pests and diseases

Image credit incomdirect.com ZIMSEC O Level Combined Science Notes: Pesticide Warning Symbols

• Pesticides are graded according to their toxicity i.e.
• According to how harmful they are to humans.
• Every pesticide must have a label that clearly shows its “danger” level show.
• There are four common danger levels of chemicals.

Purple […]

A grasshopper. Image credit nutrainigridients.com ZIMSEC O Level Combined Science Notes: Plant pests and diseases

• In the wild there is a balance in nature.
• The are few pests and diseases that destroy plants.
• In crop plants there are more pests that cause and spread disease.
• This is because there […]
  

Safe use of chemicals. Image credit montana.edu ZIMSEC Combined Science Notes: Safety when using chemicals

• Pesticides are almost always harmful to human beings.
• They are graded according to their level of toxicity i.e. how dangerous they are to humans.
• There are no safe pesticides all are […]