Extension Teaching

Over the years I have given talks, classes, workshops and field demonstrations on numerous topics related to fruit and nut tree and crop growth, physiology and management. Many of these have been specifically related to tree pruning and fruit thinning and especially in understanding tree responses to pruning and fruit thinning.

Over the years my colleagues and I have developed several harvest prediction models for fruit and nut crops (see the Harvest Prediction Models on the Fruit & Nut Research and Information website) and I have also attempted to do some extension education on these topics. I have also been involved in the development of size-controlling rootstocks for peach and been involved in many field meetings demonstrating these rootstocks and communicating the physiological mechanism underlying size-controlling.

Biology and Technology of Fruit and Nut Tree Production
A New Course Offering: Principles of Fruit and Nut Tree Growth, Cropping and Management
Currently, I am involved in the development of an intensive course focused on understanding how trees work. Course content includes the basics of tree fruit and nut biology, and how it relates to orchard management. The 2-week course is taught by UC Faculty, Extension Specialists and Farm Advisors.

The first offering of the course was in 2013 and is offered annually in the winter. For more information, including instructor profiles, schedule, and enrollment details, click here to visit the course website.

Grower Talks

Below are the titles of some of my favorite grower talks:
Taking the Art out of Pruning
Principles of Fruit Growth
Basic Physiology of Fruit Trees
New Size-Controlling Rootstocks for Peaches and how they Work
How Spring Temperatures affect Fruit Size

Extension Publication

The following are a few papers that my colleagues and I have co-authored on some of the extension topics mentioned above:
DeJong, T.M., W. Tsuji, J.F. Doyle, and Y.L. Grossman. 1997. Do high density systems really pay? Evaluation of high density systems for cling peaches. Acta Horticulturae 451:599-604.
DeJong, T.M. 2006. Physiological and developmental principles of peach tree and fruit growth related to management practices. Acta Horticulturae 713:161-168.
Lopez, G. and T.M. DeJong. 2007. High spring temperatures decrease peach fruit size. California Agriculture 61: 31-34.
DeJong, T.M., R. Favreau, M. Allen and P. Prusinkiewicz 2008. Using computer technology to study, understand and teach how trees grow. Acta Hort 772 : 143-150.
DeJong, T.M., K.R. Day and R.S. Johnson. 2008. Physiological and technological barriers to increasing production efficiency and economic sustainability of peach production systems in California. Acta Hort 772: 415-422.
Lopez, G. and T. DeJong. 2008. Using growing degree hours accumulated thirty days after bloom to help growers predict difficult fruit sizing years. Acta Hort. 803:175-180.
Lopez, G., C. Smith, R. Favreau and T. DeJong. 2008. Using L-PEACH for dynamic simulation of source-sink behavior of peach trees: effects of date of thinning on fruit growth. Acta Hort 803:209-216.
Lopez, G., K.R. Day and T.M. DeJong. 2011. Why do early high spring temperatures reduce peach fruit size and yield at harvest? Acta Hort 903:1055-1062.

Workgroup Associations

Cling Peach
European Pear
Prune/Dried Plum
Pomology Extension Coordinating Conference (PECC)