DIVERSITY AND ABUNDANCE OF LANDING APHIDS IN TWO AREAS OF SEED POTATO PRODUCTION IN TUNISIA; RELATIVE TO THE INCIDENCE OF POTATO VIRUSES

Aphid flight activities were monitored in 2015 in two areas of seed potato production in Tunisia. Yellow water traps were used to investigate the diversity of aphidofauna and the incidence of aphids involved in potato virus transmission. A total of 9966 specimens belonged to 73 taxa were captured. The cumulative abundance recorded in Douala (first site) was much higher than in El Ogla (second site) (8768 vs 1189 specimens). The most preponderant species in Douala were Aphis spiraecola Patch (66.1%) and Aphis spp. group (13.5%). In El Ogla Rhopalosiphum padi (L.) comprised 58.9% of total catches, followed by Acyrthosiphon pisum (Harris) (12%) and Aploneura lentisci (Passerini) (10.4%). The highest values of diversity indices were recorded on April 23 th [Shannon-Wiener index (H’)=2.58; Simpson index (1-D)=0.88] in Douala and on May 12th (H’=1.70; 1-D=0.75) in El Ogla. The detection of viral infections by DAS-ELISA determined the predominance of Potato virus Y amongst five main potato viruses tested. Overall Chi-square analysis determined significant differences crossing all areas of seed and ware potatoes and season crops. The highest incidence of viruses was recorded in Douala (18.5%) while El Ogla was under the threshold value (4%). This might be attributed to the occurrence of aphids in early season known previously to be efficient vectors of PVY and to the characteristics of area including climatic conditions, altitude and landscape structure. These results provide new evidence for El Ogla as ideal site to produce healthy tubers while conversely Douala is favourable for the propagation of vectors and viruses.