Etiology and chemical control of powdery mildew of Karela (Momordica Charantia l.) caused by Sphaerotheca Fuliginea (schlecht ex fro )poll

Abstract

Powdery mildew of cucurbits is a devastating disease on cucurbits in Kenya. It is caused by either Sphaerotheca fuliginea (schlecht ex Fr.) Poll or Erysiphe cichoracearum Dc ex Mecat. Work was carried out on this disease to identify which of the two pathogens causes the disease on karela (Momordica Charantia L.) and to evaluate chemical fungicides suitable for its control. Infected karela leaves were collected from three sites in Makueni district where the crop is widely grown. The pathogen was propagated on karela plants grown in a glasshouse. Inoculation was done by shaking the infected leaves over healthy plants. Fresh and dry infected leaves were collected from the glasshouse and taken to the laboratory for the fungus identification. It was found that the fungus produced a cleistothecium with a single ascus and with no conspicous appendages. Based on this, the fungus was identified as Sphaerotheca fuliginea (Schlecht ex Pr'., Poll. Karela plants inoculated with powdery mildew spores from pumpkin (Cucurbita mixta Pang) did not develop the disease sYmptoms. Cleistothecium of Erysiphe cichoracearum Dc ex Mecat. contains two asci and it was observed to have conspicuous appendages. Six fungicides folicur, bayleton, bayfidan baycor, cercobin and daconil were tested for their effectiveness in controlling the disease. Folicur, bayleton, bayfidan and cercobin were found to control powdery mildew. Folicur was superior to the other fungicides. Baycor and daconil showed no significant control of the mildew. Phytotoxicity was observed in folicur treated plants. However, the plants tended to recover from the phytotoxicity effects even after the subsequent sprays.