Richard Gardner rtgardner3@yahoo.com 410.726.3045 Dec. 10, 2014 Biological control of Ailanthus altissima, Tree-of-Heaven, using native and indigenous organisms The biological control of Ailanthus altissima can be accomplished using native and indigenous organisms in a systems approach which bioremediates as it removes the invasive tree from local ecologies. It has been happening for at least 150 years as native organisms such as the native moth Atteva aurea adapted from native neotropical Simaroubaceae plant species as energy sources to the non-native in that family, Ailanthus altissima. The system consists of the native moth Atteva aurea, the indigenous eriophyoid mite Aculops ailanthii, native wildflowers, primarily in the Asteraceae family and various diseases in the Fusarium and Verticillium genera. At its simplest, building this system involves the planting of native flowers with compact inflorescences such as Solidago sp., Rudbeckia sp., Verbesinia sp., Clethra sp. and similar to be nectar sources for adult A. aurea. Once these nectar producing flowers are in place near stands of Ailanthus, adult A. aurea, the key to this system, are given a food source near their egg laying site/food source for their offspring. Locally, Asteraceae family members have been especially noticeable as nectaries for A. aurea adults. What I have seen while doing field research along Blue Marsh Lake in Berks County is multifaceted. The larvae of the native moth A. aurea feed exclusively on Ailanthus. Adults are generalist nectar feeders which use a wide variety of Asteraceae flowers as food sources. In particular I see A. aurea adults feeding on Verbesinia alternifolia, Rudbeckia laciniata and various Solidago sp. close to stands of Ailanthus. The nearby Ailanthus trees are often full, to the point of overwhelmed, with community webs containing A. aurea eggs, larvae and pupae. By late summer the Ailanthus trees are often completed defoliated. At the same time, throughout the summer I see claw shaped and other deformed leaves on nearby Ailanthus trees which mean that they are heavily infested by Aculops ailanthii. Other trees in the vicinity are severely sick or obviously dying with chlorotic yellowing leaves, bare branches and peeling bark. Taken together, this points to an active system which is slowly eradicating Ailanthus from that area. From my observations, my understanding is that A. aurea larvae exclusively eat Ailanthus leaves and young stems. They prefer the softest plant parts available, but will adapt to harder parts such as mature leaves as the softer food sources are consumed. The adults are generalist nectarivores which prefer to eat efficiently, i.e. flowers with compact inflorescences. Since A. aurea is originally a neo-tropical species it produces continual generations of offspring from late spring to late fall as it has not yet developed a diapause stage. This means that as summer progress there is a logarithmic population increase of the moth. Each generation is @ 4 weeks from egg to egg. Once a generation starts producing webs, subsequent generations will use and expand those webs resulting in the defoliation of the tree. As A. aurea larvae are eating Ailanthus leaves the eriophyoid mite A. ailanthii is sucking the life out of the leaves. These gall mites are often transported between trees by wind, but more effectively by using A. aurea as a taxi, phoretic transport. Once on a tree, they will overwinter in the bud scales ready to continue feeding on the fluids in the leaves in the spring. Claw shaped or otherwise deformed leaves are a sure sign of A. ailanthii infestation. Mite and moth infestation often occur in the same stands and on the same tree which strengthens the probability of phoretic transport by the mite on the moth. Both A. aurea and A. ailanthii carry pathogens such as Fusarium oxysporum and Verticillium nonalfalfae which kill Ailanthus trees. The pathogens are ingested while feeding. A. aurea ingests the pathogens while in the larvae stage. As adults they spread the pathogens either through droppings on leaves and webs or as a coating on its eggs during ovipositing. As the larvae feed wounds are created in the leaves and stems which allow the pathogens to enter and infect the tree. I assume that at the same time, because A. ailanthii feeds by sucking plant juices, when it moves from an

infected to tree to an uninfected one it will transfer pathogens to the uninfected tree. Since Ailanthus often has root grafts connecting the trees in a stand, once an infection starts in one tree, it can spread through a whole stand. To summarize, the best biological way of eliminating a stand of Ailanthus altissima is to plant a wide variety of native wildflowers from the Asteraceae family to attract adult A. aurea. As the warm season progresses from summer to fall, different members of this family bloom in succession. By thus ensuring a steady food supply for Atteva aurea adults there is a greater probability of attracting the adult moths. This leads to egg laying on Ailanthus with the resultant larvae feeding on and defoliating Ailanthus. With higher densities of A. aurea adults, there will be a greater probability of Aculops ailanthii infestation. With both A. aurea and A. ailanthii present the possibility of pathogen infection leading to tree death increases significantly. With local native wildflowers already present, there is little room for non-native invasive plants to take hold as Ailanthus trees are eliminated. Natural native plant succession will proceed from this point.

Figure 1 Atteva aurea

Figure 2 Aculops ailanthii infested leaves

Figure 3 Chlorotic leaves with Aculops ailanthii present