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Cranberry scald
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- 2. 627HORTSCIENCE, VOL. 30(3),JUNE 1995 HORTSCIENCE 30(3):627. 1995. Field Conditions Associated with Cranberry Scald Paul J. Croft Department of Geology and Geography, University of South Alabama, Life Sciences Building, Room 136, Mobile, AL 36688-0002 Additional index words. Vaccinium macrocarpon, solar injury, weather stress MPa, and 5-cm soil temperatures at 5 cm from 14 to 32C. Nearly all New Jersey growers indicated thattheyexperiencedscalddamage,withupto 25% of their crop affected. Damage occurred to shaded and unshaded fruit that were green before scalding and 1 to 2 cm in diameter. Damage varied among cultivars, with ‘Early Black’ most affected and ‘Stevens’ and ‘Ben Lear’ least affected. Losses were estimated by growers to be much lower (generally <5% of fruit damaged) for fruit cooled by sprinkler irrigation. This technique is used when air temperatures exceed 29C, a grower rule of thumb. At the Research Center, visual inspec- tions on 23 Aug. confirmed that scald damage was greatest for nonirrigated beds. Samples taken before harvest (1 Oct.) indicated that 36% of nonirrigated fruit were scalded com- pared to only 0.5% of those irrigated. A search for the same combination of weather and field conditions during berry growth for five growing seasons yielded no other instances in which the critical combina- tion of weather and field conditions occurred. During these 5 years, growers reported only minor and isolated scalding. Therefore, a spe- cific combination of weather and field condi- tionsthatleadtoanunusuallyhighdemandfor water,coupledwiththedepletionofsoilmois- ture, appears to be associated with cranberry scald. This interpretation supports the suppo- sitions and observational evidence provided by others, such as Barber and Sharpe (1971) and Renquist et al. (1989). This combination should be further investigated with regard to cranberryphysiology,phenophase,prediction, and mitigation. Literature Cited Barber, H.N. and P.J.H. Sharpe. 1971. Genetics and physiology of sunscald of fruits. Agr. Meteorol. 8:175–191. Croft, P.J. 1992. Meteorological investigation and prediction of scald. Cranberries 56(1): 6–7, 18. Renquist, A.R., H.G. Hughes, and M.K. Rogoyski. 1987.Solarinjuryofraspberryfruit.HortScience 22:396–397. Renquist, A.R., H.G. Hughes, and M.K. Rogoyski. 1989. Combined high temperature and ultravio- let radiation injury of red raspberry fruit. HortScience 24:597–599. Smart,R.E.andT.R.Sinclair.1976.Solarheatingof grape berries and other spherical fruits. Agr. Meteorol. 17:241–259. Observations of upper canopy and midcanopytemperature,soiltemperature,rela- tive humidity, soil water potential (gypsum blocks), net radiation, and precipitation were made hourly and daily. Although attempts were made to obtain fruit temperatures, the difficulties involved (such as shading, repre- sentativeness, and destructive vs. nondestruc- tivetechniques)precludedtheirmeasurement. Time-series plots of soil water potential at a 5-cm depth indicated that during 1–3 Aug. 1990 water potentials became more negative, fallingfrom–0.088to–0.83MPa.Thesemaxi- mum values occurred during the afternoon rather than in the early morning, as is typical. Mean daily values for July and August of that year were –0.059 and –0.089 MPa, respec- tively. These values suggest that the bog water table (50 cm during the event) was unable (or too slow) to recharge the uppermost soil lay- ers. Therefore, plant water demand could not bemetandplantswerevulnerabletowaterand heat stress. The soil moisture deficit devel- oped several days prior (beginning 26 July) due to the lack of significant rainfall (for the period 25 July to 3 Aug., only 0.4 mm of rain fell on the bed). Theweatherconditionsassociatedwiththe 1990 scald event included clear skies; stan- dard shelter air temperatures of 27C or higher; canopy and midcanopy temperatures up to 36 and 41C, respectively; soil temperatures at 2 cm up to 26C; and dry air (relative humidities ranging from 35% to 45%—or dewpoints ≤12C) within and above the plant canopy. For comparison, bed conditions in July and Au- gust over 5 years showed the following varia- tions: upper canopy temperatures from 3 to 39C, midcanopy temperatures from 2 to 43C, soil water potentials from –0.001 to –1.50 Scalding of cranberries (Vaccinium macrocarpon Ait., Ericaceae) may cause sig- nificant crop losses, 10% or more, in 24 to 48 h (Croft, 1992). Cranberry scald has been observed in all of the principal growing re- gions of the United States and Canada. Scald is characterized by a spherical pattern of dam- age where a physiological breakdown of fruit has occurred. Sun scald or solar injury, classi- fied by Barber and Sharpe (1971), has been examined according to the energy balance of spherical fruits by Smart and Sinclair (1976) and considered with regard to phenophase by Renquist et al. (1987, 1989). A widespread occurrence of scald in New Jerseyduring1–3Aug.1990presentedaunique opportunity to examine meteorological and fieldconditionsassociatedwithcranberryscald before and during the event. Data were col- lected at a cranberry bed located at the New Jersey Rutgers Univ. Blueberry and Cran- berry Research Center in Chatsworth. The portion of the bed in which observations were made was not irrigated during the growing season and was lightly sanded to cover the surface early in the season (May). The bed soil was a loamy sand, and the water table depth was maintained at ≈51 cm below the surface during the growing season. Receivedforpublication21Oct.1994.Acceptedfor publication 8 Feb. 1995. The Northeast Regional Climate Center, Ocean Spray Cranberries, and the AmericanCranberryGrowersAssociationprovided supportforthisstudy.ThankstoDaveFittante,Rich Hartman, Paul Eck, and Mark Shulman, and the anonymous reviewers for their beneficial contribu- tions.Thecostofpublishingthispaperwasdefrayed inpartbythepaymentofpagecharges.Underpostal regulations, this paper therefore must be hereby marked advertisement solely to indicate this fact. View publication statsView publication stats