|Van Ee, Gary|
Submitted to: Journal of American Pomological Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2002
Publication Date: 2/1/2003
Citation: ELFVING,D.C., LOMBARDINI,L., MCFERSON,J.R., DRAKE,S.R., FAUBION,D.F., AUVIL,T.D., VAN EE,G., VISSER,D.B., EFFECTS OF DIRECTED APPLICATIONS OF PROHEXADIONE-CALCIUM TO TOPS OF MATURE PEAR TREES ON SHOOT GROWTH, LIGHT PENETRATION, PRUNING AND FRUIT QUALITY, JOURNAL OF AMERICAN POMOLOGICAL SOCIETY, 57(2):45-57. 2003. Interpretive Summary: The Washington State pear industry is based primarily on mature trees on seedling rootstock. These trees are normally trained to open-center system and develop a globular-shaped canopy. Such trees produce substantial shoot growth in the tops of the trees each year. This growth must be thinned or removed annually to maintain tree height and provide satisfactory light penetration into the lower canopy. Hand removal of this vigorous growth is time consuming and expensive. Use of chemical inhibitors to remove or reduce this canopy growth is desirable. This study reports on the use of low-volume Prohexadione-Calcium application to the upper portion of the canopies of mature pear trees to reduce excessive shoot growth. Time in pruning pear trees was reduced by treatment. Prohexadione-Calcium application improved light penetration into the lower portion of the canopy. Fruit size was reduced by the use of Prohexadione-Calcium application, but no other quality parameter was influenced by use.
Technical Abstract: Low-volume application of Prohexadione-Calcium (P-Ca, Apogee, BASF Corp.) to tops of mature pear trees reduced the vigor of shoot growth in relation to time of application, number of applications and amount of P-Ca applied. However, a second, late-summer flush of elongation of reated shoots occurred in most P-Ca treatments. Untreated trees did not produce a second growth flush. If shoot elongation in the tops of treated 'Bartlett' pear trees was reduced more than 60%, the tme required for dormant pruning entire trees was also reduced. Time to summer prune 'd'Anjou' trees was reduced by treatment with P-Ca. In wo of the three trials reported here, the weight of prunings removed from whole trees was reduced inproportion t the amount of P-Ca applied to the top halves of the canopies nly. P-Ca treatment improved light penetration into the lower portion of the canopy in mature 'd'Anjou pear trees whose canopies nearly touched in the row. 'Bartlett' fruit size was decreased when high concentrations of P-Ca were applied during the cell division phase of fruit development. P-Ca produced few changes in 'Bartlett' pear fruit quality characteristics at harvest, all of which disappeared after two months of air sotrage. Chemical names used: calcium 3-oxido-4-propionyl-5-oxo-3-cyclohexene carboxylate (prohexadione-Ca); polyoxyethylenepolypropoxypropanol, dihydroxypropane, 2-butoxyethanol (Regulaid).