Estimating absolute density from relative sampling of lygus lineolaris (heteroptera: Miridae) and selected predators in early to mid-season cotton

Functional relationships of Lygus lineolaris (Palisot de Beauvois) and selected predator densities estimated with sweep net, drop cloth, whole-plant-bag samples (WPBS), and visual search were determined in early to mid-season cotton. Slopes of relative as a function of absolute densities were not different between years for most taxa. When compared against absolute density estimates (WPBS or visual search) drop-cloth estimates were generally more precise and captured a larger percentage of arthropods than 10-sweep samples of the sweep net. With few exceptions (notably Geocoris spp. nymphs) the proportion of the absolute density estimated by drop-cloth or sweep-net samples was low (ca. 10-30%). Reasonably precise relationships (R²> 0.50) of relative over absolute density were obtained for nymphs of Geocoris spp., L. lineolaris, and Orius spp.; Orius spp. adults; and spiders. Relationships using total predator counts generally had greater precision than those using individual species and stages. Adults of Geocoris spp., Coccinellidae, and possibly L. lineolaris, however, were not estimated with precision by drop-cloth or sweep-net samples.