Downy mildew on cheddar cauliflower

Asked November 9, 2017, 3:06 PM EST

Hello, I was wondering if cheddar cauliflower was susceptible to downy mildew? Since the leaves are not tied up around cheddar cauliflower while its growing, can the downy mildew spores still transfer to the head and infect it? I know white cauliflower is susceptible to downy mildew and the leaves are tied up during growth. Does the leaf tying difference between white and orange cauliflower have any effect on the spread of the disease? Thank you

Outside United States downy mildew powdery mildew

1 Response

Thank you for your question about your cauliflower. Since your questions doesn't indicate what country you are in, and you didn't attach any photos, I don't know if your plant has downy mildew or powdery mildew. I've attached photos of both types of mildew. Perhaps you can compare and distinguish. Powdery mildew is more common in the fall, but I don't know what season it is where you are since I don't know which hemisphere. You don't say whether the fungus is on the top side of the leaves, or the undersides.

Both of these mildews are fungi, and their spores are spread through the air and then land on and begin to consume whatever can be 'eaten.' They are also 'splattered' by water to other parts of the plant and other plants, which is why watering your plants at the soil level--rather than on the leaves--helps prevent this. Treatment of these fungi differs. Here is an explanation of downy mildew:

"Downy mildew causes damage from the seedling (cotyledons) to the harvest stage of growth. Leaf symptoms appear as yellowish, irregular areas on the upper surface corresponding to a white fluffy growth on the undersides of leaves. Older lesions become dry, brown and papery in texture and may cause the entire leaf to drop. Cool, moist conditions favour the disease and the head of broccoli and cauliflower curds may be infected with black spots within or on the surface.

The peak period for spore release is after sunrise. Downy mildew is spread by the wind although leaf wetness is required for infection. The fungus can survive on brassica weeds, in crop debris or soil for several months, even in the absence of a host."

Here is a description of powdery mildew: "Powdery mildew is a fungus that produces a white powdery mould on the top surface of leaves. The disease can occur through to crop maturity and its development is favoured by warm dry weather. The powdery mildew fungus, which is spread by the wind, survives on living tissue and Brussels sprouts, swedes and cabbages are mainly affected."

(Cauliflower is a fellow member of the Brassica family, so these are both pests of your plants.) Although there are a variety of other pathogens effecting brassica, detailed here, I'm limiting my answer to the two mildews. Tying up the leaves around the head of the plant just helps protect it from having spores land on it, and the variety of cauliflower is unimportant. But water can still transfer the spores onto the head, and the leaf coverage won't be of any use. You can use any fungicide approved for use on edible plants, one of which is neem oil, which is available worldwide. But your local agricultural school might have other suggestions. Please follow label directions when using any fungicide.

I hope this is helpful. Good luck!