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SEASONAL CHANGES IN THE EFFICIENCY OF McPHAIL TRAPS AND A MODEL FOR ESTIMATING OLIVE FLY DENSITIES FROM TRAP CATCHES USING TEMPERATURE DATA

Author:
KAPATOS, E., FLETCHER, B.S.
Source:
Entomologia experimentalis et applicata 1983 v.33 no.1 pp. 20-26
ISSN:
0013-8703
Subject:
Bactrocera oleae, fruits, imagos, insect traps, mark-recapture studies, models, olives, oviposition, plant ovary, regression analysis, seasonal variation, spring, summer, temperature, trapping, trees, winter, Greece
Abstract:
Seasonal changes in the efficiency of protein hydrolysate-baited McPhail traps used to monitor adult populations of the olive fly. Dacus oleae (Gmel.), on Corfu were investigated from 1976-1979. The mean weekly trap-catches of traps located on grids in 3 different parts of the island were compared with absolute population estimates of adult flies obtained from mark-recapture studies at the same sites. Trap-efficiency was then estimated by dividing the mean weekly trap-catch values by the estimated number of flies per tree, ♂ ♂ and ♀ ♀ being dealt with separately. For both sexes, trap-efficiency was low during the winter months and then higher in spring and early summer, reaching a peak in late July/August, just after the new season's olive crop became susceptible to attack. However, earlier in the summer, when the fruit was unavailable or unsuitable for oviposition and when hot dry conditions inhibited ovarian maturation, trap-efficiency was very variable and frequently fell to a low level similar to that found in winter. Excluding the highly variable mid-summer data, regression analysis indicated that over 85% of the variation in trap-efficiency was attributable to differences in mean temperature during the trapping periods. Using the calculated regression relationship between mean temperature and trap-efficiency, which was similar for both sexes, a model was developed which enables mean weekly trap-catch data to be converted into absolute population estimates of adult flies.
Agid:
130984