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Ministry of Agriculture, Food and Rural Affairs

hornworm

Hornworm larva Hornworm larva Hornworm larva Hornworm larva feeding Hornworm frass Click to enlarge.

Beginner

Scientific Name
          Manduca sexta (Tobacco hornworm)
          Manduca quinquemaculata (Tomato hornworm)

          and various other moths of the family Sphingidae

Identification
Larvae

  • Large, smooth, green to red caterpillars
  • Mature larvae measure 8 cm (3 ½ in.) in length
  • Seven or eight conspicuous white to orange v-shaped markings down each side
  • Prominent spike (horn) on its rear end
Injury
  • Entire leaves consumed, leaving petioles and stems bare

Often Confused With
N/A

Period of Activity
Hornworm larvae may be present in vineyards during the mid- to late summer. 

Scouting Notes
Hornworms are often difficult to see because of their protective colouring and because they feed on the interior of the plant during the day. At dusk they can be spotted on the outside of the plant. Look defoliation and large droppings (frass) on the ground beneath the vine.

Threshold
Hornworms are more of a concern in young vineyards with limited leaf area. Larger vines can usually tolerate some leaf area loss from their feeding.

Advanced

Scientific Name
           Manduca sexta (tobacco hornworm); Manduca quinquemaculata (tomato hornworm) and various other moths of the family Sphingidae


Identification
Larvae

  • Large, smooth, green to red caterpillars
  • Mature larvae measure 8 cm (3 ½ in.) in length
  • Seven or eight conspicuous white to orange v-shaped markings down each side
  • Prominent spike (horn) on its rear end
Injury
  • Entire leaves consumed, leaving petioles and stems bare

Often Confused With
N/A

Biology
Hornworms overwinter as pupae in the soil. The adult moth emerges in late spring. It lays eggs mainly on the underside of the grape leaf in early summer and larvae hatch 2 to 8 days later. The larva passes through 5 larval stages in 3 to 4 weeks. The fully grown larvae then burrow into the soil to pupate.

Period of Activity
Hornworm larvae may be present in vineyards during the mid- to late summer. 

Scouting Notes
Hornworms are often difficult to see because of their protective colouring and because they feed on the interior of the plant during the day. At dusk they can be spotted on the outside of the plant. Look defoliation and large droppings (frass) on the ground beneath the vine.

Threshold
Hornworms are more of a concern in young vineyards with limited leaf area. Larger vines can usually tolerate some leaf area loss from their feeding.

Management Notes
Although commercial vineyards are not usually damaged severely, small areas within a vineyard may have concentrated infestations and defoliation.  Insecticides applied for grape berry moth or leafhoppers should control eight-spotted forester as well.