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  Evaluation of Commerical Ultra Narrow Cotton Production in Arizona

  Clay, P. A.; Isom, L. D.; McCloskey, W. B.; Husman, S. H.; Silvertooth, Jeff; University of Arizona Cooperative Extension (College of Agriculture, University of Arizona (Tucson, AZ), 2000)

  Seven commercial ultra narrow row (UNR) cotton fields were monitored on a weekly basis in Maricopa County, AZ in 1999. Varieties of Delta Pine and Sure Grow were planted from April 15 to June 1 and reached cut-out after accumulating 1913 to 2327 heat units after planting. Average yield for UNR cotton was 2.1 bales per acre which was 0.4 bales per acre lower than the five year average for cotton planted on conventional row spacings. Fiber quality from gin records for 801 bales had average micronaire readings of 4.54 and grades of 11 and 21 for 74% of bales. Discounts for extraneous matter (bark, grass, and cracked seed) was 5.4% and average strength (34.8) and staple lengths (27.12) were in acceptable ranges. Total cash costs ranged from $450 to $705.
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  Johnsongrass Control in Cotton with BAS 620

  Clay, P. A.; Isom, L. D.; Silvertooth, Jeff; University of Arizona Cooperative Extension (College of Agriculture, University of Arizona (Tucson, AZ), 2000)

  Johnsongrass control with BAS 620 was 60% and 67% for the 0.124 and 0.248 lb ai/A rates respectively, 14 d after initial application. Control was comparable to Select at the corresponding rates. Control 28 d after the second application of graminicides ranged from 60% to 88%. Both rates of BAS 620 and Select as well as Fusilade DX provided the most effective control. Seed cotton yields ranged from 1347 to 3134 lbs/A and all herbicide treatments yielded significantly greater than the nontreated check.
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  Effect of Halosulfuron (Permit), CGA362622, Glyphosate (Roundup Ultra) and Pyrithiobac (Staple) on Purple Nutsedge Growing in a Fallow Field

  Veatch, Maren E.; McCloskey, William B.; Silvertooth, Jeff; Department of Plant Sciences, University of Arizona, Tucson, AZ (College of Agriculture, University of Arizona (Tucson, AZ), 2000)

  In the fall of 1999 an experiment was conducted to measure the effect of CGA- 362622, halosulfuron (Permit), glyphosate (Roundup Ultra) and Pyrithiobac (Staple) on purple nutsedge. Five rates of Permit (0.25, 0.375, 0.495, 0.75 and 1.0 oz a.i./A), three rates of CGA-362622 (3.035, 4.047, and 6.07 g a.i./A), and a single rate each of Roundup Ultra (0.75 lb a.e./A), Staple (1.5 oz a.i./A), Staple + Bueno 6 (2 lb a.i./A), and Staple + Fusilade (0.25 lb a.i./A) were applied either once or twice to field populations of purple nutsedge. Efficacy of each treatment was measured in three ways: phytotoxicity (stunting, chlorosis and/or necrosis) ratings were assigned to each plot (0 being no injury and 10 indicating death), the number of green leaves were counted on 3 large ($8 leaves) and 3 small (≤4 leaves) plants per plot at various times after treatment, and the amount of regrowth after the herbicide treatments was assessed. All of the herbicide treatments caused stunting, induced chlorosis and necrosis, and were fairly effective in controlling nutsedge plants treated at or before the 4-leaf growth stage. Only Permit and CGA-362622 effectively controlled plants treated at the 8-leaf growth stage after one application. The other four herbicides required two applications to obtain effective control. For the regrowth parameter parameters, Permit, CGA-362622 and Roundup Ultra effectively controlled regrowth, but the Staple, Staple + Bueno 6 and the Staple + Fusilade treatments did not control regrowth. Two applications of Permit at the .495 oz a.i./A or greater rates, Roundup Ultra (0.75 lb a.e./A) and 1 or 2 applications of the 6.070 g a.i./A rate of CGA-362622 controlled nutsedge with respect to all measured regrowth parameters and may be the best choices for controlling purple nutsedge.
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  Reduced Whitefly Infestations in Cotton Using a Melon Trap Crop

  Castle, S. J.; Silvertooth, Jeff; USDA, ARS, Western Cotton Research Lab (College of Agriculture, University of Arizona (Tucson, AZ), 2000)

  A second year of field experiments was completed in 1999 at MAC that explored the potential of using a melon trap crop to reduce whitefly infestations in cotton. The experimental design was altered from 1998 to gain isolation among treatment blocks by using 4 separate fields that helped to avoid the influence of one treatment upon the other. A consistent response of significantly fewer whiteflies in cotton planted within a surrounding melon trap crop, relative to the same area of cotton without the trap crop, was observed throughout the July- September sampling period. Better chemical management of whiteflies in the melons during the second season helped to reduce the large differential in whitefly densities between melons and cotton observed the previous year, but preferentially contributed to a greater differential observed between melonprotected cotton and unprotected cotton. Although the infestation buildup was delayed and the season-long densities of whiteflies in the melon-protected cotton were reduced, the action thresholds for treatment with IGRs were ultimately attained and exceeded. In the present management environment of perhaps only 1 IGR treatment per season, it is unlikely that the melon trap crop approach would provide acceptable control unless a grower was willing to tolerate lateseason whitefly densities higher than the current IPM recommendations.
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  Use of Insect Growth Regulators and Changing Whitefly Control Costs in Arizona Cotton

  Agnew, G. Ken; Frisvold, George B.; Baker, Paul; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2000)

  In 1996, two Insect Growth Regulators (IGRs), pyriproxyfen (Knack®) and buprofezin (Applaud®) became available to Arizona cotton growers for control of whitefly, Bemisia argentifolii under a Section 18 EPA exemption. This study makes use of a section-level database to examine (a) factors explaining IGR adoption and (b) how adopters of IGRs altered their overall insecticide use to control whiteflies. IGR adoption can be explained to a large extent by location effects. Adoption was more likely on sections where an index of whitefly susceptibility to synergized pyrethroids was low and on sections with higher whitefly control costs in the previous year. Adoption was inversely related to local population density. On sections where growers adopted IGRs, expenditures on synergized pyrethroid and other whitefly-specific tank mix applications fell by $62.52 per acre. On sections with no IGR adoption, tank mix expenditures fell less, by $44.37 per acre. On adopting sections, net costs of controlling whiteflies fell by $29.62 per acre, or by over $11,000 per farm.
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  Susceptibility of Arizona Whiteflies to Chloronicotinyl Insecticides and IRGs: New Developments in the 1999 Season

  Li, Yongsheng; Dennehy, Timothy J.; Li, Xiaohua; Wigert, Monika E.; Silvertooth, Jeff; Extension Arthropod Resistance Management Laboratory, Department of Entomology, The University of Arizona (College of Agriculture, University of Arizona (Tucson, AZ), 2000)

  Whiteflies are serious pests of cotton, melons, and winter vegetables in Arizona’s low deserts. Successful management of whiteflies requires an integrated approach, a critical element of which is routine pest monitoring. In this paper we report findings of our 1999 investigations of resistance of Arizona whiteflies to insect growth regulators (IGRs) and chloronicotinyl insecticides. Whiteflies collected from cotton fields, melon fields and greenhouses were tested for susceptibility to imidacloprid (Admire/Provado), and two other chloronicotinyl insecticides, acetamiprid and thiamethoxam, and to two insect growth regulators (IGRs), buprofezin (Applaud) and pyriproxyfen (Knack). Contrasts of 1999 and 1998 results indicated increased susceptibilities, on average, to both imidacloprid and buprofezin of whiteflies collected from cotton. A cropping system study showed that whiteflies collected from spring melons had significantly lower susceptibility to imidacloprid than those collected from cotton or fall melons. The opposite was found for pyriproxyfen, to which whiteflies from cotton and fall melons had lower susceptibility than those from spring melons. As in 1998, whiteflies with reduced susceptibility to imidacloprid continue to be found in certain locations, particularly in spring melon fields and greenhouses. Results of our laboratory bioassays on susceptibility of Arizona whiteflies to chloronicotinyl insecticides provided evidence of a low order cross-resistance between imidacloprid, acetamiprid and thiamethoxam. Monitoring in 1999 provided the first evidence of reduced susceptibility of Arizona whiteflies to pyriproxyfen.
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  Silverleaf Whitefly - Trichome Density Relationships on Selected Upland Cotton Cultivars

  Chu, C. C.; Natwick, E. T.; Henneberry, T. J.; Silvertooth, Jeff; USDA, ARS, Western Cotton Research Laboratory (College of Agriculture, University of Arizona (Tucson, AZ), 2000)

  We studied silverleaf whitefly (SLW) and trichome density relationships on ten selected upland cotton cultivars: Deltapine #20B, 50B and 90B, NuCOTN 33B, Stoneville 474, Fibermax #819 and 832, Siokra L-23, and 89013-114 at Maricopa, in AZ, 1999. Whitefly and stellate trichome densities were counted on leaves on main stem leaf nodes #1, 3, 5 and 7 of each cultivar. Stoneville 474 had about 2-3 times more eggs, nymphs, and adults and also had 3-30 times more branched trichomes on abaxial leaf surfaces compared with the nine other cultivars. The top young leaves on node #1 had about 6 times more stellate trichomes compared with older leaves. However, the top young leaves also had reduced numbers of eggs and nymphs (23 and 1/cm2 of leaf disk, respectively) compared with older leaves. The results suggest that other factors, in addition to trichomes, at least for young terminal leaves, affect silverleaf whitefly population development.
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  Effects of Aqueous Sprays of Silverleaf Whitefly Honeydew Sugars on Cotton Lint Stickiness

  Henneberry, T. J.; Forlow Jech, L.; Hendrix, D. L.; Steele, T.; Silvertooth, Jeff; USDA-ARS, Western Cotton Research Laboratory (College of Agriculture, University of Arizona (Tucson, AZ), 2000)

  Sprays of commercially-procured sugars that are also found in silverleaf whitefly Bemisia argentifolii Bellows and Perring [= B. tabaci (Gennadius) Strain B] honeydew were applied to clean cotton lint to determine the relationship between the sugars and cotton lint stickiness. Increasing concentrations of the sugars resulted in increasing thermodetector counts.
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  Pink Bollworm Egg Infestations and Larval Survival in NuCOTN 33b and Deltapine Cottons in Arizona

  Henneberry, T. J.; Forlow Jech, L.; de la Torre, T.; Faulconer, S; Hill, J. J.; Silvertooth, Jeff; USDA, ARS, Western Cotton Research Laboratory, Phoenix, AZ (College of Agriculture, University of Arizona (Tucson, AZ), 2000)

  The gene for the Bacillus thuringiensis var. kurstaki (Berliner) insect toxic protein is a new advance in technology for pink bollworm (PBW), Pectinophora gossypiella (Saunders), control. We conducted studies in 1999 to investigate grower concern for reduced efficacy of NuCOTN 33b (Bt cotton) (Monsanto Company, St Louis, MO) in late-season because of breakdown or non-expression of the toxic protein. We compared the susceptibility of Bt and Deltapine 5415 (Monsanto Company, St Louis, MO) (non-Bt) cotton bolls to PBW at periodic intervals during the first and second cotton fruiting cycles. We placed >200 PBW eggs per boll on the inside surface of bracts of susceptible immature cotton bolls. The artificially infested bolls were later harvested and examined for evidence of PBW infestation. High percentages of both Bt and non-Bt cotton bolls had numerous larval entrance holes in the carpel walls of the bolls. Less than 1% of the Bt cotton bolls and over 70% of the non-Bt cotton bolls were found with living PBW larvae. Bt cotton bolls of the late-season second fruiting cycle were as resistant to PBW infestation as Bt cotton bolls of the first fruiting cycle.
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  Lygus Control Decision Aids for Arizona Cotton

  Ellsworth, Peter C.; Silvertooth, Jeff; The University of Arizona, Department of Entomology & Maricopa Agricultural Center (College of Agriculture, University of Arizona (Tucson, AZ), 2000)

  Changes in insecticide use, available pest control technologies, and local crop ecology together with severely depressed cotton prices place a renewed premium on Lygus control decision aids for Arizona cotton. As part of an on-going program to develop research-based Lygus management recommendations, we investigated the impact of various timings of chemical controls on Lygus population dynamics, number of sprays, costs of control, and net revenue as well as cotton heights, trash, lint turnouts, and yields. Once there were at least 15 total Lygus per 100 sweeps, sprays were made according to the number of nymphs in the sample (0, 1, 4, 8 or 16 per 100 sweeps). Up to 7 sprays were required (15/0 regime) to meet the needs of the target threshold. Lygus adult densities were largely unresponsive to the treatment regimes or individual sprays made. Three generations of nymphs, however, were affected by the treatments with the ‘15/4’ regime harboring the fewest nymphs through July. This ‘moderate’ regime required 4 sprays and had the shortest plants, cleanest harvest, and highest lint turnouts. In addition, this regime out-yielded all other treatment regimes including the 6- (15/ 1) and 7- (15/0) spray regimes. Regression analyses of the data suggest that adult Lygus are less related to yield loss than nymphs and that large nymphs are best correlated with yield loss. Thus, spraying based on adults only would appear illadvised. Returns were highest ($747/A) for the 15/4 regime with over $100 more than the more protective regimes. Thus, there is no economic advantage in advancing chemical control when nymph levels are low. Maximum economic gain was achieved by waiting for the 4 nymphs per 100 level (with 15 total Lygus/100; 15/4) before spraying. However, waiting too long (beyond the 8 nymphs / 100 level; 15/8) resulted in significant reductions in yield and revenue. Our recommendations, therefore, are to apply insecticides against Lygus when there are at least 15 total Lygus, including at least 4 nymphs, per 100 sweeps. These recommendations are stable over a wide variety of economic conditions (market prices & insecticide costs). Continued work is necessary to verify these findings over a wider range of cotton developmental stages, varieties, and other environmental conditions.
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  Pesticide Use in Arizona Cotton: Long-Term Trends and 1999 Data

  Agnew, G. E.; Baker, P. B.; Silvertooth, Jeff; Pesticide Information and Training Office (College of Agriculture, University of Arizona (Tucson, AZ), 2000)

  Arizona pesticide use, as reported on the Department of Agriculture's form 1080, can be summarized to provide a rich picture of pest management in Arizona cotton. Limitations in the pesticide use reporting system complicate the process but do not undermine results. Overall pesticide use decreased over the period 1991 to 1998 despite a peak during the whitefly infestation of 1995. Decreases in insecticide use are responsible for most of the reduction in pesticide use. Recently released 1999 data indicates that reductions continued. Comparison of the composition of pesticide applications between 1995 and 1998 reflect the changes in pest control efforts. A new "target pest" category on the 1080 provides an even richer picture of pest management practices in Arizona cotton.
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  Evaluation of an Arid Soil Conditioner in an Irrigated Cotton Production System

  Norton, E. R.; Silvertooth, J. C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2000)

  A single field study was conducted on a sodium-affected soil at the University of Arizona’s Maricopa Agricultural Center (MAC) in 1999. Deltapine DP33B was dry planted and watered-up on 13 April 1999. Two treatments were evaluated; treatment 1 received no acid and treatment 2 received water-run acid applications. The acid used in this evaluation was sulfuric acid (H2SO4) and was applied at approximately 11 gallons acid/acre at each scheduled irrigation throughout the entire growing season. All other agronomic inputs and decisions were uniformly applied to both treatments. Lint yields were not significantly different.
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  Influence of Ironite and Phosphorus on Long and Short Cotton on the Safford Agricultural Center, 1999

  Clark, L. J.; Carpenter, E. W.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2000)

  Ironite and phosphorus were applied to plots planted to long and short staple cotton to find their effect on crop development and lint yield. The soil analysis indicated sufficient iron and phosphorous in the soil for cotton production and that yield increases from additions of these elements were unlikely. No statistically significant increases in lint yield were seen with the addition of Ironite nor phosphorous fertilizer. However, an interesting yield trend with ironite was seen in long staple cotton.
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  Cotton Fertility Study, Safford Agricultural Center, 1999

  Clark, L. J.; Carpenter, E. W.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2000)

  Three different nitrogen fertilizer regimes were practiced in this study along with an unfertilized check. The same amount of nitrogen fertilizer was sidedressed in the plots in one, two or three applications. No statistically significant differences were seen between lint yields in this study nor in the previous study, but the yield trends were very similar. Applying the fertilizer nitrogen in two equal portions at the onset of rapid vegetative growth and just before peak bloom appeared to produce the best lint yield.
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  Evaluation of a Calcium-Based Soil Conditioner in Irrigated Cotton

  Silvertooth, J. C.; Norton, E. R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2000)

  A two site evaluation of a calcium (Ca²⁺)-based soil conditioner was conducted during the 1999 cotton season. The two locations included one at the Maricopa Agricultural Center (MAC) in Maricopa, AZ and the other was on a growercooperator field in Tacna, AZ. Both studies involved the use of CN-9, a Ca – nitrate solution with 9% nitrogen and 11% Ca. At MAC theCN-9 solution was sprayed over the seedbed post planting but prior to the first water-up irrigation. At the Tacna site CN-9 was applied in a sidedress application at planting. Routine plant measurements were taken throughout the duration of both studies and lint yield estimates were made at each location at the end of the season. No significant differences due to the application of CN-9 were detected in any data collected.
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  Soil Test Calibration Evaluations for Phosphorus on Upland and Pima Cotton

  Thelander, A. S.; Silvertooth, J. C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2000)

  Numerous field experiments were conducted at a wide range of sites in Arizona from 1988 through 1999 involving phosphate (P) fertilization of cotton (Gossypium spp.). A total of 21 site-years were used to study the effects of P on both Upland (G. hirsutum L.) and Pima (G. barbadense L.) varieties. The purpose of these experiments was to evaluate University of Arizona (UA) soil fertility guidelines with respect to soil test results (NaHCO3 extractable P) and to possibly fine-tune or calibrate these guidelines in relation to soil test P, applied P, and yield for common Arizona soils used in cotton production. Results from these experiments, based on soil test information, plant measurements, and lint yield showed no significant difference (P 0.05) due to treatments for all the studies with the exception of one P study conducted in Graham County in 1998 and another P study conducted in Pinal County in 1999. The 1998 Graham County site had a preseason soil test value of 7.6 ppm NaHCO₃ extractable P. The 1999 Pinal County site had a preseason soil test value of 3.0 ppm NaHCO3 extractable P. Analysis of yield results vs. soil P show that soil test P levels greater than 5 ppm are consistently sufficient for both Upland and Pima cotton. Yield results vs. applied P (lbs. P₂O₅/acre) for both Upland and Pima did not indicate a positive response over the rates of fertilization tested (20-160 lbs. P₂O₅/acre). Based on the results from these studies, the current UA soil fertility guidelines for P fertilization of cotton appear to be valid. Furthermore, the data indicates that the UA soil fertility guidelines may be further refined to provide the following categories: < 5 ppm = high probability of response to an added P fertilization; 6-10 ppm = medium probability of response to an added P fertilization; and > 10 ppm = low probability of response to an added P fertilization.
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  Fertility Management and Calibration Evaluations on Upland and Pima Cotton

  Thelander, A. S.; Silvertooth, J. C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2000)

  Numerous field experiments were conducted during the 1997 through 1999 cotton seasons involving macro and micronutrient fertilization. The purpose of these experiments was to evaluate University of Arizona (UA) fertility guidelines with respect to soil test results and to possibly fine-tune or better calibrate these guidelines for common Arizona soils and cotton growing regimes. Field experiments studied the effects of a single nutrient or nutrient combinations on both Upland and Pima varieties. Results from these experiments, based on soil test information, quantitative plant measurements, and lint yield showed no significant difference due to treatments for all sites except for a phosphorus study conducted during the 1998 season in Graham County and a phosphorus study conducted during the 1999 season in Pinal County. All results reinforce current UA soil testing guidelines for cotton.
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  Nitrogen Management Experiments for Upland and Pima Cotton, 1999

  Silvertooth, J. C.; Norton, E. R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2000)

  Two field experiments were conducted in Arizona in 1999 at two locations (Maricopa and Marana). The Maricopa experiment has been conducted for nine consecutive seasons, the Marana site was initiated in 1994. The purposes of the experiments were to validate and refine nitrogen (N) fertilization recommendations for Upland cotton. The experiments each utilized N management tools such as pre-season soil tests for NO₃⁻-N, in-season plant tissue testing (petioles) for N fertility status, and crop monitoring to ascertain crop fruiting patterns and crop N needs. At each location, treatments varied from a conservative to a more aggressive approach of N management. Results at each location revealed a strong relationship between the crop fruit retention levels and N needs for the crop. This pattern was further reflected in final yield analysis as a response to the N fertilization regimes used. The higher, more aggressive, N application regimes did not benefit yields at any location. In 1999, fruit retention levels were low and crop vigor was high at the Maricopa site. As a result, even slight increases in N fertilization and crop vigor translated into lower yield.
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  Pima Cotton Regional Variety Trial, Safford Agricultural Center, 1999

  Clark, L. J.; Carpenter, E. W.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2000)

  Thirty long staple varieties were tested in a replicated small plot trial on the Safford Agricultural Center in Graham county at an elevation of 2950 feet. The highest yielding variety in this study was Hazera 83-208 with a yield of 1272 pounds of lint per acre. This interspecific hybrid from Israel yielded nearly 300 pounds per acre more lint than the next closest variety. The average yield in the trial was lower than in the previous year’s study. Yield and other agronomic data as well as fiber quality data are contained in this paper.
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  Effects of High Frequency Irrigation on Irrigation Uniformity II

  Martin, E. C.; Wegge, R.; Sheedy, M.; Silvertooth, Jeff; University of Arizona, Cooperative Extension (College of Agriculture, University of Arizona (Tucson, AZ), 2000)

  Another year of data was collected to determine the effects of high frequency irrigation on irrigation uniformity in cotton production. A field located at the Marana Agricultural Center was split into two treatments. Treatment one was irrigated at approximately 35% depletion of available water in the plant rootzone. Treatment two was irrigated at approximately 65% depletion in the crop rootzone. Increased frequency of irrigation has shown improved yields in many cotton studies. However, these more frequent and lighter irrigation applications may cause problems with irrigation uniformity. Frequent rains during critical time periods made it difficult to ascertain the impact of the irrigation schedule on uniformity. However, the less frequent, heavier application rate did result in a more uniform irrigation.

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