Aggregation and Sampling Plan in Three Aphidophagous Predators in a Guava Ecosystem

Studies carried out in a guava ecosystem on three aphidophagous coccinellid predators showed that Cheilomenes sexmaculata (Fabricius), was spatially aggregated throughtout, while Pseudaspidimerus circumflexa (Motschulsky) and Scymnus castaneus (Sicard) had an initial random distribution which later tended to aggregation with increased mean density. However, aggregation did not seem to influence sample number with a nonsignificant correlation. Appropriate sampling plans were developed for all the three predators. At 25% precision level, the number of trees for sampling were 18, 32 and 48, respectively for the three species. A linear model was also developed to ardve at an optimum sample number for combined or individual predator estimation. As per the linear model, for example, a mean density of 2 predators/tree would require 26 trees. The sampling plans which are on sound ecological lines have relevance in biological control studies.