Scab is the most damaging disease of pecan in the southeastern United States. Pecan trees can attain 44 m in height, so managing disease in the upper canopy is a problem. Fungicide is ordinarily applied using ground-based air-blast sprayers. Although mechanical hedge-pruning and topping of pecan is done for several reasons, improved management of scab is an important reason in the humid, wet Southeast. Resulting shoot growth on cut limbs of susceptible cultivars could lead to more severe scab. In three experiments over three years, we explored the effect of hedge-pruning trees to ∼12 to 14 m compared with non-hedge-pruned trees. All trees received fungicide treatments (air-blast sprays and ≤3 aerial applications). Hedge-pruning either had no effect, or increased or decreased scab severity only slightly on leaflets, immature, or mature fruit (a –9.95 to +14.63% difference in scab severity compared with the control). However, height in the canopy invariably had a large and significant effect on scab severity, and amounted to a 0.05 to 73.77% difference in severity between the lowest and highest sample in the canopy. Fruit weight depended on sample height, with fruit most often weighing less when collected at greater sample heights. A robust relationship between fruit weight and scab severity was found at the highest sample heights where scab was also most often severe (R 2 = 0.21 to 0.67, P < 0.0001). Hedge-pruning and topping pecan tree canopies to manage tree size will enable better fungicide coverage, reducing risk of a scab epidemic as more of the canopy is assured efficacious fungicide spray coverage.

Patch budding is a common propagation technique for pecan (Carya illinoinensis) commonly used in the central and western United States, but seldom used in the southeastern United States. Success rates vary, but 75% is normally an acceptable survival rate. Selected budwood and rootstock treatments were evaluated to improve budding success. Additional studies were conducted to evaluate bud forcing techniques that would leave the rootstock intact, allowing a second bud to be inserted if the first patch bud failed. Girdling exceptionally vigorous shoots at the base used for budwood improved success, but neither tip pruning shoots used for budwood or rootstock affected patch bud survival. Patch budding was more successful using budwood from 1-year-old branches than from current season shoots, a finding that greatly extends the window available for propagation using patch buds. The age of rootstock wood at the budding site did not affect patch bud survival. Girdling the rootstock immediately above the dormant patch bud was less effective than top removal for forcing the patch bud in the spring. Application of a lanolin paste of 0% to 5% 2,3,5-triodobenzoic acid (TIBA) or 0.02% 6-benzylaminopurine (BAP) to a girdle immediately above the patch bud was positively related to the percentage of patch buds forcing when tree tops were left intact. The combination of girdling, 5% TIBA, and 0.02% BAP resulted in 76% of the buds forcing compared with 73% forced using top removal. This approach damages trees less and enables a second chance for patch budding on a stronger tree.

Pecan ( Carya illinoinensis ) nuts with cracked shells reduce market grade and are usually removed during pecan cleaning. One type of crack is the shell suture that splits on certain cultivars with thin shells and high kernel percentages. ‘Schley’ nuts with diverse kernel moisture concentrations were dislodged from trees on cloudy and sunny days and exposed to ambient environmental conditions for 1 day on the ground. Samples were collected immediately after dislodging and after 1 day’s exposure, sealed in a plastic bag that was placed in a cooler, and then transported to the laboratory where they were assessed for kernel moisture and split sutures. The number of nuts with split sutures was unaffected by kernel moisture percentage or sunlight exposure when samples were collected immediately after dislodging. However, after 1 day, nuts with high kernel moisture percentages with high solar radiant exposure (sunny day) had substantially more nuts with suture splits than those with low solar radiant exposure (cloudy day). At the lowest kernel moisture percentages, the number of nuts with split sutures was insensitive to solar radiant exposure. During the first harvest, ‘Schley’ trees should be shaken to dislodge nuts on cloudy days and harvested before exposure to bright sunshine to minimize suture split. This probably extends to other cultivars with a history of suture split. An alternative to shaking on cloudy days, though not tested, might be to shake trees in the evening and harvest the next morning before exposure to high light conditions. Later, during the harvest season when kernel moisture was lower, sunlight exposure has little, if any, effect on suture splits.

The productive life of a pecan [ Carya illinoinensis (Wangenh.) K. Koch] orchard frequently spans two or more generations, but eventually orchards require renewal. Weather events damage tree canopies, pests affect tree health and productivity, and new cultivars offer greater yield potential or better nut quality. A popular method of orchard renewal is selective tree removal combined with interplanting new trees. Many old pecan orchards in the southeastern United States are infected with crown gall [ Agrobacterium tumefaciens (Smith and Townsend) Conn.], potentially a problem for interplanted trees. Two tree types, nursery-grafted trees and seedling trees that were grafted 3 years after transplanting, were evaluated 6 years after transplanting. Transplanted trees varied in distances from established 80-year-old trees or residual stumps after tree removal. Ten trees near the study site, located 3.6 m from crown gall-infected stumps, were excavated to determine disease incidence. No crown gall was observed on any of the 87 trees in the study or the excavated trees. Trunk diameters of interplanted trees increased as distance from the nearest stump decreased and distance from the nearest established tree increased. Leaf elemental concentrations of the 6-year-old transplants were not related to observed growth differences. Conclusions include 1) stumps promoted rapid transplant growth; 2) crown gall infections of transplanted trees were unlikely even when crown gall symptoms were obvious on adjacent trees and stumps; and 3) transplant growth was suppressed by established trees.

Pecan (Carya illinoinensis) leaf elemental concentrations are the industry standard to guide fertility programs. To provide meaningful information, a standard index tissue collected at a specific development stage is required along with established elemental sufficiency ranges. We report pecan leaf elemental sufficiency ranges used in Oklahoma that were developed based on research in Oklahoma and elsewhere. In addition, fertilizer recommendations, based on various leaf elemental concentrations, are included.

A field experiment was conducted from 1995 to 1999 in central Alabama to determine the effect of repeated applications of glyphosate herbicide on young 'Sumner' pecan trees. Herbicide treatments were applied on 'Sumner' pecan trees varying in age from newly established (first growing season) to established fourth-year growing season trees. Measurements taken included tree mortality, trunk cross-sectional area, nut yield, and nut quality in the third and fourth years of the study. Glyphosate applications were targeted at the lowest 5 to 8 cm of the tree trunk ("standard" treatment), a percentage (lowest 33%, 67%, or 100%) of the tree trunk below the first scaffold limb, or a percentage (lowest 25%, 50%, 75%, or 100%) of tree foliage to simulate situations ranging from minor spray drift to major misapplication. No adverse effects were detected when glyphosate was applied to trunks, regardless of tree age. However, repeated application of glyphosate to 75% to 100% of tree foliage resulted in a significant reduction of growth and, in some cases, tree death. Results indicate that limited contact of glyphosate with the lowest 5 to 8 cm of the trunk of the young pecan tree, which usually occurs during conventional orchard weed management, is unlikely to result in adverse effects on young pecan trees.

Six weed control programs with and without irrigation were investigated in a newly established pecan orchard. Irrigation increased crown diameter growth in only one of seven growing seasons but increased nut yield an average of 35% in the first two bearing years. Weed control program significantly influenced crown diameter beginning in the fourth growing season and continued through season six while also impacting final crown diameter. The use of postemergence (POST) herbicides increased crown diameter a minimum 4 mm vs. preemergence (PRE) herbicides. Mowing neither increased nor decreased crown diameter when used with herbicides; however, when used solely, crown diameter was 29% less. Highest growth rates were obtained with a combination PRE plus POST weed management system. Nut yields were closely linked to growth data. No differences in nut yield were observed between PRE- or POST-herbicide programs alone or in combination with mowing. Mowing alone decreased nut yield 57% vs. herbicide-based approaches. A combination PRE-plus POST-weed control program increased yield 38% vs. all other treatments.

Fourteen pecan (Carya illinoensis) clones with desirable traits selected from preliminary screenings were evaluated for scab resistance, foliage condition and foliage retention. No fungicide or insecticide sprays were applied in order to increase pest and disease pressure and to better assess suitability of the selections for low input plantings. Most clones were equal to or better than 'Elliott', the resistant standard cultivar and were superior to 'Desirable', the susceptible standard cultivar, in scab incidence and foliage condition.

gradually weakened while moving up the Cumberland Plateau and across the Appalachian Mountains before reentering the North Atlantic on 21 Aug. This single storm greatly damaged the state’s pecan industry and totally eliminated its tung industry (Kilby and Converse, 1970). Pecan nut production in Mississippi in 1970, the year after the storm, was only ≈27% of the average of that for the previous 5 years. A similar situation also occurred in Alabama, also a Gulf Coast region with a long and violent history of hurricanes. In fact, 41 hurricanes hit the Alabama coast from 1559–1996 (Longshore, 1998). In recent years, these include Camille (1969), Eloise (1975), Frederic (1979), Elena, Danny, and Juan (1985), and Erin and Opal (1995). Frederic in 1979 had a profound destructive effect on Alabama’s pecan production, destroying ≈60% of the bearing trees in two counties that were responsible for ≈60% of the state’s total production. Opal, on 4 Oct. 1995, was especially destructive to the pecan industry, with 384 km·h winds near the coast and ≈80 km·h wind gusts throughout most of the state (Wood, 1996). As many as 50% to 80% of the trees in many counties were destroyed. Opal was the strongest hurricane to reach land in the Gulf of Mexico area during October in recorded history (Kimberlain and Elsner, 1998). South Georgia possesses the largest concentration of pecan production in the eastern United States, producing ≈30% to 40% of the U.S. crop in most years (U.S. Department of Agriculture, 1975–97; Wood et al., 1990). Although most of the pecan production zone within the state is 175–500 km from the Gulf Coast, and is relatively safe from the intense winds of hurricanes, most of the state’s industry is vulnerable to substantial damage from storms tracking across the region. The state had 69 hurricanes and 30 tropical storms from 1752 to 1995 (Longshore, 1998). Eleven of the hurricanes had intensities of Category-3. The most devastating to the Georgia pecan industry was the Great Mobile Hurricane, hitting the state’s orchards with 161 km·h winds in 1952 (Longshore, 1998). Degenerate hurricanes, such as tropical storm Alberto, which hit southwestern Georgia 3 July 1994, also can cause great damage to pecan orchards. Although wind speeds had diminished enough to merit classification as only a tropical storm by the time Alberto entered Georgia, ≈112 km·h wind gusts and ≈54 cm of rain within 24 h caused considerable tree, nut, and limb loss over a wide area of the state, as well as a once-per-500-year flood in southwestern Georgia when it stalled after colliding with an entrenched high pressure system over the southern United States (Longshore, 1998).

Pecan is a difficult species to propagate by grafting. The whip graft, bark graft, and four-flap graft, the most often-used techniques for pecan grafting, require dormant scions, collected and stored for 60 to 120 days prior to spring-season grafting. Poor graft success is often blamed on handling and storage environment of the scionwood. Moisture content of packing material, waxing of cut ends, and use of polyethylene bags was evaluated in a controlled experiment in 1998 and 1999. Scions were cut in early February each year, and stored for 60 to 70 days in a household refrigerator under different treatment regimes. Scion viability was tested by bark grafting mature pecan trees in Fairhope, Ala., and Uvalde, Texas. In 1998, graft success rate was equally good among scions stored in polyethylene bags with different amounts of added moisture, whether cut ends were waxed or not. Moisture loss of the scions during storage was affected each year by the amount of water added to packing material and by waxing the cut-ends, but the differences did not impact graft success. An interaction of not waxing the cut ends and very wet packing material reduced graft success at Fairhope, Ala., but not Uvalde, Texas, in 1999.

Soil and leaf nutrient levels were compared from young pecan (Carya illinoensis [Wangenh.] K. Koch) trees mulched with leaves, pine bark nuggets, pine straw, grass clippings, or chipped limbs; and from unmulched trees with bermudagrass sod. Soil beneath grass-clipping mulch showed an increase in soil potassium (K) levels as compared to all other treatments except chipped limbs. Foliar iron (Fe) for the pine bark nuggets and leaf treatments were higher than for the pine-straw and chippedlimb treatments. Leaf manganese (Mn) levels for the grass-clipping treatment were higher than those for sod, pine straw, chipped limbs, or leaf treatments. Overall, the nutritional differences among mulch treatments were small, suggesting that growth differences were attributed to other factors.

Treatments were metham sodium at 1114 and 2228 liters ha-'; 67% methyl bromide, 33% chloropicrin (MB-67) at 392 kg ha-'. 98% methyl bromide, 2% chloropicrin (MB-98) at 450 kg ha-' ahd non-fumigated. Mulch treatments were 31.5 mm thick black polyethylene plastic a spray-on styrene-butadiene polymer dispersion (Styrofan) sprayed over beds at 959 liters ha-', and unmulched. Styrofan and plastic mulch increased marketable pepper yield similarly, compared to the unmulched control. Metham sodium at 1114 liters produced the highest marketable yield of the 5 fumigant treatments.