Southern citrus root weevil

Scientific name

Pachnaeus litus (Coleoptera: Curculionidae)

Other common names

southern blue-green citrus weevil

Similar species

northern citrus root weevil, Pachnaeus opalus

The northern citrus root weevil is found in northern Florida, but the ranges of the southern citrus root weevil and the northern citrus root weevil overlap in central Florida. The southern citrus root weevil and the northern citrus root weevil look almost identical to the untrained eye, but the southern citrus root weevil has a visible notch on the pronotumpronotum:
the dorsal surface of the first thoracic segment
, and the northern citrus root weevil has a smooth pronotal edge.

The egg masses of the southern citrus root weevil are indistinguishable from Diaprepes root weevils, which are considered a major pest. The southern citrus root weevil and the Diaprepes root weevil distributions overlap in southern Florida.

Distribution

United States: southern and central Florida.

Worldwide: Mexico.

Native to Florida and Mexico.

Diagnostic characteristics

Adults

• Snout-like mouthparts.
• Hardened forewings (elytra) that cover the abdomenabdomen:
  one of the three body segments in insects; the most posterior segment containing the heart, reproductive organs, and digestive organs
  when at rest.
• Bright blue-green, aqua, or grey 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.
• Can range in size 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 translucent.

Hosts

Citrus hosts

All Citrus species and their hybrids.

Non-citrus hosts

The southern citrus root weevil has 70 known host plants.

Host damage

Leaves

• Adult feeding on foliage results in marginal notching of leaves on young, tender shoots.
• Eggs are laid in masses on mature leaves.
• Leaves may be stuck together because egg masses contain a gelatinous substance which protects the eggs.

Roots

• Newly hatched larvae fall from the leaves and burrow into soil to feed on roots.
• 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 planthost plant:
the plant the provides sustenance for an insect
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 canopycanopy:
referring to the crown of a tree that includes the leaves, stems, and branches
during the day. An adult lifespan is 100 - 120 days.

Comments

The southern citrus root weevil is a native species that is considered to be a minor pest.

References

Weathersbee III, A.A., R.C. Bullock, T.D. Panchal, and P.M. Dang. 2003. Differentiation of Diaprepes abbreviatus and Pachnaeus litus (Coleoptera: Curculionidae) egg masses: PCR-restriction fragment-length polymorphism and species-specific PRC amplification of 18S rDNA products. Ann. Entomol. Soc. Am. 96(5): 637- 642. (http://ddr.nal.usda.gov/bitstream/10113/14521/1/IND43735402.pdf).

Futch, S.H., C.W. McCoy, J.H. Graham, L.W. Duncan, and H.N. Nigg. 2005. Field diagnosis of citrus weevil damage. Publication HS-1014. Horticultural Sciences Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. (http://edis.ifas.ufl.edu/hs260).

Authors

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