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- Author or Editor: Barclay Poling x
- HortScience x
In recent years, anthracnose fruit rot (AFR) caused by Colletotrichum acutatum J.H. Simmonds, has become an even more serious threat to strawberry plant and fruit producers in major strawberry-growing areas of North America. This highly virulent pathogen causes fruit rot, crown rot, root rot, and lesions on petioles and stolons. In fruit-production fields, the best way to control AFR is to prevent the introduction of the pathogen into the field by using anthracnose-free transplants. A critical step in controlling the disease then, lies in effective nursery management practices. Participants in this workshop outlined several key management strategies, including methods to eliminate pathogen inoculum, cultural practices that reduce host plant susceptibility, and chemical and biological control measures. Industry members stressed the importance of giving research priority to developing improved methods of nursery field sampling and detection of C. acutatum in asymptomatic plants with latent infection. Being able to rapidly and economically diagnose C. acutatum in symptomless plant material at each step in the multiyear nursery plant propagation cycle (foundation, registered, and certified plants), will help nursery growers minimize the potential of selling C. acutatum-infected transplants to fruit growers. A video recording of the 4-h workshop was produced by ASHS Video Workshop Series (http://ashs.org/resources/videoworkshopseries.html).
Active frost protection methods may be expensive, but a correctly selected and operated system can provide more consistent crops and improved cash flow in years of potentially damaging cold events at postbudbreak stages of grape development. The selection of an active frost protection system depends on a number of factors, including the prevailing climatic conditions that occur during the spring season at the vineyard location, the costs associated with different frost control systems as well as considerations related to the reliability and relative simplicity of operating the equipment associated with each method. In winegrape production areas in North Carolina, hoar (white) frosts are the predominant cold threat in the postbudbreak period. A wind machine can be a very cost-effective investment on sites that are prone to a damaging frost event in 1 of 5 years or with a higher frequency of occurrence. However, wind machines have less overall usefulness in growing areas where there is also potential for black frosts (a more damaging radiational event than a hoar frost) and frosts/freezes (events with subfreezing temperatures and winds in the range of 2.2 to 4.5 m·s−1). For black frost events, a well-designed overvine sprinkling system can provide nearly 6 °C protection; sprinkling is also an appropriate management option for frost/freeze events. Windborne freezes are far less common at the postbudbreak stages but represent the most damaging type of cold event that can occur in eastern and midwestern winegrape regions in the United States. Methods that reliably delay budbreak (e.g., dormant oils, evaporative cooling with targeted sprinklers) may represent the best near-term opportunity for growers to decrease or avoid vine injury from freeze events such as the early April Easter freeze of 2007 that devastated grape vineyards through much of the midwest and southeastern United States.
Abstract
The potential for annual cropping of strawberries in hill culture on black plastic mulch was investigated using 2 experimental plantings in southeastern North Carolina from 1982-1984. In 1982-1983, a plant density trial was conducted with freshly dug plants set in mid-October at a plant spacing of 33 cm between the double rows and spacings of 15, 20, 25, and 30 cm between plants in the row. Except with ‘Titan’, the highest strawberry yields in the spring of 1983 were obtained at the 15 cm in-row spacing. Fruit size of all cultivars was somewhat reduced at closer spacings. In a 1983-1984 trial, summer planting of dormant plants was compared to that of freshly dug plants set in mid-October. In December of 1983, record cold temperatures (− 14°C) severely damaged leaves, crown tissues, and blossom primordia of dormant plants, whereas freshly dug plants had less freeze injury and higher fruit yields the following spring.
Until recent years, there have been few attempts in the midsouth to evaluate alternative types of strawberries (e.g., day-neutrals); alternative cultural systems (e.g., tunnel culture); or specific products (e.g., rowcovers) that could be used for either season extension and/or off-season production. In the early 2000s, research was undertaken to evaluate day-neutral (DN) strawberry production in higher elevations in western North Carolina for harvest in the summer and fall. The effect of DN cultivar, plastic mulch color, planting dates, and plant types was studied in at the Upper Mountain Research Station, Laurel Springs, NC (elevation 914 m) over several seasons. In the 2004 season, the DN ‘Everest’ had yields of nearly 1 kg/plant on white plastic mulch using plugs transplanted in late Sept. 2003. However, ≈95% of ‘Everest's’ production occurred in July and August, when U.S. strawberry prices to growers in wholesale fresh markets have averaged $1.32 and $1.68 kg, respectively (2001 to 2005). Assuming a production level of ≈1 kg/plant, market prices above $2.48 kg (breakeven cost) will be needed to make day-neutral strawberry production in the southern Appalachians a profitable venture. We observed peak periods of heavy production in midsummer and more research is needed to identify cultural strategies with plastic mulches, plant types, and possibly rowcovers to increase fall fruit volumes.