Studies On Biology And Population Dynamic Of Pseudaula Caspiscockerelli In The Mangrove Of Kandelia Candel

Mangrove is a specific tree which grows in intertidal zone of tropical and subtropical coast. It is one of the highest primary productivity of the marine ecosystem and plays an important role on regulating coastal ecological balance. However, mangrove resources had decreased quickly for the reason of rapid growth of humanbing, urban expansion and inappropriate economic development on beach. Mono-cultivated mangrove forest which is favor of the outbreak of a lot of pests has become a major obstacle in protection project of mangrove scince recent 20 years. Pseudaula cockerelli is a pest of terrestrial landscape plants in a long time. However, it was found on the mangrove forest of Kandelia candel in Fujian and had formed prosperous population, which caused badly damages. Aimed to congtrol the pest, its biological characteristics and population dynamics in the mangrove were studied by means of field observations and lab feeding during 2006-2009. The main results are as follows.1. P. cockerelli in the mangrove takes place 6 generations every year in Xiamen and shows severe generation overlap. Most developmental stage of the winter population is the second instar nymph with no clear sign of over-wintering. The annual average fecundity is 72.3 eggs each femal and the most daily fecundity reaches to 91 eggs which happens in September. The annual mean sexual ratio (female: male) is 1.42:1. The individual number in the mid-tide area is higher than that in the high-tide area. Morphology of P. cockerelli in the mangroves has no significant difference when comparing with terrestrial P. cockerelli. But the second instar nymph and adult of P. cockerelli in the mangrove have thicker and whiter wax layer. Meanwhile, the second instar male nymph is covered by the testa of female adult in the mangrove, but uncovered in terrestrial host plants.2. The population of P. cockerelli in the mangrove has kept a very higher level from March to June. Its population number is generally higher in the first half year than in the second half year. The quantity of March to June will determine the annual population density. However, the population density on Michelia figo keeps a relatively higher level in the first half year, and then decreases, but increases in November. The population density on Michelia alba maintains in a steady level in the whole year, only shows a obvious peak period in May. The population density and mortality of P. cockerelli in different hosts are influenced greatly by the mean temperature, the lowest temperature and the highest temperature in a month, extreme minimum temperature and extreme maximum temperature. The population density of P. cockerelli in the mangrove is affected by changing the survival of female adult. The population on M. figo is influenced by changing the second instar nymph and male adult. While the population on Michelia alba is changing by affecting the first instar nymph and female adult. The month average rainfall has significantly influenced on population cardinal number and mortality of the second instar nymph in the mangrove. The population increasing of the second instar nymph in the mangrove is inhibited by the mean monthly relative humidity. But the average relative humidity is favorable to the development of female adult on M. figo.3. Based at the first instar nymph, life tables of P. cockerelli in different host plants were constructed. The results showed that the other factors were the key factors to influence the population in the mangrove. The key factors to influence the M.figo population and the M.alba population were the parasite and the other factors. The phase of 2th instar nymph in 1st~2nd and 5th~6th generation, the female adult in 3rd~4th generation were all the key phase to influence the population in the mangrove, but the female adult phase which were the key phases of all the population in the M.figo and M.alba. The sequence of the mean indices of population trend for P. cockerelli in different host plants was I (mangrove)>I(M. figo)>I(M. alba).4. P. cockerelli in different host plants all appeared aggregating distribution in the year period, but showed higher aggregating intensity from March to May than the other months in the mangrove. The population in the mangrove presented aggregating distribution in different intertidal zones, in which the space was lower, the time of plants immersing in seawater was longer, andits aggregation was higher. This might help the population to survive under the sea water stess.5. The supercooling points of P. cockerelli in different host plants showed no significant difference. However, initial sensitive lethal low temperature was lower in Kandelia candel than that in M. alba. All developmental stages and population of this pest in the two hosts were all highly in accord with Logistic's model. But population in Kandelia candel had better cold tolerance than in M. alba.6. The results of simulation test of seawater immersing indicated that different instars of P. cockerelli in the mangrove have dissimilar adaptability to seawater. Tidal immersing showed a certain effects on the mortality of low instar nymphs and eggs. Eggs all appeared high mortality at different immersing time. The mortality of other insect states were relative low after 2 hours immersing, and then improved gradually, and reached to the peak after 8 hours immersing. The mortality of 12 hours immersing showed no significant difference comparing with the mortality of 24 hours immersing. The normal tidal immersing of mangrove in the high-tide area was commonly less than 4 hours. Therefore, tidal immersing has no important influence on development and survival of this pest except of eggs, which was favor of the pest outbreak in the mangrove. During immersing in seawater, air membrane on the surface for the testa surficial tension was obsevered. It was considered an important cause of the adaptability against the seawater immersing.