Which methods are listed as types of chemical control of disease?

• A. Soil fumigation; Spray (chlorothalonil, maneb)
• B. Biological control; Cultural control
• C. Mechanical pruning; Varnishing
• D. Solar sterilization; Heat treatment

Answer: (A)

The main idea is recognizing chemical methods used to control disease, meaning applying chemical agents to prevent or manage infections. Soil fumigation is a chemical approach because it uses volatile chemicals applied to the soil to reduce or eliminate soil-borne pathogens before or during crop production. The spray example with chlorothalonil and maneb shows chemical fungicides applied to plant surfaces to guard against fungal diseases. Together, these illustrate how chemicals are used either in soil or as sprays to combat disease.

The other options represent non-chemical strategies: biological control relies on living organisms to suppress disease, cultural control uses management practices to reduce risk, mechanical pruning is a physical removal method, and solar sterilization or heat treatment are physical/thermal approaches.