Sampling method affects estimates of population density and reproductive maturity of summer‐form pistachio psyllids

Abstract

In this study, the effects of using three different sampling methods (yellow sticky traps, beating tray, organdy bags) on estimating the distribution through the canopy of the summer-form adults of the pistachio psyllid (Agonoscena targionii (Licht.)) was investigated throughout the vegetative period. The traps or bags were hung at two heights in the tree canopy, 3.5 m above ground and 2 m above ground. Psyllids were counted weekly, and their sex determined. adult abundance varied during the study, but all three sampling methods indicated that densities were higher in the upper canopy than the lower canopy. The percentage of females having mature eggs was lowest in late May, and highest in June and September. Sex ratios were highly variable among sampling dates and among sampling methods, at both canopy heights. Sex ratios in bags tended to be more female-biased in the lower canopy than in the upper canopy. Sticky trap counts were significantly male biased, more so in the upper canopy than in the lower canopy. Mean sex ratios differed significantly between bag and sticky trap samples at both heights, but did not differ significantly between tray and bag samples at either height. In addition, for a given tray or bag count, sticky trap catch of males was larger than catch of females, and was larger in the upper canopy than in the lower canopy. Bag counts (psyllids per leaflet) strongly increased with tray count. Z07005; Online publication date 19 September 2007 Received 24 February 2007; accepted 13 August 2007Of the three sampling methods described here, the bag samples provided direct estimates of psyllid numbers per leaflet, but this method is extremely time consuming. Bag counts (psyllids per leaflet) increased with tray count, suggesting that beat trays can be used to estimate absolute densities.

Effect of Daytime and Tree Canopy Height on Sampling of Cacopsylla melanoneura, a ‘Candidatus Phytoplasma mali’ Vector

“…(ii) Is there any difference in the distribution of C. melanoneura specimens at different canopy heights of apple trees? For some Psylloidea species, such as C. pyri , C. pyricola and Agonoscena targionii , it was shown that their adults prefer to dwell in the upper canopy [ 29 , 33 , 34 ]. The results of our study indicate that C. melanoneura also shows a non-random distribution on trees.…”

“…Some studies have reported a preference of certain psyllid species to colonize upper parts of the tree canopy. This has been documented for Agonoscena targionii (Lichtenstein, 1874) on pistachios [ 33 ], as well as C. pyri and C. pyricola (Foerster, 1848) on pear [ 29 , 34 ]. It is worth noting that higher numbers of sexually mature psyllid adults, eggs and nymphs were found in the upper canopy of pear trees [ 29 , 34 ].…”