22 MASS. EXPERIMENT STATION BULLETIN 428 



(1945), and for further selection to pure line the tomato for resistance and high 

 yielding type. 



Laboratory prepared dusts containing 5 percent Thiosan, Fermate, Spergon, 

 or Dithane (HE- 175), with 95 percent talc are fungicidal to Cladosporium spores. 

 Dusts containing 10 percent active chemical and 90 percent talc gave satisfactory 

 control of spore germination when a water suspension of spores was applied to 

 dusted slides. The Dithane dusts were injurious to tomato foliage. The use of 

 the tolerant dusts would appear to meet the demand for a suitable fungicide for 

 the control of tomato leaf mold in the greenhouse. 



Causes and Control of Decay of Squash in Storage. (E. F. Guba, Waltham.) 

 The growing season was unusually dry. Six plots of Blue Hubbard squash were 

 grown, each of an area of 7,350 square feet and comprising 34 hills. Three 

 plots were sprayed five times with Bordeaux 4-4-50 mixture comb'ned with cal- 

 cium arsenate 1 pound and spreader; three similar plots were not sprayed. The 

 unsprayed out-yielded the sprayed plots, thus confirming the results of the previ- 

 ous year. The residue of the spray persisting on the squash in storage would 

 appear to provide some protection against decay organisms, but storage up to 

 November 1944 showed no significant or consistent contrast among the six har- 

 vested lots of squash. Loss from decay was negligible. Shrinkage was greater 

 among the stored squash from the sprayed than from the unsprayed plots. These 

 results, at least in a real dry season, would appear to discourage field treatment 

 with homemade Bordeau.x mixture as a disease preventive treatment. Other 

 types of fungicides are suggested for trial. 



Interrelation of Wettable Sulfur, Lead Arsenate and Lime in Apple Spraying. 



(E. F. Guba and E. V. Seeler, Jr., Waltham.) This project is intended to improve 

 upon our knowledge of the apple spraying schedule, involving the substitution 

 of materials to avoid injury, selection of the best types of sulfur to insure the 

 greatest protection against disease, selection of the most efficient fungicide for 

 scab eradication, the efifect on the adherence of sulfur of adding lead arsenate 

 and lime, etc. As in the past, detailed reports are compiled and submitted to 

 cooperating leaders. 



The year 1944 was an off season for chemical russet injury on Red Delicious 

 and no results were obtained. The usual amount of weather russet injur}' oc- 

 curred on Golden Delicious, and as usual the greatest percentage of russeted 

 apples occurred on the unsprayed trees. The season was too dry for an evalua- 

 tion of the protective action of various sulfur pastes used. The destruction of 

 scab spores on the foliage was best accomplished with lime sulfur 32° Be 2 gallons, 

 Everett Flotation Sulfur Paste 16 pounds, and Fermate 1 J^ pounds to 100 gallons 

 of water. The results with Wettable Spergon 2 pounds, HE-175 (Dithane) 

 1^2 pounds, and DN-111 IJi pounds to 100 gallons of water were unsatisfactory. 



Effect of Soil Temperature on Leaf Shape of Tobacco. (L. H. Jones.) The 

 effect of soil temperature on the shape of leaves of Havana Seed tobacco has been 

 found to occur in the absence of a mosaic virus. The apparatus provided two 

 constant soil temperatures, a low at 70°F. and a high at 90°F. At the low tem- 

 perature the leaves developed consistently as the normal ovate shape. At the 

 high temperature the newer leaves appeared yellow spotted, light green in color, 

 narrow, and very pointed, fitting the description of what is called frenching in 

 tobacco. Inoculation of healthy plants with the leaf juice of these frenched leaves 

 failed to result in the development of any symptoms of a mosaic virus, while 

 comparable healthy plants did develop mosaic symptoms when inoculated with 

 the juice of mosaic-affected leaves. 



