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SCOTLAND COUNTY, NORTH CAROLINA, 2001
Jack S. Bacheler and Daniel W. Mott
Entomology Department
North Carolina State University
COOPERATORS: David Morrison, County Agent, and Johnny, David and Eddie Carmichael, Producers
BACKGROUND:
Location: Laurinburg
Variety and Seeding Rate: DP 451 B/ RR
Row Spacing: 38
Planting Date: May 8
At-Planting Insecticide: 6.0 lb. Temik 15 G
Growth Regulator: 6 oz. Mepiquat Chloride /acre on July 18
Fertility: 2.5 tons of chicken litter broadcast; 100 lb. 0-8-39; 18 gal. 30% N.
Weed Management: 1.0 pt. 2,4-D + 32 oz. Roundup Ultra burndown; 26 oz. Roundup Ultra Max, June 5 at 2-4 true leaf stage; 26 oz. Roundup Ultra Max under hood on June 20; 1.0 qt. Caporol + 1.0 qt. MSMA under hood on July 2.
Treatment Listing and Equipment:
1. DMI Angled- Case 950 Air Planter
2. Conventional Tillage- Case 950 Air Planter; plots disced, ripped and bedded.
3. KMC Strip-till- KMC Strip Till J.D. 7300 Planter
4. No-till- Case 950 Air Planter
5. In-row DMI- Case 950 Air Planter
Experimental Design: Replicated strip design, with 6 reps x 5 treatments of 8 rows (except for the 16-row DMI angled treatment which represented a single rep for yields and thrips data, and 2 reps for bollworm and stink bug data). The 6 reps. used in bollworm and stink bug evaluations were derived from each of the three reps being sampled twice, but separated by a distance of approx. 500 ft. Three reps were used for the yield and thrips data, except for the shorter DMI plot, which contained a single rep. The rows of the DMI plots were 306 ft. long, while the row length of the remaining treatments was approximately 2,000 ft.
Data Analysis: All field data were entered into Gylling’s PRM 5.1 software and analyzed via ANOVA, with LSD values shown in the tables.
PROCEDURES:
Thrips Assessments: Thrips sampling consisted of carefully removing 5 cotton seedlings per plot (15 total plants), putting them into Mason jars containing soapy water, taking them back to the lab for processing, and counting adults and immature thrips under a stereo microscope.
Bollworm and Stink Bug Damage Evaluations: On August 8, 50 bolls from each plot were examined for bollworm and stink bug damage. A boll was considered to have been damaged by stink bugs if it showed symptoms of internal lint damage or discoloration.
Yields: Yields were harvested with a mechanical picker on October 22. A 36% gin turnout was used to convert seed cotton to lint cotton.
RESULTS
Thrips levels were significantly higher in the conventional tillage plots, compared with the other kinds of reduced tillage treatments. This result is in keeping with previous data comparing thrips levels in conservation tillage systems vs conventional tillage. However, in this study, these huge differences may have been exaggerated by the exceptional early seedling growth in the conventional till treatment compared with the other reduced tillage treatments, resulting in a far greater leaf and plant mass in the conventional tillage plots under the conditions of this test, and thus increasing thrips levels due to the increased plant growth.
Bollworm and stink bug damaged boll levels were on the light side and statistically similar, thus no trend between tillage treatments were evident in this year’s test. David Morrison made the following observations: 1) on July 14 the DMI angled treatment had apparently higher levels of cotton aphids than the other treatments, 2) under this year’s conditions, the strip and no till plots had a more open canopy, 3) the no-till plots suffered more wilting than the other treatments, and 4) the conventional cotton emerged from the ground approximately 2 weeks earlier than the other treatments.
In the previous 2 years, reduced tillage treatments showed lower bollworm damaged boll levels than with conventional tillage.