Agriculture Reference
In-Depth Information
to use the field for seed production. Additionally,
most regions have requirements for isolation of
early-generation stocks,
2-
to
4-
year crop
rotation requirements between potato crops,
and regulations allowing only certain fields to be
planted to seed.
Production practices for seed potatoes in
the field are similar to those used to produce
commercial potato crops, with some notable ex-
ceptions. Often, seed lots are separated by one or
two blank rows, to maintain lot identity and re-
duce cultivar mixing at harvest. Lots are planted
by generation or class, with the earliest-generation
lots grouped together to provide both isolation
and identity, and the later-generation lots plant-
ed separately to prevent potential disease spread
to the pre-basic material. The spread of disease
in later-generation lots is common, since they
tend to require larger areas of land than the ear-
ly-generation material and more mechanization
for field operations (Stark and Love, 2003).
A second requirement is the need to control
adequately insects that act as vectors to prob-
lematic diseases like
Potato leaf roll virus
and the
mosaic viruses (Radcliffe and Ragsdale, 2002).
The use of an effective preventive insecticide
early season with periodic applications of other
insecticides or crop oils during the season is the
cornerstone for any effective insect manage-
ment scheme (Doring
et al
., 2006). Other pests
such as Colorado potato beetle, leafhoppers, and
psyllids also must be controlled during the
season.
Seed producers can use strategies to help
earlier-generation material stay clean by isolating
spatially (away from diseased fields) or intragen-
erationally (within the field surrounded by
plants either resistant to virus spread or that are
low spread risks). Isolation can be especially ef-
fective to help reduce the spread of vector-borne
viruses such as PVY into the material. Addition-
ally, growers can manipulate the planting and
vine killing dates of seed to avoid the times in the
season when aphid vectors are more prevalent
(Davidson
et al
., 2013). Another strategy is to
use a green border of a non-potato crop, such as
winter wheat or sudan grass, to allow aphid vec-
tors to feed and remove the virus particles from
their stylet (sucking mouth parts), as in the case
of PVY (Radcliffe and Ragsdale, 2002).
A third difference between commercial and
seed production is the use of roguing, to remove
infected plants or varietal mixtures from a lot to
help reduce the number of diseased or incorrect
plants within a seed lot. Roguing takes place typ-
ically prior to the first inspection and up to the
second inspection. Certain diseases cannot be
rogued from a lot, such as bacterial ring rot,
blackleg, brown rot and soilborne problems
like nematodes. Roguing is normally used to re-
move virus-infected plants, but is not useful if
the number of infected plants is too high (usually
above
1-
2% of the crop).
Finally, it is critical that producers control
disease spread within the crop and from sources
outside of the crop. There are numerous sites
within an operation that need attention. As de-
scribed earlier, all surfaces that may come into
contact with the tubers must be cleaned and dis-
infected on a regular basis and between oper-
ations or when switching seed lots.
Other steps include using sterile footwear
and leggings when walking in the fields planted
with seed lots, and using dip pans with an effect-
ive disinfectant at the entrance to all storages,
laboratories, and fields. Also, use of timely fungi-
cide applications can reduce fungal problems such
as late or early blight, and can help to maintain
the foliage for proper growth and yield, as well as
allowing certification personnel the opportunity
to conduct useable crop inspections for the certi-
fication process.
Harvest and storage are also similar to com-
mercial production, with the exception that
each seed lot must be harvested separately and
stored in a manner to maintain its identity. Fol-
lowing harvest, producers may sort the seed for
size to remove and market the larger commercial-
type potatoes. Heavy grading to remove diseased
or bruised tubers and field soil/debris is essential
to putting a good seed crop into the bin and setting
up the storage for the long haul (NAK, 2013).
Problems that may impact the storability of
the seed must be identified and a strategy devel-
oped to minimize potential storage issues and/or
reduce the likelihood for tuber breakdown during
the storage season. It is also essential to monitor
the seed storage facilities routinely and to check
for any tuber issues during the storage season.
At any stage of the harvest and storage cycle,
seed tubers must be handled to keep bruises and
wounds to a minimum, since these are pathways
to pathogens entering the tubers and causing
infections. Finally, sprout inhibitors may not be
