Zimmerman Pine Moth Biology and Management RICHARD S. COWLES, VALLEY LABORATORY, CONNECTICUT AGRICULTURAL EXPERIMENT STATION Zimmerman pine moth (ZPM or a close christmas-trees/information/pest-fact- Connecticut moths. The closest match relative) has been found feeding on sheets/zimmerman-pine-moth), these (only one of the 516 nucleotides in the main stems of true firs (Abies spp.) in articles have focused on damage by sequence differed) was from a Michigan and Wisconsin (Jill O’Donnell, ZPM to two-needle pines, such as D. cambiicola specimen collected from personal communication). This damage Scotch and Austrian pines, and make British Columbia. It is easy to see how appears similar to damage on the main no mention of damage to the trunks of larvae feeding under the bark could stem of Douglas-firs throughout southern Douglas-fir trees. The uncertainty have been transported with asymptomatic New England that made trees unsaleable regarding the identity of the insect is nursery stock from the Pacific Northwest (Fig. 1). These cankers, when extensive caused by the great diversity of similar, to New England, where they completed enough, cause the tops of affected trees closely related moths that feed on conifers. development and reproduced. However, to turn yellow and eventually die. The Other species that appear to be close efforts to consistently distinguish species cause of this injury was revealed from matches to D. zimmermani include D. closely related to D. zimmermani via samples containing caterpillars obtained abietivorella (the evergreen coneworm wing coloration and gene sequencing in mid-summer. Younger larvae are a moth), D. pseudotsugella, D. okaganella, may not be reliable (Roe et al. 2011). It dirty spotted greenish color (Fig. 2), D. delectella, and D. cambiicola (western appears either that (1) there are fewer and fully developed larvae may be brick pine moth). species than taxonomists have named red. Larvae push frass (insect excrement) The species D. pseudotsugella and and that interbreeding still occurs among out of the galleries in the phloem under D. cambiicola are known to feed on groups, or (2) lepidopterists fail to the surface of the bark where they feed. Douglas fir phloem tissue (Roe et al. properly sort specimens to species, and In 2017, I was able to rear out moths 2006), but neither previously have been subsequent genetic sequencing perpetuates (Fig. 3) from these larvae and to identify reported east of the Rocky Mountains. their errors. In some respects, them as most likely being ZPM, Genetic methods have been published lepidopterists have gotten species (Dioryctria zimmermani (Grote), (Roe et al. 2006) for identification of identification backwards: the moths Lepidoptera: Pyralidae). Curiously, even these moth species, because there are so identify conspecifics by scent and are though extension articles have been many look-alikes. Dr. Neil Schultes, a reproductively isolated based upon the written about ZPM in Christmas trees molecular biologist at the CAES, pheromones used by females to attract (see: https://ento.psu.edu/extension/ extracted and sequenced DNA from males for mating. Therefore, Fig. 1. Damage to the main trunk of a Douglas-fir Fig. 2. Caterpillars of Zimmerman pine moth are a Fig. 3. The adult Zimmerman pine moth is caused by tunneling by Zimmerman pine moth. dirty greenish color and have small dark spots at extremely well camouflaged against the Branches projecting outwards from or above the the base of hairs on their back. The larvae can background of the damaged tree trunk where it affected site turn yellow and may die. Check for only be observed by carefully cutting away bark to developed as a larva. the presence of frass (the reddish pellets) to expose the feeding tunnel. confirm feeding activity by Zimmerman pine moth. 20 WINTER 2020 understanding the pheromone pheromones produced by the females to attracted moths in infested Connecticut communication system, and not relying find their mates. Eggs are laid on the Christmas tree farms, which is further on wing coloration, will be critical to bark, often near previously damaged evidence that we are actually dealing properly sort individuals to species, areas. More than one year of damage with the western pine moth. I have been which then could untangle the genetic may be necessary for tops of trees to field-testing candidate pheromones to identification mess. It is important to turn yellow. Therefore, there can be try and identify the pheromone of our determine whether the population of many asymptomatic infested trees in a pest moth, but cannot yet claim success. moths causing damage to true firs in the planting. Eggs hatch in the autumn, Mating disruption uses the concept that Midwest is a host race of D. zimmermani, whereupon the young larva creates a when sufficient numbers of pheromone and has shifted from its normal shelter called a hibernaculum by dispensers distribute pheromone association with pine hosts, or has been spinning a silken protective covering on throughout a planting, it becomes misidentified and is an accidentally the bark. In the spring, larvae emerge impossible for a male to find the female introduced fir specialist. Proper and chew their way into the bark to moth. When the sexes cannot find each identification to species is a matter of feed in the phloem. Chemical control of other, then the female will remain practical importance, to allow this pest ZPM thus has three difficult options: unmated and cannot lay viable eggs – to eventually be managed via mating killing adults before they mate to lay thus breaking the life cycle. Such a disruption with the moth’s sex eggs, killing caterpillars before they have strategy can only be effective when there pheromones. a chance to burrow into the bark, or are no previously mated females entering killing larvae as they feed within the from outside the mating disruption Life history and chemical control phloem tissue. Killing adults would area. Use of pheromones in mating options – Zimmerman pine moths are require a long-residual contact insecticide disruption is an approach that only about three-quarters of an inch long, (e.g., bifenthrin), which if applied in a affects the targeted species and has no with wings folded over their back while full foliar spray could disrupt beneficial other environmental impact. Pheromones at rest. The adults would be very predatory insects. Excising specimens could be directly sprayed onto tree bark difficult to observe in a Christmas tree from trees in mid-August revealed to disrupt mating, but this approach planting, as they actively fly at night. mid-stage larvae to pupae, and so the uses “large” quantities (1.5 gram per During the day we can expect them to flight activity period of adults extends acre) of pheromone, which with ZPM hide on bark, where they are exquisitely for so long that more than one spray per would cost $180 per acre. An alternative camouflaged. Moths are expected to year would probably be required to be could be to use multiple lures to disrupt emerge from late August through effective. Efforts to target larvae in the mating. For fruit pests such as codling October. They rely on sex-attractant fall are claimed to not be effective. moth, this approach uses about 300 – Targeting the larvae in the spring would 400 dispensers per acre. With our lures, require good spray coverage of the bark this would be approximately $66 per in the interior of the tree with a long- acre for the cost of materials. A third residual contact insecticide, which can and most economical method would be be difficult to accomplish. Tests of to combine attraction of the male to a systemic insecticides, such as imidacloprid pheromone point source (which or dinotefuran, to target newly hatched necessitates fewer lures per acre than for larvae as they start to feed have not been mass disruption) with an insecticide conducted. However, the fact that applied to the zone where males will be soil-applied imidacloprid is an effective visiting, such as individual trees where treatment for Nantucket pine tip moth lures are placed. in pine seedlings suggests that basal bark sprays of this insecticide (an application References method that reduces environmental Roe, A. D., Stein, J. D., Gillette, N. E., and Sperling, risk) should be tested for preventing FAH. 2006. Identification of Dioryctria (Lepidoptera: Pyralidae) in a seed orchard at Chico, California. Ann. ZPM damage. Entomol. Soc. Am. 99(3): 433 – 488. Fig. 4 Dioryctria spp. feeding on Fraser fir in Roe, A. D., Weller, D. R., and Weller, S. J. 2011. Michigan. Photo Jill O’Donnell, MSU Prospects for mating disruption – The Complexity in Dioryctria zimmermani group: Incongruence between species limits and molecular sex-attractant pheromone claimed to be diversity. Ann. Entomol. Soc. Am. 104(6): 1207 – used by ZPM (Roe et al. 2011) has not 1220. GREAT LAKES CHRISTMAS TREE JOURNAL 21.