Several Years' Comparisons of "Good" Tomato Fungicides
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CONOVER: TOMATO FUNGICIDES 127 tee area, the maintenance of 2500-3500 ppm tire area. More specifically, the lack of cal soluble salts in the soil moisture will mean an cium could be associated with softness in adequate fertility level. During the latter fruit resulting in poor carrying quality and part of the fall crop season, the Ruskin fields with the prevalence and severity of blossom- ranged from 500 to 1000 ppm which is ex end rot. The practice of using nitrates as top tremely low. When the total soluble salt ap dressings seemed to accentuate the poor carry proaches 5000 ppm, the point of diminishing ing quality. Complicating factors were also returns as regards to tomato plant response will involved with blossom-end rot correlations. be reached. Indications are that nitrogen, potassium and Another soils test, the moisture equivalent, fertility levels in general were inadequate for as indicated in Table 4 was not associated with best quality and yields. the better crop. However, a relatively higher Plant tissue analysis proved valuable as an moisture equivalent generally indicates a soil indicator of calcium, nitrogen and potassium with more organic matter and thus a better deficiencies. The more valuable diagnostic moisture- and nutrient-holding capacity. soil tests included pH5 total soluble salts and "* Perhaps the primary factor which depletes calcium supplying power of the soil. It is be nutritional levels and upsets nutritional bal lieved that certain diagnostic tests, combined ances is leaching. As mentioned previously with good cultural practices and continued re search, will lead to improved quality and in leaching was a big factor during the fall crop season and also important toward the end of creased yields. the spring crop season. It should be empha LITERATURE CITED sized that an inadequate supply of nutrients 1. Evans, H. J. and Troxler, R. V. Relation of as well as an unbalanced supply or a specific Calcium Nutrition to the Incidence of Blossom-end Rot of Tomatoes. Proc. Am. Soc. Hort. Sci. 61:346- deficiency can affect quality as well as yield. 352. 1953. 2. Ftorsee, W. T., Jr., Hayslip, N. C. Hills, W. A. and Wolf, E. A. The Lime Requirements of Vegetable Conclusion Crops on the Sandy Soils of the Lower East Coast of Florida. Proc. Soil Sci. Soc. Fla. 11:80-89. 1951. A study of nutrition as associated with to 3. Ham son, A. R. Factors Which Condition Firm ness in Tomatoes. Food Research 17:370-379. 1952. mato quality with emphasis on chemical tests 4. Sims, G. T. and Volk, G. M. Composition of as indicators was carried out in the Ruskin- Florida Grown Vegetables I. Bulletin 438. Agr. Exp. Sta. Univ. of Fla., Gainesville, Fla. 1945. Manatee area the past two crop seasons. 5. Volk, G. M. and Bell, C. E. Some Major Factors Plant tissue and soils tests indicated that a in the Leaching of Calcium, Potassium, Sulfur and Nitrogen from Sandy Soils. Bulletin 416, Agr. Exp. general calcium deficiency existed in the en Sta. Univ. of Fla. Gainesville, Fla. 1947. SEVERAL YEARS' COMPARISONS OF "GOOD" TOMATO FUNGICIDES Robert A. Conover indicate the superiority of these fungicides both with respect to disease control and yield. Sub-Tropical Experiment Station Most reports show slight or no differences among these fungicides in disease control and Homestead variable but usually insignificant differences Zineb and nabam-zinc sulfate have given in yield. Most of these reports have presented outstanding control of many diseases of Flor the results of one or two season's work. It ida vegetables for the past 8 or 9 years. would seem that such differences—too small Within the last three years, maneb and nabam- to be statistically significant in a given experi manganese sulfate have been added to the ment—might be significant if they occurred list of fungicides that are being successfully consistently over a period of several years. used in the vegetable industry. Results of This paper reports on the results of six year's many experiments, published in the Proceed comparisons of zineb and nabam-zinc sulfate ings of this Society or in the Annual Reports on tomatoes and of three years' results com of the Florida Agricultural Experiment Station, paring these two with maneb and nabam-man- Florida Agricultural Experiment Station Journal ganese sulfate. Series No. 801. 128 FLORIDA STATE HORTICULTURAL SOCIETY, 1954 All experiments were conducted on the Sub- there have been no differences of significance Tropical Experiment Station's Highlands Farm between zineb and nabam-zinc sulfate in the in Dade County. In each experiment treat control of late blight or gray leaf spot. In ments were randomized and replicated four three year's experiments, maneb and nabam- times. Sprays were applied with a tractor- manganese sulfate have provided control of drawn, power sprayer in volume sufficient to late blight fully equal to that given by zineb give good coverage of foliage and fruit. Ap or nabam-zinc sulfate; and there were no dif plications were made on a 3 to 7 day schedule ferences between maneb and nabam-mangan- which fluctuated according to disease inten ese sulfate. sity. Cultural care of the plots approximated Tomatoes sprayed with nabam-zinc sulfate that provided commercial tomatoes in the displayed the injuries characteristic of this area. Three varieties of tomatoes were used fungicide in all experiments. Vines were during the course of these experiments: somewhat stunted; leaves were chlorotic, Grothen's Globe, 1948-49 season; Missouri rolled upward at the margin and reduced in S-34, 1949-50 and 1950-51 seasons; Home size. Some fruit showed the roughened, scar stead, 1951-52 through 1953-54 seasons. To red and sometimes scabby spots, scattered in matoes were picked in the mature-green stage. a spray-droplet pattern, that is typical of dam Fungicides were used in the following age to the fruit skin caused by nabam-zinc amounts per hundred gallons of water: zineb, sulfate. None of the other fungicides caused 2 pounds; nabam, 2 quarts plus 0.75 pounds any discernible injury, but foliage sprayed zinc sulfate (in some experiments 1 pound with maneb or nabam-manganese sulfate had zinc sulfate was used); maneb, 1.5 pounds; a darker green and more luxuriant appearance nabam, 2 quarts plus 1 pound manganese sul than that sprayed with zineb. In some cases fate. Nabam-zinc sulfate was prepared by this may have been due to a difference in ap putting the nabam in the sprayer tank when pearance of the spray residue, but mostly it about one-third of the quantity of water de appeared to be a nutritional response to the sired was present and adding the zinc sulfate manganese fungicides. (either in solution or sifting it directly into Yield records for the past six seasons from the tank) when approximately two-thirds of tomatoes sprayed with zineb and nabam-zinc the water was present. In preparing nabam- sulfate are presented in Table 1. Zineb- manganese sulfate, a concentrated suspension sprayed plants yielded an average of 36 crates of manganese sulfate was prepared in a pail per acre more marketable tomatoes than those by adding 1 pound of Techmangam to 2 gal sprayed with nabam-zinc sulfate, and 31 lons of water. Nabam was added directly to crates more in total yield. Statistical analysis the suspension with stirring. When the reac of the results indicated the former difference tion was completed in the pail, the contents to be significant at the 1% level, the latter at were added to the sprayer tank and diluted as the 5% level. Approximately 60% of the yield desired. There was no evidence of variability from zineb-sprayed tomatoes was marketable, of the tank-mixed fungicides as reflected in compared with 55% from tomatoes sprayed disease control, yield, or plant safety during with nabam-zinc sulfate. The lower percent these experiments, but some variation in color age from the latter resulted in part from dam was noted in various lots of nabam, zinc sul age to the fruit. fate and manganese sulfate used in these mix Records for the past three tomato-growing tures. seasons (Table 2) show that tomatoes sprayed Except for the 1948-49 season, when gray with maneb and nabam-manganese sulfate leaf spot (Stemphylium solani Weber) was produced approximately equal yields, both severe, late blight (Phytophthora infestans producing somewhat more than zineb-sprayed (Mont.) DBy.) was the only foliage disease of plants. On the other hand, nabam-zinc sul- consequence. In each season except the fate-sprayed tomatoes produced significantly 1948-49 season, late blight was severe, and lower marketable and total yields. Approxi upon comparison with other fungicides in the mate percentages of marketable yields for experiments, it was clear that the yields ob these fungicides were: nabam-manganese sul tained were possible only because of the ex cellent control of late blight by the carbamate fate, 58%; maneb, 58%; zineb, 56% and nabam- fungicides. In experiments during six seasons, zinc sulfate 51%. CONOVER: TOMATO FUNGICIDES 129 fable 1# Yields of mature-greeritomatoes (60-pound crates per acre) from replicated experimental plots sprayed with zineb and nabam-zinc stilfate# Season Marketable yield Total yield zineb nabam-zinc sulfate zineb nabam-zinc eulfa 1948-49 273 252 3^3 322 1949-50 287 214 440 407 1950-51 133 144 299 322 1951-52 124 77 235 211 1952-53 221 195 440 441 1953-5** 323 264 528 397 6 season average * 227 191 381 350 Difference in average yield is statistically significant at the 1$ level for marketable yield and at the 5% level for total yield. Table 2.