Florida Department of Agriculture and Consumer Services

Citrus Budwood Program FAQ

Select a question below to expand the answer.

What is budwood?

Budwood is the portion of a stem or branch with vegetative buds used in propagation of new trees. The bud eye is located at the axis of the leaf and is removed for budding or grafting a new tree.

What is a scion, rootstock and bud union?

The scion is the varietal part or the top of a tree that produces the fruit. The rootstock is the lower portion of the trunk and root system, which is mainly underground. The scion and rootstock are joined at the bud union, which is where the bud is grafted into the rootstock.

Why does propagative material have to originate from protected and approved trees?

Citrus trees may carry pathogens or diseases that are detrimental to tree growth and fruit production and may affect neighboring groves. Only by using budwood from pathogen-tested trees that are protected in greenhouse structures and are under inspection can the citrus industry achieve any degree of protection from harmful pathogens.

How frequently are scion trees tested for citrus pathogens?

Scion trees are required to be tested for citrus tristeza virus (CTV) and citrus greening (HLB) once each year. They are tested for graft-transmissible viroids, including exocortis and cachexia, once every six years by the bureau.

How long can increase block trees be used for budwood sources?

Increase block trees can be used for 36 months.

What existing graft-transmissible citrus diseases are important to control in Florida?

Viroids that cause stunting and reduced yield on trifoliate hybrid rootstocks are spread mechanically and by grafting. Citrus tristeza virus, which causes decline on sour orange rootstocks, is spread by aphids and by grafting. Psorosis, which causes production loss and eventual tree decline, is spread by grafting infected stock. The Citrus Budwood Protection Program helps control these diseases by propagating from registered stock that has been pathogen tested.