AERIAL VIDEOGRAPHIC AND DIGITAL IMAGING SURVEYS OF INSECT AND DISEASE INFESTATIONS IN SOUTH TEXAS CITRUS ORCHARDS

摘要

Research has been conducted to determine the potential of aerial videographic and digital imaging technologies for detecting and assessing insect and disease infestations in south Texas citms groves. This paper presents an overview of those studies. Citrus trees having blackfly (Aleurocanthus woglumi Ashby) infestations were detected on color-infrared (CIR) videographic imagery due to the complex it develops with sooty-mold (Capnodium citri B. & D.). The greaterthe blackfly infestation, the greater the sooty-mold deposits on the leaves, thus, producing darker foliage on the tree canopies. Highly infested trees had a dark gray to black tonal response on the CIR imagery, whereas the healthy trees showed a bright red rendition. Color-infrared digital imagery showed that healthy trees can be distinguished from trees having mild symptoms of foot rot (Phytophthora parasitica Dast) infection. The infected trees had a dull red color in comparison to the bright red tint of the healthy trees. Multiple-date image acquisition with CIR digital imagery revealed that the best time to detect severe symptoms of greasy spot infection (Mycosphaerella citri Whiteside) in citrus tree canopies was during the winter months due to fohage loss in their canopies' center portion. These findings have shown that aerial CIR videographic and digital imagery can be used for detecting and assessing insect and disease infestations in south Texas citrus orchards.