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SREF-FH-003 June 2016 woodwasp has not become a major The Sirex woodwasp, Sirex noctilio: pest in North America may be the Ecology, Potential Impact, and Management in the Southeastern U.S. many insects that are competitors or natural enemies. Some of these insects compete for resources AUTHORED BY: LAUREL J. HAAVIK AND DAVID R. COYLE (e.g. native woodwasps, bark and ambrosia beetles, and longhorned beetles) while others (e.g.parasitoids) are natural enemies and use Sirex woodwasp larvae as hosts. However, should the Sirex woodwasp arrive in the southeastern U.S., with its abundant pine plantations and areas of natural pine, this insect could easily be a major pest for the region. Researchers have monitored and tracked Sirex woodwasp populations since its discovery in North America. The most common detection tool is a flight intercept trap (Fig. 2a) baited with a synthetic chemical lure that consists of pine scents (70% α-pinene, 30% β-pinene) or actual pine branches (Fig. 2b). Woodwasps are attracted to the odors given off by the lure or cut pine branches, and as they fly toward the scent they collide with the sides of the trap and drop Figure 1. The high density of likely or confirmed pine (Pinus spp.) hosts of the Sirex woodwasp suggests the southeastern U.S. may be heavily impacted should this non-native insect become into the collection cup at the bottom. established in this region. The collection cup is usually filled with a liquid (e.g. propylene glycol) that acts as both a killing agent and Overview and Detection preservative that holds the insects until they are collected. While the The Sirex woodwasp (Sirex noctilio F.) is a large, non-stinging wasp that traps are somewhat effective, there is colonizes and kills stressed pine trees. This insect, originally from Eurasia, is still work to be done to improve our not considered a pest in its native range. However, it has become a major trapping methodology and efficiency. pest in some countries in the Southern Hemisphere (such as South Africa and Another monitoring technique is the Australia), where it was accidentally introduced. It has infested areas with use of a log cut from a live tree. This thousands of acres of planted pine in commercial plantations. So far, the Sirex log, left outside, attracts female Sirex woodwasp has not become a major pest in North America, and is found only woodwasps, who then lay eggs in in New York, Ohio, Pennsylvania, Michigan, Vermont, and Connecticut, and the the log. The log can then be placed Canadian provinces of Ontario and Quebec. However, considering the large in a cage, and adult woodwasps can amount of favorable habitat that exists in the southeastern U.S. (Fig. 1), great be captured and recorded as they potential for damage from the Sirex woodwasp exists. One reason the Sirex emerge from the log. www.southernforesthealth. 1 A B A C by a professional. Please see the A Host Trees “Resources” section at the end of this document for help in identifying a All hard pines in the southeastern local forest health professional. U.S. are either confirmed or likely hosts for the Sirex woodwasp (Table 1), which also rarely attacks Life Cycle fir, spruce, and larch15. This insect prefers pines with a diameter of 6” Development from egg to adult is 1-3 and larger, though it will attack trees years, but one year is expected in the <2” in diameter. Native pines in the B D southeastern U.S. Adults emerge in B southeastern U.S. appear to vary mid to late summer (July – August), in their susceptibility to the Sirex Figure 2. Panel intercept trap (available from only live for up to two weeks, and do Alpha Scents, Inc.: http://www.alphascents. woodwasp based on laboratory not feed – using their energy instead com/traps/traps.html) hung between two pine experiments2,6, and two pine species trees, equipped with a Sirex lure (blue bag, to reproduce13. Females drill tiny common in the Southeast – loblolly A; available from Contech Enterprises, Inc.: holes into the wood where they first https://www.contech-inc.com/) or bag of fresh and slash – are known hosts for the test the suitability of the tree (Fig. pine material (B) and collection cup (white) Sirex woodwasp in other parts of containing preservative (propylene glycol). Figure 3. Sirex woodwasp female (A, B) and male (C, D). 5). If the tree is suitable, females will the world. In some parts of Uruguay, deposit eggs, inject a toxic mucus, up to 70% damage was recorded and inoculate a symbiotic fungus. in some stands12. Thus, there is A C E G The mucus helps stress trees, while potential for widespread damage on Wasp Identifi- the fungus helps larvae digest and southeastern host trees. extract nutrients from the wood3,4,16. Adults have a black to metallic-blue Larvae can eat the fungus, and the head, black antennae, and range fungus also helps break down the Host Tree Con- from ½” – 1½” in length. Adult wood and make it easier for larvae females have black bodies with to digest. Sirex woodwasp larvae are The European woodwasp usually orange legs, and adult males are cream-colored, legless, and have a attacks trees that are already under B D F H mostly black with an orange band spine at the tip of the abdomen (Fig. some sort of stress. These stressors can across the abdomen, and black 6A). Larvae chew through the wood, include drought, poor management, hind legs (Fig. 3). All adults have a creating and enlarging meandering Figure 6. Sirex woodwasp larva (A) and competitive stand conditions (e.g. pointed spine-like projection (called a tunnels as they grow (Fig. 6B). Larvae damage (B). cornus) at the end of their abdomen. consume both wood and the fungus Females have another appendage at deposited by the female. Larvae Table 1. Host use by the European woodwasp on native pines in the southeastern U.S the end of their abdomen, called an overwinter inside their tunnels, ovipositor, which is used to drill into pupate in early summer, and exit trees Common name Scientific name Likely susceptibility? Confirmed as host? I K M wood to lay eggs. The southeastern as adults in mid- to late summer13. U.S. is home to several species of Loblolly pine Pinus taeda Very high Yes native woodwasps, many of which Shortleaf pine Pinus echinata High Yes look similar to the Sirex woodwasp Slash pine Pinus elliottii High Yes (Fig. 4). Even among individuals within a species, there can be a lot of Virginia pine Pinus virginiana High Yes variation in appearance and size. For Longleaf pine Pinus palustris Medium Yes instance, females of the woodwasp J L N Sirex nigricornis (Fig. 4M and N), Pitch pine Pinus rigida Medium Unknown which is native to North America, can Pond pine Pinus serotina Medium Unknown have a black or reddish abdomen, and males (which are uncommon, Sand pine Pinus clausa Medium Unknown and rarely captured in traps) may Spruce pine Pinus glabra Medium Unknown have a yellow stripe or entirely yellow abdomen. Because of these Table mountain pine Pinus pungens Medium Unknown Figure 4. Woodwasps similar in appearance to the Sirex woodwasp, Sirex noctilio: Sirex cyane- similarities with different species and Eastern white pine Pinus strobus Low Yes us female (A) and male (B), Eriotremex formosanus female (C) and male (D), Urocerus taxodii different color patterns, if you think female (E) and male (F), U. cressoni female (G) and male (H), U. albicornis female (I) and male (J), Tremex columba female (K) and male (L), and S. nigricornis female (M) and male (N). Erio- you’ve found a Sirex woodwasp, it is Figure 5. Dead female Sirex woodwasp with References: 6, 14, 15, and the USDA FS FHTET Steering Committee tremex formosanus, like S. noctilio, is not native to the U.S. very important to have it identified ovipositor stuck in the tree. (http://www.fs.fed.us/foresthealth/technology/pdfs/host_species_susceptibility.pdf) www.southernforesthealth. 2 www.southernforesthealth.net/ 3 suppressed or overtopped trees), emergence holes - both types of (Fig. 10) and potential competitors genetically inferior trees, or other pest holes overlap in size with emergence of native woodwasps, and experts infestations. Healthy, dominant pines holes of other insects, such as parasit- believe these insects may help, in are infrequently attacked, and very oids of woodwasps, and other wood part, to limit Sirex woodwasp popula- UNTHINNED THINNED infrequently killed 8,11. borers, who also tend to live in dead tions. Several parasitoid wasps native and dying trees and have a similar to North America attack the Sirex life cycle (i.e. immatures develop woodwasp5. In some cases, these Infestation Diagno- in wood, adults chew their way out parasitoids have caused substantial when they emerge). mortality to Sirex woodwasp popula- Affected trees can be identified by tions5, and would likely be important several characteristics. Often, the components of an integrated pest most noticeable is beads of resin Forest Manage- management program. Parasitic that run down the trunk of the tree nematode species have been ef- (Fig. 7). This is the tree’s response to The southeastern U.S. has many of fective in managing populations of females drilling into the tree to test the characteristics that make for ex- Sirex woodwasp in several Southern it for suitability. Once the eggs hatch cellent Sirex woodwasp habitat. Large Hemisphere countries and show and larvae start feeding in the wood, areas of preferred host trees (pines), some potential in North America10. needles begin to wilt and change to coupled with a mild climate and mul- These nematodes live in the tree and a yellowish, then reddish, color.

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