Virginia Cotton Research Articles

Landscape and climatic effects driving spatiotemporal abundance of Lygus lineolaris (Hemiptera: Miridae) in cotton agroecosystems

Lygus lineolaris populations have become increasingly problematic in Virginia cotton since 2013. Although production practices have changed, changes in landscape composition and climatic conditions are also anecdotally associated with increasing populations. To better understand the recent increase in L. lineolaris infestations in Virginia cotton, 56 commercial cotton fields were sampled weekly in 2017 and 2018 for a nine-week period during the growing season. Insect density was measured using sweep net and black drop cloth sampling, targeting adult and nymphal populations, respectively. Geospatial crop production and forest disturbance data were used to measure the composition and management history of landscapes adjacent to sample fields. We also used spatial climate data sets to document the relationship between increasing L. lineolaris and temperature variation. We investigated the significance of landscape composition and climatic effects increasing L. lineolaris infestation intensity using a regression modeling approach. We found the best overall predictor of L. lineolaris abundance was higher annual minimum temperatures. Several crop components in the landscape were significant, specifically corn and double-crop winter wheat and soybeans, but these habitat patches did not explain high levels of variability. Results of this study suggest that increasing minimum temperatures will favor L. lineolaris and may translate into elevated infestation intensity and increasing dependence on insecticide inputs to manage this problematic pest of cotton. Results of this study will be important to describe short- and long-term factors driving L. lineolaris infestation risk in cotton agroecosystems.

Evaluating Optimal Spray Timing, Planting Date, and Current Thresholds for Lygus lineolaris (Hemiptera: Miridae) in Virginia and North Carolina Cotton.

Economically damaging infestations of Lygus lineolaris (Palisot de Beauvois) (Hemiptera: Miridae), the tarnished plant bug, have been increasing in North Carolina and Virginia cotton since 2009. We conducted experiments to compare prophylactically timed sprays based on cotton phenology and current action thresholds based on sweep net and drop cloth sampling. In the second year of the study, we included planting date as a factor, with early and late-planted cotton. We found L. lineolaris nymph densities were reduced by at least 60% in North Carolina and 74% in Virginia in threshold plots when compared with the untreated control. Protecting the crop from first square through the fourth week of bloom afforded at least 30% control across planting dates in Virginia and at least 40% control in North Carolina. Economic returns were two to three times greater in early-planted cotton than in late-planted cotton. Treating cotton at action threshold or using prophylactic sprays from first square until the sixth week of bloom in early-planted cotton yielded over $500/ha in net returns in both North Carolina and Virginia. This study supports previous research that shows controlling L. lineolaris infestations during squaring and early weeks of flowering is critical for maximizing yield potential. Our findings also suggest that prebloom and bloom thresholds based on adult and nymphal density devised in the Mid-South may need revision in North Carolina and Virginia.

EVALUATION OF INSECTICIDE SPRAY/NO SPRAY ON CONVENTIONAL AND DOUBLE-GENE INSECT RESISTANT COTTON AGAINST BOLLWORM, 2013

Thirteen double-gene insect resistant and two conventional cotton varieties were evaluated for control of BW in Virginia cotton at the Virginia Tech Tidewater Agric. Res. & Ext. Ctr., Suffolk, VA. Each variety was treated with insecticides targeting BW, or not treated for BW. In the treated plots, double-gene insect resistant varieties received one spray of Brigade @ 6.4 oz/acre plus Belt @ 2 oz/acre on 14 Aug 6 day after BW egg threshold. Conventional varieties received two sprays for BW, Brigade @ 6.4 oz/acre at BW egg threshold on 8 Aug, and Brigade @ 6.4 oz/acre plus Belt @ 2 oz/acre on 14 Aug. Treatments were applied with a Spider Spray Trac-mounted CO2-pressurized sprayer at 16.5 gpa and 30 psi through 8002VS nozzles spaced 18 inches apart on the spray boom. Cotton was planted 17 May using 36-inch row spacing. A split-plot experimental design was used with 4 replicates; plots were 4 rows by 40 ft. Plant population was determined on 24 Jun by counting all plants in two rows per plot. External boll injury was determined by visually inspecting 25 bolls per plot for evidence of BW feeding on three dates. Yield was determined by harvesting 2 rows of each plot (80 row ft) on 13 Nov using a commercial 2-row cotton picker. Samples from each variety were ginned to determine lint versus seed and trash weight. Data were analyzed using ANOVA and LSD statistical procedures.

EVALUATION OF THRIPS MANAGEMENT PROGRAMS WITH AND WITHOUT PRE-EMERGENT HERBICIDES IN VIRGINIA COTTON, 2013

EVALUATION OF THRIPS MANAGEMENT PROGRAMS WITH AND WITHOUT PRE-EMERGENT HERBICIDES IN VIRGINIA COTTON, 2013

Boll Removal Studies Provide Insights into Compensation Ability of Virginia Cotton: A Necessary Step for Further Improvement of Insect Management Strategies

In developing management strategies for hemipteran pests in cotton (Gossypium hirsutum L.), it is important to understand the potential of plants to compensate for loss of the fruiting structures. Because of its northern latitude, Virginia has fewer available heat units relative to other cotton-producing states. Therefore, there may be limited opportunity for compensation relative to more southerly production areas. Previous work in Virginia demonstrated that cotton can sustain relatively high levels of first position square loss with no yield loss. This study evaluated the impact of a single event loss of 10–14-d-old bolls via mechanical removal on cotton lint yields with the premise that boll loss would have greater impact than square loss as less time and fewer heat units are available for compensation. Field experiments examining four levels of boll removal (0, 5,15 and 20%) were conducted in 2001,2002 and 2003. Each boll removal level was imposed at three different dates, beginning 2 wks after first flower and at 3- to 5-d intervals thereafter. Yields ranged from 1103–1422 in 2001, 909–1124 in 2002, and 843–1015 kg lint per ha in 2003. There were no significant differences in lint yields among the boll removal dates or removal levels. The results of our study showed that cotton in Virginia, which approaches the northernmost latitude for cotton production, is capable of sustaining losses as high as 20% of 10–14-d-old bolls at a single removal event without affecting lint yield. Results were consistent despite the wide variation in rainfall and temperatures during the 3 study years.

EVALUATION OF SELECTED SEED TREATMENTS AND IN-FURROW INSECTICIDES, WITH AND WITHOUT AN ADDITIONAL FOLIAR BROADCAST APPLICATION AT FIRST TRUE LEAF STAGE, FOR CONTROL OF THRIPS IN VIRGINIA COTTON, 2005

Selected insecticides applied onto seed or into the seed furrow at planting were evaluated for control of thrips in Virginia cotton. 'Delta Pine 444 BG/RR' cotton was planted 3 May at the Virginia Tech Tidewater Agric. Res. & Ext. Ctr., Suffolk, VA, using 36-inch row spacing. Avicta 500FS, Cruiser 5FS, and Gaucho Grande seed treatments were applied commercially. In-furrow (IF) treatments were applied into the seed furrow at the time of planting using tractor-mounted inverted jars with lid holes calibrated to deliver exact amounts via gravity. The foliar treatments were applied with a CO2 pressurized backpack sprayer as a broadcast at 14.3 gpa and 18 psi through 8002VS nozzles spaced 18 inches apart on the spray boom. Foliar applications were broadcast on 23 May at the first sign of true leaf emergence after the cotyledon stage (BC at first true leaf). A RCB experimental design was used with four replicates; plots were four rows by 40 ft. Thrips injury to plants was determined by visually rating injury using a 0 to 5 scale, where 0=no thrips induced plant injury, 1=10% injured leaves, no bud injury; 2=25% injured leaves, no bud injury; 3=75% injured leaves, and 0 to 25% buds injured; 4=90% injured leaves, and greater than 25% buds injured; and 5=dead plants. Yield was determined by harvesting the 2 center rows of each plot (80 row ft) using a commercial 2-row cotton picker. Sub-samples were ginned to determine lint versus seed and trash weight (43% lint, 57% seed and trash). Data were subjected to ANOVA and means were separated using LSD (P = 0.01).

EVALUATION OF SELECTED IN-FURROW AND SEED APPLIED INSECTICIDES, WITH AND WITHOUT AN ADDITIONAL FOLIAR BAND OR BROADCAST APPLICATION, FOR CONTROL OF THRIPS ON VIRGINIA COTTON, 2002

Selected insecticides applied either onto seed or into the seed furrow at planting, both with and without an additional foliar band or broadcast treatment, were evaluated for control of thrips in Virginia cotton. 'Paymaster 1199 R' cotton was planted 29 Apr at the Virginia Tech Tidewater Agric. Res. & Ext. Ctr., Suffolk, VA, using 36-inch row spacing. In-furrow (IF) treatments were applied into the seed furrow at the time of planting using tractor-mounted inverted jars with lid holes calibrated to deliver exact amounts via gravity. Gaucho 480 seed treatment (seed) was applied commercially. The foliar treatments were applied with a CO2 pressurized backpack sprayer either as a 12 to 14-inch band (FB) over the row at 17.0 gpa and 22 psi through one 8004E flat fan nozzle per row, or as a broadcast (BC) at 14.3 gpa and 18 psi through 8002VS nozzles spaced 18 inch apart on the spray boom. Foliar applications were made on 17 May at the first sign of true leaf emergence after the cotyledon stage and on 29 May at the 2-3 true leaf stage. A randomized complete block experimental design was used with four replicates; plots were 4 rows x 40 ft. Thrips injury to plants was determined by visually rating injury using a 0 to 5 scale, where 0 = no thrips induced plant injury, 1 = 10% injured leaves, no bud injury; 2 = 25% injured leaves, no bud injury; 3 = 75% injured leaves, and 0-25% buds injured; 4 = 90% injured leaves, and > 25% buds injured; and 5 = dead plants.Yield was determined by harvesting the two center rows of each plot (80 row ft) using a commercial 2-row John Deere cotton combine. Sub-samples were ginned to determine lint versus seed and trash weight (40% lint, 60% seed and trash). Data were analyzed using ANOVA and LSD statistical procedures.

EVALUATION OF GAUCHO, CRUISER AND TEMIK, WITH AND WITHOUT AN ADDITIONAL BROADCAST APPLICATION, FOR CONTROL OF THRIPS IN VIRGINIA COTTON, 2002.

EVALUATION OF GAUCHO, CRUISER AND TEMIK, WITH AND WITHOUT AN ADDITIONAL BROADCAST APPLICATION, FOR CONTROL OF THRIPS IN VIRGINIA COTTON, 2002.

EFFICACY OF SELECTED INSECTICIDES FOR CONTROL OF BOLLWORM ON VIRGINIA COTTON, 2002.

Efficacy of selected insecticides was evaluated for control of Bollworm (BW) in Virginia cotton. 'FiberMax 989 R' cotton was planted 2 May at the Virginia Tech Tidewater Agric. Res. & Ext. Ctr., Suffolk, VA, using 36-inch row spacing. All treatments were applied with a CO2 pressurized backpack sprayer calibrated to deliver 10 gpa at 39 psi through one TX10 hollow cone nozzle over the top of each of the two center rows of each plot. Insecticides were applied two times, the first at egg threshold (30 Jul) and the second in 6 days (5 Aug). Egg threshold applications were made based on the presence of 10 or more BW eggs per 100 plant terminals, or 2 or more per 100 fruit, i.e., squares or bolls. A randomized complete block experimental design was used with four replicates; plots were 4 rows x 40 ft. Boll damage was determined by sampling 25 randomly selected bolls per plot. Samples were taken at roughly weekly intervals after the occurrence of egg threshold. Yield was determined by harvesting the two center rows of each plot (80 row ft) using a commercial 2-row John Deere cotton combine. Sub-samples were ginned to determine lint versus seed and trash weight (40% lint, 60% seed and trash). Data were analyzed using ANOVA and LSD statistical procedures.

EVALUATION OF SELECTED IN-FURROW APPLIED INSECTICIDE/NEMATICIDES, WITH AND WITHOUT AN ADDITIONAL FOLIAR INSECTICIDE BAND, FOR CONTROL OF THRIPS ON COTTON, 1998.

EVALUATION OF SELECTED IN-FURROW APPLIED INSECTICIDE/NEMATICIDES, WITH AND WITHOUT AN ADDITIONAL FOLIAR INSECTICIDE BAND, FOR CONTROL OF THRIPS ON COTTON, 1998. Selected insecticide/nematicides applied into the seed furrow at planting, with and without an additional foliar insecticide band, were evaluated for control of thrips in Virginia cotton. 'Delta and Pine Land 51' cotton was planted 30 Apr at the Virginia Tech Tidewater Agric. Res. & Ext. Ctr., Suffolk, VA using a 36-inch row spacing. In-furrow treatments (IF) were applied at the time of planting using tractor-mounted inverted jars with lid holes calibrated to deliver exact amounts via gravity. Gaucho 480 seed treatment was applied commercially. The foliar band was applied in a 12to 14-inch band over the row with a CO2-pressurized backpack sprayer calibrated to deliver 17.0 gpa at 22 psi through one 8004E flat fan nozzle per row. A RCB design was used with four replicates. Plots were 4 rows by 40 ft. Thrips injury to plants was determined by visually rating injury on a 0 to 5 scale, where 0 = no thrips-induced plant injury, 1 = 10% injured leaves, no bud injury; 2 = 25% injured leaves, no bud injury; 3 = 75% injured leaves, and 0 to 25% buds injured; 4 = 90% injured leaves, and greater than 25% buds injured; and 5 = dead plants. Yield was determined by harvesting the 2 center rows of each plot (80 row-ft per plot) using a commercial 2-row John Deere cotton combine. Sub-samples were ginned to determine lint versus seed and trash weight (41% lint, 59% seed and trash). Data were analyzed using ANOVA and LSD, or Duncan's new multiple range statistical procedures.

Selected Pyrethroid and Non-Pyrethroid Insecticides for Control of Cotton Bollworm on Cotton, 1997

Abstract Two field trials were conducted to evaluate efficacy of selected pyrethroid (Field Trial 1) and non-pyrethroid (Field Trial 2) insecticides for control of bollworm in Virginia cotton. ‘Delta and Pine Land 51’ cotton was planted 2 May at the Virginia Tech Tidewater Agric. Res. & Ext. Ctr., Suffolk, VA using a 36-inch row spacing. All treatments were applied with a CO2-pressurized backpack sprayer calibrated to deliver 10 gpa at 39 psi through one TX10 hollow cone nozzle over the top of each of the 2 center rows of each plot. All applications were applied at egg threshold (based on the presence of 10 or more bollworm eggs per 100 plant terminals, or 2 or more per 100 fruit, i.e., squares or bolls) and again in 5 days. A RCB design was used with 4 replicates; plots were 4 rows by 40 ft. Boll damage was determined by sampling 25 randomly selected bolls per plot. Samples were taken at roughly weekly intervals after the second insecticide treatment until bolls were matured beyond the susceptible stage. Yield was determined by harvesting the 2 center rows of each plot (80 row ft per plot) using a commercial 2-row John Deere cotton combine. Lint values were calculated as 37% of total plot weights, assuming 63% was seed and trash. Data were analyzed using ANOVA and LSD statistical procedures.

Different Insecticide Rates and Application Schedules for Control of Bollworm on Cotton, 1996

Abstract Efficacy of two insecticide applications, applied either as two standard (low) rates or as one standard followed by one high rate, was evaluated for control ot bollworm on Virginia cotton. ‘DPL 51’ cotton was planted 10 May at the Virginia Tech Tidewater Agric. Res. & Ext. Ctr., Suffolk, Va. using a 36-inch row spacing. All treatments were applied with a CO2 pressurized backpack sprayer calibrated to deliver 10 gpa at 31 psi through one TX10 hollow cone nozzle over the top of each of the two center rows of each plot. All applications were applied at egg threshold (based on the presence of 10 or more boll-worm eggs per 100 plant terminals, or 2 or more per 100 fruit, i.e., squares or bolls) and again after 5 days. A RCB experimental design was used with 4 replicates; plots were 4 rows by 40 ft. Boll damage was determined by sampling 25 randomly selected bolls per plot. Samples were taken at roughly weekly intervals after the occurrence of the egg threshold. Yield was determined by harvesting the 2 center rows of each plot (80 row ft per plot) using a commercial 2-row John Deere cotton combine. Lint values were calculated as 37% of total plot weights, assuming 63% was seed and trash. Data were analyzed using ANOVA and LSD statistical procedures.

Selected Non-Pyrethroid Insecticides for Control of Bollworm on Cotton, 1996

Abstract Efficacy of selected non-pyrethoid insecticides was evaluated for control of bollworm in Virginia cotton. ‘DPL 51’ cotton was planted 10 May at the Virginia Tech Tidewater Agric. Res. & Ext. Ctr., Suffolk, VA, using a 36-inch row spacing. All treatments were applied with a CO2-pressurized backpack sprayer calibrated to deliver 10 gpa at 31 psi through one TX10 hollow cone nozzle over the top of each of the two center rows of each plot. All applications were applied at egg threshold (based on the presence of 10 or more bollworm eggs per 100 plant terminals, or 2 or more per 100 fruit, i.e., squares or bolls) and again in 5 days. A RCB experimental design was used with 4 replicates; plots were 4 rows by 40 ft. Boll damage was determined by sampling 25 randomly selected bolls per plot. Samples were taken at roughly weekly intervals after the occurrence of the egg threshold. Yield was determined by harvesting the 2 center rows of each plot (80 row ft per plot) using a commercial 2-row John Deere cotton combine. Lint values were calculated as 37% of total plot weights, assuming 63% was seed and trash. Data were analyzed using ANOVA and LSD statistical procedures.

Selected Insecticide/Nematicides for Control of Thrips in Virginia Cotton, 1995

Abstract Efficacy of selected insecti-cide/nematicides was evaluated for control of thrips (primarily F. fusca) in Virginia cotton. ‘Sure-Grow 501’ cotton was planted 1 May at the Virginia Tech Tidewater Agric. Res. & Ext. Ctr., Suffolk, Va. using a 36-inch row spacing. All treatments were applied into the seed furrow (IF) at the time of planting, granules using tractor-mounted inverted jars with lid holes calibrated to deliver exact amounts via gravity; liquids (IF, spray) with a CO2 pressurized tractor-mounted sprayer calibrated to deliver 5.0 gal/acre at 24 psi through one SS8001E flat fan nozzle mounted just above planter disks and turned parallel to the row direction to deliver the spray fan into the seed furrow. Gaucho seed treatment was applied commercially. A RCB design was used with 4 replicates; plots were 4 rows by 30 ft. Adult and immature thrips were counted on 3 dates by cutting and placing 5 plants per plot into jars containing soapy water. Thrips were filtered and counted in the laboratory. Thrips injury to plants was determined by visually rating injury using a 0 to 5 scale, where 0 = no thrips induced plant injury, 1 = 10% injured leaves, no bud injury; 2 = 25% injured leaves, no bud injury; 3 = 75% injured leaves, and 0 to 25% buds injured; 4 = 90% injured leaves, and greater than 25% buds injured; and 5 = dead plants. Flower number was used as a measure of plant maturity as affected by thrips injury. Flowers were counted one time on 19 Jul in 6 row ft per plot. Yield was determined by harvesting the 2 center rows of each plot (60 row ft per plot) using a commercial 2-row John Deere cotton combine. Lint values were calculated as 37% of total plot weights, assuming 63% was seed and trash. Data were analyzed using ANOVA and LSD, or Duncan’s new multiple range statistical procedures.

Different Application Schedules and Insecticide Rates for Control of Bollworm in Virginia Cotton. 1995

Abstract Different application schedules with insecticides at different rates were evaluated for control of bollworm in VA. ‘Sure-Grow 501’ cotton was planted 1 May at the Virginia Tech Tidewater Agric. Res. & Ext. Ctr., Suffolk, VA, using a 36-inch row spacing. All treatments were applied with a CO2 pressurized backpack sprayer calibrated to deliver 14.5 gpa at 50 psi through three, D2-13 disc-core hollow cone nozzles per row, one over the top of the row and one on each side. Four application schedule/insecticide rate combinations were tested: 1)3 applications at the standard rate, the 1 st at the egg threshold, the 2nd in 5d, and the 3rd in l0d; 2) 2 applications at the standard rate, the 1st at the egg threshold, the 2nd in 5d; 3) 2 applications, the 1st at the egg threshold using 1.6x the standard rate, and the 2nd in 5d using the standard rate; 4) 1 application at the egg threshold using 1.6x the standard rate. Egg threshold application was based on the presence of 10 or more bollworm eggs per 100 plant terminals, or 2 or more per 100 fruil (squares or bolls). A RCB experimental design was used with 4 replicates; plots were 6 rows by 30 ft. Boll damage and bollworm numbers were determined by sampling 25 randomly selected bolls per plot. Samples were taken at roughly weekly intervals after the occurrence of the egg threshold. Yield was determined by harvesting the 2 center rows of each plot (60 row ft per plot) using a commercial 2-row John Deere cotton combine. Lint values were calculated as 37% of total plot weights, assuming 63% was seed and trash. Data were analyzed using ANOVA and LSD statistical procedures.