اختبار مدى مقاومة عزلات فطر Venturia inaequalis للمبيدات الفطرية المستعملة في لبنان

Abstract EN

Apple scab, caused by Ventuna inaequalis (Cke ) Wint Is one of the major apple diseases worldwide The disease cause severe losses in apple orchards in Lebanon in the mountaincous areas particularly so in Akkar A total of 230 isolates of V.

inaequalis were collected from 23 orchards and single-spore colonics were prepared In vitro tests were conducted to evaluate the level of resistance to ben/tmitlaxolcs and sterol biosynthesis inhibitors (SBI).

All isolates tested except one were resistant to bcnomyl and thiophanate-methyl at lpgml-l.

The majority of isolates were not inhibited at concentrations as high as SOyg mr' in mycelial growth.

Similarly, the majority of the isolates were not inhibited by bcnomyl at I, 5, and 50 pg.ml1 in spore germination tests Preliminary in vivo tests with benotnyl concerning resistance to benzimidazoles correlated well with the in vitro results All isolates were inhibited by fenanmol at 0.25 pg.ml' indicating that all isolates can be considered sensitive to this fungicide However, the sensitivity levels varied among the various isolates with the F.D*i for fenanmol ranging between 0 002 and C 052 pg.ml1 and for fluzilazol between 0 001 and 0 018 Mg «nl' The ED*j of two new SBIs.

that were not yet commercialized in Ixbanon at the tunc the test was performed ranged from 0.009 to 0.025fxg.ml1 for bromocunazol and Irom 0 008 to 0.039ngmi' for fcntxicona/ol.

both indicating a good level of in vitro activity.

These results indicate that resistance to benzimidazoles is w idespread in Lebanon while resistance to SBIs was not detected.