Diaprepes root weevil

Scientific name

Diaprepes abbreviatus (Coleoptera: Curculionidae)

Other common names

sugarcane rootstalk borer, West Indian weevil

Similar species

larvae and pupae of the Fuller rose beetle, Naupactus cervinus

larvae of white-fringed weevil, Naupactus leucoloma

Distribution

United States: California, Florida, Puerto Rico, Louisiana, and Texas.

Worldwide: Dominican Republic, Jamaica, and the Lower Antilles.

Native to the Caribbean.

Diagnostic characteristics

Adults

• 0.95 - 1.90 cm (0.37 - 0.75 in.) in length.
• Numerous color forms including black with minute white, red-orange, yellow scales on the elytra. Scales wear off leaving the appearance of black stripes on the elytra.
• Hardened forewings (elytra) cover the abdomenabdomen:
  one of the three body segments in insects; the most posterior segment containing the heart, reproductive organs, and digestive organs
  .
• Clubbed (geniculate) antennae.

Larvae

• 10 or 11 larval instars.
• Up to 2.5 cm (1.0 in.) in length.
• White body with variable light and dark areas on the headhead:
  one of the three main body segments in insects; the anterior-most segment containing the many sensory structures including the eyes, antennae, and mouthparts
  capsule.
• Legless grubgrub:
  an immature stage in the life cycle of insects; larvae of beetles are often referred to as grubs
  .

Eggs

• 1.2 mm (0.05 in.) in length and 0.4 mm (0.02 in.) in width.
• Glistening and yellowish-white.
• Smooth and oblong.
• Clustered in between two leaves or inside a folded leaf.

Hosts

Citrus hosts

All Citrus species and their hybrids.

Non-citrus hosts

This pest has a very wide host rangehost range:
the range of species that a particular organism can feed on to achieve successful growth and reproduction
, attacking more than 270 species of plants in 59 plant families, many with economic significance as well as ornamentals and wild plants, including:

• all cruciferous vegetables, Brassica oleracea
• Acacia spp.
• Crotalaria spp.
• guava, Psidium guajava
• kumquat, Fortunella spp.
• oak, Quercus spp.
• papaya, Carica papaya
• potato, Solanum tuberosum
• strawberry, Fragaria spp.
• sugarcane, Saccharum spp.
• sweet potato, Ipomoea batatas

Host damage

Leaves

• Semi-circular notching by adult beetles is common but can resemble damage by caterpillars or grasshoppers.

Roots (and twigs)

• Primary damage is caused by larval feeding.
• Girdlinggirdling:
  removal of the bark, phloem, and cambium tissues around the entire circumference of the effected plant part (branch, root, or trunk) that results in the death of the wood beyond that point; characteristic damage inflicted by specific insects like beetle larvae
  may occur above ground.
• Tree death may occur by feeding from a single larva if the large laterallateral:
  with an orientation pertaining to the side
  roots or the crown area of the roots are damaged.
• Tunneling by the larvae can cause secondary infections by fungi or fungus-like organisms.

Biology

The female deposits a single layer of eggs in clusters of 30 - 260 eggs between two leaves or inside the folded edge of a leaf. The female weevil secretes a thick, gelatinous substance that glues the leaf edges together.

Newly-emerged, grub-like larvae drop from leaves to the soil surface and burrow into the soil and feed on small fibrous roots. As they moltmolt:
process of shedding the external skeleton during periods of growth; occurs between successive instars of a larva or nymph
, they burrow into larger roots. Larvae are unable to burrow into dry soil. Larval instars 3- 9 are the most aggressive feeders and may girdle the root system and kill the plant. The last two larval instars (10 and 11) feed very little, and enter a quiescent, pre-pupal period. The pupae remain in a pupal chamber in the soil for 15 - 30 days.

When adults emerge from the pupal chamber, they may walk on the soil surface, or fly a short distance. Adult weevils will not emerge from soil that is dry and compacted. Therefore, irrigation or rainfall promotes adult emergenceemergence:
used to describe the completion pupation that culminates in the appearance of the adult form of an insect
. The life cycle may extend from 5 -18 months depending upon the temperature and soil moisture. Adult weevils are capable of strong flight for a short duration and distance. They feed during the early morning and late afternoon, leaving scattered excrement on the leaves and hiding among the foliage during the day.

References

Grafton-Cardwell, E.E., K.E. Godfrey, J.E. Peña, C.W. McCoy , and R.F. Luck. Diaprepes Root Weevil, Pub. 8131. University of California, Division of Agriculture and Natural Resources (www.cdfa.ca.gov/phpps/PDEP/pdfs/Diaprepes.pdf).

Lapointe, S.L. and J. Shapiro. 1999. Development of Diaprepes abbreviatus. Effect of soil moisture on development of Diaprepes abbreviatus (Coleoptera: Curculionidae). Flor. Entomol. 82: 291-299. (http://www.fcla.edu/FlaEnt/fe82p291.pdf).

Texas Department of Agriculture. 2006. Citrus Root Weevil - Diaprepes abbreviatus. (http://www.agr.state.tx.us/agr/main_render/0,1968,1848_27455_0_0,00.html?channelId=27455).

Weissling, T.J., J.E. Peña, R.M. Giblin-Davis, and J.L. Knapp Jr. 2009. Featured creatures fact sheet: Diaprepes abbreviatus (Linnaeus) (Insecta: Coleoptera: Curculionidae). EENY-024. University of Florida. (http://edis.ifas.ufl.edu/in151).

Authors

Martin, K.W., J.A. Weeks, A.C. Hodges, and N.C. Leppla