Environmental Entomology (2010) 39, 368-377

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Benjamin C. Legaspi Jr. and Jesusa Crisostomo Legaspi (2010)
Field-level validation of a CLIMEX model for Cactoblastis cactorum (Lepidoptera: Pyralidae) using estimated larval growth rates
Environmental Entomology 39 (2), 368-377
Abstract: Invasive pests, such as the cactus moth, Cactoblastis cactorum (Berg) (Lepidoptera: Pyralidae), have not reached equilibrium distributions and present unique opportunities to validate models by comparing predicted distributions with eventual realized geographic ranges. A CLIMEX model was developed for C. cactorum. Model validation was attempted at the global scale by comparing worldwide distribution against known occurrence records and at the field scale by comparing CLIMEX "growth indices" against field measurements of larval growth. Globally, CLIMEX predicted limited potential distribution in North America (from the Caribbean Islands to Florida, Texas, and Mexico), Africa (South Africa and parts of the eastern coast), southern India, parts of Southeast Asia, and the northeastern coast of Australia. Actual records indicate the moth has been found in the Caribbean (Antigua, Barbuda, Montserrat Saint Kitts and Nevis, Cayman Islands, and U.S. Virgin Islands), Cuba, Bahamas, Puerto Rico, southern Africa, Kenya, Mexico, and Australia. However, the model did not predict that distribution would extend from India to the west into Pakistan. In the United States, comparison of the predicted and actual distribution patterns suggests that the moth may be close to its predicted northern range along the Atlantic coast. Parts of Texas and most of Mexico may be vulnerable to geographic range expansion of C. cactorum. Larval growth rates in the field were estimated by measuring differences in head capsules and body lengths of larval cohorts at weekly intervals. Growth indices plotted against measures of larval growth rates compared poorly when CLIMEX was run using the default historical weather data. CLIMEX predicted a single period conducive to insect development, in contrast to the three generations observed in the field. Only time and more complete records will tell whether C. cactorum will extend its geographical distribution to regions predicted by the CLIMEX model. In terms of small scale temporal predictions, this study suggests that CLIMEX indices may agree with field-specific population dynamics, provided an adequate metric for insect growth rate is used and weather data are location and time specific.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Jesusa Crisostomo Legaspi

Research topic(s) for pests/diseases/weeds:
environment - cropping system/rotation

Pest and/or beneficial records:

Beneficial Pest/Disease/Weed Crop/Product Country Quarant.

Cactoblastis cactorum Pakistan
Cactoblastis cactorum Kenya
Cactoblastis cactorum Mauritius
Cactoblastis cactorum South Africa
Cactoblastis cactorum Bahamas
Cactoblastis cactorum Cuba
Cactoblastis cactorum Mexico
Cactoblastis cactorum Puerto Rico
Cactoblastis cactorum Argentina
Cactoblastis cactorum Brazil (south)
Cactoblastis cactorum Paraguay
Cactoblastis cactorum Uruguay
Cactoblastis cactorum Antigua and Barbuda
Cactoblastis cactorum Cayman Islands
Cactoblastis cactorum Montserrat
Cactoblastis cactorum Saint Kitts and Nevis
Cactoblastis cactorum United States Virgin Isl.
Cactoblastis cactorum U.S.A. (SE)
Cactoblastis cactorum Australia (NT+QLD)
Cactoblastis cactorum Saint Helena