There are several harmful and yield decreasing arthropod pests, which live within plant tissues, causing almost unnoticeable damage, e.g. Ostrinia nubilalis Hbn., Cydia pomonella L., Acanthoscelides obtectus Say. Their ecological and biological features are rather known. The process leading to the damage is difficult to trace by means of conventional imaging techniques. In this review, optical techniques-X-ray, computer tomography, magnetic resonance imaging, confocal laser scanning microscopy, infrared thermography, near-infrared spectroscopy and luminescence spectroscopy-are described. Main results can contribute to the understanding of the covert pest life processes from the plant protection perspective. The use of these imaging technologies has greatly improved and facilitated the detailed investigation of injured plants. The results provided additional data on biological and ecological information as to the hidden lifestyles of covertly developing insects. Therefore, it can greatly contribute to the realisation of integrated pest management criteria in practical plant protection.

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The velvet longhorned beetle, Trichoferus campestris (Coleoptera: Cerambycidae) is a serious wood‐boring pest that is a major threat to the phytosanitary condition of forests and orchards. Its worldwide expansion is a major concern for plant health. We have collected all bibliographical references, phytosanitary reports and authentic photographic evidence from entomological websites to determine the worldwide distribution of T. campestris. The theoretical directions of the spreading and actually occupied area of this arthropod pest were determined over the whole Holarctic range. Furthermore, the potential distribution area was calculated using cumulated temperature in the growing season averaged over 15 years both in the Palearctic and Nearctic regions. Holarctic expansion of the species, including the main parts of North America and Eurasia, is clearly indicated. Its populations occur in 29 countries to date, supported by documentation from 64 publications and 30 online forums. Its spread is continuously westward in the Palearctic; in the Nearctic, the spread was first southward from the Great Lakes region then eastward from Utah. The species has excellently adapted to circumstances of freight by ship and plane, as wood is often used, ensuring optimal conditions for the pest. In addition, the active spreading achieved by flying is an important factor contributing to its expansion. The primary criterion for controlling the species would be the introduction of a monitoring system in affected and exposed areas.

Oulema melanopus L. (Coleoptera: Chrysomelidae) is one of the most serious pests of winter wheat that causes peeling of the epidermis and tissue loss. The complex mapping of the physiological responses triggered by O. melanopus as a biotic stressor in winter wheat has not been fully explored with the help of non-invasive imaging and analytical assays, yet. The aim of the present work was to study the effect of O. melanopus on the physiological processes of winter wheat, especially on the extent of lipid peroxidation and antioxidant activity derived from tissue destruction, as well as photosynthetic ability. The results of the measurements enabled the identification of the antioxidant and lipid-oxidation–related physiological reactions, and they were reflected in the dynamics of non-invasive biophoton emissions. Our non-invasive approach pointed out that in the case of O. melanopus infestation the damage is manifested in tissue loss and the systemic signaling of the biotic stress may have reached other plant parts as well, which was confirmed by the results of antioxidant capacity measurements. These results indicate that the plant reacts to the biotic stress at a whole organizational level. We identified that the antioxidant and lipid-oxidation–related physiological reactions were reflected in the dynamics of two aspects of biophoton emission: delayed fluorescence and ultra-weak bioluminescence. Our research further supported that the non-invasive approach to stress assessment may complete and detail the traditional stress indicators.

Holarctic expansion of Neoclytus acumiantus acuminatus due to its polyphagous character has been a major concern for plant health, which raises several questions about its spreading directions. I have examined all bibliographical references, phytosanitary reports and authentic photographs from the online sources in the quest of the determination of the worldwide distribution and flight phenology of N. a. acuminatus. The expansion, including the western Palearctic regions as well as several Neotropical habitats, is proven and has become more intense in the last decades. It can be found mostly on the Holarctic region including 21 countries, which is supported by 51 publications. Its spreading mostly northward and eastward in the Palearctic is continuous due to anthropogenic effects, climate change as well as movement of infested materials. Flight phenology and population densities as a function of habitats were mapped. The detection in novel habitats of this pest due to imported wood materials and products is envisaged in the foreseeable future. The primary criterion for controlling the species adapted to the commercial trade and climatic change would be the elaboration of a monitoring system in affected and exposed areas.

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Sunflower production plays an important role in global industrial oil production. Two-spotted spider mite, Tetranychus urticae, is a dangerous, polyphagous arthropod pest with a cosmopolitan distribution, which can endanger the economic features of global sunflower production. It is widely known that pests trigger various reactions in host plants. Among these, detection of ultra-weak photon emission (UPE) enhanced upon infestation is a novel, non-invasive method suitable for the visualisation and monitoring of both biotic and abiotic stress in living tissues. In the present study, the increase in ultra-weak UPE triggered by biotic stress caused by T. urticae in Helianthus annuus was measured. UPE response of injured plants differed from that of the control plants, which was reflected by a difference in bioluminescence intensity. In leaves attacked by T. urticae the onset value of average photon count detected by the sensor and expressed in cps (counts per second) was one order of magnitude higher on average as compared to that revealed by uninjured leaves. Furthermore, UPE emission in infested leaves resulted in an abrupt decrease in the ultra-weak photon emission intensity when assayed as a function of time. The use of this non-invasive imaging technique has allowed the detection of the injury induced by T. urticae, as a biotic stressor.

To determine the cotton bollworm migrating population rate in Hungary, we examined the weights and the front wing morphological feautures of trapped moths. We used sex pheromone traps to monitor field populations during the maize vegetation cycle period in 2008. We examined moths trapped at various times, and measured their body mass (m) and morphological features, namely the front wing quotient (fWQ = quotient of length of front wing/width of front wing), modified wing loading (WL = weight of moth/surface of front wing), and the relative thorax size (RTS = width of thorax/width of head). The data were analysed by Student t-test, anterior wing abrasion and darkness were analysed by a Adobe Photoshop 7.0 software. The Hungarian appearance of three cottom bollworm generations in 2008 was also observed. Based on the examined morphological features we found regularity in body mass, front wing quotient and modified wing loading changes during the flight period. The specimens trapped in the first and third part of the flight period had lower body mass, larger wing surface, longer wings and more favourable modified wing loading than the specimens trapped in the middle of the flight period. The abrasion and colour of the anterior wings of cotton bollworms were concordant to morphometric investigations. The abrasion in darker spots E1 and E3 clearly showed a more intensive usage of the wings in case of specimens trapped at the beginning and at the end of the flight period.