Detection of rubber tree orchards infested by Meloidogyne exigua using vegetation indexes obtained from satellite images

Hevea brasiliensis natural rubber production is strategic for the world economy. Meloidogyne exigua causes the main root disease in this crop in Brazil. Its early diagnosis allows better pest management, reducing losses. This study aimed to identify rubber tree orchard areas infested by M. exigua using remote sensing and vegetation spectral indices—normalized difference vegetation (NDVI) and simple ratio (SR)—generated from the RapidEye® satellite constellation images. Orchards under tapping in Minas Gerais state (irrigated) and Goias state (without irrigation) were sampled during the rainy season and soil, root and total nematode density were estimated. Although significant interactions between nematode density and vegetation spectral indices were found, none had determination coefficient (R2) greater than 0.31. Descriptive statistics of both orchards did not identify differences between the areas and root or total nematode density; however, nematode density in the soil in the Goias orchard was 236% greater than in the Minas Gerais orchard, while both spectral vegetation indices were lower in the former. Such differences might be a consequence of irrigation. Pearson’s, Spearman’s and Kendall’s correlations between nematode density and NDVI presented greater coefficients than SR for every parameter in both orchards. NDVI can be used to distinguish non-infested rubber tree orchard from one infested by M. exigua.