The Studying Of Occurrence And Harmfulness Of Picea Crassifdia Seed Insects

This article discusses the current situation of research in conifer seed insects of home and abroad and outbreaks and harmfulness of Picea crassifolia seed insets. Because of the rampant outbreaks serious harmfulness of seed insects, the quantity and quality of picea crassifolia seed have reduced largely, which badly influences the ecological ruction of forest. So ,carrying out the study on its outbreaks and harmfulness can provide some clues for to prevention and control of seed insects.Through investigating, fourteen kinds of seed insects which affect female and male flower, cones and seeds of picea crassifolia are observed, mainly including pseudotomoides strobilellus L. Pammene ochsenheimeriana Z , Dioryctria schat2eella F. And torymus caudatus B, The four kinds of insects above often occur in mixture, I divides the distribution of picea crassrfolia seed insects in Qilian mountain into four regions.With regard to the severity, area and harmfulness of ports in seeds the east forestation area of Qilian mountain is greater ehan the west forestation area; marginal sparse forest area as well as unsoundly managed seed stands severer than densely forsetsed stand, and pure forest severer than mixed forests.Flat lend forest suffers greater attacks which weakens with the inerense of altitude, but strengthens with the reduction of precipatation in the mountain.Newly established mother trees stands in highes elevation as well as the mixed stands suffer the insect attacks slighfly.These are no obviouo clifferense among differenr shope directions, No attacks have been observed in the seed stands far away from the natured forest.The four species of seed pest attack in the same niche. There quantitieo fall in a geometric progression pattern, pseudotomoides strobilellus L and torymus caudatus B are dominant populations in the niche of picea crassifotia, causing the severest damage to the seed, the four specieo of seed pests have each coexistence.Investigation of the loss caused by the pests indicates that the number of pest attacked cones as in logarithm relations with average pest densities per cone, that the wefficienly of pest attacked seeds loss in linear relation with pests densities; that the loss caused by per pest attack is greater while the density is small, kind decrenoe while the density increases, but will reach to a stable level afterwards. The quality of the seeds declines with the posts density increases.Study on the life cycle of cones show that cones mainly suffer freezing damage, diseasecud pest attacks ,causing the loss of seeds from 15.7% to 21.3%, pest caused loss of seed reaches 11.4% to 53%.The results aboves reveal the law of outbreaks of picea crassifolia and its harmfulness, providing a refereut basis for the prevention and con frol of picea cran ifotcil.