The gypsy moth is one of the most devastating forest pests in North America. The Ohio Department of Agriculture, in common with other state agencies involved in the Gypsy Moth Suppression Program, uses aerial sketch mapping each year to map gypsy moth damage. We compare results obtained from Landsat 5 and Landsat 7 to locations determined by aerial sketch mapping to locate gypsy moth infestations in Ohio. The haze-corrected ratio of Landsat band 4 (near infrared) to band 3 (red) detects changes of leaf area. We subtract the ratio values from two dates to determine the change. As in previous studies, we search for the defoliation caused by the gypsy moth by subtracting the ratio values of frames acquired in early June and late June. Unlike previous studies, we use the subsequent refoliation that takes place between late June and late July as part of the signal. This is seen as large positive ratio subtraction values between early June and late June and large negative ratio subtraction values between late June and late July. Pixels that exhibit these attributes are candidates for gypsy moth defoliation. The use of three frames to analyze both defoliation and subsequent refoliation results in a stronger, less ambiguous signal of gypsy moth damage and pinpoints the locations of the most severe defoliation. The most severe defoliation often marks the location of egg masses. Although we reduced the ambiguity caused by agricultural anomalies, this procedure also detected areas with significant wild grapevine infestations.

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