The aim of this experiment was to determine plant responses to Coccus hesperidum L. infestation on two host plants. Groups of five lemon and five fern plants were colonised by various numbers of mobile C. hesperidum instar nymphs. After 6 months, all scale insect individuals were counted on each plant. According to the insect density, the plants were divided into a five-degree series. In all density classes of host plants tested, the infestation of scale insects decreased the chlorophyll and carotenoid content as well as the value of three indicators of photosynthetic activity. The strongest decrease in the analysed pigments was observed for the smallest abundance of insects (first-class density) in lemon leaves and in second-class density in fern leaves. The strongest reactions of the chlorophyll fluorescence indicators were observed in density classes III and IV in the fern leaves and density classes IV or V in the lemon leaves. The reactions depended on the specific properties of plants and abundance of insects feeding on them.

The study aimed at comparing the changes in the content of free amino acids, phenolic compounds and the activity of PAL and TAL caused by two piercing-sucking arthropods: the grape mealybug (Pseudococcus maritimus Ehrh.) and the two-spotted spider mite (Tetranychus urticae Koch) in the leaves of orchid and strawberry, respectively. The obtained results show that the amino acid content and the ratio of amino acids to phenolic compounds increased in both plant species infested by the mealybug and the mite. However, such response was weakly dependent on changes in activity of the analysed enzymes. The pest feeding affected accumulation of the phenolic compounds, since the induction of the PAL activity in mealybug-infested orchid leaves during the first 5 h of the experiment preceded the increase in phenolic compounds during the first week of insect feeding. Instead, the increased activity of TAL was accompanied by elevated levels of phenolic compounds in the leaves of strawberry infested by mites. Mechanisms of biochemical plant responses induced by infestation of the studied herbivorous arthropods are discussed.

Plant chemical composition is an important determinant of host plant-insect interactions. For many insects sugars are the main factors determining the acceptability of a plant. This study investigated changes in plant chemical composition and differences in sugar composition of different host plants induced by the feeding of Coccus hesperidum L. (Hemiptera: Sternorrhyncha: Coccoidea). Present in plant extracts and honeydew there were three monosaccharide sugars: glucose, fructose and arabinose, and one disaccharide - sucrose. Arabinose was only found in extracts of Ficus benjamina plants. The sugar content of the honeydew was greater than in the extracts of control plants and lower than that in the extracts of infested plants. The honeydew collected from C. hesperidum feeding on the three plant species differed significantly in sugar content. Extracts of coccid infested plants of the three species used in this study contained more sugar than the un-infested control plants. The results show that honeydew composition of scale insects differ and the differences reflect the chemical composition of the host plants.

We examined the effects of feeding by the polyphagous insect Coccus hesperidum on its host plant Nephrolepis biserrata under different intensities of infestation. As an effect of scale insect feeding there were significant changes in the values of parameters reflecting the state of cell membranes. N. biserrata plants reacted to the biotic stress by increasing guaiacol peroxidase activity and decreasing catalase activity. Our data show that these processes play key roles in plant tolerance mechanisms, here the fern’s response to insect feeding. The observed complex reaction of N. biserrata testifies to actively proceeding, complex and very often contrasting mechanisms triggered with the aim of neutralizing the effects of biotic stress and enabling normal cell functioning in plants attacked by scale insects.

Sustainable and organic plant production uses natural products and natural self-regulation processes occurring in the ecosystem. The awareness is growing and the demands of consumers are higher and higher. One solution is to use various methods, as an alternative to pesticides. It is also very important to care for the stored crops after harvesting especially using non-chemical methods. The physical method of plant protection consists in treating the harmful organism with physical factors such as temperature, its same light and radiation, controlled atmosphere, special packaging, pressure, various sounds, ozone, and low-temperature plasma. The availability of effective application techniques opens up new possibilities for the storage of crops in order to maintain their health and quality for a long time. This review focuses on the analysis of physical methods of postharvest protection, especially the latest methods using ozone and low-temperature plasma. As a result, consumers of agricultural crops will be able to consume food free of insects, mycotoxins and pesticide residues.

Insect pests have major effects on agricultural production and food supply. Pest control in conventional crop management in orchards is mainly based on agrochemicals, which entails economic, health and environmental costs. Other approaches, such as biological methods or products based on biologically active substances and sex pheromones used for mating disruption, have faced some implementation challenges, particularly in relation to invasive insect species. The key for appropriate insect pest management is to identify the species and understand its biology and behaviour. Pest management systems should monitor, detect and inform fruit growers about changes in insect distribution, population ecology, possible damage level and economic loses. Comstockaspis perniciosa (San José scale—SJS) is a model example of a pest against which the method of integrated pest management should be adopted. This review presents a case study to support this statement.