ID

424-234

Authors as Published

Patrick M. Phipps, Professor, Plant Pathology, Tidewater AREC; Darcy E. Partridge, Postdoctoral Associate, Plant Pathology, Tidewater AREC; and Jon D. Eisenback, Professor, Nematology, Virginia Tech

Acknowledgements

The applied research described in this publication was supported by grants from the Virginia Cotton Board and private industry. The authors thank Ames Herbert Jr., Virginia Tech, IPM Program Coordinator; Joel Faircloth, Extension Cotton Specialist; and Glenn Chappell, Prince George County Extension Agent, for reviewing this publication. The authors also recognize Steve Byrum, Barron Keeling, and Ed Hobbs for their help in carrying out each field trial and data processing.

Disease Incidence and Losses

Rhizoctonia and Pythium damping-off were the most common cause of seedling disease and reduced plant populations (Table 1). Although stand losses were as much as 30 percent, the impact on yield was minimal because of the crop’s remarkable ability to compensate. One plant every 12 to 18 inches is generally enough to achieve a good yield, except in years with heavy crop stress caused by weather, insects, weeds, or diseases. Other factors that contributed to slow emergence and poor stands in 2006 were seed with low cool germ, periods with soil temperatures below 60ºF or air temperatures below 40ºF after planting, heavy rainfall, and/or planting seed too deep (0.75 in. or deeper). The optimum depth of planting is usually about 0.25 to 0.5 inches. Crop damage by southern root-knot nematode, Meloidogyne incognita, accounted for the heaviest loss of yield in fields planted continuously to cotton for five years or longer. No significant losses to reniform nematode, Rotylenchulus reniformis, were detected in 2006. Instances of yield losses to stubby root were found, but overall it was less destructive than southern root knot. Sting nematode continues to cause severe damage in cotton, but occurrences are usually spotty and confined to localized areas in sandy-textured soil. As in previous years, the Columbia lance nematode was not detected in 2006. Below-normal rainfall in July and August and below-average accumulations of degree days (DD60) in May, June, September, and October were thought to account for cotton not achieving record yields in 2006.


Table 1

Seasonal Degree Days, Rainfall, and Crop Growth in 2006

Rainfall in June, September, and October was 5.75, 4.64 and 4.62 inches above normal, and in May, July, and August was 0.96, 2.21, and 3.21 inches below normal, respectively (Table 2). Rainfall during the period from May to October totaled 36.4 inches, which was 8.7 inches above normal. Minimum air temperatures averaged near normal (±1°F) in June, July and September, 2°F above normal in October, 3°F above normal in August, and 2°F below normal in May. Maximum air temperatures were near normal (±1°F) in May, June, July, and October, 2°F below normal in September, and 4°F above normal in August according to records from a NOAA station (44-4044) at the Tidewater AREC in Suffolk. Cool temperatures in April and May slowed the speed of emergence in fields planted to cotton. Below normal rainfall in March (-3.16 inches), April (-1.44 inches) and May (-0.96 inch) allowed land preparation and planting to proceed in a timely manner across most of southeastern Virginia. Cotton showed good emergence and vigor after air temperatures reached into the 70s and 80s in May. Periods of drought stress in July and August caused wilting and stunting of crops, especially in fields with sandy textured soils and without irrigation. Above normal rainfall in September (+4.64 inches), October (+4.62 inches) and November (+2.96 inches) caused major delays in completing the harvest. Frost occurred in western portions of the Tidewater area on 14 October. Freeze occurred on 26 October when nighttime temperatures dropped into the upper 20ºF range.

Cotton degree days (DD60) from 1 May to 31 October totaled 2,053 or 120 below the 12-year average (Table 3). As the harvest season approached, many fields exhibited delayed maturity, but good yield potential. Months with below-average accumulations of degree days included May, June, September, and October.

The relationship of total rainfall and degree days to growth and yield of cotton in 2006 showed that the cotton crop received rainfall that was 5.9 inches above normal and 120 degree days below the 12-year average (Table 4, Fig. 1). While pinhead square was about a week late, the first flowers and first open bolls appeared within three days of the 12-year average. Dry weather stress in July and August were expected to reduce yield and suppress incidence of hardlock.

 

Tables 2,3 and 4

 

Figure 1
Figure 1. Degree days, rainfall, and crop development in 2006 at Suffolk.

Nematode Control Trials

The response of cotton to seed and in-furrow nematicide treatments in a field infested with stubby root nematode (R. L. Smith Farm, Branchville). Soil at the field site was loamy fine sand and was prepared for planting by ripping and bedding rows in stale beds of cotton from the previous two seasons. Plots were planted on 3 May. Treatments were main plots of four 30-foot long rows spaced 36 inches apart and subplots were two rows planted to ST 4575 BR (susceptible to southern root-knot) and ST 5599 BR (partially resistant to southern root-knot). A split-plot design was used with replications in four randomized complete blocks. Seed used in each treatment were from the same lot of each variety. Personnel with Syngenta Crop Protection applied Avicta Complete Pak. The base treatment of fungicide on ST 4575 BR was Baytan/Thiram/Allegiance and ST 5599 BR was treated with Apron XL/Maxim/ NuFlow. The in-furrow treatment with KC791230 15G 5 pounds per acre was applied at planting. Treatments with Temik 15G were applied in-furrow at planting with and without a side-dress application on 10 July. A foliar spray of Orthene 97 at 8 ounces per acre was applied to all plots on 31 May for thrips control. Thereafter, standard practices were followed for cotton production in Virginia. Soil samples for determining nematode populations were collected on 7 September and a composite sample of replications was prepared for each treatment and variety. A soil elutriator and sugar flotation method were used to process samples. Yield was determined by hand-harvesting 6-foot sections of rows or a total of 12 feet of row in each plot.

Stand counts averaged 1.82 and 1.76 plants per foot of row for ST 4575 BR and ST 5599 BR on 31 May, respectively (not shown). All treatments improved seedling vigor (Fig. 2) and suppressed thrips damage significantly. KC791230 and Temik in furrow significantly improved plant vigor ratings across both varieties, while all treatments improved vigor significantly above the untreated check (Table 5). All treatments had significantly reduced thrips injury in both varieties when evaluated on 9 June, and all treatments significantly increased numbers of flowers and plant height as of 21 July compared to the untreated check. ST 5599 BR had increased height over ST 4575 BR, while ST 4575 BR had significantly more flowers and open bolls on 15 September than ST 5599 BR. Nematode populations in soil ranged from 0 to 10 lesion, 20 to 100 stunt, and 50 to 270 stubby root nematodes per 500 cm3 soil on 7 September (not shown). Southern root-knot nematode was not detected. Numbers of open bolls on 15 September were significantly higher for ST 4575 BR than ST 5599 BR, but no significant differences were found in treatments. All treatments, except Temik 15G 5 pounds per acre in furrow, significantly increased lint yield above the untreated check. Temik 15G 5 pounds per acre in-furrow followed by a side-dress application resulted in lint yields that were significantly greater than other treatments.

 

Figure 2
Figure 2. Visual differences in treatments with and without either Temik 15G or Avicta Complete Pak in 2006 at R.L. Smith Farm, Branchville.

Table 5

 

Response of cotton to Avicta Complete Pak on seed and Temik 15G in-furrow in a field lacking nematode problems (Jason Holland Farm, Suffolk). Soil at the field site was Eunola loamy fine sand and was prepared for planting by ripping and bedding rows in stale beds of cotton from the previous season. Plots were planted on 16 May. Treatments were main plots of four 30-foot long rows spaced 36 inches apart and subplots were two rows planted to ST 4575 BG/RR (susceptible to southern root-knot) and ST 5599 BR (partially resistant to southern root-knot). A split-plot design was used with replications in four randomized complete blocks. Seed used in each treatment were from the same lot of each variety. Personnel with Syngenta Crop Protection applied Avicta Complete Pak. The base treatment of fungicide on ST 4575 BR was Baytan/ Thiram/Allegiance, and ST 5599 BR was treated with Apron XL/Maxim/NuFlow. Temik 15G was applied infurrow at planting on 16 May. A foliar spray of Orthene 97 at 8 ounces per acre was applied to all plots on 30 May for thrips control. Thereafter, standard practices were followed. Soil samples for determining nematode populations were collected on 27 July, and a composite sample of replications was prepared for each treatment and variety. A soil elutriator and sugar flotation method were used to process samples. Plots were harvested with a two-row spindle picker. Yield in bales per acre was determined by weight of seed cotton and the gin turnout for samples taken from replicated plots.

Stand counts averaged 2.03 and 1.95 plants per foot of row for ST 4575 BR and ST 5599 BR on 13 June, respectively (not shown), and the effect of treatment was not significant. Both Avicta Complete Pak and Temik 15G improved plant vigor and reduced thrips injury significantly compared to the untreated check (Table 6). Nematode populations in soil ranged from 15 to 30 stubby root and 360 to 633 spiral nematodes per 500 cm3 soil on 27 July (not shown). Southern rootknot nematode was not detected. Flower counts on 20 July and open bolls on 4 October were significantly greater in ST 4575 BR, but the effect of treatment was not significant in either variety. Both treatments showed increased plant height on 20 July, but only the response to Temik in furrow was significant. In analysis of data combined across varieties, plots treated with Avicta Complete Pak resulted in significantly higher yields than the untreated or Temik-treated plots (P=0.10).

 

Table 6

 

The response of cotton to seed and in-furrow nematicide treatments (Tidewater AREC Farm, Suffolk). Soil at the field site was Kenansville loamy fine sand. Land was prepared by ripping and strip-tilling rows in wheat stubble. Plots were planted on 25 April. Treatments were main plots of four 30-foot long rows spaced 36 inches apart and subplots were two rows planted to ST 4575 BR (susceptible to southern root-knot) and ST 5599 BR (partially resistant to southern root-knot). A split-plot design was used with replications in four randomized complete blocks. Seed used in each treatment were from the same lot of each variety. Personnel with Syngenta Crop Protection applied Avicta Complete Pak. The base treatment of fungicide on ST 4575 BR was Baytan/Thiram/Allegiance and ST 5599 BR was treated with Apron XL/Maxim/NuFlow. The in-furrow treatment with KC791230 5 pounds per acre was applied at planting. Treatments with Temik 15G were applied in-furrow at planting with and without an additional side-dress application on 10 July. Foliar sprays of Orthene 97 at 6 ounces per acre were applied to all plots on 12 and 31 May for thrips control. Thereafter, standard practices were followed. Soil samples for determining nematode populations were collected on 26 July, and a composite sample of replications was prepared for each treatment and variety. A soil elutriator and sugar flotation method were used to process samples. All plots were harvested with a two-row spindle picker.

Stand counts averaged 1.82 and 1.68 plants per foot of row for ST 4575 BR and ST 5599 BR on 23 May, respectively (not shown). ST 4575 BR had significantly more plants than ST 5599 BR. ST 4575 BR had increased plant vigor on 10 June compared to ST 5599 BR. Since the treatment by variety interaction was not significant for any of the recorded factors, data analysis included the combined effects of treatments and varieties. All treatments increased plant vigor over the untreated check. The treatments of Temik and KC791230 applied in furrow at planting promoted the greatest increase in plant vigor in both varieties. No differences between varieties for thrips injury were observed on 10 June. Treatments with Temik and KC791230 reduced thrips injury compared to the untreated check across both varieties. Avicta Complete Pak reduced thrips injury significantly only on ST 4575 BR. The effect of treatments on plant height was not significant when combined across varieties, and small but significant differences were detected when data were compared within a variety. ST 4575 BR had significantly more flowers on 20 July and open bolls on 15 September compared to ST 5599 BR. Treatments with Temik and KC791230 in-furrow significantly increased flower and open boll counts over the untreated check. Temik applied in furrow followed by a side-dress application failed to increase flower counts, but did significantly increase open boll counts. Plant parasitic nematodes in soil on 26 July ranged from 78 to 128 stubby root, 165 to 303 ring, and 30 to 58 root-knot nematodes. Stubby root was the only nematode thought to be present at numbers that may have caused some root damage. Varieties were not significantly different in yield. Avicta Complete Pak on seed, KC791230 in furrow, and Temik in furrow followed by a side-dress application produced yields that were significantly greater than the untreated check.

 

Table 7

 

Evaluation of Syngenta seed treatments for control of southern root knot nematode (Rick Morgan Farm, Suffolk). Soil at the field site was Rumford loamy fine sand and was planted to cotton continuously since 2001. Land was prepared for planting by ripping and bedding rows in stale beds of cotton from the previous season. Personnel with Syngenta Crop Protection applied seed treatments. Seed of DP 444 BG/RR were planted on 10 May. Temik 15G 5 pounds per acre was applied to the seed furrow at planting. Treatments were replicated in four randomized complete blocks and plots were two 30-foot long rows spaced 38 inches apart. Dynasty + Cruiser was the reference standard seed treatment without nematicide. A foliar spray of Orthene 97 at 8 ounces per acre was applied to all plots on 31 May for thrips control; thereafter, standard practices were followed for cotton production in Virginia. Soil samples for determining nematode populations were collected on 7 September, and a composite sample of replications was prepared for each treatment. A soil elutriator and sugar flotation method were used to process samples. All plots were harvested with a two-row spindle picker on 15 November.

Plant height on 24 July was reduced in plots treated with A14905E compared to treatments with A14905B and A14905H, but none of the treatments were significantly different from the standard treatment with Dynasty + Cruiser on seed or Dynasty + Temik 15G in furrow (Table 8). The effect of treatments on flowering and root galling was not significant. A14905E on seed had the highest number of open bolls on 19 September, while treatments of Dynasty + Cruiser, Dynasty + Cruiser + Avicta, and A14905B had significantly lower numbers of open bolls. The treatment of Dynasty + Cruiser + Avicta resulted in the highest lint yield, while A14905A, A14905B, A14905E, and Dynasty + Temik had significantly lower yields.

 

Table 8

 

Comparison of Bayer seed treatments for control of southern root-knot nematode (Rick Morgan Farm, Suffolk). Soil was prepared by ripping and bedding rows in stale beds of cotton from the previous season. The soil type was Rumford loamy fine sand that had been planted to cotton annually since 2001. Personnel with Bayer CropScience applied seed treatments on top of the seed vendor’s base fungicide treatment. Included were ST 4575 BR (susceptible to southern root knot) and ST 5599 BR (partially resistant). Plots consisted of two 30-foot long rows spaced 38 inches apart. The treatment with Temik 15G 5 pounds per acre was applied to the seed furrow at planting on 10 May. Orthene 97 at 8 ounces per acre was applied to all plots on 31 May for thrips control. Thereafter, standard practices were followed. Soil samples for nematode populations were collected on 5 September, and a composite sample of replications was processed by a soil elutriator and sugar flotation method. All plots were harvested with a tworow picker on 15 November.

Stand counts were not significantly different and ranged from 1.89 to 2.1 plants/ft of row for ST 4575 BR and 1.75 to 1.90 plants/ft of row for ST 5599 BR on 7 June (data not shown). BCSTON + L1505A, which contained Avicta, increased early season growth in ST 4575 BR (Table 9) and ST 5599 BR (Table 10) significantly over that of other treatments according to height measurements on 24 July. Open bolls counted on 18 September were not significantly different across treatments in either variety. Counts of southern root knot nematode were above thresholds for causing crop damage in both varieties. Root galling was suppressed the greatest by Temik 15G on ST 4575 BR, but not significantly more than BCSTON + L1505A. Root galling was lower on ST 5599 BR, with some significant differences across treatments. The effect of treatments on open boll counts and yields were not significantly different in either variety.

 

Table 9


Table 10

 

Response of cotton varieties to southern root-knot nematode and applications of seed and in-furrow treatments (Rick Morgan Farm, Suffolk). Soil at the field site was Rumford loamy fine sand and was prepared for planting by ripping and bedding rows in stale beds of cotton from the previous season. Seed of each variety were from the same seed lot and treated with the vendor’s base fungicide treatment. Treatments were main plots of twelve 30-foot long rows spaced 38 inches apart and subplots were two rows of each variety. The seed treatment with Avicta Complete Pak was applied by personnel with Syngenta Crop Protection. The treatment with Temik 15G 5 pounds per acre was applied to the seed furrow at planting on 10 May. A foliar spray of Orthene 97 at 8 ounces per acre was applied to all plots on 31 May for thrips control. Thereafter, standard practices were followed. Soil samples for determining nematode populations were collected on 5 September, and a composite sample of replications was processed of each treatment/variety by a soil elutriator and the sugar flotation method. All plots were harvested with a two-row picker on 15 November.

Variety had a significant effect on stand, root galling, plant height, open bolls, and yield (Table 11). Root galling was the only factor to be affected significantly by treatment. Stand counts ranged from 1.40 to 1.91 plants per foot of row on 7 June (data not shown). ST 5599 BR and/or Temik 15G were the only factors to reduce root galling significantly as reported on 28 June. Ratings on 5 December indicated that Temik 15G and Avicta Complete Pak on seed reduced root galling significantly and that ST 5599 BR had significantly lower root galling than other varieties. Either Avicta Complete Pak on seed or Temik 15G in furrow tended to increase flower counts as of 15 July, but not significantly more than the untreated check. Counts of total bolls were not significant for treatment or variety. Populations of plant parasitic nematodes in composite samples of soil from plots of each variety and treatment showed 400 to 6,880 root-knot juveniles, 20 to 390 spiral nematodes, and 30 to 470 stubby root nematodes per 500 cm3 of soil. Yields were significantly different for variety, but not treatment in the combined analysis of yield data. However, there was a trend for increased yield by each variety when treated with either Avicta Complete Pak or Temik 15G. This increase ranged from 0.22 bales acre with Avicta Complete Pak to 0.37 bales acre with Temik 15G in furrow.


Table 11b

Evaluation of Chemicals and Variety Selection for Control of Nematodes in Cotton

Patrick M. Phipps, Darcy E. Partridge, and Jon D. Eisenback

Summary:

  1. 2006 growing season: Rainfall in June, September and October was 5.75, 4.64 and 4.62 inches above normal and May, July, and August was 0.96, 2.21, and 3.21 inches below normal, respectively. Total rainfall from May through October was 36.4 inches or 8.7 inches above normal. A total of 2053 DD60 units were accumulated in the 2006 growing season or 120 units below the 12-year average from 1995 to 2006. Yields of cotton lint are estimated to average 717 pounds per acre or 1.5 bales per acre in 2006.
  2. Avicta Complete Pak compared to Temik 15G for thrips control: Some trials showed increased damage by thrips in plots without Avicta Complete Pak on seed or Temik 15G in furrow. All trials were over sprayed about three to four weeks after planting with Orthene 97 8 ounces per acre upon emergence of the first true leaf to control thrips and increase the opportunity to measure the crops response to nematode control. It seems likely that this treatment also benefited performance of plots treated with Avicta Complete Pak on seed as well as Temik in-furrow.
  3. Avicta Complete Pak compared to Temik 15G for nematode control: Trials having numbers and kinds of nematodes below threshold levels for crop damage showed yield increases to Avicta Complete Pak and Temik, which may be attributed to thrips control. Trials with southern root-knot nematode above thresholds for crop damage showed significant early season suppression of root galling by Temik in 5 of 6 varieties, whereas the effects of Avicta Complete Pak were not significant. Late season root galling was suppressed significantly by Temik and Avicta Complete Pak on 3 of 6 varieties.
  4. Avicta Complete Pak compared to Temik 15G for yield of cotton: The yield of cotton treated with Avicta Complete Pak on seed or Temik in furrow was often similar and significantly higher than the check. ST 5599 BR showed significantly less root galling than other varieties, and produced significantly higher yield than all but one of six varieties. Overall, the performance of Temik 15G and Avicta Complete Pak was similar, and often significantly superior to the check in fields with stubby root and/ or southern root-knot nematode.

 

Reviewed by Pat Phipps, Extension Specialist, Tidewater Agricultural Research and Extension Center


Virginia Cooperative Extension materials are available for public use, reprint, or citation without further permission, provided the use includes credit to the author and to Virginia Cooperative Extension, Virginia Tech, and Virginia State University.

Issued in furtherance of Cooperative Extension work, Virginia Polytechnic Institute and State University, Virginia State University, and the U.S. Department of Agriculture cooperating. Edwin J. Jones, Director, Virginia Cooperative Extension, Virginia Tech, Blacksburg; M. Ray McKinnie, Administrator, 1890 Extension Program, Virginia State University, Petersburg.

Publication Date

May 1, 2009