Common stork’s-bill is an annual spring or winter dicotyledonous weed, whose seedlings appear in autumn and spring, mainly on sandy soils.

A characteristic feature of this species is the red coating on cotyledons and the first leaves.

It has a spindle-shaped, thin, whitish, branched root. Stem height ranges from 10 to 50 cm, branched at the base, erect, hairy, with reddish tinge at the bottom.

Cotyledons are ovate, heart-shaped at the base, with two, three, or four lobes, the lateral lobes rounded, 7-8 mm long. True leaves are pinnately divided with deeply incised segments, sessile, opposite or alternate. Inflorescence is an umbel on a long peduncle, consisting of lilac or pale purple flowers (upper flowers with a lighter or darker spot). The fruit is a five-part, spindle-shaped schizocarp, finely tuberculate, dark brown, golden hairy, with a beak. Seeds are cylindrical, elongated, smooth, reddish-brown in color.

Occurrence and harmfulness

Common stork’s-bill occurs mainly in cereal and root crops on sandy, acidic, clay soils.

Its harmfulness is due to the fact that it develops throughout the entire growing season, under almost all weather conditions.

Control

Mechanical method

The long period between planting and potato emergence is a critical period (ideal conditions for weed development), which can be used for mechanical treatments. These are carried out using machines available on the farm, e.g., hilling machines, light harrows, inter-row cultivators, etc. Their main task is to create the most favorable conditions for rapid weed germination, followed by their destruction through subsequent cultivation operations. Maximum effectiveness (over 90%) is achieved when weeds are at the seedling stage, but as weeds grow, effectiveness drops to around 40%. This system heavily depends on weather and soil conditions. In very wet springs, mechanical methods are difficult to implement. On heavily infested fields, it may even have the opposite effect, as damaged couchgrass rhizomes are stimulated to grow more vigorously. Additionally, the mechanical system is the most labor- and cost-intensive due to multiple passes. It is most often used in small farms for self-sufficiency and in organic systems. Before potato emergence, 3 to 6 treatments should be performed at 6-8 day intervals. After emergence, the number of cultivations should not exceed 2-3, as delays increase the risk of damage and spread of pathogens with sap, and may excessively dry the soil (especially light soils).

Mechanical-chemical method

The most effective and widely used weed control system. It allows savings on mechanical cultivation, which is used much less than in purely mechanical systems. After planting, hilling is performed two or three times, followed shortly before emergence by herbicide application, after which no further cultivation is performed. At this growth stage, identifying weed species can be difficult, so the treatment log kept by each professional user of plant protection products serves as the basis for herbicide application. It allows determining which weed species may pose a threat in a given field.

Chemical method

The most effective method is the use of herbicides, which for this species are most effective at the seedling stage; the more vigorous the growth, the lower the effectiveness. Herbicides in potatoes are applied in two main periods: before emergence and after emergence. Before using a herbicide, consult its label for information on timing and doses. Some active substances have medium effectiveness (average sensitivity of the species), so results may be unsatisfactory, especially in heavy infestations or advanced growth stages.

On heavily infested fields, a non-selective herbicide containing glyphosate can be applied, known as a simplified system. Its success depends on the presence of weeds, as glyphosate is absorbed only by leaves and cannot contact potato sprouts (they would be destroyed!). Even potato shoots just below the soil surface may be damaged (photo A, B). Adjusting application timing to weather, mainly temperature and rainfall, is crucial. Pre-emergence herbicides applied too late, when potato shoots are just below the soil surface, can be damaged by heavy rain. Some pre-emergence herbicides may also be applied in early potato growth (approx. 5 cm high), e.g., prosulfocarb + metribuzin.

Post-emergence herbicides should be applied no later than the row closure stage to ensure coverage of weeds and avoid accumulation of spray on potato plants. Due to long pre-harvest intervals, post-emergence herbicides cannot be used for early harvest!

Active substances for pre-emergence control of common stork’s-bill: linuron, with medium sensitivity to most active substances. Post-emergence: no active substances are effective against this species.

Compiled by: Dr. Eng. Janusz Urbanowicz