水稻生育期对褐飞虱和白背飞虱卵巢发育及起飞行为的影响

The effects of rice growth stages on the ovarian development and take-off of Nilaparvata lugens and Sogatella furcifera

研究了取食分蘖初期、拔节期和孕穗抽穗期稻株上的褐飞虱和白背飞虱成虫的卵巢发育和起飞情况。其中,水稻生育期对褐飞虱的影响相对较小,不同生育期稻株上试虫的卵巢发育级别羽化后的4d内均无显著差异,羽化后第5天的褐飞虱在孕穗抽穗期卵巢发育最快,分蘖初期最慢,拔节期居中。褐飞虱的起飞率在各个生育期均无显著差异。白背飞虱卵巢发育、起飞率均受水稻生育期的显著影响,在水稻分蘖初期,卵巢发育最快,孕穗抽穗期则卵巢发育最慢,拔节期居中,水稻分蘖初期,起飞率最低,孕穗抽穗期起飞率最高,拔节期居中。结果表明,水稻生育期对两种飞虱卵巢发育和起飞行为的影响明显不同。认为水稻生育期对两种飞虱卵巢发育与起飞行为的不同影响,应是水稻田间白背飞虱发生较早、褐飞虱发生较晚的一个重要原因。

The brown planthopper （Nilaparvata lugens （St？l）） and white-backed planthopper （Sogatella furcifera （Horváth）） represent two of the most important insect pests of rice in Asia, causing severe damage to rice production. Both belong to long-distance migratory insects but differ in the time when they reach maximum density during rice-growing season. S. furcifera generally reaches its peak of occurrence when rice is before the filling stage; while N. lugens reaches its peak at the rice filling stage. It is possible that the same rice stage might impact the two planthopper species differently, thus leading to such a seasonal difference in population growth. To test this, we inoculated newly-emerged adults onto rice plants at each of the three developmental stages, i.e., early tillering stage （about 40-d old, with 2-3 tillers）, jointing stage （about 60-d old, the longest internode 〈 2 cm） and booting-to-heading stage （about 75-80-d old）. The level of ovarian development and take-off rate were then measured daily from the 2nd to the 5th day and from the 1st to the 5th day after emergency, respectively. Ovarian development from 2nd to the 5th day was largely dominated by grade Ⅰ, Ⅱ, Ⅲ and Ⅳ, respectively, with three exceptions including the 4d- （dominated by grade Ⅱ） and 5d-old S. furcifera females （grade Ⅲ） at booting-to-heading stage plants, plus the 5d-old S. furcifera females （grade Ⅲ） at jointing stage plants. For ovarian development in N. lugens females, in vast majority of the cases the three rice stages showed comparable proportion of females at each of the detected ovarian development grades, we only observed significant difference between early tillering stage （73.2% of the females at grade Ⅳ） and booting-to-heading stage （89% at grade Ⅳ） on the 5th day. In contrast, the grade of ovarian development displayed much larger differences among the three rice stages for both 4d-and 5d-old S. furcifera females. In particular, over 86% of the females from rice early tillering stage developed into grade Ⅲ on the 4th day and into grade Ⅳ on the 5th day, versus less than one quarter of the females from the booting-to-heading stage. To a similar extent, the ratio of females at grade Ⅲ was 4.2：1 between jointing stage and booting-to-heading stage on the 4th day, along with a ratio of up to 6.8：1 between early tillering stage and jointing stage for the 5d-old females at grade Ⅳ. As for the take-off rate, while little variation was seen for N. lugens across the three rice stages, noticeable differences were revealed for 1d-, 4d- and 5d-old S. furcifera adults, with early tillering stage being constantly associated with the lowest take-off rate and booting-to-heading stage with the highest take-off rate. Thus, our results demonstrated a profound effect on the development of S. furcifera by a change of rice stage, as compared to relatively limited effect on N. lugens development. Furthermore, among the three rice stages, early tillering stage is most favorable and booting-to-heading stage is least favorable for S. furcifera development, a trend appearing to be reversed in N. lugens. Taken together, our analysis offers a plausible explanation for why the peak of S. furcifera comes before that of N. lugens.