Fallopia convolvulus (black bindweed)

Cultural Control

According to Holm et al. (1991), tillage implements and rotations have only limited success in controlling F. convolvulus because of its large seedbank, the ability of seeds to emerge from great depth, the persistent emergence of new seedlings throughout the growing season and the large quantities of seeds produced by the plants.

Nevertheless, there are several methods suggested which could be used to reduce possible yield losses caused by this weed. Koch (1964) observed a stimulation in emergence of F. convolvulus by harrowing, which could be taken advantage of in the control of this weed in cereal cultivation. Gruenhagen and Nalewaja (1969) and Messersmith and Nalewaja (1969) stated that higher seeding rates of the crop result in a reduction of relative yield losses through competition of F. convolvulus in wheat or flax. Moreover, Smith (1980) found out that a significant reduction of F. convolvulus could be attained by discing after barley harvest.

Different results have been published regarding the effects of tillage techniques as a means for weed control. Thompson et al. (1984) and Dessaint et al. (1993) concluded that no-tillage cultivation or reduced tillage resulted in increasing densities of F. convolvulus in comparison to conventional tillage, whereas Hoffman-Kakol et al. (1982) observed a reduction in the relative abundance of F. convolvulus in directly drilled maize after rye. Nielsen and Pinnerup (1982) also reported a decline in F. convolvulus populations caused by reduced cultivation in spring barley.

Although effective for the control of other weeds, harrowing in the dark showed no significant influence on emergence of F. convolvulus seedlings in comparison to daylight harrowing in Swedish field trials (Ascard, 1992).

According to Rajczyova (1978), monocultures of winter wheat and spring barley lead to an increase in F. convolvulus incidence.

Biological Control

Adkins and Sowerby (1996) revealed that the weed Parthenium hysterophorus has allelopathic potential against P. covolvulus. They used leachate from the leaves of P. hysterophorus to depress germination and seedling growth of F. convolvulus and several other weeds.

In a search for potential biological control agents for weeds, species of Botrytis were isolated from seedlings of F. convolvulus infected with pathogenic fungi in Canada (Mortensen and Molloy, 1993). In Argentina, the fungus Puccinia polygoni-amphibii was found to cause sufficient damage to warrant investigation as a biocontrol agent against F. convolvulus (Dal-Bello and Carranza, 1995).

F. convolvulus can reduce crop yields by competition, especially in highly infested fields (Friesen and Shebeski, 1960; Nakoneshny and Friesen, 1961; Dosland and Arnold, 1966; Fabricius and Nalewaja, 1968). Friesen and Shebeski (1960) showed that 56 and 210 plants per m² can reduce wheat yields by 15 and 25%, respectively. Crop seed weight and protein contents can also be negatively affected (Nakoneshny and Friesen, 1961; Gruenhagen and Nalewaja, 1969).

By climbing up the crop, F. convolvulus causes lodging in grain crops (Neururer, 1961; Hume et al., 1983), and can cause harvesting problems when its vines wrap around moving parts of machinery (Forsberg and Best, 1964; Fabricius and Nalewaja, 1968).

In addition, high weed densities can raise the moisture content of harvested grain (Neururer, 1961) and contribute to heating in storage when harvested with cereals as a seed contaminant (Holm et al., 1991). F. convolvulus produces large amounts of seed and they are often difficult to separate from grain crops, because of their similar size. Therefore, F. convolvulus is a serious contaminant of seed stocks in several places in the world (Gooch, 1963; Bogdan, 1965).

The general importance of this weed is due to its ability to emerge throughout the growing season. Forsberg and Best (1964) showed that late-emerging seedlings are likely to escape herbicide spraying and could be a potential source of re-infestations, especially where competition from other weeds has been eliminated.

Furthermore, F. convolvulus may serve as an alternate host for disease organisms affecting crops (Cooper and Harrison, 1973; Bendixen et al., 1979).

According to Holm et al. (1991), F. convolvulus is ranked as a principal or serious weed in 20 crops of 41 countries. It is one of the most important weeds of cereals in Argentina, Canada, Kenya, South Africa and the USA; maize in the former Soviet Union; and sugarbeet in Spain. It is a principal weed of cereals in Argentina, Australia, Canada, UK, Finland, New Zealand, Tanzania, and the USA; maize in Italy; flax in Australia, Brazil, Canada, and the USA; potatoes in Chile; sugarbeet in former Czechoslovakia, UK and Germany; beans in England; vegetables in Argentina, Bulgaria, Chile, UK and New Zealand; peas in Bulgaria and New Zealand; onions in Argentina and UK; and sorghum in Italy.