Team 4015
1 Kolten Tani
2 Melia Furst
3 Adrian Abecede
4 Jordan Abe
5 Jake Tsuchiyama
6 Jake Kubota
7 Kaua Moses
8 Jacob Tokuhama
9 Marisah Goo
10 Jared Davis
Taro Skit
The terrain of Hawaii is widely varied giving the plants a myriad
of ecosystems. Hawaii is well known for its sugar cane, pineapple, coconut,
bananas, macadamia nuts, guava, papaya, and coffee. (Students dress as these
different crops).
Our focus is on Taro (Kalo).
According to the president (Mr. Tottori) of the HPC Foods, as Hawaii
develops, agriculture land is being converted to other usage and many crops are
vanishing such as pineapple, sugar, rice, and possibly taro.
The Tottori family founded a small poi-milling operation called
Honolulu Poi Co. back in 1946.
In Hawaii, taro is a vital part of the cultural and agricultural
traditions of the Hawaiian people. Prior to western contact, when the
population of Hawaii consisted exclusively of Hawaiians, taro was the major
food staple. There were more than 300 recognized forms.
Today, although taro shares its role as a staple with rice,
potatoes, pasta, and bread, it remains an important crop to the many cultures
of Hawaii. Its starchy corm, or underground stem, is eaten principally as poi,
prepared by mashing the cooked corm. Its steamed leaves (luÔau) and flowers
(pua) can be eaten alone, but are generally used in dishes with meats, fish,
coconut milk, and other vegetables.
Taro is a perennial herb consisting of a cluster of long-petioled,
heart-shaped leaves that often reaching 30 cm or more.
There are two types of production methods: "Upland" taro
production (also known as "dryland") and "wet" taro
production (also known as "wetland," "lowland," paddy or
"flooded").
Taro Production in Hawaii
In 1999 there were 190 taro farms in Hawaii, the majority of which
were on the island of Hawaii, the Big Island. Taro is grown on all islands but
is concentrated on the islands of Hawaii and KauaÔi.
Many farms are about one acre although farms on KauaÔi tend to be
larger than those located elsewhere.
The three segments of the taro industry in Hawaii are poi, table
and luÔau production. Most taro is grown for poi (420 acres). The remainder (80
acres) is table taro served as slices or chunks. Japanese, Chinese, or Samoan
taro cultivars as well as some Hawaiian cultivars are used as table taro. A
very small area is devoted to luÔau, or leaf production. While Bun Long, a
Chinese cultivar, is the major luÔau cultivar, some of the Hawaiian cultivars
are superior in quality.
Unlike most crops, the cost of pest control (30.6%) represents a
significant portion of gross receipts. Labor to hand-weed accounts for nearly
80% of the total pest control costs.
Upland vs. Wet Taro Production Practices
Taro can be grown under upland conditions, which means that the
fields are rain-fed or irrigated but not flooded. Most of the taro in the world
is grown under upland (dry) conditions. In Hawaii, upland taro (kalo maloÔo)
has been grown for hundreds of years.
"Wet" taro (kalo wai; literally, "water taro")
is grown under frequently or constantly flooded conditions. Flooded taro
production, a technique practiced by Hawaiians for centuries, is also used in
Okinawa, Taiwan, the Philippines, the Cook Islands and other countries. Banked,
flooded plots for taro production are called loÕi. Wet taro can take 9 to 15
months to mature, depending on the variety.
Upland Taro Production
The number of plants grown in a given space (the planting density)
affects taro disease prevalence and yield. The planting material, or huli, for
the next crop comes from the crop being harvested. If huli are planted close
together (both within and between rows), the crop will yield more corm (makua)
but have fewer cormels (Ôoha). Conversely, the further apart the huli is
planted, the more Ôoha produced.
However, high plant density may make it easier for insect pests to
move among them, and if sunlight and air circulation are too restricted,
diseases can occur more readily. Spacing huli too far apart, on the other hand,
will make it difficult for the leaves to form a complete weed-suppressing
canopy. The best spacing involves a trade-off among these factors.
Insect Pests
There are relatively few insect pests of upland taro. However, if
left unchecked, some can destroy the entire crop. The most important pests are
the taro root aphid and leafhoppers.
The taro root aphid is a tiny sucking insect found primarily on
roots and corm. When populations are high it can also be found on the above
ground portions of the plant around the base of leaf sheaths and on young
leaves. Plants infested with root aphid appear stunted, the leaves may be
yellow and the roots and corm may rot. The aphids produce masses of fine,
cottony, waxy threads that cover them on the roots and leaf stalks (petioles).
Currently, taro root aphids are found only on the Big Island and
OÔahu. There is a quarantine on transport of planting materials, huli and Ôoha,
from the Big Island (see References, p. 96, for the publication by D. Sato et
al.). A taro crop planted with huli infested with taro root aphid will never
provide adequate yield, especially if periods of drought occur
Heavily infested taro must be removed and destroyed, with care
being taken to include all culls and unharvested cormels. The field must be
given a thorough and deep cultivation to drive away ants and to promote root
degradation. After cultivation, the field must be left fallow or planted to
non-taro crops for at least one year.
Leafhoppers suck sap from the petioles and leaf blades.
Oviposition wounds cause dark spots on the petioles.
Other less economically damaging insect (and related) pests
include mealybugs, green aphids, earwigs, rose beetles, whiteflies, snails, and
slugs. Ants are an occasional pest but are important because of their symbiotic
relationship with aphids. The aphids provide a sweet food-source for the ants.
In return, the ants protect the aphids from their natural enemies. Ants
"herd" mealybugs, taro root aphids, and green aphids, thus
contributing to the spread of these destructive pests.
Non-chemical insect pest management
Growers routinely use several non-chemical insect pest management
practices. As with disease management, growers are advised against spreading
pests from one patch to another on planting material, in water, and on
vehicles, equipment, tools, footwear, or clothing. They are also advised to use
compost to increase soil organic matter and soil "health" making
their taro more resistant to pests. Maintaining the proper moisture
requirements also helps. When possible growers plant taro in areas unaffected
by pests. Some growers try to maintain wide strips of open land between taro
plots. However, the high cost of land and the limited amount of land suitable
for taro production, makes this management option somewhat limited. Growers
must sometimes leave their fields fallow or plant non-host crops. Some growers
have used trap crops to draw pests away from taro (this may also permit pest
control with insecticides not approved for use in taro, but approved on the
trap crop). There are a few natural predators of the insect pests and growers
are encouraged to promote or protect them.
Insecticides
Other than a few insecticides containing Bacillus thuringiensis,
there are no insecticides specifically registered for use on taro. The taro
root aphidÕs waxy covering confers some resistance to insecticidal soaps. Also,
the aphidÕs habit of living mostly on the roots makes it difficult to reach
with insecticides. However, insecticidal soaps may sometimes be used to
disinfest huli of taro root aphids before planting. When used, the
concentration of active ingredient in the product is usually about 1 percent.
Diseases
There are three major diseases caused by microbes and one major
disease caused by nematodes, microscopic roundworms that live in the soil.
Pythium root rots cause stunting. Infected taro plants have a fringe of roots
at the base of the petioles. They are easy to pull out or knock over and
usually smell bad. In its early stages, Phytophthora leaf blight occurs as small
dark brown or purple lesions with an amber ooze in the center. Older lesions
are zonate with white fuzz of sporangia on the outer edge. The sporangia are
prominent in the morning. Pythium and Phytophthora are the major diseases of
upland taro. The loss of green coloration in the leaves and a feathery pattern
or other distortions of the leaf can be used to identify the third disease,
Dasheen mosaic, caused by a virus.
Cultural Control of Diseases
Because taro is vegetatively propagated, the quality of the next
crop depends on carefully selecting and handling planting material from the
current harvest. In order to avoid crop loss and poor quality taro, farmers
only use huli from healthy, pest-free corms. Huli from diseased or
pest-weakened plants can result in yield loss and quality reduction of the
subsequent crop.
Cutting tools must be disinfected at regular intervals to prevent
the spread of pathogens. Collecting huli in batches is a practical compromise
for lowering the probability of transferring pathogens with cutting tools and
the need for efficient harvesting. Knives used for a given amount of harvest
are traded off for knives which have been soaked in a disinfectant such as
diluted bleach (0.5% NaOCl), 70% alcohol (ethanol or isopropanol), or 3% hydrogen
peroxide. The knives are rinsed of soil and sap before being disinfected.
The healthy appearing huli are trimmed further before being
thoroughly washed in clean water and dipped in a disinfectant such as 0.5%
NaOCl. Huli are totally submerged in the disinfectant for a timed minute to
prevent damaging the cutting. They are then removed from the disinfectant bath,
drained and allowed to air dry in a cool, clean area. The huli are cured for 3
to 5 days to allow wound periderm to form over the cut surfaces and to allow
culling of diseased huli.
Hot Water Disinfestation
Hot water may be used for disinfesting huli of some insect pests
as well. Huli are immersed in 120oF water for six minutes then quickly cooled
by immersing it in cool water. Hot water treatments are an effective way to
control nematodes in dormant cormels of dasheen cultivars used for planting.
Fallows for Disease Suppression
Fallows are a means of reducing pathogen populations in the field.
Fallowing is a general "best management practice" used by most good
taro farmers. However, economic realities mean compromises must be made on the
fallow's length, soil moisture level, and weed-free status. At least a
three-month fallow with two tillings is advised for reducing taro disease pathogens.
A year is better. One month might be acceptable if the risk of losing the crop
is low or if other factors make taking the risk necessary.
Other Non-Chemical Management Methods
In most cases, growers attempt to control diseases by maintaining
good production practices. In addition to those practices described above, the
following are also recommended:
*
Establish plant and row spacing and orientation that allows for quick drying of
leaf surfaces.
*
Isolate plantings (e.g., three small, separate patches instead of one large
patch).
*
Prepare the soil well and amend it before planting if calcium, magnesium, or
phosphorus are needed. Monitor plant calcium levels by leaf analysis, and
maintain calcium at recommended concentrations to prevent development of
Pythium corm rot. Add lime material before planting to raise soil pH to
6.0-6.8.
* Rotate
taro with other crops.
*
Intercrop if possible.
*
Incorporate compost and apply surface mulch.
* Rogue
(kill and remove) diseased plants, taking them far from the planting area and
destroying them by burying, burning (if allowed), or composting
Weeds
Weeds are a constant problem. Farmers attempt to stimulate weed
seeds to germinate and grow before the taro is planted and then eliminate them
all at once. Several techniques can be used to eliminate weed seedlings before
they become firmly established.
Weed control in wet taro production is a major concern. Weeds in
taro loÔi can out-compete a taro plant during establishment and slow its growth
in the maturation phase. Unfortunately, intermittent draining and drying of the
loÔi provides conditions for weed growth.
Vertebrate Pests
Most of the comments provided in the section on Upland Taro Production are also applicable to wet taro production with some minor differences. Apple snails (Pomacea canaliculata) can be a problem in wet land taro. There are no registered molluscicides. A few farmers have tried baits around their loÔi or have tried to force the snails to congregate in small pools where they can be scooped out by hand. Cayuga black ducks have also been used with limited success. Crayfish may also be a problem because they damage the loÔi bank. Currently, farmers use traps to reduce crayfish populations.