The Study Of The Corn Canopy Hyperspectral Character And Yield Loss After Damaged By Asian Corn Borer And Maize Curvalaria Leaf Spot

In this paper, the corn canopy hyperspectral character and yield loss were studied after infested by Asian corn borer, Ostrinia furnacali and maize curvalaria leaf spot, Curvalaria lunata at the two maize varieties in 2005 and 2006. One was highly susceptible to Asian Corn Borer, and the other one was highly susceptible to Maize curvalaria leaf spot. The ASD FieldSpec HandHeld was used to collecte the canopy spectrum at different damage level and growth stages of maize, and meanwhile, the disease index and leaf feeding rating were surveyed. The yield loss was measured at the harvest. The data were analyzed with statistics and main results were summarized as follows:1. The reflectance of canopy spectrum after infested with maize curvalaria leaf spot were getting bigger in the red region (630nm～724nm) but were getting smaller in the near infrared region (745-900nm) along with the increase of the disease indexes.The significant differences were shown among the control and 4 disease treatments.2. When the maize was damaged by the Asian Corn Borer, negative correlation coefficients were shown between leaf feeding rating and the reflectance of spectrum from 400nm to 900nm. The correlation coefficients in the near infrared region were higher than those in other spectrum regions. Comparing the corn canopy hyperspectral character of damaged by the insect pest with the disease, the reflectances of spectrum in the near infrared region have the higher negative correlation with leaf feeding rating and the disease index, respectively, so that the region from 745nm to 900nm can be used as the sensitive band for estimating the occurrence of the Asian corn borer and the maize disease.3. The changing of the chlorophyll content were different after damaged with the ACB and Maize Curvalaria Leaf Spot.There were no significant differences among the chlorophyll contents of 5 infested levels with ACB, While after damaged by the Maize Curvalaria Leaf Spot, the leafs chlorophyll contents were remarkable decreased and more significant differences among the 5 infested levels were found. 26 days after infesting, the chlorophyll content in the treatment of the highest disease index (78%) was lessen 1.41mg/g than that in the control.4. After damaged by the ACB and Maize Curvalaria Leaf Spot, the maximum of the first derivative value of canopy spectrum and the near infrared sprectrum values have significant negative correlation with the yield loss. Both can be used to assess yield loss(L). The equation for Maize Curvalaria Leaf Spot was L(dis)=53.8-3231.5P'(max), r=-0.84^**; the equation for ACB was L(borer)=84.93-224.79 R₈₁₀, r=-0.75^**,5. The 4 vegetation indexes of the reflectance of spectrum form the red spectrum region and the near infrared region were calculated according to the reported equations. All of them have a significant negative correlation with the leaf feeding rating (LF) or the disease index (DI). The vegetation index RDVI was the best one to assess LF or DI. The two equations are: for Maize Curvalaria Leaf Spot, DI= 123.27-167.71RDVI, r=-0.83; for ACB, LF=42.145-71.965RDVI, r=-0.634。...