September 3, 2019 – You have probably noticed these small translucent insects up to 2 mm in size that have been annoyingly „biting“ us this summer. They are called oak lace bugs (Corythucha arcuata) and are pests of oaks. Native to North America, they were first spotted in Europe in 2000.
In Croatia, this pest was first observed in 2013 near the Bajakovo border crossing and the first rest stop after the border crossing. In 2014 it spread to most of the Spačva basin, which is home to one of the most valuable and largest common oak complexes in Europe. In 2015 and 2016 it remained only in the area of the Spačva basin. In 2017, however, it was discovered in most parts of the lowland continental Croatia and in 2018 its spread intensified. Today, unfortunately, almost all the stands of common oak (Quercus robur), the area of over 200,000 ha, are infected and it is starting to spread on sessile oak (Quercus petraea), which makes up most of the forests in the hilly areas.
Oikon’s team of experts from the Laboratory for Remote Sensing and GIS led by dr. Alen Berta mapped their spread through Croatia based on remote sensing methods (via satellite) and the damage they cause to forests, which you can see from these images.
Although this insect is not a good flyer, due to its count and size, it has been carried along the largest traffic routes and truck stops. Just imagine its abundance when there are 4-5 generations a year and each individual insect lays up to 100 eggs, which means that a single insect that survives the winter inside the bark has up to 10 billion great-grandchildren in the fall. Yes, over 10,000,000,000 of them from just one insect!
The insect sucks chlorophyll from the leaves, which is why they turn brown, and the trees cannot photosynthesize to produce food so they starve. The question is how much longer will our most valuable oak withstand this “diet”, which in some areas has already lasted for around 5-6 years.
For more information about the project our team of experts have done on the oak lace bug: https://oikon.hr/the-study-about-effectiveness-of-measures-for-prevention-of-spreading-of-the-oak-lace-bug/