This tool is part of the Citrus Resource

Citrus Pests

 

Northern citrus root weevil

 

Scientific name

 

Pachnaeus opalus (Coleoptera: Curculionidae)

Similar species

 

southern citrus root weevil, Pachnaeus litus

The southern citrus root weevil, Pachnaeus litus is found in southern Florida, but the distribution of the northern citrus root weevil and the southern citrus root weevil overlap in central Florida. The northern citrus root weevil and the southern citrus root weevil look almost identical, but the southern citrus root weevil has a visible notch on the pronotum, and the northern citrus root weevil has a smooth pronotal edge.

Distribution

 

United States: eastern United States.

Worldwide: Mexico.

Native to the eastern United States.

Diagnostic characteristics

 
Adults
  • Snout-like mouthparts.
  • Hardened forewings (elytra) cover the abdomen when at rest.
  • Bright blue-green, aqua, or gray in color.
  • Size of adults is 8.5 - 14 mm (0.33 - 0.55 in.) in length.
Larvae
  • White, grub-like insects with well-developed brownish-black chewing mouthparts.
  • Size ranges from 12.7 - 25.5 mm (0.5 - 1.0 in.) in length.
Eggs
  • Egg masses consist of 25 - 50 eggs.
  • Cylindrical.
  • Cream-colored to transparent.

Hosts

 
Citrus hosts

All Citrus species and their hybrids

Non-citrus hosts

Northern citrus root weevil has been identified on 27 different hosts in Florida with no particular affinities for certain plant families.

Host damage

 
Leaves
  • Eggs are laid in masses on mature leaves.
  • Leaves may be held together by a gelatinous substance which protects the eggs.
  • Eggs hatch in about 7 - 10 days.
  • Adults feeding on foliage result in marginal notching of leaves on young, tender shoots.
  • Leaf injury by adult weevils seems to be a minor problem only associated with young trees and has no apparent effect on mature trees.
Roots
  • Newly hatched larvae fall from the leaves and burrow into soil to feed on the roots of citrus trees.
  • Larval feeding results in a weakened and stressed tree.

Biology

 

A female lays about 4,000 eggs in her lifetime. Adults usually emerge from the ground mid-May through mid-July. Eggs are laid directly on the host plant foliage and hatch in 7 - 10 days, depending on the moisture level. Larvae drop to the ground to feed underground on the roots for about one year then pupate below ground. Throughout the year, adults can be found in the early morning and late afternoon but move deeper into the canopy during the day. An adult lifespan is 100 - 120 days.

References

 

Duncan, L.W., M.E. Rogers, C.W. McCoy, S.H. Futch, J.H. Graham, and H.N. Nigg. 2011. Florida Citrus Pest Management Guide: Citrus Root Weevils. University of Florida. (http://edis.ifas.ufl.edu/cg006).

Authors

 

Weeks, J.A., A.C. Hodges, and N.C. Leppla

 

Citrus Pests
Content last updated June, 2012
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