R.E Mickle¹, G. Rousseau and G.A. Cormier
¹ REMSpC Consulting

SERG Project #2001/01
Year of Project: 2006
Report Received: 2007

In many jurisdictions, the prioritization of forests for protection of timber loss from insect infestations results in a mosaic of stand sizes requiring treatment. Some Protection Planning System (PROPS) maps have shown that 50% of the stands had areas that were less than 7 ha. For operational aerial spray programs developed to protect stands with PROPS projected timber losses greater than 40 m3/ha, 50% of the stands (median size 7 ha) would receive less than 50% of labeled rate if treated in high (>10 kph at aircraft height) winds using a standard spray practice.

Forest Protection Limited and others through SERG-International have supported research and trials to investigate aerial application changes to improve deposit targeting into forested blocks. One of the earliest forestry trials involving flight line offsets and multiple passes on upwind lines (1997) have shown that deposit and drop density improvements up to 2.8 fold can be achieved in small blocks. In 1999, one framework for a smart guidance system was proposed that incorporated real-time meteorology coupled with the AGDISP model to predict spray fate and therefore alter spray guidance. Today with the integration of key technologies such as the ADAPCO Wingman GX and the Aventech AIMMS-20, smarter guidance (optimized spray) is now a reality.

The purpose of this Forest Protection Limited R&D project was to determine if better deposit (more drops) could be achieved using the best tools available (optimize spray) compared with a standard spray. In January and February 2006, trials were completed over open ground to evaluate deposit differences from a set of standard and optimized aerial applications to small (8 ha) and larger (64 ha) blocks. Block orientations (best and worse case scenarios) for the small blocks were investigated. An AT-802 aircraft equipped with flow control, auto booms, onboard meteorology, radar altimeter, ten atomizers and a new generation aerial management system was flown. The aircraft target height was 22.8 m and was calibrated for an application rate of 1.5 litres/hectare spraying Btk. Atomizer RPM was set to produce a 50μm VMD spray. Winds for all trials were brisk, ranging from 11 kph to 22 kph. Deposit and active ingredient was measured on Kromekote cards (>5 000) and drop density was determined as a measure of deposit efficacy. Past trials over forest indicate drop densities of Btk exceeding 20 drops/cm² on softwood tree foliage provide high efficacy against the eastern spruce budworm.

Improved deposit targeting into small blocks was achieved using the Wingman GX aerial management system’s real-time optimization. Problems with the AIMMS-20 firmware and the Micronair flow turbine at the time of the study compromised the extent of improvement. Using standard guidance, two thirds of the small 7 ha block received little or no deposit (< 5 drops/cm²). Under the best conditions, 11% of the small block kromekote cards received deposit >20 drops/cm². Using optimized guidance for crosswind sprays, the area in small blocks receiving low deposit (< 5 drops/cm²) was significantly lowered (2.5 fold) regardless of block orientation. Still, typically 25% of the small block area received low deposit using optimized guidance. Deposit of 20 drops/cm² and greater was significantly higher (3 fold) using optimized guidance especially for the best block orientation. As expected the poorest deposit targeting occurred on a small block using either guidance option when flight lines were within 30o of the wind direction.

In the second part of the trial, block deposit improved in the larger 64 ha block regardless of guidance option. For standard guidance, deposit improvement was noticeable at all winds speeds. In higher winds, 30% of the cards in the 64 ha block received greater than 20 drops/cm². Using optimized guidance, significant improvement was noted especially during high winds. Wind speed had little impact on targeting as flight line offset was adjusted accordingly. Seventy percent (61-75%) of the block received greater than 20 drops/cm² in winds up to 10 knots. Lower deposit was generally found along the upwind edge of the block, a situation that could be improved through flow adjustment or multiple line spraying.

In spite of having two key equipment problems during the trial; the AIMMS-20 firmware and the pulse readings from the Micronair flow turbine (see Addendum), improved deposit targeting into the target blocks was achieved.