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United States Department of Agriculture

Agricultural Research Service

Title: Plant Growth Regulator Effects of Fungicides Applied to Hop for Control of Powdery Mildew

Authors
item Nelson, M.E. - WASHINGTON STATE UNIV
item Eastwell, K.C. - WASHINGTON STATE UNIV
item Ocamb, C.M. - OSU
item Mahaffee, Walter
item Kenny, S.T. - WASHINGTON STATE UNIV
item Grove, G.G. - WASHINGTON STATE UNIV

Submitted to: Proceedings of the International Hop Growers Scientific Commission
Publication Type: Proceedings
Publication Acceptance Date: May 16, 2003
Publication Date: June 24, 2003
Citation: Nelson, M.E., Eastwell, K.C., Ocamb, C.M., Mahaffee, W.F., Kenny, S.T., Grove,G. G. Plant Growth Regulator Effects Of Fungicides Applied To Hop For Control Of Powdery Mildew.

Interpretive Summary: This work examines whether application of certain fungicides resulted in decreased yields of hop independent of the disease losses caused by hop powdery mildew. Several fungicides were applied on a calendar program throughout the growing season to large plots of hop 'nuggets' (a variety resistant to hop powdery mildew). Applications of tebuconazole during burr and cone development resulted in reduced cone size and weight.

Technical Abstract: Recently there have been reports of plant growth regulator (PGR) effects and resulting yield reductions associated with applications of fungicides for control of hop powdery mildew. Three trials were conducted to determine if fungicide applications can result in reductions in yield or quality, evaluate importance of growth stage on that activity, and identify potential problems with new products. Reductions in cone size and/or weight were observed with applications of tebuconazole (Folicur) in all three trials. An increase in beta acid (on a percent weight basis) was detected with tebuconazole applied during the burr (bloom) and cone development stages. Results suggest that PGR effects associated with tebuconazole can be avoided if applications are restricted to pre-burr. No PGR effects were observed with any other products tested.

Last Modified: 12/25/2014
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