Lentil – Foliar Diseases

Ascochyta/Mycosphaerella Blight
CAUSED BY	Caused by Ascochyta fabae f. sp. Lentis. Can spread rapidly on stubble or seed in a field with cool, wet conditions. Spores are spread through rain splash – they can survive up to five years on the soil surface and up to 30 years in the seed.
Symptoms	Symptoms appear on leaflets, pods and stems as tan spots surrounded by a dark margin. Tiny black specks known as pycnidia occur in the centre of the spot. Branch tips wilt, turn brown and often die – premature drop occurs from infected leaflets. Can also cause flower and pod abortions – infected seeds turn purplish-brown and are often shriveled and smaller in size (severely infected seed can also have whitish patches of mycelia, strands of threadlike material, with tiny black pycnidia on the surface).
PREVENTION AND CONTROL	Bury all crop residues. Avoid seeding next to the previous year’s pulse fields. Allow at least four to five years between lentil crops. Avoid seeding next to any previous year’s lentil or pea fields since spores can spread by wind. Use disease free seed. Have lentil seed examined for Ascochyta presence by an accredited seed lab. If pathogen-free seed cannot be found, use seed with as low a level of Ascochyta as possible, and have the seed treated. Bury all crop residue, to prevent the fungus being spread by wind and rain.
IMPACT	This disease is the third highest pathogen impacting lentil yields.

Sclerotinia Stem or Pod Rot (White Mould) White Mould On Lentil White Mould on Lentil
CAUSED BY	Caused by Sclerotinia sclerotiorum (Lib.) de Bary (often called white mould or pod rot). Sclerotinia stem and pod rot flourishes under dense canopies and high humidity Lentil crops are at increased risk of Sclerotinia infection if grown in rotation with other susceptible crops, such as canola, pea, or sunflower. All lentil tissues, (i.e. leaves, stems, pods, and flowers), can be infected by spores of Sclerotinia. Plants older than six weeks are significantly more susceptible. This decrease in resistance, combined with wet weather late in the growing season and a heavy plant canopy, may explain why Sclerotinia is more of a problem in maturing lentil crops. The critical infection period is during the flowering stage. When the lentil seed is harvested, sclerotia are either harvested with the seed or fall to the ground. It overwinters as sclerotia, small black resting bodies in the soil, apart from the host. Only sclerotia in the top 6 cm of soil can produce apothecia. Sclerotia buried deeper remain dormant and can survive in the soil for five to seven years, until conditions for apothecia formation are favourable.
SYMPTOMS	The first sign of White Mould is the appearance of a light brown, water-soaked discolouration on the stem, leaves, or pods and a cottony threadlike growth in the collar region, if the temperature and humidity levels remain high. A water-soaked area appears that spreads both upwards and downwards. Dark brown spots then develop on the stem, and the entire plant eventually turns brown. Affected plants often appear wilted and ripen prematurely due to rotting stems; lodging is common in affected areas. Stems, when split open, exhibit characteristic white fungus growth — numerous, black, hard resting bodies (sclerotia) may be present in the pith. Affected plants yield poorly and often die prematurely. With Pod Rot, this occurs at the base of the style with a small water-soaked lesion appearing on green tissue at the end of the pod. With Stem Rot, the symptoms are more common in the node area. Whitish, threadlike mats develop over the affected areas and over time, cause the tissue underneath to turn soft and decay – black, hard bodies (sclerotia) form in the mat and within the stem and pods. Affected plants often appear wilted and ripen prematurely due to rotting stems – lodging is common in affected areas.
PREVENTION AND CONTROL	Bury all crop residues deeply. Crop rotation – use a four to five-year rotation out of susceptible crops such as canola, bean, field pea, or sunflower. Fungicide use for control of Sclerotinia Stem Rot in the majority of pulse crops is not cost-effective because, once the canopy closes, the fungicides cannot reach their target. Four to five-year rotation out of susceptible crops (canola, mustard, sunflower, dry bean). There are foliar fungicides registered for the control of Sclerotinia stem rot on lentils. As with Botrytis, achieving the necessary coverage of infected stems often makes treatment difficult.
IMPACT	Sclerotinia White Mould may occur in maturing lentil crops under high moisture conditions that promote vegetative growth and lodging, and can cause economic losses. This disease is tied for fourth for most impactful pathogen impacting lentil yields.

Botrytis (Grey Mould)
CAUSED BY	Caused by Botrytis cinerea Pers. ex Fr. Grey Mould in lentil can be seed-borne, stubble-borne, air-borne and soil-borne, and can attack at various stages of plant growth. Infected seed produces infected seedlings, which die before emergence or soon after. On older plants, a greyish mould is observed, which quickly spreads under moist conditions. Grey Mould can occur as a rot on pods, stems and leaves on pea plants or on fresh seed and pods in transit or storage. Grey Mould favours cool temperatures, high humidity, wet soils, and dense canopies.
SYMPTOMS	On young plants that emerge, the Grey Mould appears as a grey mouldy growth visible at the soil surface. On older plants, it appears as a fuzzy grey or dirty white mouldy growth on flowers, pods, or lower areas of the stem. The infected sites first develop small water-soaked lesions that expand to form large brown lesions with concentric zones. Under humid conditions, massive greyish-brown spores are produced to cover the infected tissues. They can often develop sclerotia in the form of small black specks on old infected tissues. These lesions spread to the entire lower foliage. As the disease progresses, wilting, premature ripening, failure of pods to fill, and dead infected crop areas occur. Pod infection causes the most damage, and clinging blossoms provide a humid environment from which the tip of the young pod can be infected – small, oval, water-soaked lesions develop and spread up the pod (these lesions are tan at first but turn greyish with age and often develop sclerotia in the form of small black specks).
PREVENTION AND CONTROL	Treat seed or plant disease free seed. Use wider row spacing or lower seeding rates to improve air circulation in the crop. No fungicides are registered for control in many of the pulse crops, and control products in bean are not considered economical. Potassium fertilizer in potassium deficient soils reduces the severity of Grey Mould in lentil.
IMPACT	This disease is tied for fourth for most impactful pathogen impacting lentil yields.

OTHER CAUSES:

These aren’t considered to be a disease, but can be confused with diseases.

Heat Canker
CAUSED BY	Not caused by a pathogen, but occurs from contact of young tender shoots with soil hot from exposure to the sun. Occurs on seedlings in late May and early June when very hot weather occurs.
SYMPTOMS	The base of the stem is pinched at the soil surface, the leaves turn yellow and the plant usually wilts, falls over and dies Below the soil surface, the stem and roots remain plump, white and healthy. High soil temperatures (28˚C) favour this disease.
PREVENTION AND CONTROL	Seeding in a north-south direction and shading provided by stubble offers some protection against heat canker.

Special thanks to Saskatchewan Pulse Growers and Manitoba Pulse and Soybean Growers.