• Effect of fungicide treatments on incidence of powdery mildew of pecan and on pecan nut quality

      Olsen, M.; Rasmussen, S.; Nischwitz, C.; Wright, Glenn; Kilby, Mike (College of Agriculture, University of Arizona (Tucson, AZ), 2002-02)
      Powdery mildew of pecan, caused by Microsphaera ulni, was observed on pecan shucks by the latter part of June 2000 in a commercial pecan orchard near Sahuarita, Arizona. Results of 1999 studies indicated that infection does not reduce nut quality. In order to determine effects of fungicide treatments and to substantiate results from 1999, preventive applications of micronized sulfur and azoxystrobin were initiated on June 8, 2000 in selected clusters in both Wichita and Western varieties. Trials were established in plots that had a high incidence of powdery mildew in 1999. Whole nut weights, kernel weights, or color ratings were not significantly different among clusters of nuts that were treated with fungicides and untreated nuts that were infected with powdery mildew. Percent disease incidence was 100% in untreated clusters, 0% in clusters treated with azoxystrobin every two weeks, and 5.3% (Wichita) and 8.8% (Western) in clusters treated with sulfur three times early in the season. Results indicate that disease did not affect nut weight or quality and that early preventive fungicide treatments are effective in controlling infections.
    • Effect of Powdery Mildew on Pecan Nut Weight and Quality

      Olsen, M.; Rasmussen, S.; Nischwitz, C.; Kilby, M.; Wright, Glenn; Kilby, Mike (College of Agriculture, University of Arizona (Tucson, AZ), 2000-10)
      Powdery mildew of pecan, caused by Microsphaera ulni, results in discoloration of pecan shucks, but its effects on yield and quality of kernels are not known. In 1999, powdery mildew was observed on pecan shucks by the latter part of June in a commercial pecan orchard near Sahuarita, Arizona. The fungus continued to be active throughout the summer. However, results of a field test comparing diseased and healthy nuts from two varieties of pecans indicate that powdery mildew did not affect nut weight or quality. Whole nut weights, kernel weights, color ratings or percentage of discarded nuts were not significant between paired clusters of nuts that were treated with fungicides and remained disease free and untreated nuts that were infected with powdery mildew. Although shucks may have a high percentage of area covered by powdery mildew, results from this trial indicate that fungicide treatments are not warranted.
    • Evaluation of Temik (aldicarb) for the Control of the Pecan Aphid Complex for Pecans Grown in Arizona

      Kilby, Michael W.; Wright, Glenn; Kilby, Mike (College of Agriculture, University of Arizona (Tucson, AZ), 2000-10)
      This experiment was conducted to extend the label for Temik use in Arizona pecan orchards for aphid control. Spring application of Temik controlled both yellow and black aphids throughout the season and significantly increased yield.
    • Foliar Applications of Boron to Pecan Trees Does Not Affect Fruit Set

      Kilby, Michael W.; Call, Robert; Wright, Glenn; Kilby, Mike (College of Agriculture, University of Arizona (Tucson, AZ), 1998-09)
      Boron was applied as a foliar spray to pecan trees in a pecan orchard located in Cochise County. Single or repeated application prior to pollination did not affect nutlet set. Leaf analysis indicated that the boron levels in all trees were in the sufficient range for optimum growth and production.
    • Influence of Nut Cluster Position on the Incidence of Viviparity for the Pecan Cultivars "Western Schley" and "Wichita"

      Gibson, Richard; Kilby, Michael; Wright, Glenn; Kilby, Mike (College of Agriculture, University of Arizona (Tucson, AZ), 1998-09)
      Vivaparity, a significant quality- reducing condition found in pecans grown in warm, temperate climates, was evaluated by location of the pecan nut within the cluster in two varieties, "Wichita " and "Western Schley". Percentage vivaparity was not affected by position.
    • Pecan Leaf Tissue Nutrient Concentrations: Temporal Relationships and Preliminary Standards

      Walworth, James; Kilby, Michael; Wright, Glenn; Gibson, Rick (College of Agriculture, University of Arizona (Tucson, AZ), 2002-11)
      Leaf samples were collected from five trees each of Bradley, Cheyenne, Sioux, Western Schley, and Wichita at Picacho, Arizona and five trees each of Bradley, Western Schley, and Wichita at Las Cruces, New Mexico, and analyzed nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, iron, copper, manganese, boron, and copper at two-week intervals from mid-May to Mid-October, 2000. Yield, average nut weight, and percent kernel data were collected for each individual tree. Leaf tissue analysis indicated that concentrations of nitrogen, phosphorus, potassium and sulfur decreased. The overall trends were for zinc levels to declined, although they increased at the end of the season. Boron, calcium, magnesium and manganese, and iron concentrations increased during the growing season. Copper concentrations were variable. Preliminary nutrient standards are presented and compared to existing standards. Most nutrients were within recommended ranges, but magnesium levels were much higher than the top of the Arizona and New Mexico sufficiency ranges. Manganese was higher than the Arizona sufficiency range, but within that of New Mexico, whereas zinc was higher than the New Mexico range, but within that of Arizona.
    • Pecan Variety Study on the Safford Agricultural Center

      Clark, L. J.; Carpenter, E. W.; Wright, Glenn; Kilby, Mike (College of Agriculture, University of Arizona (Tucson, AZ), 2000-10)
      In 1986 a replicated study of eight varieties of pecans was planted on the Safford Agricultural Center at an elevation of 2954 feet above sea level. The objective of the study was to determine which varieties would produce best under the saline conditions found in the Safford valley. WO-3, the highest overall producer of the study, produced the best yield in 1999, with a yield over 2600 pounds per acre. This paper also contains kernel percentages and other nut characteristics found in the study during the 1999 harvest seasons and a summary of the yields since 1997.
    • Pecan variety study on the Safford Agricultural Center 1997-1998

      Clark, L. J.; Carpenter, E. W.; Wright, Glenn; Kilby, Mike (College of Agriculture, University of Arizona (Tucson, AZ), 1999-11)
      In 1986 a replicated study of eight varieties of pecans were planted on the Safford Agricultural Center at an elevation of 2954 feet above sea level. The objective of the study was to determine which varieties would produce best under the saline conditions found in the Safford valley. This paper contains yield, kernel percentages and other nut characteristics found in the study during the 1997 and 1998 harvest seasons. Cheyenne and WO-3 were the highest yielding varieties in 1997 and 1998, respectively. The respective yields were 1894 and 2286 pounds per acre.
    • Pecan yields and nut quality as influenced by soil trenching and tree pruning

      Gibson, Richard; Nunan, Linda; Kilby, Michael; Wright, Glenn; Kilby, Mike (College of Agriculture, University of Arizona (Tucson, AZ), 1999-11)
      Trenching and pruning applications were placed on mature Wichita pecan trees in Maricopa, Arizona in 1998. Yield and nut quality data from the test are presented. Unfortunately, the cool, favorable growing weather minimized quality degradation during the growing season and confounded the test. Data presented probably do not reflect the true benefits of the treatments.
    • Performance of mature pecan varieties in the low desert 1997 and 1998

      Gibson, Richard; Nunan, Linda; Kilby, Michael; Wright, Glenn; Kilby, Mike (College of Agriculture, University of Arizona (Tucson, AZ), 1999-11)
      Mature pecan trees at Picacho, Arizona were evaluated for variety performance during 1997-98. Total average yield per tree, percent kernel and percent viviparity were observed. During 1997, a severe viviparity year, only Bradley, Cheyenne, Souix and Tejas showed viviparity values of 20% or lower. Tejas did not return an acceptable percent kernel leaving Bradley, Cheyenne and Souix as potential varieties able to withstand low desert growing conditions on a regular basis. In 1998, the cool growing season confounded the test and no conclusions were drawn from the data.
    • Performance of Mature Pecan Varieties in the Low Desert of Pinal County 1997-1999

      Kilby, Michael; Gibson, Richard; Wright, Glenn; Kilby, Mike (College of Agriculture, University of Arizona (Tucson, AZ), 2000-10)
      Twelve varieties of pecans were evaluated for yield, viviparity, and nut quality. The commercially recommended varieties 'Western Schley' and 'Wichita' produced the greatest yields but also had the highest percentage of pregermination. The varieties 'Cheyenne' and 'Sioux' exhibit great potential for commercial production in the low desert of Arizona.
    • Population Dynamics of Pecan Aphids and Their Green Lacewing Predators in Insecticide-Free Pecans

      Hunter, Martha; Petersen, Mette; McElween, Melinda; Kilby, Michael; Wright, Glenn; Kilby, Mike (College of Agriculture, University of Arizona (Tucson, AZ), 2000-10)
      Field surveys of aphids and their natural enemies were conducted in a 30 acre unsprayed block of 'Wichita' pecans in Southeastern Arizona (FICO, Sahuarita) during the growing seasons of 1997, 1998, and 1999. Each season showed a different pattern of aphid population development. In general, numbers of the more damaging black pecan aphid, Melanocallis caryaefoliae were always lower than those of the blackmargined pecan aphid Monellia caryella and no serious aphid damage by either species was observed. Two species of green lacewings were the dominant natural enemies in the orchard, and eggs could be found throughout the season.
    • Quantification of Pecan Water Stress for Irrigation Scheduling

      Garrot, D. J. Jr.; Kilby, M. W.; Fangmeier, D. D.; Husman, S. H.; Kilby, Michael W.; Bantlin, Marguerite (College of Agriculture, University of Arizona (Tucson, AZ), 1990-12)
    • Rejuvenation of mature pecan trees by pruning

      Kilby, Michael; Gibson, Richard; Wright, Glenn; Kilby, Mike (College of Agriculture, University of Arizona (Tucson, AZ), 1999-11)
      Neglected mature 'Wichita' pecan trees were rejuvenated using various pruning techniques in 1997. Trees were pruned using proven horticultural techniques which included dehorning (cutting main scaffolds to within 2 feet of trunk) and cutting main scaffolds by 50%. To date the treatments have resulted in an increase in yield when compared to trees that received no pruning. In 1999 the grower has developed an orchard management program conducive to maximum production.
    • Rejuvenation of Neglected, Mature "Wichita" Pecan Trees By Corrective Pruning

      Gibson, Richard; Kilby, Michael; Wright, Glenn; Kilby, Mike (College of Agriculture, University of Arizona (Tucson, AZ), 2002-02)
      An attempt was made in 1997 to rejuvenate neglected, mature 'Wichita' pecan trees in a commercial Pinal County grove by applying two types of heading back pruning cuts. The treatments were applied during the dormant season prior to the growing season. The trees were pruned using proven horticultural techniques which included dehorning (cutting main scaffolds to within 2 feet of the trunk) and cutting main scaffolds by 50%. After four years of data, the trees receiving no pruning treatments are producing as well or better than trees to which the pruning treatments were applied. The data suggests that a return to normal irrigation and fertilization practices alone will return neglected, water-stressed trees to normal productivity as early as trees that have been headed-back.
    • Revitalizing "Wichita" Pecan Productivity Through Corrective Pruning - First Year Results

      Gibson, Richard; Kilby, Michael; Wright, Glenn; Kilby, Mike (College of Agriculture, University of Arizona (Tucson, AZ), 1998-09)
      A pruning study was established in stressed pecan trees to identify effective means of returning unproductive trees to full productivity. The study was comprised of two pruning systems and one untreated check. The number of nuts harvested from pruned trees was lower than that harvested from the unpruned trees, but the quality of the nuts from the pruned trees was improved when compared with the unpruned trees.