DECKER & BUCHANAN: EFFECTS OF RUST ON NECTARINES 333

2. Loucks, K. W. 1936. Spraying experiments forthe protectant fungicides. Plant Dis. Reptr. 55:898-902. control of certain grape diseases. Fla. Agr. Exp. Sta. Bull. 4. Parris, G. K. and L. H. Stover. 1947. Spraying grapes 294. 16 pp. for disease control in Florida—1945-1947. Proc. Fla. State 3. Neely, Dan. 1971. Deposition and tenacity of foliage Hort. Soc. 60 :93-94.

THE EFFECT OF RUST (TRANZSCHELIA DISCOLOR (F. CHL) TRANS. & LITR.) ON TREE PERFORMANCE AND FRUIT YIELD OF 'EARLY AMBER1 PEACH AND 'SUNGOLD' NECTARINE

Phares Decker Under favorable environmental conditions the dis ease develops on fruit and foliage causing serious IFAS Plant Pathology Department financial losses. The disease in Florida may remain Gainesville active on nursery trees through the winter and and rust infection has been observed on mature trees in D. W. Buchanan February (1). The relatively dry weather and low humidity found in North Central Florida from IF AS. .Fruit Crops Department February through May causesthe disease to de Gainesville velop slowly. Following the onset of the rainy season the disease may develop rapidly and if un Abstract Rust (Tranzschelia discolor) on stone controlled may cause complete defoliation by early fruit caused premature defoliation by September September. However, fruit infection has never been 5, 1972 on unsprayed 'Early Amber' peach and observed in Florida. 'Sungold' nectarine trees growing at the horti The uredospores produced during the growing cultural research unit. season become lodged in the leaf and bud scales Trees sprayed with zineb 5 times during the and serve as a source of inoculum for spring in growing season retained normal foliage through fection. Once established in the leaves the disease November 15, 1972 while trees sprayed with sul becomes severe only under hot, wet and humid fur and Triforine retained normal foliage through conditions. In North Florida, Georgia and Alabama October 25, 1972. the disease seldom appears before August and Unsprayed 'Early Amber' peach trees bloomed normally does not cause serious defoliation before 3 to 5 days earlier than trees sprayed with fungi frost. The disease has been reported from North cides. In 1973 fruit yields were increased by 30% Carolina, but it is not considered to be of economic on trees sprayed with zineb, while Triforine and importance (4). sulfur increased yields by 26 and 30% respec tively over unsprayed trees. Fruit yields of 'Sun- gold' nectarines sprayed with zineb and sulfur Materials and Methods were 35% more than unsprayed trees. Triforine In the summer of 1972 zineb, Triforine (Cela sprays did not increase fruit yields. W-524) and sulfur were compared with unsprayed checks on 'Early Amber* peach and 'Sungold' :.. Rust of peach and nectarine [(Tranzschelia dis nectarine trees. Individual plots consisted of 1 row color (F. Chi.) Trans, and Litr.)] is of economic of 27 peach and 12 nectarine trees. Four replicated importance in many parts of the world, and has plots were used in the experiment. The experiment vbeen reported from Australia, New Zealand, China, was conducted on the Horticultural Research Unit, Japan, Europe, North and South America (2). Gainesville, at least ten miles from any commercial Disease severity is correlated with periods of fruit planting. The fungicides were applied at10- warm, humid weather during the growing season day intervals using a power sprayer equipped with of the fruit trees. In Australia, New Zealand and an adjustable hand gun. The sprays were applied Southwestern parts of the United States rust may at approximately 200 PSI, in sufficient volume to appear a few weeks after the leaf buds unfold. wet the foliage thoroughly. Five applications were made during the summer growing season.

University of Florida, IFAS, Journal Series No. 5147. Unsprayed plots exhibited severe defoliation in 384 FLORIDA STATE HORTICULTURAL SOCIETY, 1973 late August and were completely void of leaves by riety (3). In this experiment the amount of bloom September 5, 1972. Trees sprayed with zineb re and final fruit set was quite variable. The un tained near normal foliage through November 15 sprayed trees were less thrifty and produced weak or until the first frost. Trees sprayed with sulfur appearing bloom. The fruit set was light and no and Triforine were intermediate as to defoliation thinning was required. In spite of the variation in between unsprayed and zineb sprayed trees. bloom and fruit set significantly greater yields The original plots were maintained as a com were harvested from trees sprayed with zineb or mercial planting through fruit harvest 1973. In sulfur than from unsprayed trees (Table 1). The sect and disease pests were controlled during the low yield from Triforine sprayed trees can be ex 1973 fruit growing season. Fruit yields from se plained by individual tree vigor and fruit set. lected trees were used to evaluate the effects of the rust disease. Discussion

Results The unusually heavy rust infection of 'Early Amber' peach and 'Sungold' nectarine in 1972 The earliest bloom in 1973 appeared on the un caused complete defoliation of unsprayed trees by sprayed 'Early Amber* peach trees approximately early September, 1972. In 1973 severe defoliation 5 to 7 days ahead of the bloom on the sprayed of unsprayed trees was first observed in late Sep trees. The bloom developed over a period of 10 tember. The variation in rust severity from year days and appeared weak. Although no cold injury to year is influenced by the amount of early in to bloom or fruit set was recorded during the fection, hot, wet and humid weather favorable for spring, the final fruit set was light. Thinning of disease development and spread. Fruit trees de the fruit for commercial production required little foliated in August or September developed fewer more than breaking-up fruit clusters. Fruit set and weaker fruit buds than trees which retain was heaviest on the fungicide sprayed trees. The normal foliage until November. Early defoliated growing season proved favorable and a commercial trees are also subjected to increased hazards from crop was harvested. winter injury, insect and disease pests. Prema The yields from the fungicide sprayed trees turely defoliated fruit trees with low chilling re were greater at the 99% probability level by the quirements tend to bloom earlier than mature de Duncan's New Multiple Range Test than the yield foliated trees. The earlier bloom and fruit, which from the unsprayed trees (Table 1). The yield occurs as a result of early defoliation in the fall, from the sulfur sprayed trees was significantly are more likely to be killed by frosts occurring in less than the yields from trees sprayed with zineb January and February. or Triforine. The decreased yield from unsprayed In these experiments the benefits are in favor trees is correlated with the amount of rust and of the fungicides for rust control. The seasonal defoliation recorded in 1972 (1). cost per acre for rust control includes 5 spray op No difference in the date of first bloom was erations and 10 lbs of zineb at a cost of $5.00. The observed between the sprayed and unsprayed increased value of the fruit from the zineb sprayed nectarine trees. This was correlated with the peach trees was approximately $626.00 per acre higher chilling requirements of the 'Sungold' va- over the fruit from the unsprayed trees. This is calculated on the basis of 108 trees per acre and fruit valued at .50 cents per pound. Nectarines Tabie 1. Influence of fungicides on rust control as measured valued at .60 cents per pound increased the returns by fruit yield of 'Early Amber' peach and 'Sungold' nectarine. $648.00 per acre for the fruit from zineb sprayed trees over the fruit from unsprayed trees. These Average Yield (lbs) per Tree of 'EarTy Amber1 Peach and 'Sungold' Nectarine results were recorded for 1973 following a heavy rust infection in 1972. These test plots will be maintained for further evaluations. The effects on Chemicals Sprayed on Foliage the yearly performance and life span of the fruit Cuitivars Sulfur Zineb Triforine Check trees from repeated premature defoliation will be Early Amber 32.6B* 37.4C 37.5C 25.8A evaluated. Sungold 25.3C 25.3C 14.OA 15.3B Rust on 'Early Amber' peach and 'Sungold' nectarine was effectively controlled with five ap * Values not having common letters are significant at 99% level plications of zineb applied at 10-day intervals dur- by Duncan's New Multiple Range Test. ADLERZ & MORTENSEN: SEED CHALCID DAMAGE TO GRAPES 335

ing the summer season of 1972. Five applications Literature Cited

of sulfur or Trif orine increased the fruit yields as 1. Decker, P. and D. W. Buchanan. 1972. Chemical Con compared with no spray but was less effective than trol of fruit and foliage diseases of stone fruit. Fla. State Hort. Society V. 85, p. 324-326. zineb. 2. Dunegan, J. C. 1938. The rust of stone fruit. Phyto pathology 28:411-427. 3. Sharpe, R. H. and C. E. Arnold. 1971. Peaches and nectarines in Florida. U. of Fla. Exp. Sta. and Ext. Serv. Cir. No. 299A. 4. Smith, C. F. and C. N. Clayton. 1972. Peach disease and insect control. N. C. State Univ. Agr. Ext. Serv. Cir. No. 407.

SEED CHALCID DAAAAGE, DISTRIBUTION, AND CONTROL ON CENTRAL FLORIDA BUNCH GRAPES

W. C. Adlerz and J. A. Mortensen lished record of its occurrence in Florida. Prior to this the insect had been reported only from IFAS Agricultural Research Center New York, Connecticut, Ohio, Michigan, and Cali Leesburg fornia (5). Specimens in the National Collection are from New York, Ohio, Connecticut, and Vir Abstract. A seed chalcid (Prodecatoma cooki ginia (B. D. Burks, personal communication). (Howard)) new to Florida has been observed on Cultivated grape and Virginia creeper (Parthe- bunch grapes since July 1971. Development of nocissus sp.) are the only reported hosts of this the insect from egg to adult takes place within insect and it was referred to by Crosby (3) as developing grape seeds. Damage consists of "the seed-chalcis of the Virginia creeper". empty seeds, and tunnels formed by adult wasps The purpose of this paper is to report pre burrowing through the grape flesh and skin to liminary observations on the central Florida dis emergence. Peak abundance of emerged wasps in tribution and abundance of this insect, the nature 1972 was in the last week in June, about 2 weeks and extent of its damage in grape, and initial before harvest. Damage was found in bunch observations on its control. grapes in 6 out of 9 central Florida counties sur veyed. In limited grower tests, damage was re duced where adult insects were controlled before Materials and Methods egg laying by spraying with malathion. Wasp activity near grapes was monitored with yellow, 5x10 in. sticky board traps prepared the Grapes in a dooryard planting in Sumter same way as for aphid trapping (1). Traps were County were examined in July 1971 after reports hung from grapevine trellis wires close to the of severe insect injury. The observed injury con underside of the foliage canopy. In 1972 11 traps sisted of holes in the berries caused by emergence were set out at 5 locations in Lake and Sumter of adult insects, toughened grape pulp around Counties within 8 miles of the Agricultural Re emergence tunnels from seed to skin, and seeds search Center at Leesburg (Table 1). Trapped mined by larval feeding. Due to the nature of wasps were removed from the sticky boards with these injuries the insects were tentatively identified a scalpel, cleaned in xylene, and processed through as seed chalcids. Subsequently, wasps reared from 1:1 xylene-95% alcohol, and 95% alcohol, to 70% infested grapes or excised from emergence tunnels alcohol in which they were identified under a dis were identified as Prodecatoma cooki (Howard) secting microscope. The central Florida distribu by Dr. B. D. Burks, Systematic Entomology Lab tion of this insect and some measure of grape oratory, Entomology Research Division, Agricul varietal susceptibility was determined by a survey tural Research Service, USDA, Washington, D. C. conducted between June 27 and July 5, 1972 of 20560 (2). The report of preliminary observations home plantings in 9 counties (Table 2). on this insect by Adlerz (2) was the first pub- Results

Florida Agricultural Experiment Stations Journal Series No. 5138. Wasp activity was detected under 'Blue Lake*