Empty Bud Symptom on Pear Trees

In search for a means to prevent and control the recently wide-spread empty bud incidents on the pear trees in southern China, the regularity and cause of the disease were investigated. Interviews and field trips at 5 major pear-growing counties including Jianning, Qingliu, Mingxi, Jianou, and Dehua in Fujian, were conducted. And the pathogen isolation, insect dissection and microscopic observation on the collected samples were performed in the laboratory. In 2017, the infected area in the country totaled 14 951.4 hm² with an estimated loss on fruit yield of 597 000 tons. The disease gradually worsened starting from the floral bud sprouting and flowering periods of the plants. On the affected plants the florescence was prolonged for more than 5d, and the number of inflorescence per plant, flowers per inflorescence, and fruits per infructescence decreased by 71.02%, 55.07% and 53.85%, respectively, as compared to a normal tree, at an extremely significant difference level. The symptoms shown on a plant could be (a) with no new shoots nor flowers, (b) with only new shoots but no flowers, (c) with only flowers but no new shoots, or (c) with new shoots and scant flowers. Significant differences on the occurrence of the empty bud incidents were observed among different varieties. The disease occurred extremely significantly more frequently at orchards that used rain shelters, were located at low altitude, and/or had pear trees that experienced severe early defoliation. Under a microscope, phomopsis, Colletotrichum and 3 other pathogens, as well as the phytophagous tarsonemid mites, were found on the samples of the diseased plants. Serious decline and death of floral buds on the pear trees were resulted in recent years. However, at present the infection could only be preliminarily determined to be phomopsis.