Do Grubs Eat Orange Tree Roots?

Pest Identification

• All varieties of citrus, including orange trees, are prone to infestation from the newly hatching larvae or grubs of the diaprepes root weevils. The pests infest over 270 different plant species from 59 plant families. Citrus trees are among the more common hosts. During her lifespan of about 147 days, the adult female lays nearly 5,000 eggs that hatch within a week to 10 days.

Damage

• The grubs of the diaprepes root weevil damage roots extensively as they feed on not only the roots and tubers but also any other underground portions of infested plants. The grubs start their feeding from the smallest roots of orange and other citrus trees. As the grubs grow larger in size, they move to larger root areas. Damage eventually girdles all the lateral roots or the trees' crown areas.

Symptoms

• Common symptoms of diaprepes root weevil grubs feeding on plants include wilting and discoloration of foliage. Eventual defoliation of trees follows. Orange and other citrus trees frequently do not reveal any symptoms of the pest until the roots have been heavily damaged. Orange trees growing in poorly drained soil are more prone to infestation. Damaged trees are also more likely to be infected with root rot Phytophthora fungi.

Control

• Keep tree roots in good health with timely fertilization and adequate watering. Plant trees in well-drained soil and avoid overwatering, as wet soil promotes infestations. The use of parasites Aprostocetus vaquitarum and Quadrastichus haitiensis are among the biological control option for the pests. Insecticides are only minimally effective, as the grubs are well insulated from the chemicals in the soil.