What is known to be a major cause for the breakdown of disease resistance in crops?

Repeated use of a single class of chemicals without variation is known to contribute significantly to the breakdown of disease resistance in crops. This practice exerts selective pressure on pathogens, allowing those individuals that are resistant to the applied chemicals to survive and reproduce. Over time, the population of the pathogen can shift, leading to a dominance of resistant strains. This phenomenon is commonly referred to as resistance development or resistance management, and it highlights the importance of employing integrated pest management strategies that include rotating different classes of chemicals and using various control methods.

In contrast, using diverse chemical treatments can help mitigate resistance by ensuring that pathogens are exposed to a range of modes of action. Infrequent crop rotation may also contribute to maintaining disease pressure, as certain pathogens can build up in the soil when the same crops are planted repeatedly. Planting only hybrid seeds might not directly cause resistance breakdown, but it limits diversity and potentially increases vulnerability to specific pathogens if those hybrids are not resistant to the same diseases. Thus, the choice of repeatedly using a single chemical class stands out as the key factor in fostering the breakdown of disease resistance in crop systems.