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Vito S. Polito, Kirk D. Larson and Katherine Pinney

Bronzing of strawberry (Fragaria ×ananassa Duchesne) fruit that is not the result of arthropod feeding or chemical spray application occurs frequently in California's central coast strawberry production region from late spring through midsummer, a period characterized by relatively high temperature, low relative humidity, and high solar irradiance. The cause of this phenomenon is not known, but in preliminary trials, intermittent, midday misting of plants and increased drip irrigation rate resulted in reduced incidence of fruit bronzing. To characterize the bronzing phenomenon and its development in strawberry fruit tissues, we conducted an anatomical and histochemical examination of bronzed fruit. Bronzed and nonbronzed fruit were sampled over a range of fruit maturities. Results show that bronzing derives from a lesion at the cortical surface early in the fruit's development. Epidermal cells become radially compressed and the cell contents coalesce into a densely staining mass. The cuticular layer becomes disrupted and discontinuous. As the fruit develops, densely staining materials, possibly phenolic precipitates, accumulate within subepidermal cells of bronzed fruit, subepidermal cell walls thicken, and intercellular spaces fill with pectic substances and other densely staining materials. Results are consistent with reports of sunscald injury from other fruit species, and raise the possibility that strawberry bronzing occurs in response to heat or solar radiation injury.

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T.K. Hartz, J.E. DeVay and C.L. Elmore

Soil solarization, alone and combined with metam sodium (MS), was evaluated as an alternative to methyl bromide and chloropicrin (MBC) fumigation, the standard soil disinfestation technique in the California strawberry (Fragaria ×ananassa Duch.) industry. Tests were conducted in two consecutive annual production cycles in Irvine, Calif., an environment representative of the coastal strawberry production area. Solarization treatments were applied from late July through September for October plantings. Treatments were equally effective in reducing baited populations of Phytophthora cactorum [(Lebert and Cohn) J. Schröt] (1989-90) and P. citricola Sawada (1990-91) when compared to pathogen survival in nontreated soil. Solarization and MBC reduced Verticillium dahliae Kleb inocnlnm in 1989-90, but MBC gave superior control in 1990-91. Solarization significantly controlled annual weeds, but was less effective than MBC. In 1989-90, solarization alone increased strawberry yield 12 % over the yield of nontreated plots; when combined with MS, yield increase was 29%, equivalent to that achieved with MBC fumigation. Treatments were equally effective in increasing yields in the 1990-91 test. Chemical names used: sodium N -methyldithiocarbamate (metam sodium), chloropicrin nitrotrichloromethane (chloropicrin).

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Colleen Kennedy, Luis F. Osorio, Natalia A. Peres and Vance M. Whitaker

alleles confer resistance to powdery mildew ( Lyngkjaer et al., 2000 ). When a homolog (PpMlo1) of the barley resistance gene from peach ( Prunus persica ) was expressed in antisense orientation in Fragaria × ananassa LF9, resistance to P. aphanis was

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Pedro Domínguez, Juan J. Medina, José M. López-Aranda, María T. Ariza, Luis Miranda, Iraida Amaya, José F. Sánchez-Sevilla, Rosalía Villalba and Carmen Soria

Since 2000, the high significance of strawberry ( Fragaria ×ananassa Duch.) production in Huelva, located on the southwest coast of Spain, has led public and private institutions to increase the releasing of new cultivars that are well adapted to

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Bielinski M. Santos, Camille E. Esmel, Silvia Slamova and Elizabeth A. Golden

Three separate field trials were conducted to determine the most appropriate planting dates for intercropping cucumber (Cucumis sativus), summer squash (Cucurbita pepo), and muskmelon (Cucumis melo) with strawberry (Fragaria ×ananassa), and their effect on ‘Strawberry Festival’ strawberry yields. ‘Straight Eight’ cucumber, ‘Crookneck’ summer squash, and ‘Athena’ muskmelon were planted every 15 days from 25 Jan. to 23 March. None of the three intercropped species affected strawberry yield up to 60 days before the end of the season on 25 March. Cucumber yield responded quadratically to planting dates, rapidly increasing from 25 Jan. to 23 Feb. and declining afterward. Warmer temperatures favored summer squash yield, with the highest yields when planted on 23 Feb. or later. Muskmelon yields decreased as air temperatures increased, and the best planting dates were between 25 Jan. and 9 Feb. In summary, cucumber and summer squash seemed to be favored by planting under warmer temperatures, whereas muskmelon thrives under cooler weather.

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Rodrigo Figueroa, Douglas Doohan and John Cardina

Common groundsel (Senecio vulgaris) is an increasingly important weed in strawberries (Fragaria ×ananassa), a crop in which open space within and between rows is susceptible to infestations. Cultivation, hand hoeing, and registered herbicide are only partially effective in controlling common groundsel, and tolerance or resistance to herbicides is common in this species. Field and greenhouse studies were conducted to identify and select herbicides for controlling common groundsel in newly planted strawberries. Herbicides applied to strawberries within 1 week after planting in 2000 were: terbacil and simazine alone and tank mixed with napropamide; pendimethalin, dimethenamid, metolachlor, ethofumesate and sulfentrazone. Based on selectivity and efficacy observed in this preliminary experiment, sulfentrazone and flumiclorac were selected for further evaluation in 2001 and 2002. Strawberry tolerance of sulfentrazone and flumiclorac 1, 3, 6, and 18 weeks after application (WAA) was similar to that of the registered herbicides terbacil and napropamide, but injury was greater than in hand weeded plots. Plants sprayed with 300 g·ha–1 (4.3 oz/acre) sulfentrazone produced yields similar to terbacil treated plants, but with less plant stunting. Tolerance of newly planted `Allstar' and `Jewel' was affected by the interaction of soil pH and sulfentrazone rate. Plant stunting 3 WAA increased with sulfentrazone rate, reaching 68 and 61% in `Allstar' and `Jewel', respectively, with the highest rate [400 g·ha–1 (5.7 oz/acre)] and high soil pH (7). `Allstar' grown in low pH (5) and treated with sulfentrazone (400 g·ha–1) showed only 8% stunting, whereas `Jewel' was not stunted 3 WAA at the same rate and pH. Both cultivars recovered (50% less stunting) from the severe injury observed when sulfentrazone was applied to high pH soils. However, at low pH both cultivars were stunted more at 6 WAA than at 3 WAA. Plant diameter for both cultivars was 25% higher when they were grown in the lower soil pH. Fruit yield was not affected by the sulfentrazone rates evaluated (0 to 400 g·ha–1). Sulfentrazone was active at four stages of common groundsel growth: preemergence (PRE), cotyledon (COT), early post (EPOST) seedlings at the four-leaf stage, and late post (LPOST) seedlings at the10-leaf stage. The calculated 50% growth reduction (GR50) value for PRE and COT stages was 50 g·ha–1 (0.7 oz/acre), whereas the GR50 for EPOST and LPOST stages was 100 g·ha–1 (1.4 oz/acre). Sulfentrazone controlled common groundsel when applied PRE and COT, but at EPOST and LPOST stages sulfentrazone did not provide complete control, although plant height was reduced 80% to 90% compared to untreated plants. Results indicated that common groundsel is controlled in the field with 150 and 300 g·ha–1 (2.1 and 4.3 oz/acre) of sulfentrazone applied before seedling emergence. The least strawberry injury occurred when sulfentrazone was applied immediately after transplanting at 150 and 300 g·ha–1, although crop tolerance was reduced under conditions of high soil pH (>6.5) and varied with cultivar.

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Vance M. Whitaker, Luis F. Osorio, Natalia A. Peres, Zhen Fan, Mark Herrington, M. Cecilia do Nascimento Nunes, Anne Plotto and Charles A. Sims

The leading strawberry ( Fragaria × ananassa ) cultivar grown in Florida is currently ‘Florida Radiance’ ( Chandler et al., 2009 ; U.S. Patent PP20,363) which was commercialized in 2009 and by the 2015–16 season, accounted for ≈70% of the acreage

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Vance M. Whitaker, Craig K. Chandler, Natalia Peres, M. Cecilia do Nascimento Nunes, Anne Plotto and Charles A. Sims

The leading strawberry ( Fragaria × ananassa ) cultivar grown in Florida over the past decade is ‘Strawberry Festival’ ( Chandler et al., 2000 ), which occupied as much as 60% of Florida acreage before the introduction of ‘Florida Radiance

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Andrew R. Jamieson, Kevin R. Sanderson, Jean-Pierre Privé and Roger J.A. Tremblay

‘Wendy’ strawberry ( Fragaria × ananassa Duchesne) was commercially introduced in Canada in July 2006 by the Atlantic Food and Horticulture Research Center (AFHRC) of Agriculture and Agri-Food Canada. ‘Wendy’, a short-day cultivar, ripens in the

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Andrew R. Jamieson, Kevin R. Sanderson, Jean-Pierre Privé and Roger J.A. Tremblay

‘Valley Sunset’, a short-day strawberry ( Fragaria × ananassa Duchesne ex Rozier), was commercially introduced in Canada in May 2009 by the Atlantic Food and Horticulture Research Center of Agriculture and Agri-Food Canada (AAFC). ‘Valley Sunset