Recently, I was asked to comment on the merits of allelopathy as a factor in crop production.

According to Ferguson and Rathinasabapathi, “allelopathy refers to the beneficial or harmful effects of one plant on another plant, both crop and weed species, by the release of chemicals from plant parts by leaching, root exudation, volatilization, residue decomposition and other processes in both natural and agricultural systems.”

First, some definitions that relate to allelopathy.

• Allelochemical–in this case, a toxic chemical produced by a plant


• Phytochemical–a chemical compound that occurs naturally in a plant


• Phytotoxic--poisonous to plants


• Toxicity–the negative effect of a substance on a plant


• Synthetic herbicide–herbicides formed through a chemical process or chemical synthesis

With the continuing, increasing occurrence of herbicide-resistant (HR) weeds in agricultural systems, there is renewed interest in determining how/if allelopathy might be used as a possible option in weed control systems.

Allelopathic effects can be and have been measured in controlled environment settings such as a laboratory or greenhouse, but replicating the effects in the field has been and continues to be difficult.

Research has left little doubt that the presence of a phytochemical that is toxic to plants of another species will have an adverse effect on those plants. However, equating the toxicity of the phytochemical to its availability and effect in the natural environment of the target plant species is often not accomplished.

According to Colquhoun, effective demonstration of allelopathy on plant growth and development and its reliable application in agricultural pest management have been minimal. The use of allelopathic cover crops such as rye has resulted in the greatest application of allelopathy in agriculture.

Very little is known about the mode of action of allelochemicals or how plants of a particular species avoid reputed allelochemical effects in a natural setting. Even though there is a growing body of literature that implicates allelopathy in plant to plant relationships/interactions in a natural agricultural setting, the translation of this knowledge into its use or place in managing weeds in agricultural production systems has been slow.

The study of allelopathy and discerning its importance for agricultural production systems will only be advanced if current and forthcoming research results can be translated into new technologies that can be used for weed management and/or reduced dependence on synthetic herbicides.

Composed by Larry G. Heatherly, Oct. 2012, larryheatherly@bellsouth.net