Obolodiplosis robiniae

(Haldeman, 1847)

locust gall midge, black locust gall midge

Obolodiplosis robiniae is a small (: ) to eastern North America that has become a significant pest in Eurasia. The is on Robinia species, particularly black (Robinia pseudoacacia), forming distinctive leaf margin roll through gregarious larval feeding. First described from Pennsylvania in 1847, it was detected in Asia in 2002-2003 (Japan, Korea) and Europe in 2003 (Italy), subsequently spreading explosively to 26 European countries and much of China. Climate modeling predicts substantial northward range expansion under warming scenarios, with suitable potentially increasing by 35% by 2070. The reduces tree growth and productivity, causes early leaf abscission, and facilitates attacks by wood-boring .

Obolodiplosis robiniae by (c) Stephen Thorpe, some rights reserved (CC BY), uploaded by Stephen Thorpe. Used under a CC-BY license.

Obolodiplosis robiniae by (c) Alexis Tinker-Tsavalas, some rights reserved (CC BY), uploaded by Alexis Tinker-Tsavalas. Used under a CC-BY license.

Obolodiplosis robiniae by no rights reserved, uploaded by Stephen James McWilliam. Used under a CC0 license.

Pronunciation

How to pronounce Obolodiplosis robiniae: //ˌoʊbəloʊdɪˈploʊsɪs rɒˈbɪni.aɪ//

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

are minute typical of . cause diagnostic leaf margin roll on Robinia leaflets—thickened, downward-curved margins that enclose gregarious larvae. Galls appear as curled or rolled edges along leaflet margins, often with 1-6 galls per leaflet. Mature galls may show color changes from green to reddish as photosynthetic pigments degrade. The is distinguished from other Robinia-feeding gall midges by the specific gall and marginal location. Seasonal timing aids identification: adults emerge in spring, with 2-4 per year in invaded regions.

Images

Habitat

Urban and suburban areas where ornamental or weedy black trees occur; forest edges and disturbed with Robinia presence. range in eastern North deciduous forests. range spans temperate Eurasia from 21°-66°N, primarily in semi-humid to semi-arid regions where black locust grows vigorously. Climate modeling indicates strong temperature dependence, with optimal conditions in areas matching black locust's fastest growth rates.

Distribution

to North America: eastern United States (Pennsylvania, New York) and southeastern Canada (Ontario, Quebec, New Brunswick, Nova Scotia, Prince Edward Island, British Columbia). in Eurasia: discovered 2002-2003 in Japan, Korea, and Italy; by 2007 spread to 26 European countries including Austria, Germany, France, UK, Sweden, Ukraine; in China detected 2004 in Hebei, now in 17 provinces. Rapid eastward expansion from Italy to Ukraine (2000 km, 2003-2006). Predicted to continue northward expansion with climate warming.

Seasonality

emerge in spring following as diapausing . In temperate Europe, completes 2-4 annually depending on conditions: two generations on mature trees ( declining in summer), two additional generations possible on root suckers from midsummer onward. Peak occur in late spring. In Korea, seasonal distribution studies show fluctuation within tree crowns throughout growing season.

Diet

; feed exclusively on Robinia . Gregarious feeding on leaf parenchyma induces formation. Nutritive tissue within galls rich in starch and octadecanoic acid (C18:0), which serves as primary larval food source. plants include black (Robinia pseudoacacia), bristly locust (R. hispida), and clammy locust (R. viscosa).

Host Associations

Robinia pseudoacacia - primary black , main throughout range
Robinia hispida - bristly
Robinia viscosa - clamy
Robinia pseudoacacia 'Aurea' - golden-leaved

Life Cycle

Overwinters as diapausing within or soil. emerge in spring. Females on developing leaflets. Larvae are endophytic, feeding gregariously within leaf margin galls. occurs within gall or in soil. time varies: 2-4 generations per year possible in optimal conditions. Multiple overlapping generations common in mid-to-late season on root suckers.

Behavior

Gregarious larval feeding induces characteristic leaf margin roll by thickening and bending leaflet margins downward. Up to 5-6 may occupy a single gall. occur throughout the growing season from initial leaf development until leaf fall. High cause early leaf abscission and reduced . Facilitates secondary attack by longhorn () and () through tree stress or gall damage.

Ecological Role

pest with significant negative and economic impacts. Reduces growth and productivity of trees, diminishes ornamental value, and can cause tree mortality through facilitation. In range, likely maintained at lower by co-evolved . In invaded range, subject to by and native , particularly Platygaster robiniae (), which can achieve 40% rates. Potential value as biological control agent against weedy black in some contexts, though generally considered detrimental.

Human Relevance

Significant forestry and urban tree pest in Europe and Asia. Causes aesthetic damage to ornamental black , reduces timber productivity, and increases tree vulnerability to fatal secondary borer . Subject to and management efforts by forestry departments. Scientific model for studying spread, climate change impacts on pest distribution, and - former interactions. -level sequenced (2024).

Similar Taxa

Dasineura robiniaeAnother on Robinia; forms different (blister or pouch galls rather than margin rolls)
Phyllonorycter robiniella (: ); also on black locust but causes blotch mines rather than
Parectopa robiniella ; similar and but different damage
Appendiseta robiniae ; to North America, in Europe, causes leaf curling and production rather than