Preliminary Study On Diapause Of Apolygus Lucorum And Adelphocoris Suturalis

In recent years, with the adjustment of cotton planting structure, the mirids which have replaced cottonworm have been become the most important hazard of pests on most cotton in China. Furthermore, these pests have spread to a range of other crops, e.g. Chinese date Zizyphus jujuba, grape Vitis vinifera. Apolygus lucorum and Adelphocoris suturalis are of the two important populations, which mainly distribution in the Yangtze valley and Yellow River drainage area. Overwintering is an important part of the life cycle of Apolygus lucorum and Adelphocoris suturalis. In this paper, The author preliminary studys of diapause of two mirids according to the overwintering.The major findings are as follows:The overwintering A. lucorum eggs and A. suturalis eggs could not hatch as usual at appropriate conditions (temperature 26℃, humidity 80±5% RH, light: L: D = 16:8), which indicated that the overwintering eggs were diapause. The non-diapause eggs of A. lucorum showed red eyespots when being incubated after five days under the same conditions and then turned yellow green. In contrast, the diapause eggs did not show red eyespots under the same conditions, but remained yellow. The non-diapause eggs of A. suturalis had respiratory horns but diapause eggs had not. Two red eyespots appeared in non-diapause eggs within 5 days under the same condition. The two characters can be used to distinguish diapause eggs from non-diapause eggs.The temperature is not the factor of diapause of two mirids, but photoperiod is the mian factor. A. lucorum eggs and A. suturalis can produce diapause individuals if the larval accept photoperiod treatment, which sensitive instar is 1st instar. The rate of diapause is different as the nymphs of different ages received the same light stimulus. Taking 1st instar nymphs as the standard, the critical photoperiod of A. lucorum eggs and A. suturalis was 13h16min, 13h14min respectively. Two mirids diapause eggs almost hatched no eggs Under the optimum conditions through 120 d treatment. under 4℃lower temperature and full sunshine ,the diapause eggs that be treated beyond 30 days can effectively relieve diapause eggs, but 35℃high temperature has not impact.The variation of diapause rate of dirrerent geographic populations is different. The diapause rate declined with increasing Dimensions according to the eggs oviposited at the fist day under the optimum conditions. The rate of diapause reached over 80%, which eggs wer produced by the last adult from different regions under appropriate conditions in early period. But the rate of diapause gradually decreased in pace with the elapse of spawning date, except for YuanYang region.The author gathered A. lucorum and A. suturalis from early August 2009 to midmonth of October in Henan region. The results showed that: The tuo mirids began to producee diapause eggs at the end of August. The most of the eggs had entered diapause By the mid-September. In addition, the rate of diapause decreased significantly when eggs were produced by two mirids which were gathered in 27th August.