Chemical Type Active ingredient Application rate Pre-harvest interval (days) A Herbicide Glyphosate 3 litres per hectare Not applicable B Fungicide Mancozeb...

(a) The chemical the farmer should choose to treat a fungal disease on vegetables is Chemical B (Mancozeb), because it is a fungicide. [1] Chemical A is a herbicide (used to kill weeds, not treat disease), and Chemical C is an insecticide (used against insect pests). Only a fungicide targets fungal pathogens.

(b) Protective equipment the farmer should wear when handling any of these chemicals includes (any two): [2]

1. Rubber gloves to protect the hands from chemical absorption through the skin. [1]
2. A face shield or goggles to prevent splashes reaching the eyes. [1]

Other acceptable items include waterproof overalls or an apron and rubber boots.

(c) Chemical A (Glyphosate) is a herbicide, meaning it kills plants. [1] If applied to the vegetable crop at flowering stage, it would damage or kill the crop plants because glyphosate is non-selective and does not distinguish between weeds and crop plants. [1] This is why the pre-harvest interval for Chemical A is listed as "Not applicable" - it is intended for use on land before planting or on weeds away from the crop, not on a growing crop.

(d) The pre-harvest interval (PHI) ensures that the chemical has broken down or degraded to a level safe for human consumption before the crop is harvested and eaten. [1] Different chemicals have different rates of breakdown depending on their chemical stability and persistence in plant tissues, so each chemical requires its own specific waiting period. [1] Chemical C (Dimethoate) has the longest interval at 21 days because it is more persistent and breaks down more slowly than Chemical B (14 days), meaning it takes longer to reach safe residue levels. [1]