Biological Control of Powdery Mildew on Zinnia (Zinnia elegans, L) Using Some Biocontrol Agents and Plant Extracts

Powdery mildew is a potentially serious disease of Zinnia (Zinnia elegans). The disease is caused by theair-borne fungus Erysiphe cichoracearum and it is an occasional disease of Zinnia in Egypt. Culture filtrates ofTrichoderma harzianum, Epicoccum sp., Streptomyces endus and an actenomycetal isolate in addition to twoplant extracts i.e. miswak (Salvadora persica) and henna (Lawsonia inermis) were evaluated to control powderymildew disease of Zinnia plants. Culture filtrates of the aforementioned biocontrol agents were used as 25 and50%. Bioassays were conducted under field conditions during the two successive seasons of 2006 and 2007 atthe Experimental Farm of the Fac. of Agric., Kafr El-Sheikh Univ., Egypt to test the efficacy of these culturefiltrates applied to protect Zinnia plants from powdery mildew disease.Spraying zinnia plants four times, beginning from June 15th with one week interval by a hand atomizer underfield conditions with the previously culture filtrates and the two plant extracts gave sufficient control to powderymildew disease. The obtained results showed that, all used treatments led to significant decrease in both diseaseincidence and severity compared with control treatment. The highest disease incidence inhibition was obtainedwhen Epicoccum sp. and T. harzianum were used as 50% (v/v) sterilized water followed by henna and miswakextracts were used, respectively. Sprayed plants recorded best results for most growth characters, peroxidase(POX) and polyphenol oxidase (PPO) enzymes activity compared unsprayed one. In conclusion, biocontrolagents and some plant extracts can be substitutes to fungicides as an alternative and safe method for controllingpowdery mildew disease of Zinnia.