Organic Control of Pear Psylla in Pear with Trunk Injection

Abstract

Organic production of pears is challenging in part because OMRI (Organic Materials Review Institute) approved biopesticides are short lived when applied as foliar sprays. Trunk injection is an alternative method of insecticide delivery that may enhance the performance of biopesticides for control of pear psylla. The objective of this study is to compare the efficacy of azadirachtin and abamectin in the control of pear psylla using two different application methods, airblast sprayer and trunk injection. Trunk injections of azadirachtin and abamectin were compared to airblast applications of equal labeled rates on 33-year-old Bartlett Pear trees (Pyrus communis L., var "Bartlett"). The azadirachtin and abamectin trunk injected treatments performed equally or better than the two airblast applications in the control of the pear psylla. The trunk injected trees from the first season provided a moderate level of control into the second season, one year after the injections. This study suggests that trunk injection is a superior delivery system for biopesticides used in organic pear production.

Keywords: abamectin; azadirachtin; pear psylla; trunk injection.

Figure 1

Mean number of pear psylla eggs (A) and nymphs (B) per 50 leaves in 2017 evaluations for the untreated and azadirachtin treatments. Values with ** above them represent a significant difference (p ≤ 0.05) between the untreated and both injection and airblast treatments.

Figure 2

Mean number of pear psylla eggs (A) and nymphs (B) per 50 leaves in 2017 evaluations for the untreated and abamectin treatments. Values with * above them represent a significant difference (p ≤ 0.05) between the untreated and the trunk injected treatment only. Values with ** above them represent a significant difference (p ≤ 0.05) between the untreated and both injection and airblast treatments.

Figure 3

Mean number of pear psylla eggs (A) and nymphs (B) per 50 leaves in 2018 evaluations for the untreated and azadirachtin treatments. There was no significant difference found between any of the treatments (p ≤ 0.05).

Figure 4

Mean number of pear psylla eggs (A) and nymphs (B) per 50 leaves in 2018 evaluations for the untreated and abamectin treatments. Values with ** above them represent a significant difference (p ≤ 0.05) between the untreated and both injection and airblast treatments.

Figure 5

Mean residue from leaf samples taken in 2017 azadirachtin trunk injection and airblast treatments (A) and of abamectin trunk injection and airblast treatments (B). Samples were taken 1, 7, 14, 28, 56, and 84 days after treatment (DAT). Residue is presented as ppm (µg/mL) above the level of detection (LOD) (abamectin LOD = 0.001 ppm) (azadirachtin LOD = 0.005 ppm). No residue was detected after 28 DAT for both abamectin and azadirachtin.