By: Dr. Celal Tuncer
Dr. Celal Tuncer is full professor of entomology at Ondokuz Mayis University, Faculty of Agriculture, Department of Plant Protection, Samsun, Turkey. He has more than 35 years of experience in the field of agricultural pest management and his focus is specifically on hazelnut pests. He is also an advisor of the Black Sea Hazelnut and Products’ Exporters Union for pest management.
The brown marmorated stink bug (BMSB), Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), an invasive insect, has become one of the most serious pests in many countries over the last two decades. It spread out from its native land, East Asia (China, Taiwan, Japan, and Korea) to many other countries in Asia, Europe and America, and more recently into North Africa. BMSB has a very polyphagous behavior, meaning it feeds on various crops, and therefore it is a serious threat to a wide variety of orchard fruit, nut, vegetable, field crops and ornamental plants. Economically important crops such as peach, pear, apricots, plums, apples, cherry, persimmons, tomatoes, corn, soybean, grape, kiwi, oranges, almond and hazelnut are some of the main host plants of BMSB in its distribution area. In general, BMSB reproduces one or two generations each year, depending on location and year. There are two main negative effects caused by BMSB: firstly, overwintering adults in spring and in-season adults, and nymphs feed on different parts of the plant, especially on fruits, and this affects crop productivity and quality, secondly, BMSB is a significant nuisance to homeowners because of the unpleasant odor they emit; adults in large numbers enter sites including homes and other human-made structures for overwintering in autumn.
Distribution of BMSB in Turkey
BMSB was found for the first time (a few specimens) in Istanbul, Turkey in 2017. However, the first substantial population of BMSB was determined to be in the Artvin province, which is located on the border with Georgia. It is assumed that BMSB spread into Turkey from Georgia which had been heavily infested at that time. From the first observation year and onward, the BMSB population and infested area continued to increase, spreading quickly to other provinces such as Rize, Trabzon, Giresun, Ordu and Samsun on the Black Sea coast of Turkey. At the same time, the western part of the country, specifically Istanbul and the adjacent provinces of Yalova and Sakarya in the Marmara region, were also experiencing an increasing population of BMSB. This brings about the possibility that BMSB might have entered Turkey from two different points. As of today, nearly 10 provinces of the country have already been infested by BMSB, but only two provinces, Artvin and Rize have a comparatively higher population than others in the agricultural and natural area. On the other hand, over the last few years, in Istanbul, homeowners have started to complain that many BMSB adults have entered homes for overwintering and have released their repelling odor. Public and governmental attention to BMSB and its pest status has been increasing year by year in Turkey.
Pest Status of BMSB in Turkey
After the first appearance of BMSB in Turkey, researchers conducted studies on its pest potential, monitoring, biology, damage, host plants and management. Government institutions started a project to monitor the population abundance of BMSB in infested areas and to monitor the spreading of this pest to other provinces; this project has been supported by the Black Sea Hazelnut and Products’ Exporters Union since 2018. Monitoring efforts included different types of pheromone traps, in addition to visual inspection and the beating sheet method. Furthermore, some private companies started to carry out similar studies on BMSB, especially in hazelnut growing areas. During this period, there were many meetings and media activities related to BMSB, which were organized in different provinces and included the printing of posters and leaflets for public awareness. Current studies have shown that BMSB can produce one or two generations per year in Turkey. Currently, hazelnut, corn, kiwi, persimmon, apple, peach and grape are the main crops threatened by BMSB in high population areas. Since the BMSB population is comparatively low in some provinces and even absent in a large part of the country, the damage is not very high in agricultural fields as of now. However, due to further infestation of BMSB in other regions of Turkey, many other agricultural crops will likely be under risk. The risk analysis of BMSB shows that the Black Sea coastline region of the country has the most suitable ecological conditions for the development of this insect. Hazelnut is by far the most important and prevalent crop in the Black Sea region of Turkey and this region provides nearly 65% of total world hazelnut production. Experiences from other hazelnut-growing countries (Georgia, Italy and USA) indicate that BMSB is a very serious pest for hazelnut crops, and causes substantial damage, both qualitatively and quantitatively. Therefore, it is predicted that hazelnut will be the main crop that may be affected by a BMSB invasion in Turkey. Although a large impact on agricultural crops from BMSB has yet to be observed, it must be kept in mind that the economic damage to agricultural crops usually occurs 5 to 10 years after a pest is established.
Management of BMSB in Turkey
Since there is not a large population of BMSB in main agricultural lands yet, insecticide applications are very limited in some local fields. The method of mass trapping with pheromone is used to a limited extent, and aggregated adults in autumn are removed and killed mechanically. Because BMSB can affect a very large agricultural area and there are well-known side effects of pesticide applications in addition to the restrained success of other control methods, for a long term, the Ministry of Agriculture has decided to implement classical biological control for BMSB by importing the samurai wasp, Trissolcus japonicus. The Black Sea Agricultural Research Institution in Samsun has been authorized for this purpose. The institution has prepared mass-rearing parasitoid production facilities in 2021 and continues to work on this mission.
Samurai wasp rearing facility. Picture courtesy of Dr. Celal Tuncer.