44 Experiment Station Bulletin 367 



herbicide control and pasture management, including fertilization, should 

 proceed hand-in-hand to bring about effective weed control. 



A. R. Hodgdon 



PLANT PATHOLOGY 



The Testing of New Pesticides 



Six applications for each of 18 fungicide treatments were made dur- 

 ing the 1945 season on New Hampshire Victor tomatoes to control Al- 

 ternaria solmii. Single hill units with 10 replicates for each treatment 

 used were arranged in a randomized block. The concentrations of the 

 materials used and their effect on control of defoliation were as follows: 

 Dithane (Disodium ethylene bisdithiocarbamate) (^-lOO -|- ZnS0 4 and 

 lime**), Puratized (Phenyl mercuri triethanol ammonium lactate) ( 1-20,- 

 000**), Bordeaux (3-3-50**), Zerlate (Zinc dimethvldithiocarbamate) 

 (2-100**), Copper oxychloride sulphate (6-100**), Phygon (2.3-dich- 

 loro-l,4-naphthoquinone) (1-100**), Fermate Dust (Ferric dimethyldi- 

 thiocarbamate) (10-90*), Tribasic CuS0 4 (3-100*), Spergon (Tetra- 

 chloro-para-benzoquinone) (1-100*), Fermate + DDT (2-.6-100), Fer- 

 mate (2-100), Fermate (1-100), Fermate Dust + DDT (10-3-87), Bis- 

 muth Subsalicylate (P/3-IOO), Fermate (1-100) + sticker, Q15 (Lauryl 

 isoquinolinium bromide) ( ^ -100), No Fungicide. Average weights in 

 pounds of marketable tomato fruit per plant for each treatment were: 

 Zerlate (8.20**), Puratized (7.93**), Phvgon (7.70**), Fermate 2-100 

 (7.47**), Tribasic CuS0 4 (7.34**), Fermate 1-100 (7.09*), Bismuth Sub- 

 salicylate (6.30*), Fermate 1-100 + sticker (6.00*), Dithane (6.00*) Fer- 

 mate Dust (6.00*), Fermate + DDT (5.80), C.O.C.S. (5.67), Bordeaux 

 (5.50), Fermate Dust + DDT (5.30), No Fungicide (5.00), Spergon 

 (4.80), Q15 (3.98). None of the fungicides prevented eventual com- 

 plete defoliation by Alternaria. Definite injury to foliage was noted 

 with Dithane, and stunting of the plants was indicated with Bordeaux and 

 Copper oxychloride sulphate. 



M. C. Richards, R. C. Jones 



The Department of Entomology, co-operating, applied DDT in the 

 form of Gesarol A-3-Copper dust (3 per cent DDT) throughout the 

 1945 season as a control for potato insects in foundation stock plots of 

 Mohawk and Sebago potatoes. A total of six applications was made, be- 

 ginning July 7. 



Excellent control of flea beetles and Colorado potato beetles, and 

 tarnished plant bugs was obtained. In the case of potato aphids, injury 

 was prevented, but some aphids could be found especially on the lower 

 leaves late in the season. These were principally the green peach aphid, 

 an important vector of potato leaf-roll virus. The results indicate that 

 while this form of DDT will give excellent control of potato insects 

 grown for table stock, it cannot be expected to solve the problem of leaf- 



*Significantly (19:1) better than "No Fungicide". 

 'Highly significant (99:1). 



