A study on different sampling techniques for dubas bug, Ommatissus lybicus (Hem.: Tropiduchidae)

The dubas bug, Ommatissus lybicus Bergevin, is a key pest of date palm, Phoenix dactylifera L. in Iran. This study was conducted in a date palm orchard in Farashband (Fars Province) to investigate the different sampling methods and population fluctuations of dubas bug nymphs in first generation. The results showed that the nymphs emerged at early April, their population density reached to peak at 30 April, and finally declined to a few numbers at early June. Results showed that there was a significant correlation between different sampling methods. Using correlation analysis, it was shown a high and significant correlation between nymph densities on mature date palm and on offshoots (R2=0.96). Results showed that yellow sticky traps could be a relatively appropriate variable to estimate population densities on date palms. Also, results showed that the honeydew secretion begun approximately three weeks after nymphal emergence, however its peak was happened one week after the peak of nymph densities. Regression analysis of Taylor model showed that in exception of one sampling method, all other three sampling methods were significant. Based on R2 and P of regression analysis, Iwao’s model was more appropriate than Taylor model for sampling of dubas bug honeydew. In order to determine the optimal sample size, the Green's and Kuno's method with constant accuracy of 0.2 were used. Based on Green's method, whenever the average density of dubas bug on mature and offshoot date palm leaflet is 10, the number of required samples with a precision level of 0.2 would be 38 and 47 leaflets, respectively. Whenever the average density of this pest in each yellow card is 200, the number of required samples would be 19 cards.