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CONTROL OF SILVERLEAF WHITEFLY AND INCIDENCE OF TOMATO YELLOW LEAF CURL VIRUS ON STAKED TOMATO WITH INSECTICIDES AND RESISTANT VARIETIES, 2006

CONTROL OF SILVERLEAF WHITEFLY AND INCIDENCE OF TOMATO YELLOW LEAF CURL VIRUS ON STAKED TOMATO... (E63) TOMATO: Lycopersicon esculentum (Mill.) ‘Florida 47’ ‘Tygress’ CONTROL OF SILVERLEAF WHITEFLY AND INCIDENCE OF TOMATO YELLOW LEAF CURL VIRUS ON STAKED TOMATO WITH INSECTICIDES AND RESISTANT VARIETIES, 2006 Philip A. Stansly University of Florida/ IFAS Southwest Florida Res. and Ed. Center 2686 State Road 29 North Immokalee, FL 34142-9515 Phone: (239) 658-3427 Fax: (239) 658-3469 Email: pstansly@ufl.edu Robert E. Riefer Silverleaf whitefly (SLW): Bemisia argentifolii Bellows & Perring Reduced yield due to whitefly-borne tomato yellow leafcurl virus (TYLCV) is a major constraint to tomato production in southwest Florida. Integration of insecticidal control and disease resistant varieties would provide benefits of both management tactics to avoid yield loss. On 22 Feb, tomato seedlings from a commercial greenhouse were transplanted at 18-inch spacing on 2 sets of 3beds 240 ft in length and covered with polyethylene film mulch, black side up. The center bed in each set of 3 was planted in the TYLCV-susceptible ‘Florida 47’ and left untreated to serve as the untreated check and as source of whiteflies and virus. The remaining 8 treatments (Table 1) were randomized among 31 ft. plots in a complete block design replicated 4 times. Liquid formulations of Platinum and Admire Pro were applied as soil drenches in 50 ml of solution 2 days later. Approximately 20% of the fertilizer was preplant soil incorporated with the remaining 80% applied through drip irrigation. Foliar sprays were applied with a single row high clearance sprayer operating at 200 psi and 2.4 mph with the spray delivered through two vertical booms fitted with yellow Albuz® hollow cone nozzles, each delivering 10 gpa. Two nozzles per boom were used to apply 40 gpa when plants were small, additional nozzles being added later to maintain spray coverage to a maximum of 4 nozzles per boom to deliver 80 gpa. As nozzles were added, concentration was adjusted to maintain a constant product rate per acre. Fungicides Kocide and Manzate 75 DF were applied weekly to control foliar diseases at rates of 3 lbs and 1.5 lbs per 100 gal, respectively. Eleven weekly evaluations of whitefly adults were made beginning 15 Mar by beating 1 side of 8 plants per plot with a 9 x 13 inch pie pan painted black and coated with spray-on oil. Immature stages were monitored 10 times weekly beginning 30 Mar by counting all whitefly stages appearing in a 2 cm area ring placed on each leaflet of the 3 terminal leaflets collected using 1 trifoliate leaf removed from the 6th node of 4 centrally located plants in each plot. Plants were evaluated weekly for the presence of TYLCV symptoms. Fruit was harvested weekly for 5 weeks from the 8 plants per plot beginning 4 May. Number and weight of marketable fruit and culls were recorded. Average numbers of whitefly adults during the first six weeks of the trial were low, although numbers increased dramatically during the subsequent five weeks. Most adult whiteflies were observed on untreated ‘Tygress’ plants, although not significantly more than on untreated ‘Florida 47’ (Table 2). Numbers of adults on plants treated with the low (8 oz) rate of Platinum followed by the standard spray combination were not different from either check. Fewest whiteflies were observed on plants treated with Admire at planting, followed by the low rate of NNI-0101, though not less than plants receiving the same treatments except with the higher rate of NNI-0101. These in turn were not significantly different from plants sprayed with the standard combination or with oil following the Admire drench. Fewest whitefly eggs were seen on plants sprayed following the Admire drench with the high rate of NNI-0101 twice and Courier once or weekly with JMS Stylet oil. There were no differences compared to the checks exhibited by the other treatments. More small nymphs were seen over all sample dates on untreated ‘Florida-47” then all treated plants, with no differences between untreated varieties. Fewest small nymphs were seen on plants drenched with Admire and receiving the standard sprays or the high rate of NNI- 0101, although not significantly so compared to all other treatments except JMS oil. More large nymphs were seen on unsprayed ‘Florida 47’ than unsprayed ‘Tygress’, with no differences between this latter control and all remaining treatments except the high (11 oz) rate of Platinum. No virus symptoms were seen on the ‘Tygress’ plants except for one possible case in an unsprayed plot. However, few plants were observed with symptoms of TYLCV until the end of the trial, and the distribution of symptomatic plants did not seem to correlate well with whitefly populations on the susceptible variety. For instance, plants treated with 11 oz of Platinum exhibited significantly higher incidence of diseased plants than the check. All treated plants yielded more marketable fruit than untreated plants, with most harvested from ‘Tygress’ receiving the standard treatment, although not significantly more than all other treatments except plants oil, Platinum and the control. Similarly, fewest culls were taken from plants receiving the standard treatment regardless of variety, though not significantly less than plants receiving either rate of Platinum, NNI-0101 or oil. In conclusion, resistant varieties showed little or no virus symptoms, although yields were not significantly different from susceptible plants, probably because of low virus incidence. NNI-0101, a feeding inhibitor, provided control of whiteflies comparable to the standard treatment of adults. Weekly oil treatment after the Admire drench also provided good whitefly control although the yield suffered somewhat, comparable to plants treated with Platinum at the low rate followed by the standard spray regimen. The trial did not demonstrate a clear advantage to using the resistant variety under conditions of low virus pressure, but there was certainly no disadvantage in utilizing this form of insurance against the worst consequences of whitefly and TYLCV. Table 1. Treatment Week insecticide applied Rate No Cultivar Product amt/acre 1 2 3 4 5 6 7 8 9 10 11 12 13 14 1 Tygress untreated --- 2 Florida 47 untreated --- 3 Tygress Admire Pro 4.6L 7 fl oz x Oberon 2SC 8 fl oz x x Knack .86L 9 fl oz x x 4 Florida 47 Admire Pro 4.6L 7 fl oz x Oberon 2SC 8 fl oz x x Knack .86L 9 fl oz x x 5 Florida 47 Platinum 2SC 8 fl oz x Oberon 2SC 8 fl oz x x Knack .86L 9 fl oz x x 6 Florida 47 Platinum 2SC 11 fl oz x Oberon 2SC 8 fl oz x x Knack .86L 9 fl oz x x 7 Florida 47 Admire Pro 4.6L 7 fl oz x JMS Stylet Oil 1 % v/v x x x xx xxx x x 8 Florida 47 Admire Pro 4.6L 7 fl oz x Courier 40SC 12 fl oz x NNI-0101 0.2 lb x x x 9 Florida 47 Admire Pro 4.6L 7 fl oz x Courier 40SC 12 fl oz x NNI-0101 0.3 lb x x x Table 2 Adults Eggs Small nymphs Large nymphs TYCLV Marketable Unmarketable Treatment (no./8 beats) (no./6 cm²) (no./6 cm²) (no./6 cm²) (%) (lbs/8 plants) (lbs/8 plants) 1 21.3a 1.6abc 4.13ab 0.68b 1.3bc 20.3c 58.0ab 2 18.6ab 2.5ab 5.70a 1.55a 6.3bc 19.8c 62.9a 3 10.4cde 1.55abc 1.2cd 0.38bc 0.0c 40.8a 35.6d 4 12.1cd 0.75c 1.03d 0.3bc 10.5ab 35.2ab 36.8c 5 15.9abc 2.6a 1.30cd 0.23bc 5.3bc 28.9b 49.8bc 6 14.0bc 2.5ab 1.63cd 0.05c 28.3a 34.7ab 45.0cd 7 10.4cde 1bc 3.13bc 0.58b 2.3bc 32.4b 44.7cd 8 6.1 e 1.25abc 1.48cd 0.38bc 2.3bc 35.5ab 48.3bc 9 7.1de 1.13abc 0.78d 0.33bc 7.8abc 34.2ab 49.3bc Means within each column not followed by the same letter are significantly different (LSD, P < 0.05) http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Arthropod Management Tests Oxford University Press

CONTROL OF SILVERLEAF WHITEFLY AND INCIDENCE OF TOMATO YELLOW LEAF CURL VIRUS ON STAKED TOMATO WITH INSECTICIDES AND RESISTANT VARIETIES, 2006

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Abstract

(E63) TOMATO: Lycopersicon esculentum (Mill.) ‘Florida 47’ ‘Tygress’ CONTROL OF SILVERLEAF WHITEFLY AND INCIDENCE OF TOMATO YELLOW LEAF CURL VIRUS ON STAKED TOMATO WITH INSECTICIDES AND RESISTANT VARIETIES, 2006 Philip A. Stansly University of Florida/ IFAS Southwest Florida Res. and Ed. Center 2686 State Road 29 North Immokalee, FL 34142-9515 Phone: (239) 658-3427 Fax: (239) 658-3469 Email: pstansly@ufl.edu Robert E. Riefer Silverleaf whitefly (SLW): Bemisia argentifolii Bellows & Perring Reduced yield due to whitefly-borne tomato yellow leafcurl virus (TYLCV) is a major constraint to tomato production in southwest Florida. Integration of insecticidal control and disease resistant varieties would provide benefits of both management tactics to avoid yield loss. On 22 Feb, tomato seedlings from a commercial greenhouse were transplanted at 18-inch spacing on 2 sets of 3beds 240 ft in length and covered with polyethylene film mulch, black side up. The center bed in each set of 3 was planted in the TYLCV-susceptible ‘Florida 47’ and left untreated to serve as the untreated check and as source of whiteflies and virus. The remaining 8 treatments (Table 1) were randomized among 31 ft. plots in a complete block design replicated 4 times. Liquid formulations of Platinum and Admire Pro were applied as soil drenches in 50 ml of solution 2 days later. Approximately 20% of the fertilizer was preplant soil incorporated with the remaining 80% applied through drip irrigation. Foliar sprays were applied with a single row high clearance sprayer operating at 200 psi and 2.4 mph with the spray delivered through two vertical booms fitted with yellow Albuz® hollow cone nozzles, each delivering 10 gpa. Two nozzles per boom were used to apply 40 gpa when plants were small, additional nozzles being added later to maintain spray coverage to a maximum of 4 nozzles per boom to deliver 80 gpa. As nozzles were added, concentration was adjusted to maintain a constant product rate per acre. Fungicides Kocide and Manzate 75 DF were applied weekly to control foliar diseases at rates of 3 lbs and 1.5 lbs per 100 gal, respectively. Eleven weekly evaluations of whitefly adults were made beginning 15 Mar by beating 1 side of 8 plants per plot with a 9 x 13 inch pie pan painted black and coated with spray-on oil. Immature stages were monitored 10 times weekly beginning 30 Mar by counting all whitefly stages appearing in a 2 cm area ring placed on each leaflet of the 3 terminal leaflets collected using 1 trifoliate leaf removed from the 6th node of 4 centrally located plants in each plot. Plants were evaluated weekly for the presence of TYLCV symptoms. Fruit was harvested weekly for 5 weeks from the 8 plants per plot beginning 4 May. Number and weight of marketable fruit and culls were recorded. Average numbers of whitefly adults during the first six weeks of the trial were low, although numbers increased dramatically during the subsequent five weeks. Most adult whiteflies were observed on untreated ‘Tygress’ plants, although not significantly more than on untreated ‘Florida 47’ (Table 2). Numbers of adults on plants treated with the low (8 oz) rate of Platinum followed by the standard spray combination were not different from either check. Fewest whiteflies were observed on plants treated with Admire at planting, followed by the low rate of NNI-0101, though not less than plants receiving the same treatments except with the higher rate of NNI-0101. These in turn were not significantly different from plants sprayed with the standard combination or with oil following the Admire drench. Fewest whitefly eggs were seen on plants sprayed following the Admire drench with the high rate of NNI-0101 twice and Courier once or weekly with JMS Stylet oil. There were no differences compared to the checks exhibited by the other treatments. More small nymphs were seen over all sample dates on untreated ‘Florida-47” then all treated plants, with no differences between untreated varieties. Fewest small nymphs were seen on plants drenched with Admire and receiving the standard sprays or the high rate of NNI- 0101, although not significantly so compared to all other treatments except JMS oil. More large nymphs were seen on unsprayed ‘Florida 47’ than unsprayed ‘Tygress’, with no differences between this latter control and all remaining treatments except the high (11 oz) rate of Platinum. No virus symptoms were seen on the ‘Tygress’ plants except for one possible case in an unsprayed plot. However, few plants were observed with symptoms of TYLCV until the end of the trial, and the distribution of symptomatic plants did not seem to correlate well with whitefly populations on the susceptible variety. For instance, plants treated with 11 oz of Platinum exhibited significantly higher incidence of diseased plants than the check. All treated plants yielded more marketable fruit than untreated plants, with most harvested from ‘Tygress’ receiving the standard treatment, although not significantly more than all other treatments except plants oil, Platinum and the control. Similarly, fewest culls were taken from plants receiving the standard treatment regardless of variety, though not significantly less than plants receiving either rate of Platinum, NNI-0101 or oil. In conclusion, resistant varieties showed little or no virus symptoms, although yields were not significantly different from susceptible plants, probably because of low virus incidence. NNI-0101, a feeding inhibitor, provided control of whiteflies comparable to the standard treatment of adults. Weekly oil treatment after the Admire drench also provided good whitefly control although the yield suffered somewhat, comparable to plants treated with Platinum at the low rate followed by the standard spray regimen. The trial did not demonstrate a clear advantage to using the resistant variety under conditions of low virus pressure, but there was certainly no disadvantage in utilizing this form of insurance against the worst consequences of whitefly and TYLCV. Table 1. Treatment Week insecticide applied Rate No Cultivar Product amt/acre 1 2 3 4 5 6 7 8 9 10 11 12 13 14 1 Tygress untreated --- 2 Florida 47 untreated --- 3 Tygress Admire Pro 4.6L 7 fl oz x Oberon 2SC 8 fl oz x x Knack .86L 9 fl oz x x 4 Florida 47 Admire Pro 4.6L 7 fl oz x Oberon 2SC 8 fl oz x x Knack .86L 9 fl oz x x 5 Florida 47 Platinum 2SC 8 fl oz x Oberon 2SC 8 fl oz x x Knack .86L 9 fl oz x x 6 Florida 47 Platinum 2SC 11 fl oz x Oberon 2SC 8 fl oz x x Knack .86L 9 fl oz x x 7 Florida 47 Admire Pro 4.6L 7 fl oz x JMS Stylet Oil 1 % v/v x x x xx xxx x x 8 Florida 47 Admire Pro 4.6L 7 fl oz x Courier 40SC 12 fl oz x NNI-0101 0.2 lb x x x 9 Florida 47 Admire Pro 4.6L 7 fl oz x Courier 40SC 12 fl oz x NNI-0101 0.3 lb x x x Table 2 Adults Eggs Small nymphs Large nymphs TYCLV Marketable Unmarketable Treatment (no./8 beats) (no./6 cm²) (no./6 cm²) (no./6 cm²) (%) (lbs/8 plants) (lbs/8 plants) 1 21.3a 1.6abc 4.13ab 0.68b 1.3bc 20.3c 58.0ab 2 18.6ab 2.5ab 5.70a 1.55a 6.3bc 19.8c 62.9a 3 10.4cde 1.55abc 1.2cd 0.38bc 0.0c 40.8a 35.6d 4 12.1cd 0.75c 1.03d 0.3bc 10.5ab 35.2ab 36.8c 5 15.9abc 2.6a 1.30cd 0.23bc 5.3bc 28.9b 49.8bc 6 14.0bc 2.5ab 1.63cd 0.05c 28.3a 34.7ab 45.0cd 7 10.4cde 1bc 3.13bc 0.58b 2.3bc 32.4b 44.7cd 8 6.1 e 1.25abc 1.48cd 0.38bc 2.3bc 35.5ab 48.3bc 9 7.1de 1.13abc 0.78d 0.33bc 7.8abc 34.2ab 49.3bc Means within each column not followed by the same letter are significantly different (LSD, P < 0.05)

Journal

Arthropod Management TestsOxford University Press

Published: Jan 1, 2007

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