EFFICACY OF SOME BIOCONTROL ORGANISMS, ANIMAL MANURES AND FUNGICIDES ON CONTROLLING OF POTATO BLACK SCURF AND STEM CANKER DISEASE

Abstract

In the last few years, stem canker and black scurf disease caused by Rhizoctonia solani Kuhn (teleomorph Thanathephorus cucumeris [Frank] Donk) are among different diseases important attacked potato crop under the Egyptian climate conditions. Eight fungal isolates were isolated from diseased plants representing different localities in different governorates i.e. El-Kassasen (Ismailia Gov.), Kafer El-zayat (Gharbia Gov.), El-Katatba (Minofya Gov.), Housh-Essa (Behera Gov.), El-Badrashen (Giza Gov.), Behdal (Minia Gov.), Dairoot (Assiut Gov.) and Shandaweel (Sohag Gov.). The obtained isolates differed in their culture color, number and size of sclerotia. Isolates which isolated from El-Kassasen, Kafer El-zayat, El-Khatatba, El-Badrashen and Behdal, were belonging to AG-3 anastomosis group. Under greenhouse conditions this isolates were tested for their pathogenicity to potato (Lady-Roseta cv.), during summer growing season 2015 and gave high rates of infection to potato plants. In this manner, the isolate which obtained from El-Badrashen (Giza Gov) was the highest aggressive one and causing the highest percentage of stem canker and black scurf. In separate experiments under greenhouse conditions, a number of biocontrol organisms,animal manure extracts and fungicides were evaluated alone in their efficacy to reduce the infection of potato stem canker and black scurf diseases.With regard to bioagents test, Trichoderma harzianum at concentrate 2.0% improving percentages of eyes germination and reduce dead sprouts of potato and decrease of stem canker and black scurf incidence, compared with Bacillus subtilis and algae treatments. While, animal manure test, Pigeons extract at concentrate 2.0%, gave the highest effect on reducing of stem canker and black scurf incidence compared to Chicken extract. In fungicides experiment, Rizolex (Tolchlophos-methyl) when used before soil inoculation give the best effect in reducing of non-germinated eye, dead sprouts and incidence of stem canker and black scurf compared to Monceren (Pencycuron). On the other hand, the effect of different treatments on the content of potato plants of phenols and oxidative enzymes were studied. In this respect T. harzianum, gave the highest content of phenols and activities of oxidative enzymes Peroxidase (PO) and Polyphenoloxidase (PPO).