Monitoring of western corn rootworm damage in maize fields by using integrated radar (ALOS PALSAR) and optical (IRS LISS, AWiFS) satellite data

Abstract

The structure of a healthy, western corn rootworm (WCR) free cornfield shows straight rows in a clear order and upstanding corn stalks. The WCR larval infection causes wilted broken corn stalks lying randomly on the ground. That means the damage itself causes physical and visible disorder in the cornfield. Our goal is to assess and identify the disorder and structural changes caused by WCR using polarimetic radar images (ALOS PALSAR). We used three different individual features (monoculture-feature, optical-feature and radar-feature) derived from remote sensing data to identify WCR larval damage. The integrated assessment of the three features can give more accurate WCR damage identification than to assess features separately one-by-one. We carried out retrospective examinations and operational regional assessment in 2008 to test the efficiency of our remote sensing methodology. As a result of the retrospective examinations, the accuracy of damage identification was 61–70% with the one-by-one evaluation of the remote sensing features. The accuracy of damage identification is higher than 80% with the integrated evaluation of the three features. In 2008, through the operational regional assessments, we could identify 1085 ha (175 spots) of WCR damaged cornfields using our remote sensing methodology. We double-checked 10 of the identified spots on the ground. Only one spot of the 10 was WCR free. Five spots showed low WCR infection which appeared in smaller damage spots. One spot presented mid-scale and three spots high-scale damage. This project demonstrates the potential in the integrated assessment of optical and radar satellite images to assess and identify the disorder and structural changes caused by WCR larvae as well as other agricultural damages. Using polarimetric radar technique increased the accuracy significantly. By the successful development, this project can effectively contribute to the WCR identification, spread monitoring and control in Hungary as well as in the European Union.