130 J.E. FAUST, J.M. DOLE, AND R.G. LOPEZ
Most commercial cuttings are identified by the specific greenhouse
and bench that they were harvested from. This information is carried
on the label that accompanies the cuttings during packaging and trans-
port to the customer and provides a means of tracing the origin of any
problems that may arise at the customer’s propagation facility. Positive
indication of a pathogen may result in the stock block being destroyed as
a means of limiting the potential for further spreading of that pathogen.
For this reason, stock-plant growers generally create multiple blocks of
each cultivar so that one infected area does not cause a crop failure for
the entire production season.
The enormous risk involved with pathogen infection results in exten-
sive efforts made for testing, identifying, and preventing pathogen infec-
tion during the build-up and general production phases of stock-plant
production. The sensitivity of these issues creates a situation where the
disease management protocols and methods are held in a highly pro-
prietary manner by cutting production companies.
Pest control during stock-plant production also has extremely high
standards. A single egg of a pest discovered in a shipment at a port-of-
entry can result in the entire shipment of cuttings being quarantined
and is either destroyed or in the United States, gassed with methyl bro-
mide. As a result, stock-plant growers have a zero-tolerance policy for
pests. Pesticide-application programs are rigorous and continuous, and
considerable effort is put into scouting. Pests are excluded from the
greenhouses with insect screens placed across all of the vents. Exter-
nal doorway entrances to the greenhouses consist of a vestibule area for
hand cleaning and footbaths followed by a second doorway.
D. The Greenhouse Environment
- Temperature. The primary role that temperature plays in stock-
plant production is its direct effect on the leaf-development rate and the
subsequent cutting-production rate (Chong 2005). However, tempera-
ture control is limited for stock-plant production in tropical and sub-
tropical locations because these greenhouses are usually unheated and
rely on passive ventilation for cooling. Active ventilation, for example,
exhaust fans, is not typical because of the necessity for excluding pests;
thus, the vents are covered with insect screens that restrict air flow.
Consequently, the greenhouses can become quite hot and humid during
sunny days. For this reason, many stock-plant producers construct
greenhouses at relatively cool, high-elevation locations. In recent years,
greenhouse construction has emphasized taller greenhouse structures