|Skaria, Mani - TX A&M CITRUS CTR-WESLACO|
Submitted to: Biannual Workshop in Color Photography and Videography in Resource
Publication Type: Proceedings
Publication Acceptance Date: May 16, 2001
Publication Date: December 1, 2004
Citation: Fletcher, R.S., Escobar, D.E., Everitt, J.H., Skaria, M., Davis, M.R. 2004. Aerial videographic and digital imaging surveys of insect and disease infestations in south texas citrus orchards. Biannual Workshop in Color Photography and Videography in Resource. CD-ROM. Interpretive Summary: Insect and disease infestations cause a reduction in citrus production throughout the Lower Rio Grande Valley of Texas. Ground surveys are used to evaluate these problems, but they are time consuming, expensive, and do not provide a detailed assessment of an orchard. Therefore, growers, extension agents, agricultural consultants, etc., are looking for quick and deffective ways for detecting and assessing disease and insect problems in citrus groves. This paper presents a review on the use of aerial videographic and digital imaging systems as potential tools for surveying insect and disease infestations in south Texas citrus orchards. Blackfly infested citrus trees could be differentiated from healthy citrus trees on color-infrared (CIR) videographic imagery. Mildly foot rot-infected trees had a dull red appearance on CIR digital imagery; whereas, healthy trees appeared in a bright red color. Temporal analysis of CIR digital imagery revealed that citrus trees with severe symptoms of greasy spot infection were easily detected during the winter months due to foliage loss in their canopies' center portion. These results suggested that airborne videographic and digital imagery have the potential for detecting and assessing insect and disease problems in citrus orchards. The near-real-time capabilities of these systems provided an efficient and quick way of assessing citrus grove conditions. These findings should be of great interest to citrus growers, extension agents, pathologists, consultants, etc., for citriculture pest management.
Technical Abstract: 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 citrus 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 greater the 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 foliage 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.