Introduction of Corythucha arcuata in Italy. Addition to the EPPO Alert List
In northern Italy, in May 2000, a few adults of an unusual insect were observed on Quercus robur trees in the Parco delle Groane (north of Milano). The insect was identified as Corythucha arcuata (Heteroptera, Tingidae), a North American species which was previously absent from Europe. Since then, C. arcuata has been observed in several other areas (in parks or along roads) in Lombardia and Piemonte regions which suggests that it was introduced some years ago. In Italy, C. arcuata has been observed on Quercus robur, Q. pubescens and presumed hybrids of Q. robur x Q. petraea. It can be recalled that a related species C. ciliata (sycamore lace bug) was introduced into Italy in 1964 and then rapidly spread within Europe. It still causes problems in particular on urban Platanus trees in many countries in southern Europe.
In North America, C. arcuata occurs in southern Canada and in most states of USA. Its host plants are essentially oaks (Q. acuminata, Q. alba, Q. macrocarpa, Q. muehlenbergii, Q. prinoides, Q. prinus, Q. rubra) and Castanea americana. It is occasionally reported on Acer, Malus and Rosa. Adults and nymphs feed on the underside of the leaves, as a result of which discoloration appears on the upper leaf surface. Heavily infested leaves turn yellowish to whitish and often drop prematurely. In addition, the lower surface of the leaf is littered with dark nymphal skins, eggshells and scattered dots of brownish-black excrement which reduce phytosynthesis. Adults have broad, transparent, lace-like wing covers and are about 6 mm long. Nymphs are black and covered with spines. Adults overwinter in bark crevices. In spring, eggs are laid on the underside of the leaf usually along leaf veins. There are 5 nymphal stages from eggs to adults. A complete cycle may develop in 30 to 45 days, and several generations (1 to 3) can be observed per year. Preliminary observations done in Italy suggested that C. arcuata could complete 3 generations per year. In USA, C. arcuata is considered as a pest of amenity trees and chemical treatments are sometimes applied in nurseries and parks. Apparently, it is not considered as a forest pest. It is felt that the introduction of this pest into Europe may represent a threat for forest and amenity oaks.
Corythucha arcuata (Heteroptera, Tingidae), the oak lace bug
Why: Corythucha arcuata came to our attention because it was recently introduced into Europe (Italy). [A picture of C. arcuata can be viewed at: http://cedarcreek.umn.edu/insects/album/020014007ap.html].
Where: It originates from North America: Canada (south), USA (most states). Reported for the first time in 2000, in Italy (Lombardia, Piemonte).
On which plants: Oaks (Q. acuminata, Q. alba, Q. macrocarpa, Q. muehlenbergii, Q. prinoides, Q. prinus, Q. rubra) and Castanea americana. Occasionally found on Acer, Malus and Rosa.
Damage: Direct feeding on the leaves (discoloration of the upper surface), reduced photosynthesis and in case of heavy infestation, premature leaf fall.
Pathway: Oak plants for planting, cut branches from countries where C. arcuata occurs.
Possible risks: Oaks are very important forest and amenity trees in Europe. Past experience with a similar insect (Corythucha ciliata) feeding and damaging Platanus species showed that it was a considerable nuisance in public places, and that it was difficult to prevent natural spread of these insects and to control them especially in urban environment. Oaks grown in nurseries, along the roads, and in parks and gardens are particularly at risk. Apparently, C. arcuata is not reported as a forest pest, but the risk for European oak forests cannot be excluded.
EPPO RS 2001/057
Panel review date 2001- Entry date 2001-03
Sources
Bernardinelli, I.; Zandigiacomo, P. (2000) First record of the oak lace bug Corythucha arcuata (Say) (Heteroptera, Tingidae) in Europe. Informatore Fitopatologico, no. 12, 47-49.
INTERNET
Ohio State University Extension Fact Sheet. Lace bugs. http://www.ag.ohio-state.edu/~ohioline/hyg-fact/2000/2150.html
University of Vermont Extension. Lace bugs by G.R. Nielsen. http://ctr.uvm.edu/ctr/El/el153.htm
University of Georgia. The Bugwood Network. Oak lace bug. http://www.forestpests.org/oak/lacebug.html