A Remote Sensing Characterization of the Effects of Anastrepha striata ＆ Anastrepha ludens on Guava Cultures in Mexico

Detection of the presence of Anastrepha striata and Anastrepha ludens in guava cultures is presently done in Mexico by actually catching the flies in strategically located traps. The objective of this study is to show that it is possible to locate areas with the presence or absence of flies by remote sensing means, thereby simplifying the traditional way of detection of these plagues. In the field, groups of traps were selected where flies had been captured, as well as areas in which there was no capture in the traps. The radiometric signatures of whole trees and leaves were obtained, showing measurable differences between those specimens affected by the plague and those unaffected. Next we selected a SPOT5 image of 2007 corresponding to the study area in Calvillo, State of Aguascalientes, in Mexico, one of the major areas of guava cultures in the country. A supervised classification of the image allowed for the location of guava cultures in it. The guava culture areas obtained from this classification were validated comparing them to available maps of the cultured areas. Spectral signatures for the classes were derived from the image data. The separability of pairs of classes was also evaluated in order to maximize it. The IR/R （infrared to red ratio） ratio of the image bands was evaluated in 80 × 80 pixels around the locations of five traps where flies had been captured, and around five locations where the traps had not captured flies. Only the pixels where guava cultures were present were included in the analysis, other types of vegetation and soil coverage were rejected. We found that the index distributions with flies captured and those without flies captured cluster in two well-separated groups. We note that plotting the whole distribution of pixels around a trap yields a diagnostic view of the area, and individual index values do not provide such a view, since values with the flies＇ presence and without these overlap to some extent. Further analyses of other trap locations confirmed this separation and also revealed a third group of intermediate values between the two above, that are interpreted as locations in which the guava cultures are affected by the plague at an early stage of development, where the flies are not captured by the traps since they do not yet hatch. We concluded that it is possible to use remote sensing techniques to identify the presence ofAnastrepha striata and Anastrepha ludens in cultures of Psidium guajava L., even probably at early stages of development of the plague.

Volatile organic compound emission and biochemical properties of degraded Ultisols ameliorated by no tillage and liming

TTie Ultisols in the Rana de Canamero area in Southwest Spain showed aluminum(Al)phytotoxicity,and the clearance of natural vegetation and decades of intensive conventional agriculture caused the deplation of soil organic matter(SOM).Therefore,we studied the long-term effects of no tillage and liming using sugar beet foam(SF)and red gypsum(RG),alone or in combination,on the restoration of Ultisols affected by acidification,Al phytotoxicity,and SOM depletion.We measured the main soil chemical properties,soil microbial biomass,soil enzyme activities involved in carbon,nitrogen,phosphorus,and sulfur mineralization,and the emission of volatile organic compounds(VOCs).The results indicated that liming effectively neutralized the soil acidity in the long term and,in combination with no tillage,significantly increased soil microbial biomass and enzyme activities.Twenty-three VOCs were detected using the proton transfer reaction-time of flight(PTR-ToF)technique,and both liming and tillage changed the VOC emission patterns.The greatest difference in VOC emission pattern was observed between no-tilled un-amended soils and tilled lime-amended soils,suggesting the activation of different metabolic pathways within the microbial communities of soils under different management.Differences in VOC emission patterns could be attributed to the decomposition of carbohydrates,which were also sustained by the higher enzyme activities in the lime-amended soils.