| Abstrakt: |
In 2004 and 2005, a series of eight replicated "progressive spray" tests was conducted in NC and in GA, two in GA and six in NC. The goal of these tests was to gather information about the relationship between various spray protection levels for sucking bugs (primarily stink bugs), and its influence on boll damage and cotton yields and quality. To minimize the potential confounding effect of caterpillar damage, all tests were planted to a Bollgard II cotton variety. Each test consisted of 6 to 8 rows by 50 to 100 ft with four replicates, with initial sprays beginning at anthesis. This "most protected" treatment was sprayed weekly until the season's end, and most often received seven applications of a high rate of dicrotophos (Bidrin 8E @ 0.5 lb. ai/acre) plus the highest rate of a pyrethroid. The next 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, while in GA, southern green stink bugs, Nezara veridula (L.), were overwhelmingly the dominant species. Plant bugs, Lygus lineolaris (Palisot de Beauvois), added only minimally to the boll damage at most sites, generally being below dirty bloom and ground cloth thresholds. Additionally, most sites showed high square retention rates during the first 5 weeks of blooming. The relationship between both quarter-sized and year-end boll damage and yield was extremely variable between tests, varying from as little as 3.1 lb. of lint per 10% year-end boll damage in Union County, NC in 2005 to as much as 140 lb. of lint per 10% year-end boll damage in Tift County GA in 2005. At an Edgecombe County location, quarter-sized boll damage that averaged less that 10% during the season in the untreated check lost 106.3 pounds of lint, while the Union County location that averaged almost 25% quarter-sized boll damage only showed an 8 pound lint decrease. Protection from bug damage during the first 3 weeks of blooming appeared to have little impact on yields, while protection between weeks four and five showed a major impact on yield. This latter finding could have implications for higher thresholds during the first three weeks of blooming in situations where stink bugs are the predominant bug pest. [ABSTRACT FROM AUTHOR] |
