| Abstrakt: |
From 2004 through 2008, a series of 19 replicated "progressive spray" tests was conducted in NC, CS and in GA; 9 in NC, 4 in SC and 6 in GA. The purpose these small plot tests was to obtain information about the relationship between a range of spray protection levels for sucking bugs (primarily stink bugs), and its influence on boll damage, cotton yields and fiber quality. To minimize the possible confounding effects of caterpillar damage, all tests were planted to a Bollgard II cotton variety. Each test consisted of 6 to 12 rows by 50 to 100 ft with 4 replicates, with initial sprays beginning just after at anthesis. The "most protected" treatment was sprayed weekly until cutout, most often six or seven applications of a medium to high rate of dicrotophos (Bidrin 8E @ 0.3 to 0.5 lb. ai/acre) plus a medium to high rate of a pyrethroid (usually Baythroid 2E @ 0.03 to 0.04 lb. ai/acre). The subsequent treatment was started one week later and protected for the remainder of the season, the third a week later, and so on. In most tests, weekly data were taken on square retention, percentage of dirty blooms, ground cloth sampling for all bug species and stages, internal damage to quarter-sized bolls, damage to bolls just prior to harvest, various measurements of boll diameters (an index of overall crop/boll development), yield and quality. In NC, green, Acrosternum hilare (Say) and brown stink bugs, Euschistus servus (Say), predominated, with greens more common; in SC, green and southern green, Nezara veridula (L.) and green stink bugs were present in approximately equal numbers with fewer brown stink bugs; in GA, southern green stink bugs, were overwhelmingly the dominant species with some brown stink bugs also present, but few green stink bugs. Plant bugs, Lygus lineolaris (Palisot de Beauvois), added only minimally to the boll damage at most sites, with tests showing 1) low dirty bloom levels, 2) low numbers of plant bugs captured with ground cloth sampling, and 3) high square retention during the initial 5 weeks of blooming. Protection from bug damage during the first 2 weeks of blooming appeared to have little or no impact on yields, while protection between weeks 3 to 5 or 6 weeks of blooming showed a major positive impact on yield, and protection after the susceptible 3 to 5 week bloom period showed little return on investment. These findings further confirm the use of a dynamic threshold that utilizes higher thresholds both early and late in the bloom. Threshold evaluations undertaken from 2005 to 2008 confirmed that a 50, 30, 10, 10, 10, 30, 30 50% dynamic threshold (by week of bloom) returned greater profits when compared to other static thresholds (such as 10, 20 and 30%) under various stink bug population densities. [ABSTRACT FROM AUTHOR] |
