Rhizoctonia

Rhizoctonia solani

Names:

Brassica Damping Off
Brassica Wire Stem
Canola Damping Off
Canola Rhizoctonia Patch
Capsicum Stem Rot
Carnation Collar Rot
Collar Rot of ornamentals
Clover Rhizoctonia
Damping Off of ornamentals
French Bean Collar Rot
Lupin Rhizoctonia
Lupin Hypocotyl Rot
Potato Black Scurf
Potato Hypocotyl Rot
Potato Rhizoctonia Scab
Potato Stem Canker
Rhizoctonia
Rhizoctonia Hypocotyl Rot
Turf Brown Patch

Description:

Rhizoctonia often forms patches that are circular, up to several metres across, and contain stunted plants. The roots of these plants are much shorter than those of healthy plants of the same age. The roots are often pointed or spear shaped at their ends where the disease has rotted them off. The stem has a dry brittle rot at or above ground level that cause the plant to wilt and die at the seedling or early vegetative stage. Affected plants may re-shoot from below the diseased section of stem.

Canola

Affects seedlings causing red brown to dark brown lesions on the hypocotyl as it emerges. The cotyledons turn red and the stem is pinched at ground level and often breaks off. Plants that survive to the 3-4 leaf stage often grow on successfully.

Turf

In turf, the patches are brownish, usually circular, up to 1 metre diameter and may have a darker to black "smoke ring" edge. The grass in the centre of the patch may recover to give a dough nut shape or it may be taken over by algae and weeds.

Beans

Reddish, sunken, elongated patches on stems just above ground level.

Potatoes

New shoots may rot before emergence. Later infections cause red and yellow colouring of the leaves and the edges may curl upwards. Growth at the top of the plant may be bunched. Tuber may be malformed or have cracks and brownish black, irregular lumps (sclerotia) up to 8 mm diameter.

Stocks

Wilting foliage and sunken lesions at the base of the stem with soil particles clinging onto the fine brown hyphae.

Species Affected:

Most species are affected. There are many strains causing many symptoms.

Biology:

Generally favoured by wet warm soils but in the case Potato Rhizoctonia Scab cool moist conditions favour the disease.
Fungus lives in soil.
Infection is often associated with physical damage to the stem near ground level caused by sand blast, insects, transplanting damage or deep transplanting.
It is a common soil pathogen that may survive on crop stubble or as sclerotia for long periods.
Spread by movement of infected soil or crop residues.
Often attacks young plants or seedlings.
If sclerotia are formed these may survive in the soil for many years.

Life Cycle:


Brown patch disease cycle
(from The Compendium of Turfgrass Diseases, APS Press)

Origin and History:

Distribution:

Circular patches in the crop containing stunted plants.

Significance:

Rhizoctonia causes major yield losses in many crops.

Management and Control:

Rotate to non susceptible crops for at least 2 years.
Fungicide seed treatments provide some protection.
Cultivate soil deeper than the planting depth or deep rip.
Use adequate fertilizer to reduce the effects of the disease.
Control all weeds before planting.
Lemon grass extracts reduce the disease (892).
Plant tolerant clover varieties. See Disease Susceptibility of Clover Varieties.

Control in turf

From University of Nebraska.
Night time temperatures above 210C, high moisture and humidity, and succulent growth favour the disease. Increase air flow, reduce shading and reduce N fertilization to help control the disease. Creeping Bent and Annual Poa are sensitive species.

Brassica vegetables

Rotate area used as seed bed.
Avoid over watering and overcrowding.
Use a fungicide transplant drench.

Canola

Avoid zero tillage.

Capsicums

Rotate area used as seed bed.
Avoid over watering and overcrowding.
Use a fungicide transplant drench.

Carnations

Before planting, fumigate areas that have previously grown Carnations.
Fungicides may retard the progression of the disease.

Lupins

Plant seed 2-3 cm deep at 120 kg/ha and provide adequate P and K.
Iprodione (Rovral) provides partial control.

Potatoes

Fallow area before planting to allow plant residues to decompose.
Don't plant in cold wet conditions.
Rotate to resistant species such as Sweet Corn.
Fungicides are available but rarely profitable.

Turf

Avoid excess water and nitrogen.
Improve drainage and air circulation and reduce shading.

Related and Similar Species:

References:

1291

1291

Acknowledgments:

Collated by HerbiGuide. Phone 08 98444064 or www.HerbiGuide.com.au for more information.