Which of the following is NOT a factor in root attacks on plants?

To understand why fungus is the correct answer as not being a factor in root attacks on plants, it is important to clarify the types of organisms typically involved in this type of damage. Root attacks generally refer to direct physical damage or feeding on the root system of plants.

Aphids are known mainly as foliar pests that suck sap from the leaves; however, they can lead to indirect damage to root systems by causing stress to the plant and leading to secondary infections. Nematodes are microscopic worms that specifically target plant roots and can cause significant damage through feeding, leading to root decay and reduced plant vigor. Grubs, which are larvae of certain beetles, can also damage plant roots as they feed on organic material and roots in the soil.

In contrast, fungus does not typically attack roots directly in the manner described. While some fungi can be pathogenic and lead to root rot diseases, they do not directly feed on roots like the other organisms listed. Instead, they may colonize dead organic matter or affect roots through secondary infection processes. Thus, the association with direct attack on roots is not accurate in the context of the other pests listed.

Understanding the roles of these different organisms helps in effective pest management and injury prevention strategies in lawn and ornamental plants