Interactions between host plants and Coccus hesperidum L. (Hemiptera; Sternorrhyncha; Coccidae)

Understanding of complex relationships between the insects and their hosts is one of the main aims of current ecology and plant protection. Although a great number of Sternorrhyncha studies have been carried out on basic plant–insects interactions during the last ten years, interaction between plants and scale insects are poorly described. Therefore the following research aims were accepted in order to determine: 1) the effect of host plants on morphometric, demographic parameters and age structure of C. hesperidum developing on various host species; 2) the plant acceptance and colonization by C. hesperidum 3) the process of C. hesperidum feeding monitored in plant tissues using EPG; 4) honeydew excretion dynamics on various host plant species; 5) the response of C. hesperidum to host plant biochemical properties; 6) the effect C. hesperidum feeding on biochemical changes of colonized plants; 7) host plant susceptibility to C. hesperidum feeding. The studied material consisted of two-year old plants of Citrus limon var. Ponderosa, Ficus benjamina and Nephrolepis biserrata. The examined plant species are characterized by various degree of susceptibility on C. hesperidum feeding. Low degree is characteristic for Ficus benjamina, on which a decreased rate in a development of C. hesperidum colonies was noted with unprofitable influence of this plant on morphometric, demographic parameters, as well as feeding and honeydew of this scale insect. The studies for the first time have shown the differences in the degree of plants acceptance by C. hesperidum are conditioned by their constitutional properties: leaves structure and mainly biochemical composition. The differences in host plants colonization by scale insects result from an induction via stimulation or limitation of the concentration of substances constitutionally observed in the plants. The results obtained may be used in the practice, and especially practical application may be found for the results of the study on honeydew process and on mechanisms of plants resistance on C. hesperidum feeding.