Inoculation experiments of Bursaphelenchus eremus Rühm (Goodey)(Nematoda Parasitaphelenchidae)on Quercus robur L.

Abstract

Bursaphelenchus eremus Rühm (Goodey) occurs in declining oak forests of some European countries, althoughdata are lacking on the possibility of the nematode to colonize healthy trees. To evaluate the pathogenicity of thenematode, we carried out an inoculation test in Tuscany (central Italy) in 2007-2008: on May 2007, 32 Quercus robur L.plants (7 years old) were inoculated with an Italian isolate of B. eremus(IT37w) and 16 plants were maintained ascontrols. There were two inoculation sites on each plant: one immediately below the fresh top shoot and another 30 cmbelow the first site. All plants were kept outdoors under a zinc-coated cage covered with a cloth. After four months, 16inoculated plants and eight controls were randomly selected and each stem was cut into three parts, weighed, crushed ina grinder and subjected to Baermann funnel extraction. After 16 months, the remaining 18 inoculated and 6 controlplants were chosen and examined with the same procedure.Bursaphelenchus eremuswas obtained from the stems of all infected oak trees. The difference was in the numberof nematodes/g of fresh wood in the different plant portions both after four (F2,16=86.94) and 16 months (F2,18=400.71).The highest density was always recorded in the fresh top shoot tissue, while no nematode was obtained from the lowerstem portion. The RHS (relative host suitability) index value increased from 0.6 (4 months) to 2.1 (16 months) but itwas still too low to be accompanied by signs of wilting. Because of the resemblance between B. eremusand the PineWood Nematode, we suggest that further experimental studies are needed to evaluate the potential risk of thisnematode for different species of oaks common to the Mediterranean area, where the maximum summer temperaturesreach the optimal temperature range for B. eremusdevelopment.