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Title: Hedging and severity of pecan scab – a second year of results

item Bock, Clive
item Hotchkiss, Michael - Mike
item BRENNEMAN, TIM - University Of Georgia
item STEVENSON, KATHERINE - University Of Georgia
item GOFF, WILLIAM - Auburn University
item SMITH, MICHAEL - University Of Oklahoma
item WELLS, LENNY - University Of Georgia
item Wood, Bruce

Submitted to: Pecan Grower
Publication Type: Trade Journal
Publication Acceptance Date: 3/6/2015
Publication Date: 4/1/2015
Citation: Bock, C.H., Hotchkiss, M.W., Brenneman, T.B., Stevenson, K.L., Goff, W., Smith, M.W., Wells, L., Wood, B.W. 2015. Hedging and severity of pecan scab – a second year of results. Pecan Grower. 26: 34-47.

Interpretive Summary: Trade article.

Technical Abstract: Pecan scab, caused by the plant pathogenic fungus Fusicladium effusum, is the major disease of pecan in Georgia and elsewhere in the region. There are several reasons for hedging, and some issues may arise as a result of the hedging management practice. One of those issues might be increased disease. Three orchards n GA were chosen for the study. Within each orchard, all trees received the same orchard management (fertilization, herbicide, insecticide, fungicide and irrigation programs), with the exception of the hedging treatments applied to different trees trimmed using hedging equipment to maintain or reduce the height and width of the trees. Thus control trees (either non-hedged in the previous year, or not ever previously hedged) were compared to various hedging treatments. Results from three hedging experiments demonstrate that hedging does not increase or decrease scab severity when trees are receiving the same fungicide management program. Height influences fungicide coverage, and thus scab prevalence to a far greater degree. Based on these results from monitoring the scab epidemic in hedged and non-hedged trees in 2014, it is safe to say there is little effect of hedging on the severity of the disease. A beneficial effect of hedging might be to bring a much greater proportion of fruit within reach of efficacious fungicide coverage and thus overall improved yield and nutmeat quality in relation to the overall yield. Furthermore, hedging removes the portion of the tree at heights >45 ft not protected by fungicide. The upper canopy at heights >45 ft might be a source of inoculum early in the season. Moreover, the canopy at heights >45 ft develops scab which can be a source of inoculum for the lower parts of the tree. Removing or preventing this source of inoculum by hedging might also reduce the risk and/or severity of disease in the lower parts of the canopy. More information understanding spray coverage and penetration is desirable to explain these findings, and possibly improve disease control. Finally, these results reaffirm that scab can be extremely difficult to manage in wet years, and the results also confirm the impact of scab on fruit weight, particularly higher in pecan tree canopy, which is where fungicide coverage is less complete.