Management of powdery mildew and gray mold of cucumber by Trichoderma harzianum T39 and Ampelomyces quisqualis AQ10

Two biocontrol preparations were tested for their ability to control Spaner otheca fusca and Botrytis cinerea on greenhouse cucumber. Trichoderma harzi anum T39 (TRI-CHODEX) spray reduced powdery mildew severity by up to 97% bu t its efficacy declined to 18-55% control as the epidemic progressed. Unlik e on young leaves, on older leaves the control of powdery mildew by T. harz ianum T39 was poor. Ampelomyces quisqualis (AQ10) was very effective agains t powdery mildew, achieving up to 98% of control. Its effectiveness decline d with the progress of the epidemic but unlike the other biocontrol agent i t retained significant control capability on older leaves. Two aliphatic pe troleum distillate oil products improved the efficacy of both biocontrol ag ents. The co-application of T harzianum T39 and A. quisqualis AQ10 was test ed on cucumber plants infected with powdery mildew followed by fruit gray m old infection. It resulted in no improvement of the control of powdery mild ew, and in an improvement of gray mold control, the latter probably because of the use of additive oil (ADDQ) along with the second biocontrol prepara tion. There was no significant interference between the biocontrol agents i n the co-application treatment as compared with the application of each age nt alone; the level of population of T. harzianum T39 remained similar and the parasitism of S. fusca by A. quisqualis was not nullified. The applicat ion of T. harzianum T39 to soil instead of spraying it resulted in 75-90% l ower powdery mildew coverage on the leaves. It was concluded that the mode of action of T harzianum T39 in powdery mildew control is induced resistanc e, not mycoparasitism or antibiotic action.