Use of unmanned aerial vehicles for the diagnosis of parasitic plant infestation at the crown level in Pinus hartwegii

Forest degradation has increased in recent years due to biotic, abiotic, and anthropogenic factors. Parasitic plants are some of the main disturbance agents affecting forest resources. In temperate forests, the most frequent pest such as parasitic plants are from the genus Loranthaceae spp. Monitoring parasitic plants through traditional methods requires a large amount of time and human resources. Unmanned aerial vehicles (UAV) as a remote sensing tool have increased in popularity in different regions. UAV were used to assess the degree of infestation of Yellow Dwarf Mistletoe (YDM). In the present study, the presence of Yellow Dwarf Mistletoe (Arceuthobium globosum Hawksw. & Wiens) was identified using two information collection methods to estimate the level of infestation in a Pinus hartwegii Lindl. forest. First, the traditional method (Hawksworth) was used to estimate the degree of infestation per individual tree. Second, a remote sensing method using UAV was used to capture information at the crown level. Then, the Colorimetric Ranges at the Pixel Level (CRPL) method was used in conjunction with the decomposition of pixels with the RGB (Red-Green-Blue) model to define areas with the presence of infestation. The result of the methods was compared by calculating the pixels equivalence percentages identified as infested per level of infestation. The Hawksworth's method was used by determining three levels: level 0 (healthy) = 0-2% pixels; Level 1 (medium) = 3-5% pixels; and Level 2 (high) >= 5% pixels. The methods coincided in detecting a high level of infestation while were biased in detecting healthy trees and low levels of infestation. Nonetheless, the remote sensing method using UAV remains a viable alternative in the monitoring of mistletoe for its capacity to present an overall diagnosis of the level of infestation.

Automated summary

Forest degradation has been on the rise due to various factors, including biotic, abiotic, and anthropogenic factors. Parasitic plants, particularly from the Loranthaceae spp. genus, are a significant disturbance to forest resources. Traditional methods of monitoring parasitic plants require substantial time and human resources. Unmanned aerial vehicles (UAV) have emerged as a popular remote sensing tool in different regions. In this study, UAVs were used to assess the infestation level of Yellow Dwarf Mistletoe in a Pinus hartwegii Lindl. forest. The traditional method and a remote sensing method using UAVs were employed to estimate the degree of infestation. The comparison of results revealed that the remote sensing method using UAVs is a viable alternative for monitoring mistletoe infestation levels.