Implications of Irrigation Method and Amount of Water Application on Phytophthora and Pythium Infection and Severity of Root Rot in Highbush Blueberry

Abstract

<jats:p>A 2-year study was done in Oregon to determine the effects of irrigation method and level of water application on the development of root rot in northern highbush blueberry (<jats:italic>Vaccinium corymbosum</jats:italic> L. ‘Duke’). Plants were grown on mulched, raised beds and irrigated by overhead sprinklers, microsprays, or drip at 50%, 100%, and 150% of the estimated crop evapotranspiration requirement. Soil at the site was a silty clay loam. By the end of the first season, plants were largest with drip, intermediate-sized with microsprays and smallest with sprinklers; however, this was not the case the next season. By the end of year 2, plants irrigated by drip had less canopy cover, fewer new canes, lower pruning weights, and only half the shoot and root dry weight as plants irrigated by sprinklers or microsprays. Destructive sampling revealed that the field was infested by root rot. Less growth with drip was association with higher levels of infection by the root pathogen, <jats:italic>Phytophthora cinnamomi</jats:italic>. <jats:italic>Phytophthora</jats:italic> infection increased with water application, regardless of irrigation method, but averaged 14% with drip and only 7% with sprinklers and microsprays. Roots were also infected by <jats:italic>Pythium</jats:italic> spp. <jats:italic>Pythium</jats:italic> infection likewise increased with the total amount of water applied but, unlike <jats:italic>P. cinnamomi</jats:italic>, was similar among irrigation methods. Overall, drip irrigation maintained higher soil water content near the base of the plants than sprinklers and microsprays, resulting in conditions more favorable to root rot. Sprinklers and microsprays may be better alternatives than drip at sites prone to problems with the disease.</jats:p>

Rainfall and temperatures changes have confounding impacts on Phytophthora cinnamomi occurrence risk in the southwestern USA under climate change scenarios

“…The expectation of B, B can also be computed analytically from the soil, climate and pathogen parameters, and provides a parsimonious metric of the risk posed by Pc for a given set of environmental and host conditions. 0:8, suggesting a rate of Type 2 (predicting no Pc when Pc was in fact present) errors in the range of 0-15%; (ii) examination of disease frequency on contrasting soil types in an intensively monitored Pc affected 5 95 km forest plot (Batini & Hopkins, 1972) lead to a model prediction that Pc would occur two times as frequently on clay soils than on sandy soil; observations showed that Pc actually occurred 1.9 times as frequently on clay soils than on sandy soils; and (iii) Finally, the model reproduced the near-linear increase in Pc disease severity from 20% to 60% root destruction on irrigated blueberries as the irrigation rate was increased from 0.5 to 1 to 1.5 times evaporative demand (Bryla & Linderman, 2007). The model was validated for two case studies in Western Australia and one agricultural case study in Oregon.…”

Linking Plant Disease Risk and Precipitation Drivers: A Dynamical Systems Framework

“…To address disease severity directly we applied the model to a Pc outbreak associated with drip-irrigation of "Duke" cultivars of blueberry Vaccinium sp. reported by Bryla and Linderman (2007). Irrigation occurs three times a week at three rates, set to provide 50%, 100%, and 150% of the estimated transpiration demand ( , 358 mm over the 5-month E max growing season).…”

“…Panel D shows the predicted mean pathogen extent predicted by the model for each irrigation treatment. The bars indicate the estimated range of the "vigor class" reported by Bryla and Linderman (2007) for each treatment. The results indicate that with minimal calibration the model can forecast soil moisture conditions and the resulting pathogen se-verity, given information about the cultural environment in which the crops were grown.…”

Irrigation water sources and irrigation application methods used by U.S. plant nursery producers

“…[] report that drip irrigation was effective in reducing pathogens such as Colletotrichum acutatum that cause anthroids in strawberry production. However, if proper placement and frequency of drip irrigation are not maintained, there is a chance of soil borne diseases caused by Phytophthora and Pythium [ Bryla and Linderman , ; Hanson and May , ].…”