Neodiprion mundus
- French common name: Neodiprion mundus
- Scientific name: Neodiprion mundus Rohwer
- Kingdom: Animalia
- Phylum: Arthropoda
- Class: Insecta
- Order: Hymenoptera
- Family: Diprionidae
General information and importance
Neodiprion mundus is native to western North America. It rarely occurs at high enough population levels to be destructive. It feeds exclusively on all ages of ponderosa pine (Pinus ponderosa).
The common name ‘sawfly’ refers to the female adult’s saw-like ovipositor, which she uses to cut slits in the foliage of the host tree and deposit her eggs. Unfertilized eggs become males. Adult sawflies resemble their winged bee and wasp relatives with membranous wings. They differ with a broader “waist” between the thorax and abdomen.
Distribution and hosts
Neodiprion mundus is found throughout the range of its primary host, ponderosa pine, from the southern interior of British Columbia south to California.
Tree parts affected
Feeds on previous years’ (old) needles.
Symptoms and signs
Sawfly larvae are superficially similar in appearance to the larvae of moths and butterflies (caterpillars). Both groups have three pairs of segmented legs on their thorax and a variable number of unsegmented prolegs, or fleshy leg-like protuberances, on the bottom of their abdominal segments. Sawfly larvae have either no prolegs or six or more pairs on their abdominal segments. Caterpillars have five or fewer pairs of prolegs. Significant variation and overlap in the appearance of related sawfly species makes identification challenging unless the characteristics of several life stages can be observed.
Neodiprion mundus feeds openly in colonies. If disturbed, they raise their heads together in a defensive posture and may regurgitate fluid. Larvae consume old (previous years’) needles, causing fresh needles on the ends of the shoots to appear unharmed. Eggs may be observed in slits cut into the edges of pine needles in autumn and throughout winter. Neodiprion mundus is the largest of several sawflies that might be found on ponderosa pine trees. Mature larvae can be up to 24 millimetres in length. The brown or black head of the larvae is unmarked, and it has been reported that it can transition to a red colour in the next to last larval stage. The larval body is greyish green, with a light grey stripe on the middle of its back (middorsal) and a broad greenish grey stripe on either side (addorsal). Toward the bottom of its body, it has a light grey stripe, a dark greenish grey stripe, and a light grey stripe.
Life cycle
There is one generation per year. Eggs are placed in slits cut into the edges of pine needles by adult females in late summer. Eggs are separated by less than the length of the egg slit. The insect overwinters in the egg stage. It is likely that some embryonic development occurs before winter. Larvae hatch in May and feed until late June to early July. Mature larvae drop to the soil beneath the tree and spin a cocoon. The females produce larger cocoons than males. Adults emerge from late July to August.
Damage
Neodipirion mundus is common but rarely reaches damaging densities. Moreover, it only feeds on previous years’ foliage, so total defoliation does not occur. Localized outbreaks have been reported but are infrequent.
Prevention and management
Populations of this sawfly rarely cause significant damage. However, in some cases, shoots may become sparsely (not totally) denuded. Colonies can be removed by hand from smaller, individual trees in landscape settings.
Pest management strategies for a particular pest vary depending on several factors. These include:
- the population level of the pest (i.e., how numerous the pest is on the affected host[s]);
- the expected damage or other negative consequences of the pest’s activity and population level (either to the host, property, or the environment);
- an understanding of the pest’s life cycle, its various life stages, and the various natural or abiotic agents that affect population levels;
- how many individual host specimens are affected (an individual tree, small groups of trees, plantations, forests);
- the value of the host(s) versus the costs of pest management approaches; and
- consideration of the various silvicultural, mechanical, chemical, biological, and natural control approaches available and their various advantages and disadvantages.
Decisions about pest management strategies require information about each of these factors for informed decision-making. These various factors should then be weighed carefully in terms of costs and benefits before action is taken against any particular pest.
Pesticides registered for use against Neodiprion mundus under specific situations may change from year to year. Therefore, please search Health Canada’s Pesticide Product Information Database for currently registered pesticides and product information for use against this insect. The application of any registered product should be based on population size and applied only when necessary and against the approved life stage. It is also recommended to consult a local tree care professional. Pesticides may be toxic to humans, animals, birds, fish, and other beneficial insects. Apply registered products only as necessary and follow all directions and precautions noted on the manufacturer’s label. In some jurisdictions and situations, only a licensed professional can apply pesticides. Consulting relevant local authorities to determine local regulations that are in place is recommended.
Photos
Mature larvae feeding on ponderosa pine needle
Penultimate instar larvae feeding on ponderosa pine needle
Dion Manastyrski Centre de foresterie du Pacifique, Victoria (Colombie-Britannique) / Pacific Forestry Centre, Victoria, British Columbia
Dion Manastyrski Centre de foresterie du Pacifique, Victoria (Colombie-Britannique) / Pacific Forestry Centre, Victoria, British Columbia
Dion Manastyrski Centre de foresterie du Pacifique, Victoria (Colombie-Britannique) / Pacific Forestry Centre, Victoria, British Columbia
Selected references
Ciesla, W.M.; Smith, D.R. 2011. Diprionid sawflies on lodgepole and Ponderosa pines. United States Department of Agriculture, Forest Service, Pacific Northwest Region (R6). Portland, Oregon. Forest Insect & Disease Leaflet 179. 12 p.
Dahlsten, D.L. 1966. Some biological attributes of sawflies in the Neodiprion fulviceps complex in a brushfield pine plantation. The Canadian Entomologist 98(10): 1055–1083. https://doi.org/10.4039/Ent981055-10
Duncan, R.W. 2006. Conifer defoliators of British Columbia. Natural Resources Canada, Canadian Forest Service, Pacific Forestry Centre. Victoria, British Columbia. 359 p.
Ross, H.H. 1955. The taxonomy and evolution of the sawfly genus Neodiprion. Forest Science 1: 196–209.
Wallace, D.R; Cunningham, J.C. 1996. Diprionid sawflies. Pages 193–232 in J.A. Armstrong; W.G.H. Ives, editors. Forest insect pests in Canada. Natural Resources Canada, Canadian Forest Service, Science and Sustainable Development Directorate. Ottawa, Ontario.