Bionomics, Population Dynamics And Monitoring And Management Techniques Of European Sunflower Moth, Homoeosoma Nebulellum (Lepidoptera: Pyralidae)

The European sunflower moth, Homoeosoma nebulellum Denis et Schiffermuller (Lepidoptera:Pylaridae) is a serious pest of cultivated sunflower in northern China. It distributes in main sunflower production areas of China, likes Inner Mongolia, Jilin, Heilongjiang and Xinjiang. Larval H. nebulellum damage flower and seed of sunflower, great decrease yield and quality of sunflower. This pest has serious impacted on local economic development and farmers'income. In order to illuminate its regularity of occurrence and damage, and provide a scientific basis for its forecasting and monitoring. We investigated its hosts, developmental duration, occurrence period in field, overwintering regularity, life history, spatial distribution pattern and sampling technique of larvae and economic threshold in field of Bayannur, Inner Mongolia(N41.090, E107.22°),the major results obtained were as follows.Main Bionomics of H. nebulellum.H. nebulellum had 4 instars.The head capsule width of 1-4 instar larvae were 0.295±0.007,0.464±0.006,0.792±0.004,1.216±0.007mm. The later the larval instar, the more the body width and length of larvae increased, and obvious interleaving. The weight of 1-4 instar larvae were 0.160±0.024,1.467±0.128, 7.095±0.371,20.535±1.083mg,4 instar was gluttony preiod. Under temperature of 24℃, R.H.70% and photoperiod of L16:D8,the mean developmental duration of egg, larva, and pupa were 4.24±0.04,15.89±0.19 and 11.05±0.12 days. Preoviposition period was 9.25±1.68d. Longevity of male and female adults were 20.82±2.01 and 22.75±2.40 days, respectively. We appended sunflower jen flour to artificial diet on the basis of artificial diet of Poitout(1970) and Chippendale.(1979).The life parameters of H. nebulellum reared with this diet were closer to reared with sunflower seed, compared with artificial diet of Poitout(1970), in addition to the parameter of whole larval stage. But how to remove the excess oil of diet, improve the physical properties, so that H. nebulellum love to eat, shorten whole larval stage and breed a large scale under insectary needed further study. The highest H. nebulellum oviposition occurred 1 to 2 days after sunflower flowering, then decreased to lower levels the remained of the flowering period.65.30% occurred 1 days after the heads had opened,81.78% occurred 2 days.In the field, therefore, we should combine sunflower flowering with adult population dynamics to control this pest.Host plants, population dynamics and life history of H. nebulellum.The result of monitoring from 2008 to 2009 showed that the sunflower, Helianthus annuus L.,Garland chrysanthemum, Chrysanthemum coronarium Mill.,common cephalanoplos, Cephalanoplos segetum (Beg.)Kitam.,and common sowthistle, Sonchus brachyotus DC. in the family of Asteraceae were host plants for H. nebulellum and the last one was known as the new recorded host plant for this pest. There were two generations occurred annually in the field of this district as investigated by sex pheromone traps and filed surveys.The overwintering larvae began pupating in late April, then emerging in early May when they were not able to oviposit due to the absence of blossoming host plants, beginning period of the overwinter generation adules was May 13,full incidence beginning period was late June, and full incidence period was early July. Larvae in the first generation damaged sunflower blossoming in late July although they could also attack C. coronarium blossomed in late June, damage period was from late May to late August. Majority of the matured larvae in the first generation pupated and emerged after late July, but 9.2% of them entering diapause for hibernation. In early August, first generation adults enterred incidence beginning period, full incidence period was from mid-August to early September, ending period of adults was October 10. There were 144 days from beginning period to ending period in all.Larvae in the second generation damaged sunflower blossoming after mid-August. Most larvae began burrowing into soil for hibernation after mid-September but there were still 30% of larvae could not mature when sunflower was harvested. The immature larvae were transferred into impurities of sunflower seeds for overwintering. These results provided a scientific basis for forecasting and controlling H. nebulellum.Main behavior pattern of overwintering larval H. nebulellum.H. nebulellum had two hibernacula:soil of field and impurities of sunflower seeds. Most overwintering larvae spun cocoons at 0-4 cm of soil, larvae got less and less as the depth increasing. Overwintering larvae most like spun cocoons at 10% water content soil and between the block soil.The super cooling point of overwintering larvae rose smoothly in the overwintering period. However, the freezing point had not obvious trend. Body weight of overwintering larvae decreased smoothly in the overwintering period. Content of dissociated water decreased in the earlier stage, increased in the later stage, in contrast to content of combined water.Monitoring and management techniques of H.nebulellum.Six aggregation indexes were used to illuminate spatial distribution pattern of the larvae of H. nebulellum. The results showed that this pest had an aggregation distribution pattern. The formula of the logarithm of mean (m) and variance (S2) was:lgS2=lg0.2130+0.56391gm, which meant that the distribution pattern of the larvae got more and more evenness as the density increasing. According to Iwao regression:m*=8.1177+0.1447m, the basic element for the distribution was an individual colony in the field, and the individuals attracted each other, the individual colonies characterized with uniform distribution. The research of the aggregation meanλ(λ<2) indicated that the reason leading to aggregated distribution was environment. The theoretical sampling formula for the larval H. nebulellum was established as followed:n=911.77/m-85.53 (D=0.1)and n=227.94/m-21.38 (D=0.2).The sequential sampling formula were T1(n) T0(n)=7.40n±4.54(?) (Confection sunflower) and T1(n)T0(n)=10.05n±2.29(?) (Oil sunflower).A comparison of sex pheromone, frequency trembler grid lamp and blacklight lamp for monitoring adult population dynamics was made in Bayannur. The result indicated that the sex pheromone was better than the frequency trembler grid lamp and blacklight lamp for monitoring adult population dynamics. Therefore it was generally suitable to use the sex pheromone for monitoring adult population dynamics. The resistance of different sowing dates to H. nebulellum in sunflower in Bayannur was researched. Timely delay sowing date would improve the resistance of sunflower to H. nebulellum.The lowest damage rate and density were in the May 26.We suggested hybird sunflower should planted betweem May 26 and June 5 in Bayannur, Inner Mongolia. The regression equation of larva density and yield loss in confection sunflower and oil sunflower were y1=0.0072x1-0.0133,y2=0.0109x2-0.0395, EIL were 4% and 7%, action threshold were 7.40 and 10.05 larvae per sunflower, respectively. In recent years, sunflower varieties updated faster and faster, yield increased year by year, the price of sunflower seed volatile, so we should flexible use action threshold.