Certification Requirements
Very importantly, our citrus trees are Texas A & M University Certified Virus-Free. All budwood is from TAMU-Kingsville Citrus Center, Weslaco, Texas, and is certified virus-free by TAMU. For more info, go to http://aggie-horticulture.tamu.edu/citrus/.
State law has mandated that all commercial varieties of Texas citrus be certified as virus-free. This includes commercial citrus orchards of the Rio Grande Valley, as well as wholesale nurseries that sell trees to retailers.
The Texas A&M-Kingsville; Citrus Center in Weslaco, Texas, is the only entity in the state of Texas authorized to produce virus-free budwood. The budwood program was started in 1993 to fortify the citrus industry against the citrus tristeza virus, but having virus-free trees will also help against the threat of citrus greening."
Sweet citrus budwood is grafted, or tightly spliced, onto hardier sour orange rootstock to produce bountiful, healthy trees that do well in Texas soils. Each bud sells for 10 cents, plus a handling fee, with 60 percent of funds collected going to the Texas Department of Agriculture and the remainder plowed back into the budwood program at Weslaco.
The idea is not to make a profit but to keep the citrus industry in Texas healthy. The virus-free budwood is grown on about 4 acres of Citrus Center property in Weslaco. The foundation block, or mother trees, are replicated to produce increase trees which provide the budwood.
Texans should avoid buying trees at flea markets or from neighboring states which could carry diseases devastating to citrus trees throughout the state.
Be sure to ask your nursery or garden center for a certified tree. Certified trees will have a label and number on them. They might cost a little more, but you'll have a much healthier, more productive tree.
Citrus can be adversely affected by a number of virus diseases, many of which can be transmitted during budding. Many old-line selections of citrus in Texas have exocortis, xyloporosis and possibly other viruses. Moreover, a number of citrus trees in urban areas especially in southeast Texas, have been illegally imported from other states. Random testing over the last several years has identified a significant incidence of citrus tristeza virus among these trees.
Because of the threat of accidental introduction of citrus viruses and other diseases and pests from other citrus-producing areas, the Texas citrus industry, in cooperation with the Texas Department of Agriculture and the Texas A & M University System, initiated the citrus budwood certification program in 1993. Major objectives of this program are 1) to establish a foundation block of disease-free trees of all major commercial and non-commercial varieties of citrus grown in Texas, 2) to maintain a rigorous program of testing and retesting of foundation trees to assure continued freedom from disease, 3) to evaluate the horticultural characteristics of foundation trees to assure trueness-to-type and 4) to develop and maintain increase blocks for the production and sale of certified budwood for the production of disease-free citrus nursery trees.
This program is maintained at the Texas A & M University-Kingsville Citrus Center in Weslaco, TX, under agreement with the Texas Citrus Foundation. Its operation is overseen by the Foundation, with assistance from both an industry Technical Committee and an Advisory Committee of the Texas Department of Agriculture;
http://aggie-horticulture.tamu.edu/citrus/nursery/L2305.htm
Sanitation
The use of virus-free propagation material requires sterilization of propagation tools. Sterilization of pruning shears and budding knives can be easily accomplished by cleaning the tools throughly with warm, soapy water, then spraying them with a 10-percent solution of chlorine bleach (one part bleach to nine parts water). A small spray bottle of the bleach solution is especially handy for periodic re-treatment of propagation tools during nursery operations.
Budding tools should be re-sterilized anytime the budder changes varieties. Too, pruning tools used to remove sprouts or to trim nursery trees should be periodically re-sterilized during operation, most particularly when moving from one variety to another.
Because the bleach solution is caustic to most metals, sterilized tools should be rinsed in tap water, dried thoroughly and then given a light coating of protective oil at the end of the day.
Rootstalk Production
It is common practice in Texas to collect rootstock seed from fruit produced on root sprouts in existing orchards. However, it is recommended that seeds be purchased from certified sources or that nurserymen establish and maintain trees for rootstock seed production to assure uniformity of rootstocks year after year.
Rootstock seed are extracted from fruit normally harvested in the fall. The simplest means of extraction is to cut a horizontal ring into the fruit, just deeply enough to avoid cutting the seeds, then twist the two halves apart. An electric juicer can be used to collect the seeds, after which they should be separated from the accompanying pulp by repeated washing. Commercial seed operations commonly crush the fruit in an ice crusher, followed by treatment with pectinase enzymes at controlled temperatures, with constant stirring. The enzyme treatment essentially digests the pulp, rag and peel, leaving the seeds intact for easy separation.
Finishing
The demand for citrus trees for urban planting has increased tremendously in recent years. To meet that demand locally, some field nurseries dig trees as usual, but without the burlap wrap, and set the tree into a 2-gallon or 3-gallon standard plastic nursery container. They usually hold the trees for a couple of weeks to harden before delivery. For local delivery, where freight rates are not a factor, this procedure is adequate.
Prior to movement from the nursery, container-grown trees may benefit from a short period of hardening-off. This entails placing the trees in a holding area where they are exposed to the natural climatic elements for 2 to 3 weeks.
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