Bearing pecan [Carya illinoinensis (Wangenh.) K. Koch] trees overly stressed by crop load and premature autumn defoliation either died or were severely damaged by -3°C in mid-November. Orchard damage was associated with death of tree roots during the dormant season. Exposure of stressed trees to -5°C in mid-March produced an atypical, but distinct, bottom-to-top-of-canopy gradient in bud death and reduced growth of shoots and foliage that was consistent with the pattern of reduced carbohydrate reserves of associated support shoots. Additionally, the foliage of damaged trees contained higher concentrations of N, P, K, Ca, Mg, Mn, Fe, and B. Trees did not exhibit traditional symptoms of cold damage, thus these findings extend cold injury diagnostic criteria to include both root and tree death during the dormant season and also a distinct gradient in shoot death during early spring. Damage by cold appears to be preventable by avoiding excessive tree stress due to overcropping and premature defoliation.
During the winter of 1983-84, 2 periods of below normal temperatures caused severe damage to ‘Western’ pecan trees [Carya illinoensis (Wangenh.) C. Koch]. Leaf elemental concentrations of N, P, K, Ca, Mg, Mn, Fe, and Zn, and yield/tree, measured during 1983, were evaluated to determine their relationship to damage. The only factors significantly related to the amount of cold damage were N, P, and yield/tree. Leaf N2 and leaf P2 were inversely related, whereas yield was positively related to cold damage.
Two test sites pairing perennially cold-damaged portions of fields vs. controls for a 3rd year were assessed. Winter 1997-1998 was very mild and produced less winter injury than the previous winters. We evaluated continued recovery of the raspberry canopy and cane productivity. In contrast to the last 2 years, the previously cold-damaged plots did not show higher levels of cane dieback, percentage of cane dieback, number of dead or dormant buds per cane, and percentage of dead buds at either site. Very few secondary laterals were produced at either site, which supports previous observations that raspberry compensates for winter injury with increased production of secondary laterals. For the first time, the damaged plots actually produced higher yields mainly through a significantly increased berry number per cane at both sites. Floricane leaves in the damaged plots showed higher photosynthetic rates at the green fruit stage and after harvest at site 2. Cane size was similar across sites, although the previously cold-damaged plants had higher berry numbers per lateral. It seems the newly recovered plants in the previously damaged plots had a renewed vigor, working harder to achieve a higher yield. No differences between treatments was detected in leaf nitrogen for a third year, suggesting this may not be a factor in winter injury here. A high population of weevils was observed at one injured site, suggesting a possible interaction with cold damage.
Two sets of field experiments have been set up in Lynden, Wash., to evaluate cold damage to red raspberry `Meeker'. The locations represent newly established crops (fi eld 1) and a field that suffered reoccurring cold damages in recent years (fi eld 2), respectively. Temperature and moisture HOBOs were set up in the check and colddamaged treatments of both of the fields to record the air and soil temperatures and air moisture. The cold-damaged treatments in both fields had significantly higher cane dieback and dead buds. Cold injury significantly reduced berry yield in field 1, but not in field 2, through an steep drop in berry number per cane, mainly due to a significant reduction in lateral number/cane. Cold damage reduced primary lateral number/cane, and increased secondary lateral number/cane in both fields. Secondary laterals were shorter in length and had lower berry number/lateral than the primary ones. It proved that cold damage also delayed initiation and development of secondary laterals, and resulted in more yield loss to the plant. The cold-damaged fruiting cane had lower gas exchange rates, leaf and stomatal conductance, and transpiration rates during fruit development in both fields. It also significantly reduced fluorescence parameters Fo, Fm, Fv, T1/2, and Fq of the cold injury treatment in field 1. On a few cold days this spring, the HOBOs recorded a lower daily low temperature in the cold damaged area than in the check area.
Cucurbit plants usually are sensitive to chilling and easily damaged. Although bottle gourds, which are members of the Cucurbitaceae family, are considered as fresh vegetables in some Asian countries, their main use in recent years is to be used as rootstocks in grafted watermelon cultivation. We tested 163 bottle gourd accessions of the U.S. Department of Agriculture (USDA) genebank for cold tolerance in the early seedling stage. The experiment was conducted using controlled environment chambers with 3 chilling durations (36, 48, and 60 hours) at 4 °C. Chilling damage was rated 0 to 9 (0 = no damage, 1 to 2 = trace of damage, 3 to 4 = slight damage, 5 to 6 = moderate damage, 7 to 8 = advanced damage, 9 = plant totally dead). We rated damage separately for the cotyledons, true leaf, and growing point. Cold damage was higher at a chilling duration of 60 hours, and decreased at 48 and 36 hours. Most tolerant cultigens were PI 491272, PI 491280, PI 491281, PI 491286, and PI 491326. Most susceptible were PI 381845, PI 381846, PI 534556, PI 636137, and PI 668365.
Landscape palms were surveyed for cold damage 8 to 10 months after the coldest weather episode recorded this century in the New Orleans, La., area. Fourteen genera and 21 species of palms totaling 9039 individuals were surveyed and assigned to one of three condition categories within six geographic areas. Area 1, north of Lake Pontchartrain, was not a reliable area for the majority of the 21 species found. South of Lake Pontchartrain, areas 2-6 were considered statistically better for overall palm survival, with area 3 best followed by areas 4, 2, 5, and 6. Although species survival depended somewhat on area, 10 species were found to be statistically reliable south of Lake Pontchartrain: Brahea armata, Chamaedorea microspadix, Phoenix canariensis, Rhapidophyllum hystrix, Sabal mexicana, S. minor, S. palmetto, Sabal spp., Sabal spp. seedlings, and Trachycarpus fortune;. Two species, Phoenix reclinata and Phoenix spp., were found to be marginal and seven species were found to be unreliable: Butia capitata, Chamaerops humilis, Livistona chinensis, Rhapis excelsa, Syagrus romanzoffiana, Washingtonia filifera, and W. robusta. Due to low individual numbers, survival for three species could not be reliably estimated: Arenga engleri, Phoenix dactyfifera, and Serenoa repens.
One-year-old peach trees in nurseries at McMinnville, Tenn., were exposed to –11C on 5 Nov. 1991 before digging. The nursery owners were concerned about the relationship of tree cambium browning to potential tree performance after planting. A color scale [0 = nondamage (white) to 6 = severely damaged (brown)] showing discolored cambium of peach nursery trees was developed to rate damage. Browning was rated at 8 cm above graft union. Five trees each of nine cultivars with chill hour requirements ranging from 175 to 1050 were rated. Cultivars with <500 chill hour requirement had higher ratings. Ten `Harbite' trees from each of six size grades were rated. Trees in grades of 30- to 90-cm height had less cambium browning than trees in grades of 90 to 152 cm height. In Dec. 1992, 1-year-old `Red Globe' trees were exposed to –6 (minimum field temperature), –15, –18, –24, –30, or –35C in a programmable freezer. A subsample of five trees per treatment was rated for browning 1 day after treatment and a second subsample rated in mid February. Trees in a third subsample were grown in a nursery the following summer. Slight browning (rating = 1.6) was evident soon after exposure to –24C; however, severe browning was evident on trees exposed to –30 or –35C. Trees exposed to temperature more than –24C did not differ in height, trunk diameter, or dry weight at the end of the growing season, however trees exposed to –30 or –35C did differ. In a similar experiment, `Juneprince' trees exposed to –18C had slight cambium browning (rating = 1.2) but trees died.
Spurs of `Starkspur Delicious' trees were dipped in 0, 3, 6, 9 or 12% petroleum oil (dormant oil) or soybean oil emulsions on 26 January 1993. The spurs were cooled at 3C/hr until -9C or kept at 21C. After treatment, the flower buds on spurs were forced at 20C for 11 days and then dissected. The cambium and xylem of the spurs and the interior of the flower buds were rated for damage as indicated by browning. The experiment was repeated at the silver tip stage of buds (early March) except that treated spurs were exposed to 20C, -6C, or -9C. Neither the oil treatments nor low temperature exposure caused visual damage to flower buds or cambium in January. However, the oil treatments damaged flower buds at the silver tip stage (March). Neither petroleum or soybean oil caused visible damage to the xylem or cambium of the spurs.
In March of 1975, the News & Views newsletter of the American Horticultural Society offered the following anonymous tip under the heading of Cold Shower Treatment: “Here is a trick that will reduce the amount of damage caused by morning sunlight on frozen buds. Where plants have been lightly touched with frost, take a hand syringe and spray the vulnerable buds with water before sunlight strikes them.” The following spate of correspondence formed the basis of this “postal symposium.”
An unprecedented freeze occurred between 4 and 10 Apr. 2007, causing extensive crop loss across a large area of the United States. This event occurred late in the spring and temperatures were unusually low for an extended period. Low-temperature injury on small fruit plants was reported in 21 states. Missouri and Arkansas experienced the highest estimated percentages of crop loss of grape (Vitis spp.), strawberry (Fragraria ×ananassa Duch.), blueberry (Vaccinium spp.), and blackberry (Rubus subgenus Rubus Watson). Kentucky and Tennessee also reported high percentages of small fruit crop loss. Temperatures preceding the freeze event in the affected region were unusually warm and many of the crops were at a more advanced stage of growth than they would have been under more usual conditions. Although frost/freeze warnings were issued, the terminology used by different weather forecasters was inconsistent. Growers used various cold protection methods, but these were generally ineffective because of the stage of plant development and/or the advective nature of the freeze. Actual grape and blueberry crop losses may not be known for several years because of secondary injury to plant tissues from various pathogens.