Barton, Kathy

George Zentmyer Plant Pathologist George Zentmyer , professor emeritus of plant pathology at UC Riv - erside , received his Ph.D . in plant pathologyfrom UC Berkeley in 1938 and joined UCâ??s Citrus Experiment Station in 1944 as a plant pathologist . Zentmyer , a member of the prestigious National Acad - a leading authority on plant diseases caused by emy of Sciences , is the fungus Phytophthora , particularly Phytophthora cinnamomi , which causes severe root rot of avocado trees . His work has focused on root diseases , soil fungicides , biological control of soil pathogens and diseases of avocado trees and other subtropical and tropi - cal crops . The studies have provided a multifaceted approach to control and South America . I explored 17 or 18countries in plant diseases that threaten the multimillion dollar avocado industry . Latin American looking for sources of resistance in the many native avocados and relatives that grow in that region . You arrived in Riverside two years prior to the first issue of Califor - There were some soil fungicides that were available nia Agriculture . What brought you to Riverside ? up at that time . We experimented with those and set many field plots around San Diego , Santa Barbara , GZ : I came to Riverside because one of the early plant pa - Los Angeles counties to try and control Ventura and thologists here , Prof . William Horne , passed away in this disease by application of fungicides in the irrigation 1943and there was a search initiated to find someone to water . There were a few that showed some promise but take his place . nothing spectacular . We also did work on soil fumi - The Citrus Experiment Station was really beginning I began to research resistant types of gants . Thatâ??s when to expand and there was even more expansion in the avocado . We had a few indications , even with some of 1950sand 1960s.We were looking at an array of sub - our collections from Mexico , Guatemala and Central - fruits tropical and tropical crops including avocado America , that there was rootstock resistance . We pur - like macadamia , cacao , persimmon , and jojoba , espe - 20 to 30 years . In fact , sued that extensively in the next cially tree fruits and ornamental crops in Southern Cali - several of our selections have shown substantial resis - fornia that became extensive industries . There was also tance and several of these are now produced by the a great expansion in citrus research . Research was just nurserymen in California and various countries rou - beginning on a new disease , tristeza , known as â?? quick tinely as their preferred rootstock for planting in in - decline . â?? It posed a tremendous threat to the entire cit - fested soil . rus industry , not only here , but around the world . The This disease is still a problem around the world . horticulturists , entomologists and plant pathologists You can fumigate it in local spots and replant the tree 1950swhat was causing did not know until the early so successfull , it survives successfully , but the fungus is out it was a virus , the re - this disease . When they found in soil that has not been planted for years . search to find a control fell largely to our department , plant pathology . We found some rootstocks were resis - Looking back at your half - centuy association with the University of so there was a big expansion in rootstock research . tant , California , what would you say are the Universityâ??s most significant There were also quite a few insects that the entomolo - research and extension activities ? a gists under A1 Boyce were working on . It was quite growth period under Dr . Boyce from 1952up through 1970s . the GZ : Very remarkablewas the solving of the tristeza problems 1950s , determining this was caused by in citrus back in the When you arrived in 1944 , how did you perceive your role ? a virus , and finding rootstock with resistance and being able to control the spread of the disease.That disease decimated citrus not only in California , but in Brazil - GZ : The one major avocado disease , Phytophthora root rot , one of the originalsources of our citrus varieties . In rela - was just appearing then and it became a monstrous tion to avocado , the development of the new resistant problem for the industry . In fact , the cause of it had just rootstocks has helped to solve that huge avocadoroot rot I came , a soil been discovered about two years before problem , not only here , but in places like Israel , Australia Phytophthora cinnamomi . The big push in fungus called and South Africa . There have been new irrigation meth - avocado disease research was to find out what was ods , including the development of drip irrigation in the causing this disease , to find out what factors influenced 1960s and 1970s . Really , there are just too many to it , how the fungus survived in the soil and if we could name . There has been a very wide variety of problems find resistance and other means of control . What be - the University has been able to address and solve . 40 years came a large part of my research for the next - Kathy Barton was collecting avocado rootstock materials in Central CALIFORNIA AGRICULTURE , VOLUME 50 , NUMBER 6 38