INFLUENCE OF ADJUVANTS ON DISEASE DEVELOPMENT BY PLEOSPORA PAPAVERACEA ON OPIUM POPPY (PAPAVER SOMNIFERM) AND RESULTING YIELD LOSSES

Authors: Bailey, Bryan; Oneill, Nichole; Anderson, James

Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/22/2003
Publication Date: 5/6/2004
Citation: Bailey, B.A., Oneill, N.R., Anderson, J.D. 2004. Influence of adjuvants on disease development by pleospora papaveracea on opium poppy (papaver somniferm) and resulting yield losses. Weed Science. 52:424-432.

Interpretive Summary: Opium poppy is illegally grown in many countries for the production of the illicit narcotic drug heroin. Biocontrol strategies using the fungi Pleospora papaveracea are being studied as alternatives to current control measures. P. papaveracea produce spores that can be used in bioherbicide preparations. For a bioherbicide to be effective, formulations must be developed that optimize infection and disease development after application in the field. We evaluated formulations made up of various surfactants and other adjuvants for their abilities to enhance disease development in opium poppy after bioherbicidal applications of P. papaveracea spores. Of the adjuvants tested, Tween 20 (1% v/v) was most effective at enhancing diseases development by P. papaveracea. Within two to four weeks after application, opium poppy treated with P. papaveracea in Tween 20 (1%v/v) averaged 60% to 80% necrosis with an associated 40% reduction in yield. Tween 20 is readily available and has been shown effective as a surfactant in other bioherbicide formulations. Optimizing formulations should improve the potential for use of P. papaveracea as a bioherbicide for the control of opium poppy. This will offer drug enforcement agencies around the world new strategies for controlling illicit opium poppy production in the field.

Technical Abstract: The influences of formulation adjuvants on disease severity caused by bioherbicide applications of the opium poppy pathogen P. papaveracea were evaluated. Tween 20, Tween 80, Triton X 100, Tactic, Celgard, and Keltrol inhibited appressoria formation but not conidia germination on detached leaves. The disease severity varied from 10.7% to 82.5% necrosis in duplicate, one plant/plot, field experiments involving eight adjuvants at various concentrations plus or minus pathogen (field experiments one and two). The three best performing adjuvants, when combined with pathogen, Tactic (1% v/v), Bond (1% v/v), and Tween 20 (1% v/v), were included along with Tween 20 (0.001% v/v) in duplicate, four plants/plot, field experiments (field experiments three and four) in 1998. Tween 20 (1% v/v) plus pathogen caused the most severe disease averaging 68% necrosis within two weeks of treatment. Overall, plots treated with adjuvant plus P. papaveracea had a 22.3% reduction in capsule weight/plot as compared to plots treated with the adjuvant alone. The Tween 20 (1% v/v) plus pathogen treatment caused the largest reduction in yield, a 35.3% reduction in capsule weight/plot. Tactic (1% v/v), Silwet-L77 (0.1% v/v), Tween 20 (1% v/v), and Tween 20 (0.001% v/v) were included in duplicate, 16 plants/plot, field experiments (field experiments 5 and 6) in 1999. Again, treatment with Tween 20 (1% v/v) plus pathogen caused the most severe disease averaging 56.3% necrosis within two weeks of treatment. In 1999, plots treated with adjuvant plus pathogen averaged a 35.1% reduction in capsule weight, as compared to plots treated with the adjuvants alone. The Tween 20 (1% v/v) plus pathogen treatment caused the largest reduction in yield, a 42.6% reduction in capsule weight/plot.