65i 



SPR/.YHIG AND DUSTING 



practices and Results 



Black rot is tho most dos'tructivo fungous diser.sc of the grapo. 6/ 

 It spreads rapidly in rainy hot v/eather. The climate in Arkansas iR especially 

 favorable for the spread of black rot, an-d damage from this disease was 

 unusually severe in ijrkansas in 1929* Excessive rains during May and Juno 

 interfered i?ath spraying. All but one of the vineyards studied in Arkansas 

 wore sprayed in 1929, and black rot ruined the crop on this 10-acre vineyard. 

 A grov/er caring for 60 acres of vineyard sprayed 40 acres just before the 

 bloom but did not spray the other 20 until 2 v/eoks later. No grapes were 

 harvested from these 20 acres beCsiuse of black rot. Crops from several vine- 

 yards were so badly damaged by black rot, that after the diseased berries were 

 shaken off, less than" half the crop remained and could be sold for juice 

 purposes only. 



■ The diversity of Arkansas; in 1927, rocoiiunohdod that 4 sprays be made 

 for black rot. The first spray vras to be" applied just before the bloom; the 

 second spray, immediately after the bloom; the third spray, two weeks after 

 the second; and the foijl*th s-ray, 2 weeks aft c^r " the third. 7/ 



One fifth of the vineyard acreage studied in Arkansas wa^s sprayed 

 oithcr 4 or 5 times in 1929. (table 63.) Tv/o sprays during the season were 

 more commonly applied than cither 4 or 5. Forty-five' percent of the acreage 

 was sprayed 3 times and 28 percent ib.s sprayed twice. Because of dry weather 

 during the last half of July and August the last spray was not so necessary 

 as it would have been if rainy weather had prevailed. 



On the average, the Arkansas vineyards that received a relatively large 

 number of sprays produced more grapes than did those receiving feww3? sprays, 

 and the return per hour of labor averaged more for the vineyards that wore 

 sprayed 3 or more tim.es than for the vineyards sprayed 2 times or less, (tabl6 64,} 

 The Arkansas vineyards receiving a large number of sprays wore not cared for 

 ^more intensively than the other vineyards as indicated by ''other growing costs'* 

 per acre, Tim^eliness, as well as the proper number, is absolutely essential 

 to the control by spraying of black rot and other diseases and insects. How- 

 ever , the data collected did not permit a coraparison. of the effects of timeli- 

 ness in spraying on yields and retuims, 



A^'out one half of the vineyard acrea.^ studied in Michigan \^s sprayed 

 and about one third was dusted. A larger proportion of the vineyard acreage 

 was dusted in Michigan than in the other areas; 20 of the Michigan grcj^rs 

 interviewed depended entirely upon dust and 3 Michi^n graders applied both dust 

 and spray. However, Button 8/ found by expol^imonts at Paw Paw, Michigan, that 

 dusting for black rot control was less effective thoa apraying. 



6/ Quaintance, A. L, and Shear, C. L, Insect and Fungous Enemies of the Grape, 

 U. S. Department of Agriculture, Farmor-s' Bulletin No, 1220, 1921, Revised 19^6, 



7/ University of Arkansas, Extension Circul':rr 145^ 1927, 



8/ Button, W, G. Grape dusting experiments, 1923. Annual report of the 

 Michigan State Hortic^oltural Society^ p, 154, 



