Effect of Parectopa robiniella (Clemens, 1763) (Lepidoptera: Gracillariidae) on the photosynthetic efficiency of Robinia pseudoacacia L. trees in the forest strips of the Steppe zone, Ukraine

The photosynthetic efficiency was studied in Robinia pseudoacacia (black locust) as one of the most common forest-forming species in artificially established stands of the northern Steppe of Ukraine. Plantings of this species in the region studied were established specifically to perform protective functions such as soil erosion control, phytoremediation of disrupted landscapes, and the protection of agricultural cenoses from wind erosion. The goal of this study was to investigate (I) how Parectopa robiniella caterpillars affect the photosynthesis system of black locust; (II) what age groups of black locust trees were most vulnerable to P. robiniella attacks. The study was con- ducted in September 2022; this period corresponded to the greatest activity of the second (more numerous) generation of P. robiniella. The artificially established forest strip of R. pseudoacacia of different ages was chosen as the object of research: I - young trees (up to 15 years old); II - middle- -aged (15-25 years old), and III - old parent trees planted at the time of the forest belt creation (50-70 years old). The forest belt was situated near the Mayorka village on the right bank of the Dnieper River in the Dnipro District of the Dnipropetrovsk Oblast; it performs field-protective and anti-erosion functions. The effect of locust digitate leaf miner, P. robiniella, on the plant func- tioning was assessed by quantifying and comparing chlorophyll fluorescence parameters. The level of the miner exposure was evaluated in trees of three age groups (5-10, 15-25, and 50-70 years old). The study was performed with recording of background, maximum, stationary, and variable flu-orescence in live intact and damaged leaves using a 'Floratest' fluorometer. The level of pho- tosynthetic activity inhibition in tree leaves damaged by the miner was determined. Data from the analysis of fluorescence indicators showed significant differences between the intact and miner-damaged leaves in trees of all age groups under conditions of field-protective forest planting. A decrease in background, stationary, maximum, and variable fluorescence under the influence of phytophagous insects was recorded. This trend was most pronounced in young trees under the age of 15 years. The results of the research may open up new approaches to an assessment of the black locust plantations in the Steppe zone of Ukraine the establishment of which is aimed at performing specific protective functions.