CITRUS NURSERY PROPAGATION MANAGEMENT PRACTICES

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: HATCH
• Reporting Frequency: Annual
• Accession No.: 0217371
• Project Start Date: Jan 1, 2009
• Project End Date: Dec 31, 2013
• Program Code: [(N/A)]- (N/A)

Recipient Organization
UNIVERSITY OF FLORIDA
G022 MCCARTY HALL
GAINESVILLE,FL 32611

Performing Department
Citrus Research and Education Center, Lake Alfred

Non Technical Summary
Citrus canker (Xanthomonas axonopodis pv. citri) and citrus greening (Huanglongbing) diseases have led to significant changes in the production of citrus in Florida over the last few years. Both of these diseases disproportionately affect young trees because they both attack new vegetative flush growth. In an effort to control the spread of citrus greening in Florida significant changes in the citrus nursery industry have been made. To protect nursery trees from exposure to psyllids and possible greening infection, regulations were implemented which stipulate that as of 1 January 2007 all citrus propagation must take place in a Florida Department of Agriculture and Consumer Services, Division of Plant Industry approved structure. The environment in these new enclosed nurseries is unlike that which nursery managers are used to growing trees in and it has led to a number of new problems as well as exacerbating existing problems. This project specifically addresses those issues which are now affecting citrus nursery managers in Florida.

Animal Health Component

(N/A)

Research Effort Categories

Basic

(N/A)

Applied

(N/A)

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
205	0999	1060	100%

Knowledge Area
205 - Plant Management Systems;

Subject Of Investigation
0999 - Citrus, general/other;

Field Of Science
1060 - Biology (whole systems);

Keywords

budding

citrus propagation

budwood

citrus canker

citrus greening

huanglongbing

Goals / Objectives
The overall objective is to develop research-based data on cultural factors and management practices that affect citrus tree growth and development during propagation and nursery production to maximize production efficiency. Specific objectives of the research will focus on rootstock seed storage and viability, and improving budding success by understanding the factors that influence bud survival and growth. 1. Characterize growth, water relations, mineral nutrition, and other variables of citrus rootstock seedlings and budwood trees that may affect the development of citrus trees during propagation. 2. Develop cultural practices to maximize citrus budwood production in Citrus Nursery Stock Certification Program approved structures.

Project Methods
The diversity of environments that exist among nurseries will be characterized for light environment, temperature, humidity, and soil conditions (pH, nutrition, moisture) using appropriate sensors and dataloggers for the various parameters to ensure that studies are conducted in environments similar to those in commercial nurseries. Experiments to be conducted will involve budding trees with buds from different nurseries into the same and other nurseries, resulting in budwood production environments x budding environments factorial experiments. To determine if carbohydrate status of the budwood affects bud survival and growth a girdling trial will be conducted. Limbs supporting multiple budsticks (ca. 2 cm diameter) will be girdled by removing a 2 mm wide strip of bark around the limb. Plant water status effects on bud take and growth will be studied for both the budwood mother tree and the young budded tree. Since many nurseries are growing scion increase trees in containers to supplement their budwood production it will be relatively easy to alter budwood tree water status by increasing the time between irrigations. Budwood trees will be grown under normal irrigation practices (irrigated every 2-3 days) and drought conditions (irrigated when young growing shoots do not show full turgor recovery at dawn, approximately every 6-7 days). Studies to investigate the effects of drought stress on bud take, push and growth will be studied in a similar manner to those used for budwood production.

Progress 10/01/10 to 09/30/11

Outputs
OUTPUTS: Three factors that influence citrus nursery tree growth are currently being researched - photoperiod (day length), water stress, and nitrogen fertilization. To date work has been completed demonstrating the vegetative growth response of citrus to day length and showing that this response is phytochrome mediated. A series of greenhouse and growth chamber experiments are in process to further refine the results of this research into recommendations for citrus nurserymen. A study examining the effects of drought stress of both liners and budwood on budding success and bud growth has been completed. The water status of the budwood has no effect on survival or growth, but the status of the liner is critical. Work to analyze samples from this study for hormone levels to determine the physiological mechanism driving the observed responses is continuing. Studies similar to the drought stress work looking at N levels are planned for the coming year. PARTICIPANTS: Gur Reet Pal Singh Brar, Ph.D. candidate, Horticultural Sciences Department, UF Timothy M. Spann, Assistant Professor, Horticultural Sciences Department, UF TARGET AUDIENCES: Florida citrus nursery growers PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
Recommendations for the use of supplemental lighting in citrus nurseries have been developed based on this research. These recommendations will help citrus nurserymen grow a better product under the short days of winter.

Publications

• Brar, G.R. and T.M. Spann. 2010. Benefits of supplemental lighting in citrus nurseries. Citrus Industry 91(11):18-20.

Progress 10/01/08 to 09/30/09

Outputs
OUTPUTS: Objective: Communicate to nurserymen what factors most affect nursery tree growth and production and demonstrate the improvements in production that can be achieved by adjusting these factors through on site trials. Increased growers' knowledge of the factors that are important to citrus nursery tree production through more than 30 on-site visits and discussions with nurseries accounting for over 75% of citrus tree propagations. Educated growers through seminars at quarterly FNGLA Citrus Nursery Division meetings with approximately 125 attendees. Published two trade journal articles with information on nursery production practices and recommendations for improvements. Visited citrus nurseries in California to observe different propagation techniques and production methods and share the information learned from those visits with Florida's citrus nurserymen through personal communications and trade journal publications. Conducted or am currently conducting five demonstrations/trials in commercial nurseries. These demonstrations show nurserymen how factors such as pre-harvest bud growth conditions, tree water status and root temperatures affect tree growth. PARTICIPANTS: Timothy M. Spann (PI) Gur Reet Pal Singh Brar - graduate student conducting portions of the research as part of his dissertation work. TARGET AUDIENCES: Citrus nursery owners and managers. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
At the beginning of this program most citrus nurserymen were unaware how very minor changes in root temperature and/or soil moisture could impact tree growth and none of the nurseries were monitoring these factors. They did not realize that plants could be under significant water stress without any visible signs such that harvesting budwood under those conditions would negatively affect bud survival and growth. As a result of my work 4 of 42 citrus nurseries (accounting for more than 50% of production) are monitoring root temperatures, soil moisture or both. In addition, at least three nurserymen have changed their practices for harvesting budwood to avoid harvest during periods when plants are stressed. The nurserymen value this work as their support of this program through SHARE has totaled $12,000 to date.

Publications

• Spann, T.M. 2009. Florida citrus nursery industry status and research update. Citrus Industry 90(4): 21-22.
• Spann, T.M. 2008. Mechanical harvesting the nurseryman and grower's perspective. Citrus Industry 89(6): 20-22.