The Citrus Clonal Protection Program (CCPP) was established more than 50 years ago under the name Citrus Variety Improvement Program. Today, it stands as a cooperative program between the Citrus Research Board (CRB) and the University of California, Riverside (UCR), California Department of Food and Agriculture (CDFA), United States Department of Agriculture-Animal and Plant Health Inspection Service and the California Citrus Nursery Board (CCNB). The CCPP has been a core program of the CRB since the establishment of the marketing order in 1968. As such, the CRB has been the primary funding agency for day-to-day CCPP activities. Since 2009, the CCPP has been a part of the National Clean Plant Network (NCPN) for specialty crops. USDA-NCPN funding has supplemented CCPP activities in the past few years, providing funding for facilities and equipment upgrades. The CDFA and the CCNB have been providing CCPP with funding to execute the citrus nursery registration program for budwood and seed tree sources. UCR supports CCPP with infrastructure, facilities and all related indirect costs.

The goal of the Integrated Pest Management (IPM) core program is to conduct research to provide California citrus growers with a ‘state of the art’ IPM program. This core research program currently includes determining economic thresholds, developing sampling methods, applying insecticides in an appropriate manner, maximizing natural enemies and developing alternatives to insecticide treatments such as pheromone disruption. Advances in these methods help Pest Control Advisors and growers more effectively and economically manage pests, reduce unnecessary and ineffective treatments, manage pesticide resistance, reduce nontarget impacts on beneficial and other organisms and increase worker safety. Advances in these methods also minimize pests of export significance. Key citrus pests studied include Asian citrus psyllid, citrus red mite, katydids, citrus thrips, citrus peelminer, citrus leafminer, citricola scale, California red scale, ants, cottony cushion scale, cotton aphid, earwigs, bean thrips, mites of export significance and Fuller rose beetle. New pests and their control methods are incorporated into the IPM program as they arrive in the citrus growing areas of California or become problematic.

The aim of the integrated breeding core program is to develop or identify and evaluate new citrus scion and rootstock cultivars suitable for California conditions. Potential new scion cultivars are developed by hybridization selection and by mutation inductions while new rootstocks are developed by hybridization. Commercial cultivars from outside of California, budsport selection and Citrus Variety Collection are additional sources of other potential new scion and rootstock cultivars. In light of the increasing Asian citrus psyllid (ACP) population, and number of huanglongbing (HLB) infected trees in CA, new citrus scion and rootstock varieties that improve disease resistance are a specific focus. Varieties are also evaluated for enhanced flavor, market needs and production efficiency, all vital considerations for the citrus industry. The core program also includes ongoing lemon trials across the state and work on the University of California, Riverside campus to evaluate nutritional management and to better incorporate commercial farming practices into breeding and evaluation trials.