The Population Growth Of Meadow Moth, Loxostege Sticticalis, As Affected By Host Plant Preference

Meadow moth, Loxostege stictica/is L. (Lepidoptera: Pyralidae) is one of the most serious polyphagous insect pests in the north, northeast, and northwest China. Ovipositing and feeding preferences and mechanisms by which a suitable host plant is located by meadow moth are, therefore, critical to understand the interaction and co-evolution of meadow moth and its host plants, and design a successful integrated meadow moth management program. Preference of adult and larval meadow moth to host plants, the amounts of food intakes by larvae, the development, growth and reproduction of the insect as affected by host plants, major components and bioassay of the plant volatile chemicals, and sensilla on antenna of both male and female adults were investigated in the field and laboratory. The major progress obtained from these studies are summarized as follows: Field investigations were conducted to understand the oviposition preference of host plants by female meadow moth in an outbreak area. These were accomplished by checking and counting the eggs deposited on various crops and weed species in the field plots after a preliminary investigation. Results obtained demonstrated that most eggs were deposited on lambsquarter, Chenopodium album L. (Chenopodiaceae), followed by soybean, Glycin max L. (Leguminosae) and sugar beet, Beta vulgaris L. (Chenopodiaceae), corn, Zea mays L. (Gramineae) and potato, Solanurn tuberosum L. (Solanaceae) plants in a decreasing order. Number of eggs found on lambsquarter exceeded 50% of the eggs found on all the plant species investigated. These results were consistent to the oviposition preferences of meadow moth tested in laboratory, suggesting that C. album is the most preferred host plant for female oviposition while soybean and sugar beet are the next. To understand why female adult L. sticticalis oviposited preferably on lambsquarter, larval feeding tests were conducted in laboratory conditions. Larvae selected only lambsquarter as food when it was offered together with soybean, corn and potato plants. Soybean, however, was the most favorite food of larvae in comparison with potato and corn when lambsquarter were absent. Under such a condition, quantity of soybean intake by any instar of larvae was about half of the total amount of 3 crop species whereas the quantity of larvae intake of corn and potato were significantly decreased. Thus, the female oviposition preference is consistent to the larval feeding preference. Host plants significantly affected development and growth of larvae and pupae. Developmental periods of larvae and pupae were around 17 days when larvae were fed with larnbsquarter or soybean but those fed with corn or potato plants needed 24 days to complete their development. Furthermore, pupae from larvae fed with soybean and lambsquarter were with heavier pupal weight than those fed with corn and potato plants. In addition, larvae fed with the former two plant species had higher survival rates than those fed with potato and corn. Results also demonstrated that the development, pupal weight and survival rate were greatly improved in larvae that shifted to corn or potato plants from lambsquarter since 3rd instar, suggesting food for the first-3 instar larvae is crucial to the growth and development of meadow moth. Host plants also significantly affected adult reproduction and other parameters. Adults grown from lambsquarter had higher mating percentage, shorter preoviposition period, and gr...