Molecular Entomology, 2025, Vol.16, No.1, 19-27 http://emtoscipublisher.com/index.php/me 19 Methodological Article Open Access Laboratory Rearing Techniques of the Ostrinia furnacalis and Their Application in Bt Toxin Bioassays Rui Liu College of Life Science,Hainan normal university，Haikou, 571158, Hainan, China Corresponding email: rui.liu@126.com Molecular Entomology, 2025, Vol.16, No.1 doi: 10.5376/me.2025.16.0003 Received: 24 Dec., 2024 Accepted: 28 Jan., 2025 Published: 12 Feb., 2025 Copyright © 2025 Liu, This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Preferred citation for this article: Liu R., 2025, Laboratory rearing techniques of the ostrinia furnacalis and their application in bt toxin bioassays, Molecular Entomology, 16(1): 19-27 (doi: 10.5376/me.2025.16.0003) Abstract In this study, an artificial population of Asian corn borer (Ostrinia furnacalis) was established under laboratory conditions to provide the insect source required for Bt toxin bioassay. The initial insect source was obtained by collecting larvae and pupae from the field. Under the conditions of constant temperature of 26 ℃, relative humidity of 70%~90%, and photoperiod of 10 L: 14 D, the larvae were fed with fresh corn ears every day and their feeding and development processes were observed. It was observed that under laboratory conditions, it takes about 34~37 days for Ostrinia furnacalis to complete a generation. The average generation period of females is 36.2 ± 0.72 days, and that of males is 34.8 ± 0.72 days. The larval stage is 17-19 days, the pupal stage is 7-9 days, and the adult lifespan is 5-7 days. The larvae go through 5 instars, and the width of the head shell and the body length of each instar are significantly different. The investigation found that the feeding sites of larvae of different ages on corn plants were different. The second-instar larvae had a wider feeding range, while the older larvae mostly bored into the inside of the corn stalks to cause damage. In addition, the tolerance of larvae to Bt toxins increased with age. The established laboratory rearing method can efficiently cultivate consecutive generations of Asian corn borer, providing a standardized insect source for Bt toxin bioassay and resistance monitoring. Keywords Asian corn borer; Laboratory rearing; Life history observation; Bt toxin; Bioassay 1 Introduction The Asian corn borer (Ostrinia furnacalis) is one of the major insect pests of corn crops in Asia and the Western Pacific. In most corn-producing areas in China, the corn borer can produce 1 to 7 generations a year, and the larvae feed on a wide range of hosts, including corn, sorghum, cotton and dozens of other crops (Liu et al., 2021; Liu et al., 2023; Wang and Liu, 2023). Young larvae mainly feed on the heart leaves, filaments and tassels of corn, while older larvae bore into the stalks and cobs to feed on the grains, often causing the corn plants to fall over and the ears to mold, resulting in a reduction in corn yield, which can generally be as much as 10% to 30%. Transgenic Bt corn has high resistance to corn borers such as corn borers by expressing Bacillus thuringiensis toxin proteins. It has been widely planted around the world and is regarded as an effective means of controlling corn borers (Li et al., 2024). However, large-scale planting of Bt corn may exert continuous resistance selection pressure on target pests, and corn borer populations are at risk of evolving resistance to Bt toxins. In order to ensure the long-term plant protection effect of Bt corn, it is necessary to establish baseline data for resistance monitoring of target pests before promotion, and to continuously carry out resistance monitoring during the promotion process (Li et al., 2024; Wang et al., 2024). Laboratory artificial breeding technology is the basis for conducting biological research and resistance monitoring of corn borers. Artificial breeding can continuously provide a large number of developmentally synchronized, healthy and neat insect sources throughout the year for various experiments, such as laboratory bioassays to determine the sensitivity of corn borers to Bt toxins. As early as the 1970s, Chinese scholars began to explore the artificial feed formula and mass breeding technology of Asian corn borers, and made important breakthroughs, making large-scale indoor breeding of corn borers possible (Wang et al., 2000). Typical artificial feeds for corn borers contain nutritional components such as corn or bean powder, bran, yeast powder, vitamins, and some formulas also add agar to solidify the feed (Bernklau and Bjostad, 2008).
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