عنوان مقاله [English]
نویسندگان [English]چکیده [English]
Introduction: Investigation the relationship between herbivores and their host plant has long been one of the critical areas of study in plant science research. Herbivores should find sufficient nutritional and mineral compounds to survive on the Earth. Elm leaf beetle is one of the most destructive pests among species of elm family. This insect feeds from elm plants during its larvae and youth life cycle causing crest distortion and many other physiological problems to the host plant. These problems in turn decrease host plant’s resistance to other pests and diseases. In this vein, effects of some minerals such as nitrogen, phosphorus and potassium, in four host plants including Ulmus carpinifolia, U. carpinifolia var. umbraculifera, Zelkowa carpinifolia and Celtis coucasica , on larval development and survival of elm leaf beetle, Xanthoga lerucaluteola (Coleoptera: Chrysomelidae), were studied under laboratory conditions (26±2ᵒC, 65±5% RH and 16:8 L: D).
Material and Methods: Elm leaf beetle eggs were collected from the elm trees on the campus of faculty of natural resources at the university of Guilan, in north of Iran. Larvae were reared on different host plants in plastic jars and their biology and survival was determined. Some mineral compounds were assessed for the foliage of every host plants. Leaf nitrogen content was analyzed according to the technique introduced by Baker and Thompson. Phosphorus was measured based on Moore technique and potassium was determined by flame photometer based on Hanlon protocol.
Results and Discussion: Analysis of variance showed that there was significant difference between the four studied host plants in terms of amount of phosphorous, potassium and nitrogen. The highest and the lowest amount of phosphorous and potassium was observed in U. carpinifolia and Ta leaves respectively (F=22.56; df=8, 3 for phosphorous test and F=22.36; df= 8, 3 for potassium analysis). As for nitrogen, the amount of nitrogen is significantly higher in Azad treatment compared to other three treatments (F=168.98; df= 8, 3). In terms of survival and total larvae developmental time, first instar larvae which had reared on U. carpinifolia leaves developed into other instars in a significantly shorter time span, compared to larvae reared on other three host plants. It should be noted that larvae fed from Ta leaves did not developed into third instar; so for the fourth instar developmental time analysis only larvae fed from three other host plants were included in the analysis. In terms of pupal developmental time, analysis showed that the shortest developmental time was found in larvae reared on U. carpinifolia leaves (6.78 days) and the longest developmental time was seen in larvae fed from Azad treatments (9.32 days). As for survival of larvae, the result exhibited that larvae reared on U. carpinifolia leaves had a higher survival rate compared to larvae fed from other three host plants. Total larval developmental time of X. luteola was significantly highest on C. coucasica in comparison with the other three host plants used in the study. All larval instars showed the highest survival on U. carpinifolia and the lowest survival was found on C. coucasica. The results indicated that the larvae, which had fed on host plants with higher level of mentioned mineral, had shorter duration of development.
Conclusion: This research revealed that the mineral nutrition of host plants probably has significant effects on herbivore insects performance. It could be concluded that larvae developmental time and survival is highly dependent on the type of nutritional compounds which is probably due in turn to mineral compositions of the host plants. In other words, one can conclude that different kinds of minerals with different concentrations can probably be one of the main factors affecting developmental time and survival of larvae. It is suggested that more physical and chemical characteristics of elm tree be investigated and measured to achieve more precise result in the area of elm beetle larvae’s developmental time and survival.