Determination Using Field Cages of Damage Types Caused by Green Shield Bug Feeding on Hazelnut Kernels

Abstract

The green shield bug (GSB), Palomena prasina L., is one of the most important pests of hazelnut in Turkish hazelnut orchards where it causes serious yield and quality losses by feeding on fruits. Their feeding may result in nut abortion, shriveled, or corked kernels. Sometimes it can be difficult to link damage to insect pests because similar symptoms can be attributed to pathogens. Additionally, a high number of rotten kernels is observed in some years, and a question arises if it is caused by GSB. This study aimed to determine the damage types and frequencies caused by GSB feeding on hazelnuts through field cage experiments. Field trials were carried out in four hazelnut orchards during 2019 and 2020. Field sleeves were placed on branches in early May and field-collected adults and 3-5th instar nymphs were placed inside the sleeves at 3 different times in June and July and allowed to feed on developing nuts for 10 days. Some sleeves contained no insects and served as the control treatments. Nuts were collected from the sleeves at harvest time and examined to determine the types of kernel damage. Damaged nut frequencies (%) in sleeves with insects were 13.98 and 21.58% in 2019, and 19.60 and 25.32% in 2020 in the orchards, respectively, and were significantly higher than the control cages. Shriveled kernels (%) in the sleeves with insects sleeves differed from the control treatment in only one orchard in both years. Corked kernels (%) in the cages with insects were 12.15 and 13.79% in 2019, and 14.63 and 13.86% in 2020, in the orchards, respectively, and significantly higher than the control treatments. The amount of rotten kernels was lower in 2019 than in 2020 and significantly higher than the control treatments in one orchard during two years. These results indicate that GSB negatively affected nut quality. The corked kernel damage was clear and distinctive. Shriveled and rotten damage categories varied by orchard and year, and were most likely influenced by uncontrollable environmental conditions. © 2023 International Society for Horticultural Science. All rights reserved.