Abstract: [Objective] This study was to ascertain the impact of spatial structure on damaging degree of a natural secondary Japanese Red Pine forest in Kunyushan caused by pine needle blight, and provide academic direction for ecological control of forest pest.[Method] A six-hectares plot was set out in Kunyushan natural secondary Japanese Red Pine forest, three indexes, including mingling degree, neighborhood comparison and uniform angle, were selected and measured. The relationship between spatial structure and damaging degree of pine needle blight was analyzed. The disease incidence of host plants was used as damaging degree caused by pine needle blight based on a preliminary survey. To investigate the disease incidence, twelve twigs were pruned off randomly from four different directions (east, west, south and north) in the upper, middle and lower crown of each sample tree. Scab on needles of twigs caused by pine needle blight was observed. Disease incidence was calculated as the following formula, disease incidence (%)=length of scab/total length of needles×100%.[Result] 1) For pine needle blight on P. densiflora, all spatial structure indexes were negatively correlated with damaging degree, among which the two neighborhood comparison indexes of diameter at breast height (R²=0.962,P=0.003) and tree height (R²=0.794,P=0.043) were significantly correlate with damaging degree, and no significant relationship was found between damaging degree and Uniform angle index or mingling degree index. 2) For pine needle blight on P. thunbergii Parl, there was a negative linear relationship between damaging degree and mingling degree index (or diameter at breast height of neighbourhood comparison index), and the other spatial structure indexes were positively related with damaging degree, but all the relationship were not significant. 3) For pine needle blight on P. resinosa Ait, all spatial structure indexes were negative related with damaging degree, among which only the mingling degree index was significantly related. 4) In terms of host species, correlation between spatial structure with P. densiflora or P. resinosa was stronger than that with P. thunbergii. In terms of spatial structure, mingling degree and neighbourhood comparison were found stronger than uniform angle.[Conclusion] Among the spatial structure indexes, mingling degree and neighbourhood comparison were proved superior to uniform angle for regulating Kunyushan Web-spinning Sawfly ecologically. The relationship between spatial structure and damaging degree can be utilized, and to adapt ecological methods of rational planting and selective cutting for controlling pine needle blight damage during the course of forest management. For P. densiflora, mingling degree should be controlled beyond 0.5 to decrease damage; for P. thunbergii it should be controlled on a tolerable level; and for P. resinosa, mingling degree of middle level should be avoided. On the other hand, to take account of the difference of disease resistance among the above host plants, in order to strengthen resistance ability to pine needle blight of the ecosystem, a higher proportion of P. thunbergii and less P. resinosa should be planted for stand improvement.

Key words: pine needle blight, spatial structure, uniform angle, neighbourhood comparison, mingling degree, damaging degree