Rye pests and diseases

Ergot (Claviceps purpurea): Rye is more sensitive to ergot than other cereals. When rye contains 0.5% or more of ergot, it is considered unfit for food or feed. The ergot infection is characterised by large spur-like purplish-black bodies (sclerotinia) that replace the kernel in the rye spikelet. Ergot bodies hibernate in the field, or with the seed in storage, and germinate under favourable conditions in the spring.

The infection can be partly controlled by sowing ergot-free seed or year-old seed on land where rye has not been grown for the previous 1 or 2 years. The mowing of ergot infested grasses adjacent to rye fields is also helpful. Resistant varieties are not yet available.

Ergot bodies can be removed by immersing infested rye in a 20% salt solution. The grain is stirred, and ergot bodies float to the surface where they can be skimmed off. The salt must be washed from the seed, and the seed partly dried before it is sown.

Ergot poisoning is called ergotism and has been a curse for humanity for thousands of years. The sclerotia contain a large number of poisonous alkaloids and ingestion can be fatal. The symptoms can be roughly divided into convulsive and gangrenous symptoms.

Stem or stalk smut (Urocystis occulta): This is a common disease on rye. The symptoms appear first as lead-grey, long narrow streaks on the stems, sheaths, and blades. These streaks later turn black.

Infected plants are darker green than normal and somewhat dwarfed. The stems are often twisted or distorted, and the heads fail to emerge from the sheath. Spores can be carried both on the seed and in the soil. Disease control could be achieved by seed treatment and crop rotation where the spores are soil-borne. Resistant varieties are also available.

Anthracnose (Colletotrichum graminicola): This common rye disease is especially prevalent in humid and sub-humid climates. Infected tissues are stained brown on the leaf sheath that surrounds the diseased stem. Head infections cause shrivelled, light brown kernels. Infected plants often ripen or die prematurely. 

Rusts (Puccinia recondita and Puccinia graminis): Leaf rust: Severe infections of leaf rust are largely confined to the southern range rye production, and cause a reduction of tillering and grain yield. The disease overwinters in the leaves of rye as dormant mycelium. Destruction of plant materials in stubble fields will aid in the control of this disease. Stem rust: The early maturity of rye usually enables it to escape serious damage from stem rust. Common barberry is the alternate host. 

Insects: Rye is attacked by many of the same insects that attack other small grains. Serious losses on rye are not common. Early sown winter rye provide a favourable environment for the deposition of grasshopper eggs, which may promote grasshopper injury to other crops.