Some of the common practices used in growing almonds were developed from research conducted by Mark Freeman, who retired on July 13, after 29 years as University of California Cooperative Extension citrus and nut crops advisor for Fresno County.
Much of Freeman's research -- such as using ant bait, culling almonds that have worm damage, and applying boron -- has led to advances in almonds, the county's second leading crop behind grapes.
"He was at his best when solving problems that had stumped growers," said Jeanette Sutherlin, UC Cooperative Extension director in Fresno County.
Freeman earned his bachelor of science degree in horticulture/food science at Virginia Polytechnic Institute and State University in Blacksburg, Va., and his master of science degree in horticulture at UC Davis. Fresh out of graduate school, he began an internship with UC Cooperative Extension in 1980. Within a year, Freeman became the citrus and nut crops farm advisor in Fresno County.
Freeman and colleague Rich Coviello refined the use of baits in ant control, resulting in the reduced use of broad spectrum insecticides in almond orchards. Before the use of ant bait, almond growers routinely applied organophosphate insecticides two weeks before harvest.
"The ant work has been tremendous because ants are a major pest in almonds," said Mario Viveros, UC Cooperative Extension farm advisor emeritus who worked in Kern County. "We have thresholds based on the number of ant colonies. We count the number of colonies on the orchard floor, then, based on that, decide to treat or not to treat. It has been quite successful. They basically have replaced use of organophosphates."
"Freeman's discovery that a crack in an almond shell had to be a certain size for navel orangeworm to enter and survive in the nut was important because the pest is associated with a higher potential for aflatoxin contamination," said Tom Gradziel, UC Davis geneticist. Processors now electronically sort out almonds that have navel orangeworm damage, dramatically reducing the risk of aflatoxin contamination in remaining nuts. Freeman's preliminary research showed that if the shells were well-sealed, growers didn't have to spend as much money on controlling the pest.
Freeman collaborated with Gradziel to evaluate new almond varieties, including the recently released, high-yielding Winters variety.
"Research conducted with Mark resulted in the establishment of new standards, and a new appreciation of the role of boron in almond productivity," said Patrick Brown, UC Davis professor of plant nutrition. "Boron application is now a well-established practice in the almond industry and has contributed to many growers better realizing the yield potential of their orchards."
Working out in the field, Freeman noticed that almond trees planted on peach/almond hybrid rootstock appeared to be resistant to a pest called tenlined June beetle, which damages the roots and can kill the tree.
"We hypothesized that some almond rootstocks might be more resistant to TLJB feeding, but to this day, I do not have any strong data to back that up," said Marshall Johnson, UC entomologist with Kearney Agricultural Center in Parlier. "One thing that was always confusing was why were the grubs damaging the rootstocks of almond trees, but not peach trees even though the same identical rootstocks are used for both almonds and peaches?"
Johnson continues to study the tenlined June beetle, which feeds on the roots of walnut, apple, cherry, plum and a few other trees as well as almond trees.
Despite his retirement, growers will continue to benefit from Freeman's work. A pruning video that he produced in the 1980s in English and Spanish with Viveros is still for sale.
The Almond Board of California has acknowledged Freeman for providing almond growers with practical information based on his research through news articles, technical reports and workshops.