Reprinted from Proc. Fla. State Hort. Soc. 116:63-72. 2003. TRENDS IN FRUIT YIELD AND QUALITY, SUSCEPTIBILITY TO POWDERY MILDEW (SPHAEROTHECA MACULAR/S), AND APHID (APH/S GOSSYP//) INFESTATION FOR SEVEN STRAWBERRY CULTIVARS GROWN WITHOUT PESTICIDES IN A PASSIVELY VENTILATED GREENHOUSE USING PINEBARK AS SOILLESS SUBSTRATE AsHWIN V. PARANJPEI, DANIEL]. CANTLIFFE, AND SILVIA RONDON University of Florida, lFAS Horticultural Sciences Department Gainesville, JiL 32611-0690 son (November-January), but declined during the latter part of the season (February-March), with the exception of fruit color, which was more red during the mid-season (January-Febru- ary) compared to the early and later part of the season. Thus, Florida strawberry cultivars such as FL97-39, 'Carmine', 'Trea- sure', and 'Strawberry Festival' evaluated in this study per- formed well under protected culture in north-central Florida, however, cultivar selection should be made after considering susceptibility to fungal diseases and insect pests. CRAIGKCHANDLER Gulf Coast Research and EducationCenter 13138LewisGaUagher Road Dover. }L 33527-9664 JEFFREY K BRECHT,ELUOTT J. BRECHT, AND KIM CORDASCO Unive1:5ity Of Florida, IFAS Horticultural Sciences Department Gainesville, FL 32611-0690 Additional index words. Fragaria x ananassa, Aphidius colemani, Lysiphlebus testaceipes, Neoseiulus californicus, APhis gossypii, Tet- ranichus urticae, protected culture, biological control Abstract. Strawberry (Fragaria x ananassa Ouch.) cultivars are almost exclusively bred for field production, and limited infor- mation on their performance under protected cultivation in the U.S. is available. Seven strawberry cultivars were grown in a passively ventilated greenhouse in north-central Florida to evaluate their fruit yield and quality potential, and susceptibil- ity to powdery mildew and aphid infestation. In October, plug transplants were planted at a density of 22 plants per m2 in Po- Iygal@ troughs filled with pine bark. No insecticides or fungi- cides were used, but the biological control agents Aphidius colemani Viereck and Lysiphlebus testaceipes Cresson were used for controlling cotton aphids (Aphis gossypii Glover), and Neoseiulus californicus McGregor for controlling two- spotted spider mites (Tetranichus urticae Koch.). Early season yield (November-January), from FL97-39 was significantly greater than that of 'Strawberry Festival', 'Sweet Charlie' and 'Earlibrite', but not significantly different than that obtained from 'Carmine', 'Camarosa' and 'Treasure'. Total season yields (November-March) from FL97-39 and 'Carmine' were significantly higher than 'Camarosa' and 'Sweet Charlie', but not significantly different from 'Strawberry Festival', 'Trea- sure', and 'Earlibrite'. Percent marketable yield of 'Treasure' was higher than 'Camarosa' and 'Sweet Charlie', but not signif- icantly different from the other cultivars. FL97-39 was very highly susceptible to powdery mildew (Sphaerotheca macu- laris), 'Earlibrite' had high susceptibility, whereas the rest of the cultivars showed moderate susceptibility. Aphid infesta- tions were most severe in 'Sweet Charlie' and 'Carmine', whereas significantly lower number of aphids was observed on the other cultivars. Fruit quality variables such as firmness, soluble solids content, titratable acidity, and ascorbic acid concentration were excellent during the early part of the sea- In Florida, strawberries (Fragaria x ananassa Duch.) are grown commercially on approximately 6,900 acres, with more than 95% of the acreagelocated in the Plant City area of west- central Florida. The mild winter climate of the region allows Florida growers to produce strawberries from mid-November to the end of january, a period when strawberry production in California is low and market prices are high. In recent years, the Florida strawberry industry has been facing a number of challenges that could, in the near future, make it difficult for Florida strawberrygrowers to remain com- petitive. Methyl bromide, used asa soil fumigant by the major- ity of the strawberry growers, is scheduled to be phased-outin the U.S. by 2005 (U.S. EPA, 2002). So far, no alternative has been identified with an efficacy similar to that of methyl bro- mide in killing weed seeds,nematodes, and other soil-borne pathogens. For Florida strawberry producers, the most prom- ising alternative to methyl bromide is a combination of 1,3- dichloropropene + 17% chloropicrin. However, this alterna- tive may reduce strawberry yields by 15 percent (VanSickle, 2000). The sap beetle (Stelidota geminata), which has been quite inconspicuous until now, has emerged asa potentially se- rious pest of the strawberrycrop, especially in the latter half of the season(Chip Hinton, Fla. Strawberry GrowersAssoc., per- sonal communication). Other problems faced by the strawber- ry industry include severe cold weather during winter, restrictions on water usage for freeze protection, high labor costs, and urban sprawl. In the context of these difficulties faced by the Florida strawberry industry, soilless cultivation under protective struc- tures could provide a viable alternative for strawberry produc- tion by enhancing early yield and quality of strawberries and eliminating the need for methyl bromide. Specialized trough systems designed for protected strawberry culture can be raised or lowered for more efficient harvesting, which reduces labor costs significantly. These growing systems can accommo- date up to 244,444plants per ha (104,544plants per acre), ap- proximately five times more plants per unit area compared to conventional field culture, making it possible to produce greater yields on a smaller surface area. Strawberries grown under protected culture are cleaner since they do not come in contact with soil or splashing water. They can also be easily harvested with the stem intact for specialty marketing. The greenhouse vegetableindustry in Florida is growing every year and is presently estimated at 40 ha (Hochmuth, 2003), with only 0.5 ha of strawberries under protected culture (Tyson, This research wassupported by the Florida Agricultural Experiment Sta- tion, and approved for publication as Journal SeriesNo. N~2377. lCorresponding author. Proc. Fla. State Horl. Soc. 116: 2003. 63