First Report of Armillaria root disease of Celtis laevigata caused by A. gallica in South Carolina, USA.

Celtis laevigata (sugarberry, southern hackberry) is an important, shade-tolerant, deciduous hardwood tree species that occurs naturally in flood plains, along streams and rivers, and in urban landscapes of the southeastern USA (Kennedy 1990). In recent years, dieback and mortality of C. laevigata have been commonly observed in some areas of South Carolina (SC) and Georgia (GA) (Poole et al. 2021). In April/May of 2018, the crown conditions and root systems were examined for three C. laevigata trees in North Augusta, SC. The crown of each tree was visually assessed using the method of Poole et al. (2021). Root samples were obtained by excavating two main roots ca. 2 meters away from the stem of each tree. Tree SB474 (N33 29.472, W81 59.082, elev. 55.8 m) exhibited > 66% crown loss and decaying roots with white mycelial fans and dark rhizomorphs characteristic of Armillaria. Tree SB913 (N33 29.830, W81 59.349, elev. 58.8 m) exhibited ca. 34-66% crown loss, while tree SB914 (N33 29.837, W81 59.338, elev. 57 m) appeared healthy with no apparent crown loss. Roots of trees SB913 and SB914 appeared healthy, although rhizomorphs were attached to the root surfaces. Roots and/or attached rhizomorphs were surface disinfested and plated n a basidiomycete-selective medium (Hendrix and Kuhlman 1962). Three Armillaria isolates, one from each corresponding tree, were paired with each other, and two genets were identified (SB474 and SB913 = SB914). The two genets (SB474 and SB913) were used in somatic pairing tests against three known tester isolates for each of the following species: A. solidipes, A. mellea, A. gallica, A. mexicana, and Desarmillaria caespitosa (=A. tabescens). Pairing of isolates SB474 and SB913 showed the highest compatibility with A. gallica (isolates ST22, ST23, and M70) with 100% and 89%, respectively. These isolates were definitively confirmed as A. gallica by translation elongation factor 1α gene sequences (tef1; Klopfenstein et al. 2017) (GenBank accession nos. OM993577 and OM993578 for SB474 and SB913, respectively). GenBank nucleotide BLAST showed tef1 similarity for both SB474 and SB913 isolates was highest for A. gallica (≥98.7%; GenBank accession nos. MT761696, MT761697, and KF156772). This is the first report of A. gallica associated with Armillaria root disease of C. laevigata. Rhizomorphs on the surface of apparently healthy tree roots and root colonization in severely declining trees are a common sign of A. gallica (Baumgartner and Rizzo 2001). Pathogen colonization of root surfaces may provide an opportunity for infection of highly damaged trees, resulting in root disease (Gregory 1985). Primary agents of C. laevigata dieback and mortality in SC and GA remain undefined, but continued study is needed to confirm the role of A. gallica in C. laevigata dieback and mortality. Although pathogenicity tests are impractical for Armillaria, these A. gallica occurrences in SC further adds to our knowledge of this pathogen's distribution in the southeastern USA, where it has also been confirmed in Tennessee in hardwood forests (Bruhn et al. 1997), SC on Hemerocallis sp. (Schnabel et al. 2005), and GA on a Rhododendron/span> sp. and Quercus rubra (Hanna et al. 2020). The distribution and host range of A. gallica is likely more widespread in the southeastern USA than existing records indicate. Documenting Armillaria distribution, including A. gallica, is essential for predicting climate-change impacts on Armillaria root diseases (Kim et al. 2022). Baumgartner, K., and Rizzo, D. M. 2001. Plant Dis. 85:947-951. Bruhn, J. N., et al. 1997. In 11th Central Hardwood Forest Conference, USDA, FS, NC-GTR-188, 49-57. Gregory, S. C. 1985. Plant Path. 34:41-48. Hanna, J. W., et al. 2020. Plant Dis. 105: 1226. Hendrix Jr, F. F., and Kuhlman, E. G. 1962. PI. Dis. Rep. 46:674-676. Kennedy, Jr., H. E. 1990. Silvics of North America: 2. Hardwoods. USDA-FS. Agriculture Handbook 654. Kim, M.-S., et al. 2022. Front. For. Glob. Change 4:740994. Klopfenstein, N. B., et al. 2017. Mycologia 109:75-91. Poole, E. M., et al. 2021. J. For. 119:266-274. Schnabel, G., et al. 2005. Plant Dis. 89:683.

First Report of Armillaria Root Disease Pathogen, Armillaria gallica, on Rhododendron and Quercus rubra in Georgia, USA.

Armillaria root and butt diseases, which are a global issue, can be influenced by changing environmental conditions. Armillaria gallica is a well-known pathogen of diverse trees worldwide (Brazee and Wick 2009). Besides A. gallica causing root rot of Hemerocallis sp. and Cornus sp. in South Carolina (Schnabel et al. 2005), little is reported on the distribution and host range of A. gallica in the southeastern USA. In July 2017, three Armillaria isolates were obtained from two naturally occurring hosts in Georgia, USA and cultured on malt extract medium (3% malt extract, 3% dextrose, 1% peptone, and 1.5% agar). One isolate (GA3) was obtained in Unicoi State Park near Helen, Georgia (Lat. 34.712275, Long. -83.727765, elev. 498 m) from the basal portion of Rhododendron sp. with extensive root/butt decay, but no crown symptoms were evident (Supplementary Figure 1). GA4 and GA5 (Lat. 33.902433, Long. -83.382453, elev. 215 m) were isolated from wind-felled Quercus rubra (red oak) with root disease at the State Botanical Gardens in Athens, Georgia. GA4 was associated with a large root ball (ca. 4-m diameter) (Supplementary Figure 2), and GA5 was obtained from a mature tree with infected roots, with characteristic spongy rot of Armillaria root disease. Crown symptoms could not be evaluated because the crowns had been removed before the collections. Several other oaks with Armillaria root disease were noted throughout the State Botanical Gardens. Pairing tests reduced these three isolates (whiteish mycelia with a dark, brownish crust and rhizomorphs), to two genets with GA4 = GA5. Both genets (GA3 and GA4) were identified as A. gallica using translation elongation factor 1α (tef1) sequences (Genbank Nos. MT761697 and MT761698, respectively) that showed ≥ 97% identity (≥ 98% coverage) with A. gallica sequences (KF156772, KF156775). Also, nine replications of somatic pairing tests showed 33 - 67% compatibility with A. gallica (occurs in southeastern USA), compared with 0 - 22% for A. mexicana, A. mellea (occurs in southeastern USA), A. solidipes, and Desarmillaria tabescens (occurs in southeastern USA). To our knowledge, this note represents the first report of A. gallica on Rhododendron and Q. rubra in Georgia, USA, which has experienced severe drought in recent decades (e.g., Park Williams et al. 2017) that could predispose trees to Armillaria infection (e.g., Wargo 1996). Quercus rubra was previously reported as a host of A. gallica in Arkansas (Kelley et al. 2009) and Massachusetts (Brazee and Wick 2009), USA. In Missouri, USA, A. gallica has been reported as a weak pathogen with potential biological control against A. mellea (Bruhn et al. 2000). Other reports from several regions on various hosts suggest pathogenicity of A. gallica is associated with changing climate (Nelson et al. 2013, Kim et al. 2017, Kubiak et al. 2017). Wide genetic variation and/or cryptic speciation within A. gallica may account for differences in ecological behavior (Klopfenstein et al. 2017), but this is difficult to evaluate because Armillaria pathogenicity tests cannot be used on most forest tree seedlings. This study suggests that A. gallica is more widespread than previously known and its adverse impacts on woody plants may intensify over time, depending on the environmental conditions. Further studies are needed to determine environmental influences on A. gallica, the full distribution of A. gallica, and its effects in forests of the southeastern USA.

Matsucoccus macrocicatrices (Hemiptera: Matsucoccidae): first report, distribution, and association with symptomatic eastern white pine in the southeastern United States.

We provide the first report of Matsucoccus macrocicatrices Richards (Hemiptera: Matsucoccidae) feeding and reproducing on eastern white pine, Pinus strobus L., in the southeastern United States. Until now, M. macrocicatrices had been reported only from the Canadian Atlantic Maritimes, New Hampshire, and Massachusetts. Entomological holdings of 27 major museums in eastern North America have no historical records for M. macrocicatrices from the southeastern region. However, our field surveys and molecular analyses (DNA barcoding) have resulted in the collection and positive identification of M. macrocicatrices in Georgia, North Carolina, South Carolina, Tennessee, Virginia, and West Virginia In addition to the new geographic range, M. macrocicatrices is also being associated with dieback and mortality of all diameter classes of P. strobus leading to concern about a potential shift from its historically nonpestiferous presence on the host tree. On P. strobus, M. macrocicatrices was found embedded in cankers or present on top of the bark with necrotic tissue under their feeding area, indicating that they may be creating wounds for opportunistic pathogenic fungi to infest. Further, we found M. macrocicatrices living outside of the epiphytic mats of its symbiotic fungus, Septobasidium pinicola Snell. This study shows that M. macrocicatrices is now widespread in the southeastern United States, with implications for the future survival and regeneration of P. strobus in eastern North America.

The Association of a Longidorus Species with Stunting and Root Damage of Loblolly Pine (Pinus taeda L.) Seedlings.

A Longidorus species was consistently associated with patches of stunted and chlorotic loblolly pine seedlings at a forest-tree nursery in Georgia. Seedlings from affected areas had poorly developed root systems that lacked lateral and feeder roots. Longidorus population densities in composite soil samples from the margins of patches ranged from 9 to 67 nematodes per 100 cm3 of soil. In a growth chamber experiment, seedling root dry weight decreased with respect to the initial Longidorus dose as well as the final Longidorus populations in containers. The dry root weight of seedlings were 0.117, 0.090, 0.066, and 0.065 g in containers initially infested with 0, 50, 100, and 200 Longidorus, respectively. Lateral and fine roots were lacking on seedlings at the highest doses. Populations of Longidorus increased in all containers during the experiment. Damage to loblolly pine seedlings caused by Longidorus is a previously undescribed problem in southern pine nurseries. Proper diagnosis of the problem by nematode testing laboratories may require the use of extraction techniques specific for larger nematodes such as Longidorus.