Tree Health Survey Results of Juvenile Black Locust Clones

The black locust (Robinia pseudoacacia L.) is a significant tree species in many European countries, especially Hungary. The Hungarian Forest Research Institute initiated a project in the 1960s to improve Robinia stem quality and yield. Five newly bred clones (Laposi, Napkori, Hajdúsági, Farkasszigeti, Püspökladányi) are currently undergoing tests in three trials (Debrecen, Napkor, and Nyírbogdány). Studying the health status of these clones is vital to the cultivar certification process. In September 2022 (Napkor) and August 2023 (Nyírbogdány, Debrecen), we investigated 30 trees per clone by estimating average foliage loss per individual and observing the extent and causes of damage to the crown (canopy), branches, and trunk in each experimental plot. At the same time as the tree health survey, NDVI measurements were also performed in Debrecen using Trimble Greenseeker handheld sensor. Our results indicate that the clones possess good drought tolerance; however, the NDVI results revealed significant differences between the clones: Laposi and Farkasszigeti have the highest NDVI values (0.76 and 0.77), and Püspökladány has the lowest (0.74). Napkori is the most susceptible to fungal disease, exhibiting significant incidences of bark necrosis caused by Phomopsis petiolorum. The rate of insect damage was negligible, even with low levels of damage by leaf miners, which are very common in black locust plantations.