Presentation Type
Proceeding Paper
Publication Date
8-14-2018
Subject Category
Blueberry Pests (insects, weeds)
Description
The goal of our three-year field study (two replicated two year trials) was to evaluate the influence of fertility and disease management practices commonly implemented by Maine wild blueberry growers during the prune year. Our treatments reflected grower practices. We tested applications of chlorothalonil (formulated as Bravo®), pyraclostrobin and boscalid (formulated as Pristine®), pyraclostrobin and boscalid with diammonium phosphate fertilizer (formulated as DAP®), and a non-treated control. Measured responses included sap-feeding hemipteran insects, fungal leaf spot pathogens, premature flowering, stem growth characteristics, flower bud cluster production, leaf retention, foliar nutrients, and yield. Among plant growth measures that represent potential yield, only stem length responded consistently over both trials. Plots treated with Pristine + DAP had significantly greater stem length compared to the other three treatments. Plots treated with Pristine only were not different than Bravo treated plots, but stems were significantly longer than the non-treated control. The fungicide, Pristine, and the fertilizer, DAP applied in the prune year enhanced leaf spot disease in both years; however, the combination of Pristine and DAP did not consistently effect yields. We found a significant and diverse community of sap-feeding hemipteran incidence in the 2016 trial, but not in the 2015 trial. Only in the 2016 trial did the Pristine and DAP treatment enhance sap-feeding bugs. Multivariate analysis of variance provided evidence that leaf spot pathogens and sap feeding insect pests responded positively to nitrogen concentration in foliage. We also found that fungicides do not compensate for the enhanced disease levels brought about by fertilizer application.
Start Date
14-8-2018 12:50 PM
End Date
14-8-2018 1:10 PM
Fertilizer and fungicides: Effects on wild blueberry growth, insect attack, and leaf spot disease incidence
The goal of our three-year field study (two replicated two year trials) was to evaluate the influence of fertility and disease management practices commonly implemented by Maine wild blueberry growers during the prune year. Our treatments reflected grower practices. We tested applications of chlorothalonil (formulated as Bravo®), pyraclostrobin and boscalid (formulated as Pristine®), pyraclostrobin and boscalid with diammonium phosphate fertilizer (formulated as DAP®), and a non-treated control. Measured responses included sap-feeding hemipteran insects, fungal leaf spot pathogens, premature flowering, stem growth characteristics, flower bud cluster production, leaf retention, foliar nutrients, and yield. Among plant growth measures that represent potential yield, only stem length responded consistently over both trials. Plots treated with Pristine + DAP had significantly greater stem length compared to the other three treatments. Plots treated with Pristine only were not different than Bravo treated plots, but stems were significantly longer than the non-treated control. The fungicide, Pristine, and the fertilizer, DAP applied in the prune year enhanced leaf spot disease in both years; however, the combination of Pristine and DAP did not consistently effect yields. We found a significant and diverse community of sap-feeding hemipteran incidence in the 2016 trial, but not in the 2015 trial. Only in the 2016 trial did the Pristine and DAP treatment enhance sap-feeding bugs. Multivariate analysis of variance provided evidence that leaf spot pathogens and sap feeding insect pests responded positively to nitrogen concentration in foliage. We also found that fungicides do not compensate for the enhanced disease levels brought about by fertilizer application.