For more than two decades, remote sensing techniques have been used to detect the presence of plagues affecting plants and animals. Anastrepha striata and Anastrepha ludens are currently being detected in guava cultures in Mexico by catching the flies in properly placed traps. The goal of this study is to demonstrate that remote sensing can be used to detect locations where flies are present or absent, simplifying the traditional method of detecting these pests. In the field, groups of traps were chosen where flies were captured, as well as areas where no flies were captured in the traps. Complete tree and leaf radiometric signatures were obtained, revealing significant differences between plagued and unaffected species. Then we selected a SPOT5 image from 2007 that corresponded to the study region in Calvillo, Aguascalientes, Mexico, one of the country’s major guava cultures. Supervised classification was used to locate the guava cultures in the image. The guava culture areas derived from this classification were validated by comparing them to maps of the cultured areas that were available. The image information Each class’s spectral signatures were created using this method. The separability of pairs of classes was also evaluated in order to maximize separation between classes. The image bands’ IR/R (infrared to red ratio) ratio was evaluated in 80 x 80 pixels around the locations of five traps where flies were captured and five traps where flies were not captured. Because other types of vegetation and soil coverage were excluded, only pixels with guava cultures were included in the analysis. The index distributions with flies collected and those without flies collected were separated into two groups. According to our findings, there are two distinct groups. We note that plotting the entire distribution of pixels around a trap provides a diagnostic view of the area, whereas individual index values do not, because values with and without flies overlap to some extent. Further analysis of other trap locations supported this split and revealed a third group of intermediate values between the two above, which are interpreted as locations where guava cultures are affected by The plague at an early stage of development, when the flies are not yet hatching and thus are not captured by the traps. We concluded that remote sensing techniques can detect the presence of Anastrepha striata and Anastrepha ludens in Psidium guajava L. cultures, even in the early stages of plague development. These findings also suggest that a systematic analysis of satellite images is warranted for detecting the presence of Anastrepha striata and Anastrepha ludens, which would supplement current techniques of physical capture of flies.
Author (s) Details
Instituto Nacional de Estadística y Geografía (INEGI), Av. José María Chávez 1913, Edifico Parque Héroespiso, Prados deVilla Asunción, Aguascalientes, Ags. 20280, México.
Prof. Roman Alvarez
Instituto de Investigaciones en Matemáticas Aplicadas y en Sistemas, Universidad Nacional Autónoma de México, Ciudad Universitaria, AP 20-126, San Ángel. México, D.F. 01000, México.
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