Aerial mapping canopy damage by the aphid Essigella californica in a Pinus radiata plantation in southern New South Wales: what are the challenges?

作者：Stone Christine^*; Carnegie Angus; Melville Gavin; Smith David; Nagel Matthew

来源：Australian Forestry, 2013, 76(2): 101-109.

DOI：10.1080/00049158.2013.799055

• surveys
• sampling
• canopy
• damage
• aerial surveys
• remote sensing
• Essigella californica
• Pinus radiata
• New South Wales

Surveying the location and level of damage by insect pests and diseases, such as canopy damage by the Monterey pine aphid, Essigella californica Essig (Hemiptera: Aphididae), a common defoliating pest of Pinus radiata, is now formally embedded in the management practices of most Australian softwood-growing companies. Aerial surveys, also known as aerial sketch-mapping, are a cost-effective means of mapping broad-scale canopy damage, but their accuracy is dependent on a range of factors including the spatial and temporal expression of symptoms associated with different damaging agents. For E. californica, the most distinctive symptom is yellowing (needle chlorosis) of the crown followed by defoliation of affected needles. The aim of this study was to compare canopy damage categories obtained by aerial sketch-mapping with mean crown damage estimates derived from a systematic, plot-based sampling scheme of a Pinus radiata plantation in Green Hills State Forest in southern New South Wales with a known history of E. californica infestations. We identified significant challenges to rating accurately the level of canopy damage from E. californica by aerial sketch-mapping. While the location of chlorotic crowns may be mapped reliably, our results suggest that it is much more difficult to visually resolve different levels of canopy damage within affected stands. Using an 'incidence x severity' damage rating score, only two classes of canopy damage were confidently separated (i.e. Low (not detected or trace levels) and High (having a damage score of greater than 25%)). Accurate location of these classes of damage allows targeted, ground-based surveys for follow-up diagnostics and more detailed estimates of damage at the crown scale.

• 出版日期2013