Which pest is specifically known for causing damage to walnuts?

The pest specifically known for causing damage to walnuts is Rhagoletis completa, commonly referred to as the walnut husk fly. This pest is a significant concern for walnut growers as the larvae of the walnut husk fly feed on the developing fruit, leading to serious economic damage. The typical damage manifests as dark spots or holes on the surface of the walnuts, and can also result in premature drop or reduced quality of the nuts, both of which can negatively impact harvest yields.

In the context of walnut cultivation, effective management and control of Rhagoletis completa are vital for maintaining the health and productivity of walnut trees. Understanding its life cycle and habits can aid growers in implementing appropriate pest management strategies to mitigate the impact of this pest.

The other options listed pertain to different pests or issues. Scirtothrips perseae is primarily associated with avocado pests, Agrobacterium tumefaciens is a bacterium that causes crown gall disease in various plants, and Oligonychus perseae is related to spider mites that affect avocado rather than walnuts. Therefore, Rhagoletis completa is the most relevant and damaging pest to walnut crops.