Dr Gerhard H Verdoorn
CropLife South Africa
P
eople react fearfully when confronted with the
idea of pesticides. Commonly used products
such as paraquat (one of the best and most
unique herbicides in the world), deltamethrin
(one the most widely used pyrethroids) and imidacloprid (one of the neonicotinoids) are viewed with suspicion due to poisoning incidents or alleged impacts on
wildlife or carcinogenic potential. Meanwhile we all eat,
drink and live a merry life in a world full of chemicals
many of which are far scarier than pesticides.
The problem with public perception about pesticides is
that virtually no one understands the difference between hazard and risk. Hazard is clearly defined by the
pesticide label with the colour bands ranging from
green to red: Category IA is a red band and is highly
toxic, Category IB is also a red band and is toxic, Cate-
gory II is a yellow band is harmful, Category III is a blue
band and should be used with caution while the odd
Category IV is a green band and is practically non-toxic
under normal use circumstances. Anyone with basic understanding of hazard should be able to interpret these
categories. Using red band products require the utmost
care while using blue or green band product does not
require much more than basic safety precautions.
What is more important than the hazard is the risk
posed by pesticides and that is by no means clearly defined by any insignia on labels or products. It requires
an understanding of the toxicology, hazard classification, application procedure, target and environmental
considerations to be able to assign a particular risk to a
particular pesticide. In order to illustrate this concept of
risk, let us look at paraquat.
Some herbicides that are of very low hazard pose a very high risk to trees.