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Pine Sawflies, Neodiprion spp. (Insecta: Hymenoptera: Diprionidae)

Wayne N. Dixon

The Featured Creatures collection provides in-depth profiles of insects, nematodes, arachnids and other organisms relevant to Florida. These profiles are intended for the use of interested laypersons with some knowledge of biology as well as academic audiences.

Introduction

Pine sawfly larvae, Neodiprion spp., are the most common defoliating insects of pine trees, Pinus spp., in Florida. Sawfly infestations can cause growth loss and mortality, especially when followed by secondary attack by bark and wood-boring beetles (Coleoptera: Buprestidae, Cerambycidae, Scolytidae). Trees of all ages are susceptible to sawfly defoliation (Barnard and Dixon 1983; Coppel and Benjamin 1965).

Figure 1. Larvae of the blackheaded pine sawfly, Neodiprion excitans Rohwer, on Pinus sp.
Figure 1.  Larvae of the blackheaded pine sawfly, Neodiprion excitans Rohwer, on Pinus sp.
Credit: Arnold T. Drooz, USDA Forest Service; www.forestryimages.org

 

Distribution

Neodiprion spp. are indigenous to Florida. Host tree specificity and location will bear on sawfly distribution statewide.

Description

Six species are covered here so there is some variation in appearance. However, an adult female has a length of 8 to 10 mm, with narrow antennae on the head and a stout and thick-waisted body. This is unlike most Hymenopteran insects which have the thinner, wasp-like waist. The background color varies from light to dark brown, with yellow-red-white markings common. The two pairs of wings are clear to light brown with prominent veins.

Figure 2. Adult female Neodiprion sp.
Figure 2.  Adult female Neodiprion sp.

 

Figure 3. Adult female redheaded pine sawfly, Neodiprion lecontei (Fitch).
Figure 3.  Adult female redheaded pine sawfly, Neodiprion lecontei (Fitch).
Credit: Lacy L. Hyche, Auburn University, www.forestryimages.org

Adult

The adult male has a length of 5 to 7 mm. The male has broad, feathery antennae on the head with a slender, thick-waisted body. It generally has brown to black color wings, similar to the female.

Figure 4. Adult male slash pine sawfly, Neodiprion merkeli Ross.
Figure 4.  Adult male slash pine sawfly, Neodiprion merkeli Ross.
Credit: G. Keith Douce, University of Georgia, www.forestryimages.org

 

Figure 5. Adults of the blackheaded pine sawfly, Neodiprion excitans Rohwer.
Figure 5.  Adults of the blackheaded pine sawfly, Neodiprion excitans Rohwer.
Credit: Gerald J. Lenhard, Louisiana State University, www.forestryimages.org

Egg

The egg is small (0.5 mm wide x 1.8 mm long), green-yellow-white color and ovoid.

Figure 6. Eggs of the redheaded pine sawfly, Neodiprion lecontei (Fitch), in pine needle.
Figure 6.  Eggs of the redheaded pine sawfly, Neodiprion lecontei (Fitch), in pine needle.
Credit: Lacy L. Hyche, Auburn University, www.forestryimages.org

Larva

The length of the mature larva is 18 to 25 mm with variable coloration (see Table 1).

Figure 7. Virginia pine sawfly larva.
Figure 7.  Virginia pine sawfly larva.
Credit: Georgia Forestry Commission

 

Figure 8. Slash pine sawfly larva.
Figure 8.  Slash pine sawfly larva.

 

Figure 9. Larvae of the redheaded pine sawfly, Neodiprion lecontei (Fitch).
Figure 9.  Larvae of the redheaded pine sawfly, Neodiprion lecontei (Fitch).
Credit: Ronald F. Billings, Texas Forest Service, www.forestryimages.org

 

Figure 10. Larvae of the blackheaded pine sawfly, Neodiprion excitans Rohwer.
Figure 10.  Larvae of the blackheaded pine sawfly, Neodiprion excitans Rohwer.
Credit: Ronald F. Billings, Texas Forest Service, www.forestryimages.org

Pupa

The pupa length is similar to that of the adult. The cocoon is light brown to dark reddish-brown, papery, and 3.5 to 6.0 mm wide x 7.1 to 10.0 mm long (Coppel and Benjamin 1965; Thatcher 1971; Wilkinson 1965).

Figure 11. Cocoon of the redheaded pine sawfly, Neodiprion lecontei (Fitch), on branch.
Figure 11.  Cocoon of the redheaded pine sawfly, Neodiprion lecontei (Fitch), on branch.
Credit: Jana Albers, Minnesota Department of Natural Resources, www.forestryimages.org

 

Figure 12. Adult of a dipteran parasitoid of the redheaded pine sawfly, Neodiprion lecontei (Fitch), emerging from a cocoon.
Figure 12.  Adult of a dipteran parasitoid of the redheaded pine sawfly, Neodiprion lecontei (Fitch), emerging from a cocoon.
Credit: Arnold T. Drooz, USDA Forest Service, www.forestryimages.org.

 

Figure 13. Cocoons of the blackheaded pine sawfly, Neodiprion excitans Rohwer, in bark crevices on truck.
Figure 13.  Cocoons of the blackheaded pine sawfly, Neodiprion excitans Rohwer, in bark crevices on truck.
Credit: Arnold T. Drooz, USDA Forest Service, www.forestryimages.org

 

Biology

Mature sawfly larvae spin cocoons in the duff or pine litter, mineral soil, or under bark scales. Adult sawflies emerge by removing a cap at one end of cocoon. After mating, female sawflies lay eggs in slits sawed in pine needles. Small larvae feed on outer needle tissues; larger larvae consume entire needles. Most species prefer older foliage, but all foliage is susceptible at the end of the growing season. Larval colonies may migrate from one tree to another, especially upon complete defoliation of the host tree or high feeding competition. The number of sawfly generations (one to four) varies from year to year and according to species. Larvae may diapause (a survival behavior for adverse conditions) for more than one year (Coppel and Benjamin 1965; Wilkinson 1980).

Figure 14. Cocoons of the blackheaded pine sawfly, Neodiprion excitans Rohwer. Adults have emerged from pupal cases with the ends of the cases missing. Openings in the sides of cases indicate the emergence of a parasite.
Figure 14.  Cocoons of the blackheaded pine sawfly, Neodiprion excitans Rohwer. Adults have emerged from pupal cases with the ends of the cases missing. Openings in the sides of cases indicate the emergence of a parasite.
Credit: Arnold T. Drooz, USDA Forest Service, www.forestryimages.org

 

Figure 15. Adult female redheaded pine sawfly, Neodiprion lecontei (Fitch), ovipositing on pine needle.
Figure 15.  Adult female redheaded pine sawfly, Neodiprion lecontei (Fitch), ovipositing on pine needle.
Credit: James McGraw, North Carolina State University, www.forestryimages.org

 

Hosts

All southern pines, Pinus spp., are susceptible to sawfly infestation.

Figure 16. Oviposition damage to pine needle by the blackheaded pine sawfly, Neodiprion excitans Rohwer.
Figure 16.  Oviposition damage to pine needle by the blackheaded pine sawfly, Neodiprion excitans Rohwer.
Credit: Arnold T. Drooz, USDA Forest Service, www.forestryimages.org

 

Figure 17. Typical straw-like feeding damage caused by the redheaded pine sawfly, Neodiprion lecontei (Fitch).
Figure 17.  Typical straw-like feeding damage caused by the redheaded pine sawfly, Neodiprion lecontei (Fitch).
Credit: G. Keith Douce, University of Georgia, www.forestryimages.org

 

Figure 18. Straw-like feeding injury caused by young larvae of the Virginia pine sawfly, Neodiprion pratti pratti (Dyar).
Figure 18.  Straw-like feeding injury caused by young larvae of the Virginia pine sawfly, Neodiprion pratti pratti (Dyar).
Credit: G. Keith Douce, University of Georgia, www.forestryimages.org

 

Figure 19. Severe pine defoliation caused by the Virginia pine sawfly, Neodiprion pratti pratti (Dyar).
Figure 19.  Severe pine defoliation caused by the Virginia pine sawfly, Neodiprion pratti pratti (Dyar).
Credit: Caleb L. Morris, Virginia Department of Forestry, www.forestryimages.org

 

Survey and Detection

Early damage is evidenced by reddish-brown straw like remains of needles that are incompletely consumed by young larvae; older larvae leave only short stubs. Partially defoliated branches often have a "bottle brush" appearance. Sawfly colonies may consist of a few to over a hundred individuals. Upon disturbance, larvae may drop from branches or assume a U-bend by raising head and abdomen. An oral exudate, which can paralyze insect parasitoids and repel predators, often accompanies such displays (Barnard and Dixon 1983; Coppel and Benjamin 1965).

Figure 20. Frass under tree resulting from feeding by larvae of the redheaded pine sawfly, Neodiprion lecontei (Fitch).
Figure 20.  Frass under tree resulting from feeding by larvae of the redheaded pine sawfly, Neodiprion lecontei (Fitch).
Credit: G. Keith Douce, University of Georgia, www.forestryimages.org

 

Management

Suppression of sawfly populations by insecticides is usually successful. However, consideration should be given to conserving natural enemies (small mammals, birds, insects) through minimal insecticide use and preservation of cypress-hardwood pond stands around pine plantations. The appearance of numerous dead larvae hanging from needles, i.e., virus-infected, usually signals the collapse of a sawfly outbreak. Sawfly outbreaks are cyclical—an eight-to-10-year interval is common. A fully stocked stand and promotion of early crown closure minimizes risk of sawfly damage in pine plantations (Wilkinson 1980).

Selected References

Atwood CE. 1961. Present status of the sawfly family Diprionidae (Hymenoptera) in Ontario. Proceedings of the Entomological Society of Ontario 91: 205–215.

Barnard EL, Dixon WN. 1983. Insects and diseases; important problems of Florida's forest and shade tree resources. Florida Department of Agriculture and Consumer Services, Division of Forestry Bulletin No. 196A. 123 pp.

Coppel HC, Benjamin DM. 1965. Bionomics of the Nearctic pine-feeding diprionids. Annual Review of Entomology 10: 69–96.

Thatcher RC. 1971. Spine sawfly, Neodiprion excitans Roh. U.S. Department of Agriculture. Forest Servive Pest Leaflet 105. 4 pp.

Wilkinson RC. 1965. Neodiprion merkeli from south Florida. Florida Entomologist 48: 271.

Wilkinson RC. 1980. Pine sawflies in Florida. In Forest pest management 12th spring symposium for the Florida section of the Society of American Foresters, 3–4 June 1980. University of Florida, Institute of Food and Agricultural Sciences Resources Report 7: 53–55.

Wilson LF. 1970. The red-headed pine sawfly. U.S. Department of Agriculture Forest Service Forest Pest Leaflet 14. 6 pp.

Table 1. 

Description of pine sawfly larvae, Neodiprion spp., in Florida.

Common Name

Species

Description

Host Trees1

slash pine sawfly

Neodiprion merkeli

Ross

Two-tone head (red above, black below); yellow-green body with two faint black stripes and a large black spot on hind end of each side

slash pine

redheaded pine sawfly

Neodiprion lecontei

Rohwer

Red head; whitish or yellowish green body with three rows of irregular black spots; large black spot on hind end of each side

longleaf pine,

slash pine

blackheaded pine sawfly

Neodiprion

excitans Rohwer

Shiny black head; olive-green body with two black stripes and row of black spots; large black spot on hind end of each side

loblolly pine,

pond pine,

sand pine,

spruce pine

Virginia pine sawfly

Neodiprion pratti

pratti (Dyar)

Black head; pale green body with two black stripes and a row of black spots on each side of the body

loblolly pine,

Choctawhatchee sand pine

a pine sawfly

Neodiprion

virginianus Ross

Black head; row of distinct, nearly square black spots on each side of the body

Ocala sand pine

spruce pine

Neodiprion warreni

Ross

Black head; two dark stripes on each side of the body

spruce pine

Abbot's sawfly

Neodiprion abbotii

(Leach)

Brown-black head with a white spot on the front; yellow to pale green body with two dark green stripes on each side of the body

loblolly pine,

longleaf pine,

shortleaf pine,

slash pine

 

1 Choctawhatchee sand pine = Pinus clausa var. immuginata D.B.Ward; loblolly pine = Pinus taeda L.; longleaf pine = Pinus palustris Mill.; Ocala sand pine = Pinus clausa var. clausa (Chapm.) Vasey; pond pine = Pinus serotina Michx.; shortleaf pine = Pinus echinata Mill.; slash pine = Pinus elliottii Engelm.; spruce pine = Pinus glabra Walt