Several species of weevils feed on amaranth. Adult weevils feed on leaves, but the larvae (grubs) are more damaging because they bore into roots and stems, causing rotting and potentially lodging and predisposition to diseases. Stem-boring weevils such as the pigweed weevil (Hypolixus haerens) are the most damaging causing plants to wither and lodge. The adult weevil lays its eggs in branch crotches, and the larvae bore through stems to the root collar hollowing the stems. Feeding by larvae results in stems that are more susceptible to wind breakage, thus increasing crop losses. The larvae pupate in the stem.
In South Africa, attack by this weevil has been associated with extensive tissue discolouration, decay and cankers in branches, stems, and root collars of Amaranthus hybridus. This weevil has been found to be associated with fungi (mainly Fusarium spp) that cause tissue decay and a canker disease (Blodgett et al., 2004).
- Uproot and destroy attacked plants to reduce number of weevils and prevent damage to healthy plants.