Injector-size and the time of application affects uptake of tree trunk-injected solutions

Three different injectors, each 25 mm in length and with diameters of 6, 4, and 3 mm, respectively, were tested with low-pressure injections of 250 ml of water into 23 different species of fruit-trees, woodland and ornamental trees at different times of year. The 6 and 4 mm injectors performed well, yielding uptake of 75±100% of water volume 1 or 48 h after injection, depending on the species; however, the ornamental species Melia azedarach did not perform well with all three injectors. The 3 mm injector yielded highly irregular results. The 4 mm injector could substitute the more widely-used 6 mm injector in most cases, with the added advantage of reducing healing time. Injection uptake rates were greater on clear than on rainy days, this difference increasing with smaller-diameter injectors. Prunus species took up a high water volume when injected prior to budbreak, and this could avoid leaf burning caused by later injections of some chemicals. Uptake rates were lower during the winter rest period than during the peak growth season (spring). All these factors are to be taken into account in order to ensure the best and most ef®cient use of low-pressure injection of chemicals in agricultural, forestry or landscape practices. # 2000 Elsevier Science B.V. All rights reserved.