The Impact of Viburnum Leaf Beetle on Native Arrowwood Paul A

The Impact of Viburnum Leaf Beetle on Native Arrowwood Paul A. Weston1 and Victoria Nuzzo2

VIBURNUM LEAF BEETLE, been recently attacked by the beetle in addition to plants known scientifically as Pyrr- that had been under attack for a number of years and were halta viburni, is a small, brown nearly dead. For reference, we also took the same mea- beetle native to Eurasia that surements for arrowwood (and surrounding plants) in was accidentally introduced an area that had not yet been attacked by viburnum leaf into North America in the ear- beetle. ly 1900s. It was first detected in the U.S. in 1994, and has Wh a t w e f o u n d been rapidly expanding its range since. It is now found As expected, we found that feeding by viburnum leaf bee- throughout New England and much of New York, and is tle increased stem death and decreased flower and fruit making inroads in New Jersey, Pennsylvania, Ohio, and production by arrowwood plants, but, surprisingly, had no Michigan (a separate invasion is taking place in the Pa- significant impact on the type or abundance of neighbor- cific Northwest). ing plants. We anticipated that the rapid death of arrow- wood shrubs would create conditions that would favor Both the larvae and adult invasion by non-native species such as bush honeysuckle beetles feed on leaves of and multiflora rose. However, we found no difference plants in the genus Vi- in the vegetation growing under arrowwood compared to burnum, woody plants vegetation away from arrowwod. One possible explana- that are commonly used in landscapes and occur in many tion is that the habitat chosen for our study (old fields), natural areas. Although not all species of Viburnum are which are frequently dominated by goldenrod, might not susceptible to the pest, a number of species are heavily exhibit much change in plant community composition damaged and die after several years of repeated defolia- when a single sub-dominant species disappears. Further tion. Among the most susceptible species is Viburnum study will reveal if this stability of community composi- dentatum, commonly known as arrowwood. tion is typical in other community types.

Wh a t w e d i d Wh a t d o e s i t a l l m e a n ? We were curious to Invasion of viburnum leaf beetle has direct adverse ef- know what might fects on arrowwood, reducing flower and fruit production happen to natural ar- and gradually leading eas after arrowwood to death of attacked plants were killed shrubs. Loss of fruit by viburnum leaf production may have beetle. To answer a serious negative im- this question, we pact on both migrant conducted a project and resident song- (funded by the New birds, as well as small York State Biodiver- mammals; other re- sity Research Institute) in which we quantified the num- searchers have shown ber and type of plants growing near arrowwood shrubs. that reduced fruit availability in stopover locations has We also recorded characteristics of the arrowwood plants been directly linked to reduced songbird abundance in themselves (such as the percent of leaf area removed by both stopover and overwintering habitats. Thus, vibur- beetle feeding, number of flowers and fruits produced by num leaf beetle directly threatens arrowwood viburnum the plants, etc.). We chose plants in old fields that had and may indirectly threaten migratory songbird survival.

1Department of Entomology, Cornell University, Ithaca, NY 2Natural Area Consultants, Richford, NY September, 2008