Cotton was planted on 15 May on an Adcock sandy loam soil at the Upper Coastal Plain Research Station near Rocky Mount, NC. Bollgard plots (varieties) were 50 ft. x 2 rows, with 10-ft alleys and 4 replications arranged in a RCBD. The 3 conventional varieties consisted of 6-row plots. Temik 15G was applied in furrow at planting at 0.75 lb ai/acre for thrips control. Recommended fertility and weed management practices for this area were followed. The conventional varieties received a single Karate treatment (0.025 lb[AI]/acre) on 2 Aug with a CO2-powered back pack sprayer calibrated to deliver 8.0 GPA at 50 psi with one TX-8 Spraying Systems hollow cone nozzle per row. On 19 Aug, 25 bolls from each plot (100 per variety) were inspected for BW damage and live BW. One week later, on 26 Aug, 25 bolls from each plot were inspected for SB damage. The number of open and closed bolls was counted from 7.5 row ft of each plot on 24 Oct. This assessment provided the total number of bolls/plot, as well as the percentage of open bolls. One row of each plot was harvested with a John Deere mechanical picker on 8 Nov. All data were entered into Gylling's Pesticide Research Manager 5.0 software and analyzed via ANOVA and LSD (P = 0.05).
Boll damage from BW in the 17 Bollgard varieties ranged from a low of 1.0% in 'DP 33 B' to a significantly greater 26.0% in 'SG 125 BR', with only a few other significant differences in BW damage to bolls among varieties observed. A gene check for the Cry 1A(c) protein revealed no endotoxin in the 'SG 125 BR' seed at harvest. However, a sub sample of the of the planted seed tested positive for the protein. Thus, we are not sure whether this variety lost it's protein expression, or if a planting mistake were made. The SB damage to bolls varied widely among the Bollgard varieties, with a number of significant differences noted. Because the Bollgard Cry1A(c) endotoxin has no known activity against SB, and because stink damage to younger bolls is more problematic than with older bolls, an indirect effect of SB damage, such as maturity differences among varieties, was suspected. Maturity, as reflected in percentage of open bolls, revealed no such relationship. In the 3 conventional varieties, no SB damage was found on bolls, showing the high effectiveness of a single pyrethroid application on this species, even in small plots. Yield differences were only slightly positively correlated with insect damage (R2 = 0.282), so that most of the differences can probably be attributed to the agronomic properties of the varieties.
| Variety | (19 Aug) % BW dam. bolls |
(26 Aug) % SB dam. bolls |
(24 Oct) % open bolls |
(8 Nov) Yield (lb lint/acre) |
|---|---|---|---|---|
| SG 125 BR | 26 a | 1 ef | 56.1 a-c | 322.2 f |
| DP 655 B/RR | 6 bc | 20 a | 51.6 a-e | 428.4 a-e |
| DP 428 B | 7 b | 15 a-d | 35.0 e-f | 370.7 d-f |
| DP 458 B/RR | 4 bc | 18 ab | 29.9 f | 393.9 c-f |
| PM 1218 BG/RR | 4 bc | 16 a-c | 55.2 a-d | 394.2 b-f |
| PM 1560 BG | 7 b | 10 a-f | 65.1 a | 398.0 b-e |
| DP 448 B | 5 bc | 7 c-f | 55.5 a-d | 431.6 a-d |
| DP 409 B/RR | 1 c | 11 a-e | 62.1 ab | 405.6 b-e |
| PM 1220 BG/RR | 2 bc | 9 b-f | 42.3 c-f | 402.6 b-e |
| DP 451 B/RR | 4 bc | 7 c-f | 45.5 b-f | 374.1 d-f |
| STX 9901 BT | 4 bc | 6 c-f | 38.1 d-f | 465.9 ab |
| DP 422 B/RR | 4 bc | 6 c-f | 52.1 a-e | 358.1 ef |
| DP 33 B | 1 c | 8 b-f | 34.3 ef | 495.5 a |
| SG 501 BR | 3 bc | 6 c-f | 50.6 a-e | 416.6 b-e |
| PM 1560 BG/RR | 4 bc | 4 ef | 44.6 a | 425.3 a-e |
| PM 1330 BG/RR | 3 bc | 5 d-f | 47.6 a-f | 414.0 b-e |
| STX 9902 BT/RR | 3 bc | 4 ef | 35.2 ef | 431.4 a-d |
| ST 474 * | 5 bc | 0 f | 39.4 cf | 435.2 a-d |
| DP 51 * | 2 bc | 0 f | 46.1 b-f | 415.1 b-e |
| Fiber Max 989 * | 1 c | 0 f | 39.4 c-f | 450.7 a-c |