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- Author or Editor: Richard Ledebuhr x
Most highbush blueberries (Vaccinium corymbosum L.) in Michigan are treated annually with fungicides and insecticides with several types of sprayers. The goal of this study was to determine how sprayer type, pruning severity, and canopy development interact to affect spray deposition patterns. Deposition was measured as the percentage of the surface area of card targets that was covered following applications of black dye. Light measurements indicated that the canopy of blueberry bushes, regardless of pruning treatment, closed by the middle of June, and light levels within the canopy changed little from then until fruit harvest in August. A standard airblast sprayer that pushed spray up and through bushes provided acceptable deposition in all parts of the canopy early in the season, but later in the season, coverage was poor in the top and sides furthest from the sprayer. An above-row sprayer with fan-driven micronozzles also provided acceptable coverage throughout the bushes early in the season, but once the canopy had closed, coverage was poor in the bottom of the bush. Both sprayers were operated in bushes receiving light, moderate, and heavy pruning. The more severe pruning regimes increased the amount of spray deposited from the above-row sprayer, but not from the airblast sprayer.
Growing conditions in Michigan can threaten the yield and acceptable fruit quality of `Chardonnay' grapevines. Three grapevine training systems, mid-wire cordon (MWC), umbrella kniffin (UK), and a combination of the two (MWC-UK) were evaluated under Michigan growing conditions to determine their influence on yield, fruit quality, cluster compactness, incidence and severity of Botrytis bunch rot, and trellis fill. Vines were grown on C3309 rootstock and pruned to 44 nodes per kilogram of cane prunings. The MWC-UK treatment had an additional 30 nodes per vine retained, and the crop level on these nodes was removed after fruitset. Over a 2-year period, UK and MWC-UK trained vines had fruit soluble solids about 1 °Brix higher and yields were 48% and 63% higher than MWC trained vines, respectively. MWC-UK trained vines consistently out-performed MWC trained vines for all variables measured, while UK-trained vines provided an intermediate response.
Functional leaf area is the basis for vineyard productivity. Therefore, the leaf area displayed on a trellis will determine the productive potential of a vineyard. A device that uses a series of infrared sensors was constructed to quantify vineyard trellis fill. A vertical row of sensors on a moving over-the-row vineyard trailer recorded the interception of infrared light beams through the trellis. These values were related to the total time of measurement to calculate a percentage of trellis fill. Our device was used to quantify differences among training systems applied to `Chardonnay' grapevines. This system is quick, easy, and at least as accurate as currently used visual methods. This technique should be useful for determining the influence of various cultural practices on the development of grapevine canopies.
Highbush blueberries (Vaccinium corymbosum L.) in Michigan are treated annually with fungicides to control fruit rots caused by Colletotrichum acutatum J.H. Simmonds, Alternaria sp., and Botrytis cinerea Pers.:Fr. Control with recommended fungicide programs is often inadequate. The goal of this study was to compare the effects of two spray treatments and three levels of pruning severity on fruit rot levels in mature `Jersey' bushes. Two spray treatments were tested for 3 years: 1) recommended fungicide rates applied with a conventional airblast sprayer; 2) 67% of recommended fungicide rates applied with a multifan/nozzle, above-row sprayer. Pruning treatments included light and heavy pruning (compared for 1 year), and light, moderate, and heavy pruning (compared for 3 years). Fruit rot incidence was determined after incubating individual fruit at 100% relative humidity and 21 °C for 7 to 11 days, and after exposing 0.24-L plastic clamshell containers of fruit to simulated commercial handling. The above-row sprayer provided fruit rot control at least equivalent to the airblast sprayer even though less chemical was applied. Anthracnose rot in berries from the top of the bush canopy were reduced by pruning, but those in the bottom of the bush, and levels of other diseases were not consistently affected. Pruning also reduced yields, although the study was too short in duration to determine the long-term impact on production.