Fruit Phenology of Two Hazelnut Cultivars and Incidence of Damage by Halyomorpha halys in Treated and Untreated Hazel Groves

Abstract

Over the past decade, Halyomorpha halys has become one of the main threats to hazelnut production. Its trophic activity makes kernels inedible due to strongly detrimental effects on the organoleptic quality. Its management in Italy is still tricky due to the lack of effective native biocontrol agents and authorized and effective insecticides. A field test was performed on San Giovanni (SG) and Tonda Romana (TR) cultivars (early and late ripening, respectively) to assess the intensity of cimiciato damage with different pest management approaches (no insecticide and integrated pest management, IPM). Moreover, phenological analysis of fruits and the monitoring of stink bug species by traps and plant beating were carried out. In the untreated plots, the SG cv showed a higher cimiciato incidence with respect to the late TR cv (40% SG–NI vs. 23% TR–NI). This was probably due to the different phenological phases in which stink bugs injured the fruits. In fact, stink bug bites provoke different kinds of injuries (blanks, shriveled, and cimiciato) according to the fruit’s development period. Indeed, in the period of highest insect occurrence in the field, the fruits of the early cv (SG) were in kernel expansion, a phenological phase in which bug injuries are more likely in cimiciato defects. Lastly, the IPM did not provide sufficient fruit protection (19% SG–IPM vs. 11% TR–IPM). The interaction between the phenological development of hazelnuts and the brown marmorated stink bug represents a critical aspect in understanding and implementing effective strategies for controlling this key pest on hazelnut trees.

Terahertz imaging for non-invasive classification of healthy and cimiciato-infected hazelnuts

“…On hazelnuts, stink bugs can cause different types of damage, depending on the stage of development in which the fruit is hit. In particular: i) if the insect bites the fruit in the pre-expansion phase of the shell, hazelnuts will be almost certainly subject to drop or traumatic abortion; ii) if the fruit is bitten while the shell is expanding, a traumatic abortion of the kernel will almost always occur, therefore shells will be empty at harvest; iii) if the fruit is hit during the kernel expansion or the ripening phase, kernels will be shrivelled or they will present a high incidence of the characteristic off-flavour defined as “cimiciato” or “corked” [ [3] , [4] , [5] , [6] ]. By visual inspection, cimiciato defect can appear as one or more spots on the kernel surface (external or visible cimiciato) or the damage can be located inside the kernel, and this prevents it to be detected visually, but the injure becomes visible only after opening the fruit in two halves (hidden or internal cimiciato) [ 6 ].…”

“…The incidence of cimiciato defect is strongly related to year, cultivar and growing area. For example, in southern Italy in some cultivars the incidence of damage can even reach 35% [ 6 ], while in Turkey, on the basis of the cultivation area and season, the incidence of damage varies between 1.5% and 20% [ 12 ].…”