Anthony H. VanWoerkom

Spatial and temporal distribution of trunk-injected imidacloprid in apple tree canopies.

BACKGROUND Pesticide use in orchards creates drift-driven pesticide losses which contaminate the environment. Trunk injection of pesticides as a target-precise delivery system could greatly reduce pesticide losses. However, pesticide efficiency after trunk injection is associated with the underinvestigated spatial and temporal distribution of the pesticide within the tree crown. This study quantified the spatial and temporal distribution of trunk-injected imidacloprid within apple crowns after trunk injection using one, two, four or eight injection ports per tree. RESULTS The spatial uniformity of imidacloprid distribution in apple crowns significantly increased with more injection ports. Four ports allowed uniform spatial distribution of imidacloprid in the crown. Uniform and non-uniform spatial distributions were established early and lasted throughout the experiment. The temporal distribution of imidacloprid was significantly non-uniform. Upper and lower crown positions did not significantly differ in compound concentration. Crown concentration patterns indicated that imidacloprid transport in the trunk occurred through radial diffusion and vertical uptake with a spiral pattern. CONCLUSION By showing where and when a trunk-injected compound is distributed in the apple tree canopy, this study addresses a key knowledge gap in terms of explaining the efficiency of the compound in the crown. These findings allow the improvement of target-precise pesticide delivery for more sustainable tree-based agriculture.

Seasonal and Cross-Seasonal Timing of Fungicide Trunk Injections in Apple Trees to Optimize Management of Apple Scab

To optimize the number and timing of trunk injections for season-long control of apple scab (Venturia inaequalis), we evaluated 1 to 2 and 4 seasonal and cross-seasonal injections of potassium phosphites and synthetic fungicides and quantified residues in leaves and fruit. Phosphites accumulated in the canopy at the highest concentrations, aligned well in time with scab suppression, and gave better leaf scab control of 41.8 to 73.5% than propiconazole (16.9 to 51.5%) or cyprodinil + difenoconazole (5.4 to 17.4%). More injections of phosphites controlled leaf scab better than fewer (23.7% versus 48.2%), and more fungicide injections resulted in 21.9 to 51.1% better leaf scab control than fewer. Leaf scab control with phosphites was only 3.2 to 13.9% better with 4 cross-seasonal compared with 4 seasonal injections, while 1 to 2 seasonal compared with 1 to 2 cross-seasonal injections improved scab control only for 4.2 to 22.1%. On shoots, injected phosphites provided comparable or for 4.4 to 10.5% and 22.3 to 41.4% better scab control than spray standards. On fruit, injected phosphites slightly improved control compared with sprayed phosphites or the sprayed fungicide standard (33.4 to 40.8%). Two seasonal injections of phosphites controlled shoot scab 5.7% better than 9 spray applications. Five sprays of cyprodinil + difenoconazole controlled scab better than their injections. Fruit residues of phosphites reached 2.8 ppm and declined in all treatments except in 2 seasonal injections and phosphite sprays. Cyprodinil and difenoconazole fruit residues reached 0.02 and 0.07 ppm and declined sharply toward the end of the season. These were far below the United States, Codex, and EU MRL-s of 1, 0.8, and 0.5 ppm for difenoconazole, and 1.7, 2, and 1 ppm for cyprodinil, respectively.

Control of Codling Moth in Apple, 2014

The purpose of this test was to evaluate season-long apple programs against a broad spectrum of apple pests; with an emphasis on CM. Two-tree plots were established in a 27-yr-old planting of “Delicious” (tree and row spacing of 10 by 20 ft) located at the Trevor Nichols Research Center in Fennville, MI (Indigo Block). Treatment plots were replicated four times in an RCB design. All treatments …

Plum Curculio Control in Sweet Cherry, 2014

The objective of this trial was to test the efficacy of various compounds against PC in sweet cherry. Two-tree plots were established in an 18-yr-old “Hedelfingen” sweet cherry planting (row spacing 20 ft by 15 ft) located at the Trevor Nichols Research Center (Sweet Cherry 3). Treatments were replicated four times in an RCB design. …

Control of a Broad Spectrum of Insect Pests in Peach, 2014

The objective of this trial was to evaluate the efficacy of season long insecticide spray programs in peach, with a focus on OFM. Two-tree plots were established in an 8-yr-old planting of “Red Haven” peach trees with row spacing of 20 ft by 18 ft; located at the Trevor Nichols Research Center in Fennville, MI (Peach 8 Block). Treatments were replicated four times in an RCB design with at least one buffer …