Which pathogens are commonly associated with pest issues?

The correct answer encompasses the primary types of microorganisms that lead to diseases affecting plants, animals, and humans. Bacteria, fungi, and viruses are well-recognized pathogens that can infiltrate various hosts, causing significant damage and contributing to pest problems in agricultural and environmental settings.

Bacteria, for instance, can lead to soft rot in crops or bacterial blight, resulting in reduced yields and quality. Fungi are responsible for various plant diseases such as rusts and molds that can severely impact plant health. Viruses can also affect crops, causing stunting and deformities, ultimately leading to economic losses.

The other options present categories that do not primarily consist of pathogens. Insects, rodents, and weeds are often considered pests but are not pathogens themselves; rather, they can be vectors for pathogens or compete with crops for resources. Similarly, while spiders, mycoplasmas, and snails have their own roles in ecosystems, they do not primarily categorize as pathogens in the context of pest issues. Lastly, predators, parasites, and birds are generally seen as biological control agents rather than being classified strictly as pathogens. Thus, the focus on bacteria, fungi, and viruses effectively highlights the agents responsible for diseases contributing to pest issues.