John Letey, Jr.
University of California–Riverside (UCR) Distinguished Professor of Soil Physics and Soil Physicist Emeritus John Letey, Jr. passed away on 14 September. He was 81 years old.
He received his B.S. degree at Colorado State University and Ph.D. degree at the University of Illinois. He joined the faculty in the Department of Irrigation and Soil Science at UCLA in 1959, but with the phasing out of agriculture at UCLA, he elected to join the Department of Soil Science at UCR in 1961 and enjoyed a distinguished career in research, teaching, administration, and service at the university. During his tenure, Dr. Letey served as chair of the Department of Soil and Environmental Science from 1975 to 1980, director of the Kearney Foundation of Soil Science from 1980 to 1985, and director of the University of California Center for Water Resources from 1999 to 2003. He was instrumental in the establishment of the Environmental Sciences undergraduate major at UCR, which was one of the first of its kind in the United States. He recognized and appreciated the critical link between science and policy and built teams and research to address it.
Letey's research focused on all aspects of water quantity and quality related to irrigated agriculture that provided both applied and basic information critical to establishing sound water resource management. Topics of research included irrigation, drainage, salinity, pesticide transport, plant–water relations, nitrogen, soil aeration, and polymers. He was also recognized as one of the world authorities on water-repellent soils and the utilization of surfactants. He wrote a biography of his education and professional career that can be accessed on the following website: http://envisci.ucr.edu/downloads/johnleteycareer.pdf.
Letey was a fellow of SSSA, ASA, and AAAS and was awarded the SSSA Soil Science Distinguished Service Award in 2005 and the SSSA Soil Science Research Award in 1970. He authored or co-authored more than 300 technical publications concerning chemical, water, and gas movement through soil before retiring from UCR in 2002. In 2007, he published a fictional book titled, The Folly of Fearing Death (PublishAmerica, Baltimore).
In 2003, Letey and Ardyth Stolzy, wife of the late Professor of Soil Physics Emeritus Lewis H. Stolzy, combined the Letey Soil Environmental Fund and the Lewis Stolzy Memorial Fund into the Stolzy–Letey Endowment in Soil and Environmental Science. The Stolzy–Letey Fund is now used for the benefit and support of the students in the Department of Environmental Sciences at UCR.
Letey was a friend and mentor to students, visiting scholars, and faculty across the world. He served his research community, church, and family with great love and personal integrity. He is survived by his wife, Sonia; three children, Laura Petersen, Don Letey, and Lisa Smith; 10 grandchildren; and 11 great-grandchildren./h3>
Here's a wide range of information on drought resources from ATTRA, the National Sustainable Agriculture Information Service - https://attra.ncat.org/attra-pub/summaries/summary.php?pub=458
- Author: Jeannette Warnert
UC Agriculture and Natural Resources scientists based at UC Riverside are honing in on odors that might lure Asian citrus psyllids into traps, and other odors that will keep them away from citrus trees, reported Mark Muckenfuss in the Riverside Press-Enterprise.
Anandasankar Ray, professor in the Department of Entomology at UCR, along with two other researchers, published results recently that Ray believes are promising enough they may soon be adapted for grower use.
Ray and his team tested three attractant odors in El Monte backyards using yellow sticky traps. More than twice the number of psyllids were found in the scented traps compared to unscented traps, the article said. In time the researchers will also test chemicals that can mask odors that are pleasant to Asian citrus psyllids and some that repel the insects.
Other research projects underway at UC Riverside to combat Asian citrus psyllid and the disease it can spread were also noted in the Press-Enterprise article. They are: biological controls, including a tiny wasp imported from Pakistan that feeds on the psyllids; insecticides; developing resistant strains of citrus trees; finding a way to kill the bacteria spread by psyllids once it is in the tree; and discovering ways to identify diseased trees earlier.
Edema may be caused by any agent that stimulates an abnormal increase in the size and number of a group of inner cells. Edema can be induced by (1) spraying with some chemicals such as ammoniacal copper carbonate in an oil emulsion, (2) injuries resulting from wind-blown sand particles and sucking insects, (3) high light intensity (over 2000 foot-candles) for ivy geraniums, and (4) accumulation of water in the intercellular spaces.
The most common cause of edema is the presence of abundant, warm soil water and a cool, moist atmosphere. Under these conditions the roots absorb water at a rate faster than is lost through transpiration. Excess water accumulates in the leaf, some parenchyma cells enlarge and block the stomatal openings through which water vapor is normally released from the plant; thereby contributing to further water retention in the leaf. If this condition persists, the enlarged cells divide, differentiate a cork cambium, and develop elongate cork cells externally to form a periderm. The rupture of the epidermis by the enlarged inner cells and the periderm account for the raised, crusty appearance of older edema spots.
Changes in weather and cultural practices of growing plants usually will avoid edema. To reduce the risk of edema occurrence, the following may be helpful:
1. Avoid irrigation or watering during cool, overcast humid weather. For potted plants in greenhouses, remove saucers under pots, or discard any water that remains in the saucer 30 minutes after watering. Irrigate or water when air temperature are rising or humidity is low.
2. In greenhouses: a) reduce the humidity of the air by venting and increasing heat; b) improve air circulation; c) increase light intensity; d) space the plants farther apart; e) for potted plants use a well-drained potting medium for potted plants and avoid standing water in saucers under the pots.
3. Avoid overfertilizing, especially when the plants are growing slowly, such as during the winter months. Maintain fertility based on a soil test. Avoid low levels of potassium and calcium.
4. Avoid cultivars that are highly susceptible to edema under your growing conditions.
The black spots on the fruit start out as a clear exudate. The same for the brown spots on the leaves.
Impacts of the recent drought conditions on Central Coast avocado production, and potential impacts of continued drought conditions
Avocados are the most salt and drought sensitive of our fruit tree crops. They are shallow rooted and are not able to exploit large volumes of soil and therefore are not capable of fully using stored rainfall. On the other hand, the avocado is highly dependent on rainfall for leaching accumulated salts resulting from irrigation water. In years with low rainfall, even well irrigated orchards will show salt damage. During flowering there can be extensive leaf drop due to the competition between flowers and leaves when there is salt/drought stress. In order to reduce leaf damage and retain leaves, an excess amount of water is required to leach salts out of the roots zone. The more salts in the water and the less rainfall, the greater leaching fraction. Drought stress often leads to diseases, such as black streak, bacterial canker, and blight (stem, leaf, and fruit). Defoliation leads to sunburned trees and fruit which can be severe economic losses.
Strategies to address drought conditions
Ensure that the irrigation system is at its greatest potential and is maintained. Avocados are grown on hillsides and pressure regulation is extremely important and is frequently neglected.
Significantly prune trees to reduce leaf area. Avocado can be a very large tree, and if half the canopy is removed, there can be as much as 1/3 reduction in water use. When trees are about 15 feet tall, removing half the canopy can reduce water use by one half.
In extreme drought conditions, the canopy can be reduced to just the skeleton branches which are white washed to prevent sunburn. Water use drops to zero, and then gradually as the tree leafs out, water can be slowly reapplied, but at significantly less amounts than with the full canopy. Stumping typically results in three years' worth of crop.
In orchards that have low producing areas, because of recurrent frost, high winds, shallow soils, disease, etc. the grower could decide to completely remove those trees, thereby saving water.
White kaolin applied to leaves has been shown to reduce leaf temperatures and water loss. This can be used, but under the direction of the packing house, since if it is applied to fruit, it is very difficult to remove.
Impacts of the recent drought conditions on Central Coast citrus production, and potential impacts of continued drought conditions
Citrus is much less sensitive to salts and drought than avocado, partially because of its greater rooting depth. However, it is much more sensitive than deciduous fruit trees, resulting in smaller fruit and lower prices when drought cannot be addressed with adequate irrigation water. Drought also makes the trees more susceptible to leaf drop, and sunburned fruit.
Strategies to address drought conditions
The strategies for citrus are very similar to those for avocado. It is much more sensitive to pruning to reduce water use than avocado. Typically removing half the canopy results in half the water use. Because of thus greater control, citrus is rarely stumped.
By reducing canopy size, production can be maintained, often without loss of fruit size.
Kaolin clay can effectively reduced water use and can be applied soon after harvest without the problem of coating fruit making its removal difficult at the packing house.