Wheat dwarf

The main vector of the infection in nature is the striped wheat leafhopper Psammotettix alienus. The virus persists in the insect's body throughout its life after a short period of feeding on an infected reservoir plant.

Reservoirs of the virus in field conditions are grassy weeds such as couch grass, bromegrass, bluegrass, and other perennial grasses. Volunteer cereals can also serve as sources of infection.

The external manifestation of the disease directly depends on the growth stage of the crop at the time of infection. Early infection leads to maximum suppression of plant growth and development.

Systematically, the virus is classified as an obligate parasite, closely linked to the life cycle of its specific insect vector.

The virus mainly affects winter and spring wheat, as well as barley, oats, rye, and many wild grasses. The disease poses the greatest threat to crops in the autumn period.

Winter crop seedlings infected in the autumn often fail to survive the winter or show extremely low productivity in the spring. In spring crops, infection at early stages leads to a significant loss of yield.

Grain losses from wheat dwarf can vary from 10 to 80 percent, depending on the prevalence of the vector and seasonal weather conditions.

Affected plants stop tillering, their internodes shorten, leading to the formation of a dwarf stem shape. In some cases, complete spike sterility is observed.

Damage to plant tissues by virions leads to the disruption of physiological processes, including photosynthesis and nutrient transport, making the crop susceptible to secondary infections.

The life cycle of the disease is closely related to the migratory activity of the leafhopper. The peak of infection in winter crops occurs during the "sprouting" stage — the beginning of tillering in the autumn.

Favorable conditions for the reproduction and active migration of the vector are a dry and warm autumn with moderate temperatures. This contributes to the rapid accumulation of infection in young crops.

The spread of the virus occurs in patches, which can merge over time with a high population density of insect vectors in the agrocenosis.

In the spring, secondary infection can occur after the overwintering of leafhoppers or their migration from hibernation sites to young spring crops at the seedling stage.

The winter period in the virus life cycle passes in the bodies of overwintering leafhoppers or in the tissues of perennial weeds, which ensures the survival of the infection until the next season.

The first symptoms appear as yellowing or reddening of the leaf tips, which gradually spread to the entire leaf blade.

A characteristic feature is a significant lag in plant growth compared to healthy specimens, causing the crops to appear sparse and uneven.

Affected plants show increased tillering, forming a large number of small, underdeveloped shoots that resemble a "brush" in shape.

• Yellowing of leaves in the early tillering phase.
• Shortened internodes and stunted appearance.
• Weak root system.
• Absence or deformation of the ear.
• Reduced grain weight in case of ear formation.

Symptoms are often mistaken for nitrogen deficiency or damage by root rot, so a laboratory PCR analysis is required for an accurate diagnosis.

The primary method of control is aimed at limiting the population density of the Psammotettix alienus leafhopper during critical crop development stages.

An important agronomic practice is the optimally late sowing date of winter wheat, which allows avoiding the peak migration of leafhoppers and reducing the risk of seedling infection.

Thorough control of weeds in fields and adjacent areas is necessary, as well as high-quality incorporation of volunteer cereals after harvest.

An effective protection method is seed treatment with systemic insecticides, which protect young seedlings from pests during the first 4–6 weeks of growth.

When the pest threshold is reached in the crops, it is advisable to carry out edge or broadcast treatments with insecticides from the pyrethroid or organophosphate groups.