• Adaptation of Deciduous Fruit to the Desert Climate

      Fallahi, Esmaeil; Kilby, Mike; Tilt, Phil (College of Agriculture, University of Arizona (Tucson, AZ), 1986-12)
      Chilling requirements and maturity of several varieties of peaches and apples were studied at the University of Arizona, Yuma Mesa Agricultural Center (Southwest Arizona) in 1985-1986. Flordared, Flordabelle, Flordabeauty, Flordagold, Desert Gold and Suwanee peaches broke their dormancy earlier than other cultivars and showed full bloom between mid-to-late January. Suwanee and Desert Gold matured earlier than other tested varieties, but they produced small size fruit with low sugar content. Anna and Dorsett Golden apples showed extended blooming period due to insufficient chilling.
    • Annual Weed Control in Apples -- Spring Valley Farms 1984-85

      Heathman, Stanley; Kilby, Mike; Kilby, Michael W.; Bantlin, Marguerite (College of Agriculture, University of Arizona (Tucson, AZ), 1990-12)
    • Applying roundup to the base of lemon tree canopies: effects on leaves, flowers, fruitlets, and yield

      McCloskey, William B.; Wright, Glenn C.; Wright, Glenn; Kilby, Mike; Department of Plant Sciences, University of Arizona, Tucson, Arizona; Dept. Plant Sciences, U. of A., Yuma Mesa Agricultural Center, Yuma, Arizona (College of Agriculture, University of Arizona (Tucson, AZ), 1999-11)
      The effect of Roundup on lemon trees (Citrus limon) was evaluated by repeatedly spraying 0.5, 0.75, 1, 1.25, and 1.5 lb. a.i./acre (corresponding to 0.5, 0.75, 1, 1.25, 1.5 quarts of Roundup Ultra/acre) on the bottom 20 to 24 inches of the tree canopies, over a three year period. The Roundup applications caused significant leaf injury in the sprayed area of the canopies and there was also significant defoliation of branches at the higher Roundup rates in all three years of the study. In 1996 after three Roundup applications, increasing rates of Roundup had no effect on flower or fruitlet production in either the sprayed or unsprayed portions of the tree canopies as judged by the counts collected from branches in each canopy zone. Similarly, in 1997 after five Roundup applications, and in 1998 after nine Roundup applications, increasing rates of Roundup had no effect on flower or fruitlet production in the sprayed or unsprayed portions of the tree canopies. Spraying Roundup on the bottom of the tree canopies did not reduce total lemon yield per tree in 1996, 1997 or 1998 at any of the application rates. In all three years of the study, increasing Roundup rates had no effect on the yield of the first or second ring picks or the percentage of the total crop picked on the first harvest date. Increasing Roundup rates also did not affect fruit size at any harvest date in 1996, 1997 or 1998. Similarly, increasing Roundup application rates did not affect fruit quality at any harvest in 1996, 1997 or 1998. Thus, there was no relationship between the rate of Roundup sprayed on the trees and yield, fruit size or quality in all three years of this study. The three years of data collected in this study indicate that accidental drift or inadvertent application of Roundup onto lemon trees when spraying weeds on the orchard floor has no significant effect on lemon tree productivity.
    • Applying Roundup to the Base of Lemon Tree Canopies: Preliminary Effects on Leaves, Flowers, Fruitlets, and Yield

      McCloskey, William B.; Wright, Glenn C.; Wright, Glenn; Kilby, Mike; Department of Plant Sciences; Yuma Mesa Agricultural Center (College of Agriculture, University of Arizona (Tucson, AZ), 1998-09)
      The effect of Roundup on lemon trees was evaluated by repeatedly spraying 0.5, 0.75, 1, 1.25, and 1.5 lb. a.i./acre on the bottom 20 to 24 inches of the tree canopies over a three year period. The Roundup applications caused significant leaf injury in the sprayed area of the canopies and there was also significant defoliation of branches at the higher Roundup rates in all three years of the study. In 1996, flower and fruitlet counts were not affected by the Roundup applications and the 1998 data were inconclusive. However, flower and fruitlet counts in 1997 in the sprayed zone of the canopy were significantly reduced by Roundup and the effect increased with increasing Roundup rate. The 1996 and 1997 yield data indicated that Roundup applied to the bottom 20 to 24 inches of the tree canopies did not significantly affect lemon yield. The preliminary data suggest that accidental drift or misapplication of Roundup on to lemon trees when spraying weeds on the orchard floor has no short-term effect on grove productivity.
    • Citrus Peel Miner Marmara salictella Monitoring Techniques and Control Measures 1996-1997

      Maurer, M. A.; Kerns, D. L.; Tellez, T.; Wright, Glenn; Kilby, Mike (College of Agriculture, University of Arizona (Tucson, AZ), 1998-09)
      Citrus peel miner populations were monitored to evaluate various methods of trapping citrus peel miners. Observing 25 fruit per tree and 10 trees per block on the lower three feet of the tree canopy provided the best technique for determining the level of citrus peel miner infestations. The use of oleander plants, clear plates and green 3 inch diameter balls sprayed with Tangle-Trap were not effective in trapping citrus peel miner. In 1996, the first of September citrus leaf miner populations rose above the 10% infestation level. Success, Lorsban, Alert and Agri-Mek provided the highest mortality levels of citrus peel miner larvae. In citrus fruit, Success, Lorsban and Alert had the greatest efficacy of citrus peel miner larvae.
    • Commercial Evaluation of M-96-015 for Control of Citrus Mealybug, Woolly Whitefly and Citrus Thrips in Lemons

      Kerns, David L.; Tellez, Tony; Wright, Glenn; Kilby, Mike (College of Agriculture, University of Arizona (Tucson, AZ), 1998-09)
      M-96-015 did not appear to effectively control woolly whitefly but does appear to kill citrus mealybug. However, as with other insecticides coverage is a problem. The real benefit of M-96-015 towards citrus mealybug would occur if it prevented their spread. However, we were not able to measure this in this study. As with previous trials, M-96-015 is an effective citrus thrips material.
    • Development of Best Management Practices for Fertigation of Young Citrus Tree

      Thompson, Thomas L.; White, Scott A.; Walworth, James; Sower, Greg; Wright, Glenn; Kilby, Mike (College of Agriculture, University of Arizona (Tucson, AZ), 2002-02)
      'Newhall' navel oranges on 'Carrizo' rootstock were planted in Mar. 1997 at the Citrus Agricultural Center. The objectives of this experiment were: i) to determine the effects of N rate and fertigation frequency for microsprinkler-irrigated navel oranges on tree N status, and crop yield and quality; and ii) to develop Best Management Practices which promote optimum tree growth and production while minimizing nitrate leaching. The trees are equipped with a microsprinkler irrigation system. The experiment is a randomized complete block factorial with N rates of 0, 0.15, 0.30, and 0.45 lb N/tree/year, and fertigation frequencies of weekly, monthly, and three times per year. Unfertilized control trees are also included in the experimental design. Each of the ten treatments is replicated five times. The trees were harvested for the first time in Feb. 2001. Fruit were processed through an automatic fruit sizer, and fruit from each plot were further evaluated for fruit quality. Although unfertilized control trees had lower leaf N content than fertilized trees, fruit yield and quality of controls was no lower than fertilized trees. Similarly, there were few statistically significant differences in fruit yield and quality between trees receiving different N rates and fertigation frequencies.
    • Development of Best Management Practices for Fertigation of Young Citrus Trees

      Thompson, Thomas L.; White, Scott A.; Maurer, Michael A.; Wright, Glenn; Kilby, Mike (College of Agriculture, University of Arizona (Tucson, AZ), 2000-10)
      Microsprinkler irrigation offers excellent flexibility for site-specific management of water and nitrogen inputs for citrus orchards in the southwestern United States. Escalating water costs, declining water availability, and increasing regulation of nitrogen (N) fertilizer use are causing growers to adopt practices to improve water and N use efficiency. 'Newhall' navels on 'Carrizo' rootstock were planted in Jan. 1997 and an experiment was initiated. This experiment was continued during 1999. The objective of the experiment was to develop appropriate management guidelines for N fertigation of 3-4 year old microsprinkler-irrigated navel orange trees. Treatments were factorial combinations of three N rates (0.15, 0.30, 0.45 lb N tree⁻¹ yr⁻¹) and three fertigation frequencies (3x/year, monthly, weekly). An untreated control was included. Trunk diameter was not responsive to N rate or fertigation frequency. Leaf N in all treatments, even controls, remained above the critical level (2.5%). However, at each N rate leaf N was highest with the weekly fertigation frequency. Nitrate analyses of soil samples indicate that nitrate leaching was highest with the highest N rate and 3x/year fertigation. Frequent fertigation is recommended because it results in higher leaf N and less nitrate leaching.
    • Effect of Foliar Application of Benomyl on Severity of Septoria Leaf Spot on Pistachio in Southeastern Arizona

      Matheron, Michael E.; Kilby, Michael W.; Call, Robert; Wright, Glenn; Kilby, Mike (College of Agriculture, University of Arizona (Tucson, AZ), 1998-09)
      The fungicide, benomyl (Benlate) was foliar applied by a commercial air blast sprayer at the rate of 1.0 lb. a.i. per acre in early to late August. Treatments varied with a number of applications i.e. one or two and were compared to an untreated control. Benomyl significantly reduced leaf necrosis surrounding nut clusters and the number of leaf spot lesions when compared to control. One or two applications were equally effective in controlling Septoria leaf spot.
    • Effect of foliar boron sprays on yield and fruit quality of navel oranges

      Maurer, Michael A.; Taylor, Kathryn C.; Wright, Glenn; Kilby, Mike (College of Agriculture, University of Arizona (Tucson, AZ), 1999-11)
      A field study was designed to determine if foliar boron (B) sprays could increase fruit set and yield of 'Parent Washington' navel oranges (Citrus sinensis). Treatments consisted of two application timings (prebloom and postbloom) and five application rates 0, 250, 500, 750 and 1000 ppm B as Solubor. Leaf B levels had a significant response to both application timing and rate. There were no significant difference in fruit quality or yield.
    • Effect of Foliar Boron Sprays on Yield and Fruit Quality of Navel Oranges in 1998 and 1999

      Maurer, Michael; Truman, James; Wright, Glenn; Kilby, Mike (College of Agriculture, University of Arizona (Tucson, AZ), 2000-10)
      A field study was designed to determine if foliar boron (B) sprays could increase fruit set and yield of 'Parent Washington' navel oranges (Citrus sinensis). Treatments consisted of two application timings (prebloom and postbloom) and five application rates 0, 250, 500, 750 and 1000 ppm B as Solubor. Leaf B levels had a significant response to both application timing and rate in 1998, but there were no significant differences in 1999. There were no significant difference in fruit quality or yield in either year.
    • 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.
    • Effect of Temperature and Moisture on Survival of Phytophthora in Citrus Grove Soil

      Matheron, Michael; Porchas, Martin; Maurer, Michael; Wright, Glenn; Kilby, Mike (College of Agriculture, University of Arizona (Tucson, AZ), 2000-10)
      Before replanting a citrus grove in Arizona, different preplant cultural activities may be performed, such as immediate replanting of the new citrus grove, allowing soil to lay fallow for various lengths of time, or planting the site to alfalfa for one or more years before the new citrus grove is established. A study was conducted to compare the effect of these different cultural preplant practices on the survival of Phytophthora in citrus grove soils. In June, 1998, and July, 1999, a total of 18 soil samples were collected within mature lemon groves. Each initial bulk sample was pretested, found to contain Phytophthora parasitica, then thoroughly mixed and partitioned into 1-liter plastic containers, which were subjected to different environmental and cultural conditions. The soil in each 1-liter container was tested for the presence of P. parasitica 1 and 3.5 to 4 months later. All soil samples then were placed in the greenhouse and a 6-month-old Citrus volkameriana seedling was planted in soil samples not containing plants. Three 1-liter sub-samples from each of ten 7-liter volumes of soil incubated outside for three months were also planted to citrus in the greenhouse. The soil containing plants in the greenhouse was watered as needed for 3 months, then again tested for the presence of Phytophthora. Irrigating soil infested with Phytophthora parasitica, whether it was planted to a host (citrus) of the pathogen, planted to a non-host (alfalfa) of the pathogen, or not planted at all, did not lower the pathogen to nondetectable levels. Phytophthora became and remained nondetectable only in the soil samples that were not irrigated and subjected to mean temperatures of 35 to 37° C (94 to 98° F). On the other hand, the pathogen was detectable in some soil samples subjected to dryness at lower mean temperatures of 26 to 30° C (79 to 86° F) after a citrus seedling subsequently was grown in the soil for 3 months. A dry summer fallow period following removal of a citrus grove (including as much root material as possible) was the only cultural practice among those tested that reduced the level of Phytophthora to nondetectable levels in all soil samples tested.
    • Effective Management Tools for Septoria Leaf Spot of Pistachio in Arizona

      Call, Robert E.; Matheron, Michael E.; Wright, Glenn; Kilby, Mike (College of Agriculture, University of Arizona (Tucson, AZ), 1998-09)
      Septoria leaf spot was detected in the United States for the first time in 1964 within an experimental pistachio planting at Brownwood, Texas. The first observation of the same disease in Arizona pistachio trees did not occur until 1986. In 1988, a survey of the 2,000 acres of pistachio orchards in southeastern Arizona revealed a widespread incidence of the disease. Since the initial discovery of the disease, Septoria leaf spot has appeared annually in some of the Arizona pistachio acreage. The onset and severity of the disease is influenced by summer rainfall that occurs in this region. Disease management trials conducted since 1992 have shown that as few as two applications of chlorothalonil in July and August can virtually prevent disease development. Applications of copper hydroxide or benomyl alone or in combination also effectively arrest disease development. Leaves around nut clusters on infected trees not receiving fungicide treatments were usually senescent at crop maturity, whereas leaves on treated trees showed no sign of senescence. Pistachio trees infected with Septoria leaf spot and not treated with an effective fungicide can defoliate in the autumn up to 2 months prematurely.
    • Effects of fluid nitrogen fertigation and rate on microsprinkler irrigated grapefruit

      Thompson, Thomas L.; Maurer, Michael A.; Weinert, Tom L.; Wright, Glenn; Kilby, Mike (College of Agriculture, University of Arizona (Tucson, AZ), 1999-11)
      Microsprinkler irrigation offers excellent flexibility for site-specific management of water and nitrogen inputs for citrus orchards in the southwestern United States. Escalating water costs, declining water availability, and increasing regulation of nitrogen (N) fertilizer use are causing growers to adopt practices to improve water and N use efficiency. A three-year field experiment was initiated in the spring of 1996 on six-year-old pink grapefruit trees at the University of Arizona Citrus Agricultural Center. The objectives of this experiment are to i) evaluate the effects of fertigation frequency and fluid N application rate on the yield and fruit quality of microsprinkler irrigated grapefruit, and ii) develop best management guidelines for fluid N application frequency and rate for microsprinkler irrigated citrus. Treatments include a factorial combination of two N rates (recommended and 2 the recommended rate) and three fertigation frequencies (weekly, monthly, and tri-monthly). Minimal treatment effects were observed during the first season due to the influence of previous management practices. During the second season, fertilized trees yielded greater than the control trees. There was no significant difference between N rates, but fruit yield was generally higher with monthly or weekly fertigation. Leaf tissue samples collected during the second and third growing seasons showed increasing leaf N with increasing fertigation frequency at the high N rate.
    • Effects of Gypsum Applications on Established Thompson Seedless Grapes

      Doerge, Thomas A.; True, Lowell; Kilby, Mike; Kilby, Michael W.; Bantlin, Marguerite (College of Agriculture, University of Arizona (Tucson, AZ), 1990-12)
    • Efficacy of Insecticides to Citrus Thrips on Lemons in Yuma Arizona 1997

      Kerns, David L.; Tellez, Tony; Wright, Glenn; Kilby, Mike (College of Agriculture, University of Arizona (Tucson, AZ), 1998-09)
      Three small plot efficacy trials were conducted evaluating different insecticide rotation regimes using commercially available insecticides and the effectiveness of new insecticide chemistries to control citrus thrips. Because of its long residual activity, and ability to control post- application egg hatches, Carzol appears to be the product that best fits the petal fall application window. Agri-Mek, Baythroid, Dimethoate or Vydate are probably good follow -up insecticides. However, Agri-Mek and Baythroid will probably provide greater control, especially under hotter conditions. If temperatures are cool, Agri-Mek looks good at reduced rates. The best insecticide for subsequent applications depends on temperatures and what was previously applied. Avoid making back -to -back applications of the same materials, and Dimethoate or Vydate applications should probably be followed by Carzol to catch post- application egg hatches. Overall, Vydate appears to be very similar to Dimethoate in efficacy and residual activity, while Baythroid appears to be slightly better. Although the addition of Lannate to Dimethoate does slightly enhance thrips control, the additional cost probably does not justify the tank mix. Of the new chemistries (Alert, Success, Ni-25, and M-96-015) evaluated, Success and M-96-015 appeared to offer the best fruit protection. However, M-96-015 does not appear to be very effective in killing the thrips, but is very effective in repelling them. Also, M-96-015 will need to be applied at a high gallonage, i.e. 500 gal/A. None of the new products tested appear to fit the petal fall application window very well. Ni-25, Alert and Success appear to lack the residual activity of Carzol, and M-96-015 should not be used as a clean-up material but preventively following Carzol at petal fall.
    • Efficacy of Insecticides to Citrus Thrips on Lemons in Yuma Arizona 1998

      Kerns, David L.; Tellez, Tony; Wright, Glenn; Kilby, Mike (College of Agriculture, University of Arizona (Tucson, AZ), 1999-11)
      Two small plot efficacy trials were conducted evaluating different insecticide rotation regimes using commercially available insecticides and the effectiveness of new insecticide chemistries to control citrus thrips. Under the consistently cool conditions experienced during the first four weeks of the trial, Dimethoate, Success, Baythroid, Agri-Mek, Vydate and Carzol all of the offered adequate control and would fit well in the petal fall window. This is in contrast with previous years experiences when high temperatures within a week of petal fall would result in all treatments except Carzol requiring a re-treatment within ten days. All of the rotation schemes evaluated required three insecticide applications to get through the season, and did not appear to be greatly different in controlling thrips and producing high quality fruit under the environmental conditions experienced. However, the Dimethoate - Success - Baythroid rotation scheme was most cost effective. When temperatures were in the 70's to low 80's, Dimethoate and Vydate offered about three weeks control, Success, Carzol, Baythroid and Agri-Mek all offered about four weeks control. When temperatures were in the mid to upper 80's and low to mid 90's, Success provided about three weeks control while Carzol didn t require re-treatment for 4 weeks. Under these same temperature conditions, Dimethoate and Vydate gave about 7 to 12 days control, and Agri-Mek provided 12 to 14 days of control. Other than the one control failure with Baythroid, under warmer conditions, it provided about seven days control. In the experimentals test, AZEXP1 appeared to offer knockdown activity at temperatures less than 90 F, and only suppression at higher temperatures. AZEXP2, appeared to be a viable citrus thrips material, with activity similar to Success and Carzol. The knockdown activity of M96 appeared to be enhanced by including Dimethoate or Carzol, but will require multiple applications to achieve the level of repellency experienced in 1997.
    • Evaluation and management of a "salina" strawberry clover cover crop in citrus: first year preliminary results

      McCloskey, William B.; Wright, Glenn C.; Wright, Glenn; Kilby, Mike; Department of Plant Sciences, University of Arizona, Tucson, Arizona; Dept. Plant Sciences, U. of A., Yuma Mesa Agricultural Center, Yuma, Arizona (College of Agriculture, University of Arizona (Tucson, AZ), 1999-11)
      Two orchard floor management strategies were evaluated beginning in the fall of 1997 in a 'Valencia' orange (Citrus sinensis) grove at the University of Arizona Citrus Agricultural Center (CAC) in Waddell, Arizona. The clean culture or bare ground treatment produced more yield than the ‘Salina’ strawberry clover treatment when harvested on March 10, 1999 and the tree canopy volume of the clean culture treatment was also greater than that of the clover treatment. Yield efficiency (lbs of fruit per cubic meter of canopy) was similar in the two treatments. The clean culture treatment produced more large size fruit (size 88 and larger) and less small size fruit (size 113 and smaller) than the strawberry clover treatment. Although the yield efficiency parameter suggests that it may be possible to produce as much fruit in the clover treatment as the clean culture treatment, the total yield and fruit size distribution of the clover treatment compared to the clean culture treatment were characteristic of the negative effects of competition from vegetation on the orchard floor found in other studies. Based on previous studies, competition for water was the most likely cause of the negative competitive effect. Installation of additional tensiometers to measure soil moisture at greater depths and leaf water potential measurements to assess the degree of water stress in both treatments prior to irrigation will hopefully allow further improvement in irrigation scheduling to eliminate the negative affect of having vegetation on the orchard floor in the clover plots.