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Citrus and Date Palm Specialist - Glenn C. Wright

My role as extension specialist at the Yuma Agriculture Center is through a split appointment (60% extension, 40% research) with responsibility for developing an externally funded applied research and extension program centered on fruit crop physiology, chiefly with citrus. My position has existed in Yuma since 1935, and I am the fourth person to occupy it. Because citrus can be grown in six Arizona counties (trees are found as far east as Tucson and as far north as Bullhead City), and the commercial industry is found in four counties, my position has state-wide responsibility. I also conduct some research in the California desert citrus growing areas.

Some of my cooperative work has focused on investigating ways to improve irrigation and fertilization efficiency while not sacrificing citrus yield or quality. These projects have included the use of low volume irrigation systems, in contrast to the traditional flood, and the application of nitrogen through those irrigation systems in accordance with "Best Management Practices". Other related projects have included a determination of the ways to improve the application efficiency of flood irrigation through the use of soil moisture deficit data. Also, I am testing foliar slow release nitrogen fertilizers that may lead to more efficient nitrogen application.
I am also investigating cultural practices that may be used in improve citrus fruit packout. Packout refers to the combination of fruit size and quality that leads to the best grower return. In two separate studies, I am researching the effect of potassium applications on citrus fruit yields and quality. Plant growth regulators and citrus tree girdling are two additional cultural practices that I am investigating. Several of my projects involve orchard floor management. Together with cooperators, I investigate how traditional disking, non-traditional cultivation methods and clean culture with herbicides affects plant growth, water usage, fruit yield and quality, and weed population dynamics. We are also investigating the effects of clover cover crops on the above parameters.
I have also concentrated my efforts on citrus scion and rootstock evaluation and breeding. Some cultivars that are commonly grown in other citrus growing areas of the US do not perform well in the desert Southwest. Additionally, the Arizona citrus industry’s reliance on lemons necessitates a continual search for new lemon cultivars and rootstocks that are compatible with lemon. One major study involves the search for a rootstock that is resistant to brown heartwood rot fungus, Coniophora eremophila. In this work, we wish to determine why some rootstocks appear to be more susceptible to fungal invasion than do others.
My breeding work also is aimed toward developing new citrus scions or rootstocks that are compatible with lemon. I also evaluate new deciduous stone fruit and blackberry cultivars for their suitability to the climate of the low deserts of southern Arizona.

My extension work involves education, chiefly in regards to citrus. I speak to commercial growers, master gardeners and homeowners regarding citrus in several locations across the state annually. Additionally, I write for the local newspaper and appear occasionally on television. Also, I edit the Arizona Citrus Newsletter, a quarterly publication that is now on the World Wide Web at

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