marigold are such pollyannaish little flowers , it ’s no wonder why flower gardeners love them . But , while relatively easygoing to turn , marigolds are not without issues . Perennial and annual varieties of marigolds are susceptible to a figure of diseases , whether grown in greenhouses or out of threshold . If you line up that your marigolds repeatedly fall prey to a certain disease , consider planting a more immune variety .

Botrytis Blight

Botrytis blight is a fungal disease that often crops up after period of abnormally moist conditions . Affected marigold develop big chocolate-brown maculation of dead or break tissue . silver gray spores spot in the center of these patches are germinating fungous spore . The best treatment for botrytis blight is to immediately remove the affected flora textile ( or the total industrial plant if more than one - third of the industrial plant is affect ) and any plant debris or mulch lying in the bed .

Oedema

Marigold oedema most often light upon in late wintertime . Oedema come about when marigold roots absorb water quicker than the industrial plant can expend it . The excess water then builds up in the plant causing little , conceited blisters on marigold leaves and blossom . As the blister age , they indurate and mold white or brown wart - like gibbosity and finally cause the foliage to yellow and drop cloth . Manage oedema by boil down water in the wintertime and spacing plants further apart to increase melodic line circulation .

Powdery Mildew

Powdery mildew can be triggered by any number of fungi that bring out a white , powder - like coating on marigolds that is easily rubbed off . As the disease progresses , the leaves and bud become stunted and distorted and eventually drop . Control the bed covering of powdery mildew by pruning affected works material or chuck out of affected plants . thin wet by switching to dribble irrigation to avoid wet the leave-taking . Virulent infection can be treat with a a sulfex solution ( 3 Gram per liter of water ) .

Southern Bacterial Wilt

Southern bacterial wilt mostly impact marigold grown in warm mood . In early level of the disease , the leafage wilts , becomes stunt and turns a visible radiation yellow or grey - green color . Within a week or two , the works will die . The only cure is to plant resistant marigold cultivar like Cupid , Papaya Crush , Sparky Mix or Gypsy Dancer .

Damping Off

Damping off disease most commonly affects seedling marigold . Affected flowers develop spots or rings of deadened tissue paper . The weakened tissue paper causes the seedlings to collapse and eventually die . To heal dampen off , get the picture up the stirred marigolds then sterilize the soil by spraying a Dithane Z-78 answer ( 2 grams per liter of urine ) .

Flower Bud Rot

Flower bud guff is triggered by the fungus Alternaria dianthi which cause young marigold bud to shrivel and brown and leaves to develop spots of dead tissue on their border . Control bud rot by spraying marigolds with a Mancozeb solution ( 2 grams of per cubic decimeter of H2O ) .

Collar Rot

Marigolds with collar rot modernise grim lesion on their stems and rot around the pinch . Affected marigold should be draw in up . Sterilize the soil before re - planting and trim down down on watering – inordinate moisture lend to the disease .

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