Abstract：
Pecan is a valuable nut crop cultivated in the southeastern US. Among the major yield-limiting factors in the region is scab, caused by the plant pathogenic fungus Venturia effusa. Managing scab in tall trees (15 to 25+ m) in pecan orchards is challenging due to the limitations of getting sufficient spray coverage throughout the canopy. We explored the effects of hedge-pruning on scab in three orchards: 14 m tall cv. Desirable trees winter hedge-pruned on alternate sides to 11 m (site 1), 18 m tall cv. Stuart trees hedge-pruned on both sides simultaneously to 11 m (site 2), and 15 m tall cv. Caddo trees winter hedge-pruned in winter vs. summer to 11 m (site 3). At site 1 and 2 hedge-pruned trees were compared to non-pruned control trees. All trees received recommended fungicide applications to control scab via air-blast sprayer. Disease incidence and/or severity was assessed at different sample heights on shoots, foliage and fruit during three seasons (2020, 2021, and 2022). At site 1 the hedge pruned trees often had significantly or numerically more severe scab on foliage and fruit compared to the control trees, although the differences were mostly small. The frequency of mature fruit with scab severity <10% was greatest on control trees in 2021 and 2022. At site 2, there were few differences between hedge-pruned and control trees (on fruit, scab severity was either significantly less on hedge-pruned trees, or not different to the control), but the frequency of mature fruit with scab severity <10% was consistently greatest on hedge-pruned trees. At site 3, scab intensity was low, and there were no significant differences in scab severity between winter- and summer-pruning treatments. At sites 1 and 2 there was generally more severe scab at greater sample heights compared to low in the canopy. At site 3 there was little effect of height on disease. The benefit of hedge-pruning likely increases with tree height in scab-susceptible cultivars. If a tree is >~15 m tall, a greater proportion of the fruit will be within reach of efficacious spray coverage from air-blast sprayers.
摘要：
山核桃是美国东南部种植的一种有价值的坚果作物。该地区主要的产量限制因素之一是赤霉病，由植物病原真菌Venturia引起。由于在整个冠层中获得足够的喷雾覆盖率的局限性，在山核桃果园的高大树木（15至25m）中管理sc疮具有挑战性。我们在三个果园中探索了树篱修剪对sc疮的影响：14m高的cv。理想的树木冬季修剪至11m（场地1），18米高的简历。同时在两侧修剪Stuart树树篱至11m（场地2），和15米高的简历。卡多树冬季修剪树篱与夏季至11m（站点3）。在站点1和2处，将树篱修剪的树木与未修剪的对照树木进行了比较。所有树木都接受了推荐的杀菌剂应用，以通过鼓风喷雾器控制结痂。在芽上的不同样品高度评估疾病发病率和/或严重程度，三个季节的树叶和水果(2020年、2021年和2022年)。在地点1，与对照树相比，树篱修剪的树在叶子和果实上通常具有明显或数字上更严重的结痂，尽管差异大多很小。在2021年和2022年，对照树上结痂严重程度<10％的成熟果实的频率最高。在站点2，树篱修剪树和对照树之间几乎没有差异（在水果上，在树篱修剪的树木上，结痂的严重程度明显减少，或与控件不同)，但是在树篱修剪的树上，结痂严重程度<10％的成熟果实的频率始终最高。在部位3，结痂强度低，冬季和夏季修剪治疗之间的结痂严重程度没有显着差异。在位置1和2处，与冠层中的较低相比，样本高度较高的结痂通常更严重。在部位3处,身高对疾病的影响很小。在sc病易感品种中，树篱修剪的好处可能随树高而增加。如果一棵树>15米高，更大比例的水果将在来自鼓风喷雾器的有效喷雾覆盖范围内。
