Watch out for glyphosate contamination

The repeated use of the herbicide glyphosate has been found to compromise fruit production. James Dick, co-owner of production consultancy DNS Crop Institute, spoke to Glenneis Kriel about this problem.

- Glenneis Kriel

FAST FACTS

The herbicide glyphosate can build up in the soil and plant tissues.

Glyphosate contamination is mostly a problem in clay soils with low acidity.

Symptoms of contamination are numerous, ranging from production decline to increased susceptibility to diseases.

Glyphosate is considered an indispensable weed-management tool for both fruit and grain producers. However, it has recently become associated with a number of problems in crop production.

James Dick, co-owner of DNS Crop Institute, says that in certain Grabouw orchards, he has noticed a decline in production, as well as chlorosis and retarded growth in the apical reaches of some trees. Individual trees in orchards growing in heavier soils also exhibit typical symptoms of trace element deficiency.

While the exact cause of these problems is complex and uncertain, Dick suspects that glyphosate might be a major contributing factor.

“Glyphosate was originally developed by Stauffer Chemical in the 1960s as a chelating agent, which means it can bond to metal elements such as iron, manganese, zinc, calcium, nickel and copper. Monsanto then patented it as a herbicide in 1974,” says Dick.

Glyphosate kills plants by blocking a critical enzyme pathway known as the shikimic acid pathway. The enzyme is essential for plant respiration, so a plant that receives a full dose of glyphosate cannot survive unless it is engineered or evolves to be resistant. Glyphosate also weakens a plant’s defences against infectious organisms.