Viral Control

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A) Baculovirus particles, or polyhedra; B) Cross-section of a polyhedron; C) Diagram of polyhedron cross-section. Electron micrographs (A&B) by Jean Adams, graphic © by V. D'Amico.

Background

Insect-specific viruses can be highly effective natural controls of several caterpillar pest. Baculoviruses are pathogens that attack insects and other Arthropods. The viruses are extremely small (less than a thousandth of a millimeter across) and are composed of DNA that codes for genes needed for the virus to replicate. Since the genetic information is easily destroyed by exposure to sunlight an ineffective virion is protected by a protein coat called a polyhedron. (see image) They are obligate parasites so they have to be in a host to reproduce. Most Baculoviruses must be eaten by the host to produce a fatal infection.

Habitat

Any crop or habitat effected by caterpillars. See table one.

CROP
INSECT PEST
VIRUS USED

Apple, pear, walnut and plum

Codling moth

Codling moth granulosis virus

Cabbage, tomatoes, cotton, (and see pests in next column)

Cabbage moth, American bollworm, diamondback moth, potato tuber moth, and grape berry moth

Cabbage army worm nuclear polyhedrosis virus

Cotton, corn, tomatoes

Spodoptera littoralis

Spodoptera littoralis nuclear polyhedrosis virus

Cotton and vegetables

Tobacco budworm Helicoverpa zea, and Cotton bollworm Heliothis virescens

Helicoverpa zea nuclear polyhedrosis virus

Vegetable crops, greenhouse flowers

Beet armyworm (Spodoptera exigua)

Spodoptera exigua nuclear polyhedrosis virus

Vegetables

Celery looper (Anagrapha falcifera)

Anagrapha falcifera nuclear polyhedrosis virus

Alfalfa and other crops

Alfalfa looper (Autographa californica)

Autographa californica nuclear polyhedrosis virus

Forest Habitat, Lumber

Douglas fir tussock moth (Orgyia psuedotsugata)

Orgyia psuedotsugata nuclear polyhedrosis virus

Forest Habitat, Lumber

Gypsy moth
(Lymantria dispar)

Lymantria dispar nuclear polyhedrosis virus
Tabel One

Left: Cabbage looper larva killed by nuclear polyhedrosis virus. J.Ogrodnick

Right: Imported cabbageworm infected with granulosis virus (above) and healthy (below). J.Ogrodnick

Pest controlled

Viruses can affect a large number of pest species. However, they are extremely specific in the pest they can control. See table one.

Representative baculovirus life cycle. Graphic by V. D'Amico.

How it works

After being ingested, the virus inter the insects body through the gut. They replicate and can disrupt components of an insect's physiological functions, interfere with the insects feeding and egg laying and movement. After the insect dies, it will dissolve and leave viral particles on the foliage for other insects to consume.

Virus-killed caterpillar.Photo by Roger T. Zerillo.Animation by Vince D'Amico

Effectiveness

  • In microbial insecticide trials in Maryland using viral against, the viral agents proved as effective as the bacterial agent (Bacillus thuringiensis).
  • Trials on cole crops in New York yielded results equivalent to applications of chemical insecticides.
Negatives
  • The viral applications may be deactivated in sunlight and may be effective for only a few days after application
  • Very specific host damage
  • Cost of commercial production for broader host targets
Positives
  • Very specific host damage
  • No negative impact on plant, mammals, birds, fish, or even beneficial insects (important when used in an IPM program)
  • Viruses can be stored frozen for many years

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© 2000 Julie Vidic, Dan Shields and Bryan Pennix. All Rights Reserved, except for the images, which retain their own copyrights.
This site was designed by Julie Vidic, Dan Shields and Bryan Pennix for MBI 699.W in August of 2000.