• Topics: Entomology and Nematology  | Pine Pest Insects  |  Featured Creatures collection  | Family: Diprionidae (conifer sawflies)  | Dixon, Wayne N 

Pine Sawflies, Neodiprion spp. (Insecta: Hymenoptera: Diprionidae)¹

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.

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 3. 

Adult female redheaded pine sawfly, Neodiprion lecontei (Fitch).

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 5. 

Adults of the blackheaded pine sawfly, Neodiprion excitans Rohwer.

Egg are 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.

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

Figure 7. 

Virginia pine sawfly larva.

Figure 8. 

Slash pine sawfly larva.

Figure 9. 

Larvae of the redheaded pine sawfly, Neodiprion lecontei (Fitch).

Figure 10. 

Larvae of the blackheaded pine sawfly, Neodiprion excitans Rohwer.

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 12. 

Adult of the redheaded pine sawfly, Neodiprion lecontei (fitch), emerging from a cocoon.

Figure 13. 

Cocoons of the blackheaded pine sawfly, Neodiprion excitans Rohwer, in bark crevices on truck.

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 end of 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 15. 

Adult female redheaded pine sawfly, Neodiprion lecontei (Fitch), ovipositing on pine needle.

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 17. 

Typical straw-like feeding damage caused by the redheaded pine sawfly, Neodiprion lecontei (Fitch).

Figure 18. 

Straw-like feeding injury caused by young larvae of the Virginia pine sawfly, Neodiprion pratti pratti (Dyar).

Figure 19. 

Severe pine defoliation caused by the Virginia pine sawfly, Neodiprion pratti pratti (Dyar).

Survey and Detection

Early damage is evidenced by reddish-brown strawlike 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 insectan parasites 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).

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).

For more management information see: Insect Management Guide for Forest and Shade Trees (http://edis.ifas.ufl.edu/TOPIC_GUIDE_IG_ Forest_and_Shade_Trees)

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 p.

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 p.

Wilkinson RC. 1965. Neodiprion merkeli from south Florida. Florida Entomologist 48: 27l.

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 p.

Tables

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other extension publications, contact your county Cooperative Extension service.

U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Millie Ferrer-Chancy, Interim Dean.

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