 



