Comparative Study On Bionomics And Ecologics Of PH₃-resistant And Susceptible Strains Of Rhyzopertha Dominica.

Rhyzopertha dominica (Fabricius) ( Coleoptera: Bostrichidae) is a worldwild stored-product pest. It distributes in tropical and subtropical regions chiefly. Its host range is wide. Larvae have strong mandibles and cause tremendous damage by attacking whole grains and fragments. More than one beetle may be found in one grain. It is very difficulty to control when it feeds inside the grain. It is one of the most resistant pest of stored-product to insecticide. To provide basis for integrated pest management of R. dominica, the thesis compares difference of biological and ecological characters between PH₃-resistant strain and susceptible strain of R. dominica.1 Comparative study on biological characters of susceptible and PH₃-resistant strains of R. dominica (F.)The resistance folds of PH₃-resistant strain of R. dominica used in this study is 16.16. Sex ratio of R. dominica is less than 1 and sex ratio of PH₃-resistant strain is smaller than that of susceptible strain. Weight and length between susceptible and PH₃-resistant strains have not significant difference and correlation. Both susceptible and PH₃-resistant strains prefer flour to whole and fragment and prefer wheat to rice.2 Influence of temperature and food on development of susceptible and PH₃-resistant strains of R. dominica2.1 Influence of temperature on developmental duration of susceptible and PH₃-resistant strains of of R. dominicaTemperature have significant influence on development of R. dominica. High temperature and low temperature will increase the developmental duration. Developmental duration of susceptible strain of R. dominica are longer than that of PH₃-resistant strain. Food have significant influence on the developmental duration of larva and pupa, but no influence on the developmental duration of egg. Developmental duration of R. dominica feeding on maize flour is longer than that feeding on wheat.2.2 Interacted influence of temperature, strain and food on developmental duration of R. dominicaInteraction of temperature and strain and food and temperature have strong influence on developmental duration of R. dominica, except for adult. Interaction of strain and food did not influence developmental duration of egg. larva and pupa. Interaction of temperature, strain and food have strong influence on developmental duration of egg. but no influence on developmental duration of larva and pupa.2.3 Regression Analysis between developmental rate and temperatureThe relationships between developmental rate of susceptible and PH₃-resistant strains and temperature accord with Logictic curve generally at different condition. But relationships between developmental rate of 3^th instar, 4^th instar and 5^th instar and temperature are in accord with Quadratic curve.2.4 Relationship between larva instars of R. dominica and temperature.larvae feeding on maize flour pupate from 3^th instar to 6^th instar in all experimental temperature except 31℃in this study and from 3^th instar to 5^th instar in 31℃. larvae feeding on wheat flour pupate from 3^th instar to 5^th instar and the pupation percentage of 4^th instar is the biggest.2.5 Developmental threshold temperature and sum of effective temperatures ofsusceptible and PH₃-resistant strains of R. dominicaDevelopmental threshold temperature and sum of effective temperatures of egg of PH₃-resistant strain is higher than that of the susceptible strain, but developmental threshold temperature and sum of effective temperatures of larva and pupa is lower than that of the susceptible strain. Developmental threshold temperature of R. dominica feeding on maize flour higher than that of feeding on wheat flour in same strain. But sum of effective temperatures of R. dominica feeding on maize flour smaller than that feeding on wheat flour in same strain.2.6 Survival ratio of each stage of R. dominica in different conditionsEach stage of R. dominica at 22℃and 37℃has smaller survival ratio than that at other temperatures. Survival ratio of 1^th larva instar and 2^th larva instar are smaller than that of 3^th and 4^th. Survival ratio of susceptible strain is larger than that of PH₃-resistant strain. R. dominica feeding on maize flour has higher survival ratio than feeding on wheat flour.3 Humidity influence on development of PH₃-resistant and susceptible strains of R. dominica3.1 Developmental duration of PH₃-resistant and susceptible strains of R. dominicaat different humidities.Developmental duration of PH₃-resistant strain are shorter than that of susceptible strain in 32% RH,55% RH and 75%RH, but longer than that of susceptible strain in 84%RH and 90%RH. The range of developmental duration of R. dominica is 61.73～56.53d at 32%RH and longer than that at other experimental humidity. But The developmental duration reduces to 30.86³5.16d at 84%RH and shorter than that at other experimental humidity.3.2 Survival ratio of PH₃-resistant and susceptible strains of R. dominica atdifferent humidities.The survival ratios of PH₃-resistant strain and susceptible strain of R. dominica are different at different humidities. High humidity and low humidity reduce the survival ratio of R. dominica. Survival ratio of immature stage of susceptible strain is higher than that of PH₃-resistant strain. Survival ratio of immature stage of R. dominica feeding on maize flour is bigger than that feeding on wheat flour.3.3 Humidity influence on larva instar.Feeding on maize flour, larvae of PH₃-resistant and susceptible strains of R. dominica are pupate from 3^th instar to 8^th instar in 32%RH. In 55%RH and 90%RH, larvae of susceptible strain pupate from 3^th instar to 7^th instar and larvae of PH₃-resistant strain pupate from 3^th instar to 8^th instar. In 75%RH, larvae of PH₃-resistant and susceptible strains are pupate from 3^th instar to 6* instar, but pupating from 3^th instar to 5^th instar in 84%RH. Feeding on maize flour, larvae of susceptible strain of R. dominica pupate from 3^th instar to 5^th instar in 32%RH but PH₃-resistant strain from 3^th instar to 7^th instar. Larvae of susceptible strain of R. dominica are pupate from 3^th instar to 5^th instar in 75%RH but PH₃-resistant strain from 3^th instar to 6* instar. Larvae of PH₃-resistant and susceptible strains of R. dominica pupate from 3^th instar to 7^th instar in 55%RH, but pupating from 3^th instar to 5^th instar in 84%RH. In 90%RH, larvae of susceptible strain of R. dominica pupate from 3^th instar to 6^th instar but PH₃-resistant strain from 3^th instar to 8^th instar. The number of instar of larva feeding on wheat flour is less than that feeding on maize flour. The number of larva instar of susceptible strain are less than that of PH₃-resistant strain at the same condition.4 The influence of temperature, humidity and food on reproductive ability of PH₃-resistant and susceptible strains of R. dominicaThe higher temperature, the shorter pre-oviposition period. The pre-oviposition period of susceptible strain is shorter than that of PH₃-resistant strain. The number of egg oviposited in a day by one female at 37℃is more than that at 25℃. One susceptible strain female can oviposit more eggs than PH₃-resistant strain female does. The number of egg oviposited in a day by one female feeding on maize flour is more than that feeding on wheat flour.5 Population dynamics of R. dominica at different conditions5.1 Population dynamics of PH₃-resistant and susceptible strains of R. dominica atdifferent temperaturesPopulation number of susceptible strain of R. dominica within 100d or 130d is more than that ot PH₃-resistant strain. , but less than of PH₃-resistant strain after 160d. The population numbers of PH₃-resistant and susceptible strains of R. dominica are biggest at 160d, in 28℃, being 194 and 209. Through regression analysis on the population dynamics of R. dominica, we find only population dynamics of PH₃-resistant strain at 25℃and 37℃according with Logistic developmental model and others according with Quadratic developmental model.5.2 Population dynamics of R. dominica feeding on different foods and in differentshapesWe find population number of R. dominica feeding on fragment is more than that feeding on flour and the population number feeding on whole maize or wheat is the least Population number of R. dominica feeding on wheat is larger than that feeding on maize. Through regression analysis on the population dynamics of R. dominica, we find population dynamics of R. dominica feeding on wheat according with Logistic developmental model, the others according with Quadratic developmental model.