Aggregation patterns of Bemisia tabaci in response to insecticide applications

Tonhasca Athayde Tonhasca, John C. Palumbo, David N. Byrne

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


We measured the effect of insecticide applications on the distribution patterns of the sweet potato whitefly, Bemisia tabaci (Gennadius), in fields of cantaloupe, Cucumis melo L., in Yuma, Arizona. Whitefly infestations were measured by counts of adults, eggs, first to mid/fourth instars, and late‐fourth instars (‘red‐eyed’) nymphs. Adults were sampled from the entire leaf, and immature stages were counted in a 1‐cm2 area of a leaf. The indices b (Power Law), β (Patchiness regression) and Id (Morisita) indicated that all life stages were aggregated, but results for the three indices were not similar for determining the relative aggregation levels between treatments. In general, indices β and Id indicated higher aggregation in insecticide‐treated fields, whereas b had mixed results. The Morisita index was sensitive to a few unusually high means among a series of low densities in the treatment plots, what could be attributed to refuges due to failure in the insecticide applications. Despite the usefulness of the Power Law and the Patchiness regression for describing the relationship between spatial or temporal variability and mean densities, we suggest that Id is more appropriate for expression of spatial distribution because it is based on a precise definition of aggregation. 1994 The Netherlands Entomological Society

Original languageEnglish (US)
Pages (from-to)265-272
Number of pages8
JournalEntomologia Experimentalis et Applicata
Issue number3
StatePublished - Sep 1994


  • Bemisia tabaci
  • Morisita index
  • aggregation patterns
  • sampling
  • spatial distribution

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Insect Science


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