Improved juvenile spittlebugs populations quantitative sampling

Spittlebugs (Hemiptera Aphrophoridae) have been rising celebrity as one of the most representative species, Philaenus spumarius Linnaeus, 1758, shown to be the vector of Xylella fastidiosa pauca in the Apulian OQDS epidemics. The juvenile vector population size knowledge is one of the crucial data in establishing an effective control strategy while choosing action thresholds, tuning control action intensity and estimating control efficacy. The first experience on spittle quantitative sampling by direct in-field scrutiny revealed the approach to be very expensive regarding needed time and workforce. Moreover, population size gathered data showed not to be congruous among the fifth pre-imaginal instars. Divergence in observation being possibly due to the small size of the early juvenile instar, the spittle inconsistency and the inherent difficulty to collect them all from a herb volume that can grow as 0.5-0.8 m3/m2. To quantify at our best the spittlebug juvenile population size and to compare conventional and innovative sampling methods, we realised conventional and innovative spittle sampling on two side by side homogenous Sub-Sampling Units. A five-person squad sampled weekly from February to May 2017 in three different field management models: uncultivated, no-tillage and conventional tillage olive orchards. The squad sampled a total 4,5 m2 exploring one management per day/week and scrutinizing 18 random Sub-Sampling Units (SSU=transect) of 0,25 m2 (0,25 m * 1 m) each. Namely 16 SSU by conventional and 2 by innovative technique. Both conventional and innovative sampling were destructive, contrary to the EFSA-funded field surveys that are conservative, which implicated the field collection of most or all of the plants framed by the transect. For conventional sampling, collected plants were scrutinised in the lab by the naked eye, lighted magnifying glass or loupe or stereoscope counting juveniles and storing them in 75% EtOH. In case of conventional sampling, each SSU required about 80 minutes of worktime. The innovative sampling method consists in a triple sequential rinsing of collected plant in saline solution. The washing dissolves the spittle and pick up from the plants accurately and safely the juveniles, that dive into the saline. As plant removal is complete, the saline is filtered through a non-woven piece of fabric to collect juveniles that rest alive on the tissue. This innovative technique, we call AquaSamPling (ASP), as well as reducing overall worktime, requiring 45 minutes per SSU, has proven to be 20-50% more effective in term of collected juveniles than the conventional one