General Production Information (1)
Potatoes can be grown in all three Delaware counties.
Cultural Practices
Potatoes are produced in greater quantities worldwide than any other vegetable. Members of the nightshade, potatoes are related to tomatoes, peppers and eggplants. The edible portion of the potato plant is the underground tuber that serves as food storage. Potato setting, or tuberization, occurs six to eight weeks after planting, or when the plant is in the early bud stage. In Delaware approximately 5,000 acres of potatoes are grown annually and shipped throughout the eastern United States and Canada. Many good varieties do well in Delaware:
Round Whites - Superior, Kennebec, Haig and Katahdin
Red Potatoes - Norland and Red LaSoda
Russets - Russet Burbank and Belrus
Planting
Plant potatoes any time the weather permits after March 15 until April 15. If potato tubers (which are used as seed) are cut, seed pieces should be blocky and average about 2 ounces. Seed pieces should be cut the day before planting to allow healing. Plant them in 36-inch rows with the seed pieces dropped every 9 to 12 inches. Maintain soil pH at 5.5 to 6 to control scab, although many varieties are now scab resistant.
Potatoes respond to high fertilization and frequent watering. Apply
3 to 4 pounds of 10-10-10 per 100 square feet. Sidedress when the plants
are 6 inches high with 1/2 pound of ammonium nitrate per 100 foot of row.
Cultivate weeds when they are young, before rows close in.
Major
Insect Pests in Delaware
Colorado
Potato Beetle(CPB)
Damage and Life Cycle
The Colorado potato beetle, Leptinotarsa
decemlineata, is the most important insect pest in potatoes in the
Northeast. Uncontrolled populations can completely devastate a potato field
by late July (5). Adults overwinter in the soil and emerge from late April
through May, when they invade host crops. Adults mate after they are established
on the plants (8). This first generation of adults feeds on the foliage
of emerging plants and can do considerable damage when populations are
high, although young plants usually can outgrow the damage (5, 8). Females
deposit eggs in clusters on the underside of leaves. A single female can
produce about 500 eggs in a 3 week period before she dies. The larvae hatch
in 4 to 8 days and feed on foliage for about 3 weeks, often stripping plants
of leaves and leaving only the main branches. Because eggs are laid in
clusters, larvae are distributed in clumps throughout the field (8). Larvae
grow through several stages, all of which feed on the foliage (5). When
mature, they construct a small spherical cell in the soil at the base of
the plants, where they pupate. The second generation of adults emerges
in 5 to 10 days, and beetles mate to produce a second generation of larvae.
Adult beetles and larvae continue feeding on potato plants, but damage
in midsummer is less severe because plants are larger and because beetle
egg production is inhibited at temperatures above 80oF. In Delaware,
beetles go through 2 generations and a partial third each growing season
(8).
Frequency of Occurrence
The Colorado potato beetle is the most
economically important insect pest of potatoes in the mid-Atlantic and
throughout the Northeast (5). It is an important management issue every
year in Delaware. The proximity of a field to overwinter sites is an important
factor affecting the severity of early season infestations (8).
Management
A variety of strategies are used in
combination by Delaware growers to manage Colorado potato beetle populations.
Crop rotation is critically important, and the growers plant potatoes as
far as possible from fields previously planted in potatoes or other solanaceous
crops. Scouting and treatment thresholds, as well as careful insecticide
selection are also important (6).
When potatoes are planted in fields
adjacent to beetles overwintering sites, a preplant or planting application
of Imidacloprid (Admire) may be used (6) Fields are scouted twice weekly
following plant emergence, and the number of colonizing adults is noted.
Often adult numbers are not numerous enough to justify insecticide treatment
and growers delay spraying until after the first generation of eggs have
hatched (8). In Delaware, approximately 70% of the potato acreage is scouted
for CPB. Throughout the season thereafter, fields are scouted weekly for
CPB to determine the need to spray. At least 10 sites per field are inspected
along a V- or W-shaped path. At each site, one stem from each of five adjacent
plants are examined, and the number of CPB adults, large larvae and small
larvae are counted. As a general guideline, if more than 50 adults or 75
large larvae or 200 small larvae are counted per 50 stems, an insecticide
treatment is applied (6).
Chemical Controls
If Colorado potato beetle populations
are expected to be high, as in situations where crop rotation is limited,
a preplant or at-planting application of imidacloprid (Admire 0.9-1.3 fl
oz 2F/1,000 row ft) is used as a preventative measure (6). According to
the label, Admire is applied as a banded application during seedbed preparation,
or in the furrow at planting, or is sidedressed on either side of the potato
row at planting.
Foliar treatments are applied on an as-needed basis, based on scouting and established thresholds. Choice of insecticide is influenced by local adaptation of Colorado potato populations, which have developed varying levels of resistance to a number of products. The following foliar products are labeled for use on potatoes in Delaware:
abamectin (Agri-Mek 8-16 fl oz 0.15EC/A)-
used on < 2% of the acres; best used on small to medium size larvae
cryolite (Kryocide, Prokil cryolite
10-12 lb 96WP/A) - used on 5% of the acreage; still provides very good
control of larvae, not readily available
Ecozin ( Azadiractin-(11-21 fl oz EC/A). Not used in DE
azinphos-methyl (Guthion 1.5 pt 2L/A)Not used in DE
phosmet (Imidan 2 lb 50WP/A); used
on < 2% of the acres; only fair control
imidacloprid
(Provado 3.75 fl oz 1.6F/A.) [Provado is not used in fields treated with
Admire at planting.] ; used on 80% of the acreage; very effective for CPB
Endosulfan (Thiodan l.33-2.67 pt 3EC/A)
; used on 2% of the acreage
oxamyl (Vydate L 1-4 pt 2L/A) Not
used in DE
Bt:
Bacillus
thuringiensis tenebrionis (Novodor, Raven) Used only for small larvae.
The first application is made when eggs begin to hatch and treatment is
repeated at 5 to 7 day intervals for as long as small larvae are present.
Not used in DE
spinosaid ( Spintor - 4-6 oz/acre)
- labelled in 1999 - used on 80% of the DE acreage in 1999 - good CPB control
Insecticide Resistance Management
The Colorado potato beetle has proven
to be quite adaptive, and in some areas of the U.S. beetle populations
have developed resistance to all major classes of insecticides. Insecticide
management to slow the development of resistance is critical to insuring
the continued effectiveness of the available chemical insecticides (9).
Growers use all available management strategies for this pest, including
crop rotation, scouting, following established treatment thresholds, and
alternating insecticides with different modes of action (6). When insecticides
are used, proper timing, rates, and good spray coverage are important.
The same insecticide is not used for subsequent generations of beetles
in the same field. Piperonyl butoxide is a chemical used by some growers
in combination with organophosphates or pyrethroids to slow resistance.
It works by blocking one of the beetle's resistance mechanisms and thereby
increases insecticide effectiveness.Further,
it is important to be mindful of Colorado potato beetle resistance when
managing other insect pests in potato (6).
Alternative Controls
Genetically Engineered Varieties
Genetically engineered varieties of
potatoes which express the toxic Bacillus thuringiensis tenebrionis
protein are available and provide season-long control of Colorado potato
beetles (6). These are very resistant to Colorado potato beetle damage
(3).
Cultural Practices
Crop rotation is a critically important
means of reducing or delaying Colorado potato beetle infestations (9).
Potatoes are not planted in fields where solanaceous crops were planted
the previous year, so that overwintering adults have a longer dispersal
route to find potato hosts (8). The resulting reduction or delay in colonization
affects the rate of resistance development in the beetle population and
can greatly influence the overall success of a Colorado potato beetle management
program (9).
Natural Enemies
Colorado potato beetles have several
natural enemies, but these do not normally provide sufficient control of
the pest (9).
Potato Leaf hopper
Damage and Life Cycle
Potato leafhopper is an annual serious
pest of potatoes that causes significant crop damage, even when populations
are low (9, 11). It also attacks beans and a range of other vegetable crops.
Adults overwinter in the South and move into the mid-Atlantic area each
spring (11). Adults insert eggs singly into stems or leaf veins of susceptible
plant species. Eggs hatch in 7 to 10 days, and nymphs develop into adults
over a period of 2 to 3 weeks (9). Both adults and nymphs feed by piercing
the underside of leaves and sucking plant juices. As they feed, they inject
a toxin into plant tissues which is taken up by the plant and inhibits
normal development by disrupting the flow of nutrients from photosynthetic
tissues to the rest of the plant (9, 11). Early symptoms of leafhopper
feeding include a rolling and yellowing of the leaves. Leaves later turn
brown and die (9). High levels of leafhoppers in potatoes can cause extensive
leaf-yellowing known as "hopper burn," although many varieties show few
symptoms of hopper burn and yet can incur significant yield losses (6,
9). Yield losses from potato leaf hoppers can be substantial (9).
Frequency of Occurrence
Potato leafhopper is a serious annual
pest of potatoes in Delaware. Even relatively low numbers of leafhoppers
can cause a significant yield reduction (9). Because nymphs are susceptible
to desiccation, populations tend to be lower during very dry summers (11).
Management
Fields are monitored from early June
through early August for the buildup of potato leafhoppers (6). Sweep net
samples are used to monitor adult populations and leaves are inspected
for the presence of nymphs (11). Growers make a foliar insecticide application
when adult counts exceed 1 per sweep or if more than 1 nymph per 10 leaves
is found (6). Admire applied at planting and foliar insecticides applied
on as an needed basis are the only means of controlling potato leafhoppers.
Chemical Controls
The following insecticides are labeled to control leafhoppers on potatoes in Delaware:
Preventive Applications: imidacloprid
(Admire 0.9-1.3 fl oz 2FS/1,000 row ft) [According to the label, Admire
is applied as a banded application during seedbed preparation or in the
furrow at planting or sidedressed on either side of the potato row at plating.]
- used
on 30% of the acreage, providing good control
Rescue Treatments:
imidacloprid (Provado 3.75 fl oz 1.6F/A.)
[Provado is not used in fields treated with Admire at planting.] used
on 60% of the acreage,; provides good control
permethrin
(Ambush 3.2-12.8 fl oz 2EC/A or 4-8 fl oz Pounce 3.2EC/A) ; used on 30%
of the acreage; good control
esfenvalerate (Asana XL 5.8-9.6 fl
oz 0.66EC/A) used on <
5% acreage; good control
dimethoate
(0.5-1 pt 4EC/A) used on <
2% of the acreage
disulfoton (Di-Syston 13.5-20.5 lb
15G/A ; Broadcasted and incorporated before planting or applied in the
seed furrow or in a band on each side of the seed furrow. An additional
application may be sidedressed after plants become established (6).] Not
used in DE
phosmet (Imidan 2 lb 50WP/A) ; used on < 5% of the acreage
methomyl (Lannate--1.5-3 pt LV/A) Not
used in DE
endosulfan (Thiodan l.33-2.67 pt 3EC/A)
Not used in DE
oxamyl (Vydate L 1-4 pt 2L/A) ) Not
used in DE
Alternative Controls
No alternative controls are used in
the management of this pest.
Aphids: Green Peach Aphid, Potato
Aphid, and Melon Aphid
Damage and Life Cycle
Several species of aphids feed on potatoes,
and all inflict similar types of injury to plants. Aphids overwinter as
eggs on a variety of host plants. Green peach aphids overwinter in the
south and migrate into our area, or overwinter in greenhouses and are introduced
with bedding plants. Potato aphids overwinter as eggs on wild and cultivated
rose plants, and certain weed species including lambsquarters, yellow mustard,
and redroot pigweed (5) Aphid nymphs hatch in spring and feed until they
mature. Adults of this first generation reproduce sexually, bearing live
young which mature into winged adults and migrate onto crops. This generation
feeds on plants and rapidly reproduces asexually, with a generation time
of 5 to 7 days. Many overlapping generations occur, and populations can
increase rapidly. Most species of aphids produce a winged, sexually reproductive
generation near the end of the growing season (9).
Green peach aphids and potato aphids
are the most important of several aphid species that attack potatoes in
Delaware. The melon aphid can also cause significant damage. All three
aphid species attack plants throughout the growing season, but damage is
usually worst in May and June, and again in the fall. Aphid infestations
commonly begin in small scattered areas over the field. Aphids are found
primarily on the underside of the leaves, where they suck sap from the
plant. Green peach aphids favor mature lower leaves while potato aphids
are found primarily on terminal leaves and young stems (8). Infested leaves
curl downward and may turn brown and die (9). When infestations are heavy,
aphid damage can reduce plant vigor, size and yield, and may kill the plants.
(8).
Frequency of Occurrence
The green peach aphid is a major pest
of potatoes everywhere they are grown (10). The green peach aphid and the
potato aphid are the most common species of aphids found on potatoes grown
for the fresh market in the Northeast (5). The melon aphid is also found
on potatoes in our area (6). Aphids are present every year, but typically
affect potato yields only when their populations reach very high levels.
Management
Fields are scouted for the presence
of aphids 2 or 3 times during the growing season, in May and early June
for the potato aphid, and in late June for the green peach aphid (8). Scouting
is done by looking for wilting and curled leaves throughout the field.
When aphids are detected, more intense sampling is done to determine infestation
levels and natural enemy activity. An insecticide is applied to control
potato aphids and green peach aphids if combined counts exceed 2 per leaf
prior to bloom, 4 per leaf during blooming, or 10 per leaf within 2 weeks
of vine killing. For melon aphids, the thresholds are lower: 1 per
leaf prior to bloom, 2 per leaf during blooming, or 5 per leaf within 2
weeks of vine killing (6).
Chemical Controls
The following insecticides are labeled to control aphids on potatoes in Delaware:
imidacloprid (Admire 0.9-1.3 fl oz
2FS/1,000 row ft) [According to the label, Admire is applied as a banded
application during seedbed preparation or in the furrow at planting or
sidedressed on either side of the potato row at plating (Label).] used
on 30% of the acreage; very good control
imidacloprid (Provado 3.75 fl oz 1.6F/A.)
Provado is not used in fields treated with Admire at planting. Used on
10% of the acreage
dimethoate
(0.5-1 pt 4EC/A) [Potato aphid only] ; not used in DE.
methomyl (Lannate--1.5-3 pt LV/A) [The
most effective product against melon aphid] - ; not used in DE
methamidophos (Monitor 1.5-2 pt LV/A)
[Potato aphid and green peach aphid only] -used
on < 5% of the acres in recent years in DE
endosulfan (Thiodan l.33-2.67 pt 3EC/A) [Potato aphid and green peach aphid only] None in DE
oxamyl (Vydate L 1-4 pt 2L/A) [Potato
aphid and green peach aphid only] None in DE
Alternative Controls
Natural Enemies
Aphids may be controlled naturally
by parasitic wasps and a variety of predators, including lady beetles and
their larvae, lacewing larvae, and syrphid fly larvae. When making a treatment
decision, natural enemy populations are considered (8). During periods
of high humidity, fungal diseases may also help reduce aphid populations.
European corn borer (Ostinia
nubilalis)
Damage and Life Cycle
The European corn borer feeds on a
wide variety of crops, including potatoes. It overwinters as a mature larva
in its burrow in the sweet corn stalk or in the stem of a different host
plant (5). Larvae pupate in late April or early May, and adults emerge
in late May or early June (11). Female moths lay their eggs on the underside
of leaves or on stems (9). A single female can produce as many as 500 eggs
during her lifetime (5). Eggs hatch in 4 to 7 days (depending on temperature)
and young larvae feed on plant foliage for 7 to 12 days before boring into
the stems (11). Stem damage weakens the plant by interfering with translocation
of water and nutrients. This insect produces 2 to 3 generations a year
in the mid-Atlantic area (11). The stem boring activities of the first
larval generation cause the most damage to potatoes in Maryland (9). Insecticide
sprays made to control other potato pests in July and August, and the availability
of preferred hosts, prevent later generations from causing extensive damage
to potatoes (5).
Frequency of Occurrence
European corn borer is a major pest
of field corn and sweet corn throughout the United States and Canada, and
feeds on a large range of other host plants, including potato (5). The
timing and extent of damage to the potato crop can fluctuate from year
to year and from region to region (12). Moth populations can fluctuate
considerably annually as well (13).
Management
A degree-day system has been established
for predicting the life stages of the first generation. Scouting begins
at 500 degree days and continues through 700 degree days or when egg masses
are less numerous. Scouts count egg masses on the undersides of leaves
on the bottom half of the plant. More than 1 egg mass per 25 leaves may
indicate a problem. Black light traps are also used to monitor populations
of adults. Catches exceeding 25 adults per night indicate that adult may
produce enough eggs to justify an insecticide treatment (9).
Chemical
Controls
Proper timing of foliar insecticide
sprays is critical for successful control. Growers apply the first spray
when 10-25% of the terminal tips have entry holes. A total of 2 or 3 applications
are made on a 5 to 10 day schedule. If a pyrethroid (Ambush, Asana XL,
Baythroid or Pounce) is used, the first application is made when 8 to 10
European corn borer moths are being trapped in local pheromone or blacklight
traps. Two to 3 additional applications are then made at 5 to 7 day intervals,
based on moth activity (6).
The following insecticides are labeled to control ECB on potatoes in Delaware (6):
Rescue Treatments:
azinphos-methyl (Guthion 1 qt 2L/A)
None used in DE
methamidophos (Monitor 1. 5-2 pt 4EC/A) used on < 2% of the acreage;
effective control
methyl
parathion (Penncap-M 2-4 pt 2FM/A) ) used on < 2% of the acreage in
DE; provides effective control
permethrin (Ambush 3.2-12.8 fl oz 2EC/A
or 4-8 fl oz Pounce 3.2EC/A)used
on 40% of the acreage ; very good control
esfenvalerate (Asana XL 5.8-9.6 fl
oz 0.66EC/A) used on < 2% of the acreage ; poor corn borer
control
spinosaid ( Spintor 4 - 6 oz/acre)
used on 30% of the acreage ; good control
Alternative Controls
Resistant Varieties: none available
that are commercially used in Delaware.
Natural Enemies
There are several natural enemies of
European corn borer, but these rarely provide sufficient control. Also,
enemy populations are often depleted by the use of insecticides to control
European corn borer and other pest species in potatoes (5).
Wireworms
Damage and Life Cycle
Wireworms, the larvae of click beetles
(Elateridae), feed on a variety of crop and non-crop plants. Several species
of wireworms attack potatoes and can damage seed pieces, roots, and tubers.
Most species spend 2 to 4 years in the larval stage, so adults and immatures
may be present during the growing season (10). Adults emerge in May or
June. Eggs are deposited in the soil in late spring (5). Larvae infest
the soil, hollowing out seed pieces, pruning roots, and feeding on developing
shoots. This damage makes plants more susceptible to fungal infection and
other diseases. Damaged tubers have round entry holes. After 2 to 4 years
of development and feeding, mature larvae pupate in the soil before emerging
as adults to continue the cycle. Larvae and pupae overwinter deep in the
soil (10).
Frequency of Occurrence
Wireworms are considered a major pest
problem in potatoes. Populations are often greater in fields previously
planted in cereal crops (10). Wireworm populations are also favored by
planting into situations with heavy amounts of crop residue, continuous
small grains, or a rotation with field corn with no soil insecticide at
planting.
Management
Soils can be sampled for wireworms
prior to planting in fields that have a history of infestation, or fields
previously planted in cereal or sod (10). As a general guideline, a soil
insecticide is needed if 5 or more wireworms are found in 20 soil samples.
Chemical
ControlsSoil insecticides are the only chemical means for controlling
wireworms. They are applied in the spring when the soil temperature at
the 6-inch depth is at least 50o F (10o C) and soil
moisture is equivalent to that desired for planting. Frequently, the insecticide
is applied immediately before or at planting.
The
following products are labeled for use in Delaware. (6):
Preplant Application:
diazinon (21-28 lb 14G/A, broadcasted
and incorporated into soil just before planting) to be used on 10% of the
acreage in 2000
disulfoton (Di-Syston 13.5-20.5 lb
15G/A, broadcasted and worked into soil 2 to 3 inches) Not used in the
Delaware
ethoprop
(Mocap 40-60 lb l0G/A, broadcasted and incorporated just before planting)
method not used in DE
At Planting Application:
disulfoton (Di-Syston 13.5-20.5 lb
15G/A, broadcasted and worked into soil 2 to3 inches) ; not
used used Delaware
ethoprop
(Mocap 30 lb l0G/A, in the row) ; used on 30% acres in DE; fair - good
control
phorate (Thimet 15 oz 15G/1,000 ft
of row) ; - used on 30% of the acreage; fair control
Alternative Controls
Crop rotation or frequent cultivation of the soil may help to reduce wireworm populations in the soil. Growers avoid planting in fields high in organic matter (5).
Minor Insect Pests in Delaware
Cutworms
Damage and Life Cycle
A number of cutworm species attack crop plants. They are active mainly at night, and hide in soil or debris during the day (5). Variegated cutworms feed primarily on potato foliage on lower stems. Black cutworms feed mainly on stems at or below the soil surface, but will also feed on foliage (6). First generation larvae may attack young seedlings, often snipping stems near the soil surface (5, 6). Most cutworm species overwinter as late instar larvae (5). Adults emerge in early to mid summer, and are present in our area during July and August (6). Some species, possibly the black cutworm, overwinter farther south and adults migrate into our area (15). Females deposit eggs on debris, grasses, or weed leaves and stems (5). Weedy or minimum-tillage fields are favored egg-laying sites (6). Eggs hatch in 5 to 14 days, depending on species (5, 15). Larvae develop through several instars, feeding on plants for weeks before pupating in the soil. Cutworms may also attack exposed tubers through cracks in the soil, leaving shallow feeding holes (5, 6). One to three generations occur each year, depending upon species (5).
Frequency of Occurrence
Cutworms are a minor pest of potatoes
in Delaware (14). There is considerable variation in this pest regionally.
Moth populations can fluctuate considerably from year to year as well (13).
In dry years, low lying areas of the field are more subject to attack than
other areas (6).
Management
For cutworms that feed below the ground,
neither foliar nor systemic insecticides are effective. In fields where
high cutworm populations are expected, a broadcast incorporated insecticide
may be applied and worked into the soil immediately prior to planting.
Whether or not this strategy is used, fields are scouted for cutworm damage
after plant emergence. Protective sprays are applied if more than 6 variegated
cutworms are found per plant, or if more than 10% feeding damage is incurred.
Also, if cutworms are actively cutting plants, a contact insecticide is
applied at the base of plants at night (6).
Chemical Controls
Insecticides should be applied at the
base of plants at night, with a high volume of water, to achieve the best
possible control (5). The following insecticides are labeled to control
cutworms on potatoes Delaware (6). In 1999, damage was significantly higher
however, no sprays have been applied for this pest in Delaware
Esfenvalerate (Asana XL 5.8-9.6 fl oz 0.66EC/A)
Methomyl (Lannate 1.5-3 pt LV/A) [variegated cutworm only]
permethrin (Pounce 4-8 fl oz 3.2EC/A)
carbaryl (Sevin 2.5 lb 80S/A)
carbaryl (Sevin bait 40 lb 5% bait/A)
Alternative Controls
A number of predators and parasites
help to reduce cutworm populations, including birds, ground beetles, parasitic
wasps and flies, and diseases (5, 10). Plowing in the fall may be used
to destroy some life stages (5). Good weed control is important, since
moths often favor weedy sites to deposit eggs (6).
Potato Flea Beetle
Damage and Life Cycle
Potato flea beetle (Epitrix cucumeris)
is common throughout the Northeast and is known to transmit early blight
and bacterial ring rot. It feeds on a variety of crops including eggplant,
tomatoes, peppers, and potatoes. Adult beetles overwinter in crop debris
or weedy areas near fields and become active in early spring. They feed
on a variety of herbaceous plants until potatoes emerge. Eggs are deposited
on the soil at the base of plants, about 100 eggs per female. Larvae emerge
after about 10 days and burrow into the soil, where they feed on roots,
sprouts, and tumors, weakening plants and sometimes killing seedlings.
They pupate in the soil. Adult beetles emerge and burrow to the surface.
They climb onto plants and chew small holes in the foliage which can facilitate
the entry of plant pathogens. Beetles may also spread diseases from plant
to plant as they feed. The life cycle takes 4 to 6 weeks to complete. There
are two to three generations per year in Delaware. Young plants attacked
early in the season suffer the most damage (5).
Frequency of Occurrence
Potato flea beetle is an occasional
pest in our area, but it is usually controlled by insecticide applications
made to control other insect pests (3).
Management
Chemical control specifically for flea
beetles is not needed every year, probably due to inadvertent control of
beetles by insecticide applications made for other insect pest species
(3). Chemical control may be utilized when the first generation population
is high, to reduce the potential for disease transmission and prevent later
populations from reaching economic levels
Chemical Controls
The following insecticides are labeled
to control flea beetles on potatoes in Delaware (6)
Preventive Applications
imidacloprid (Admire 0.9-1.3 fl oz
2FS/1,000 row ft) [According to the label, Admire is applied as a banded
application during seedbed preparation or in the furrow at planting or
sidedressed on either side of the potato row at plating.] -mainly
used for CPB, aphid and PLH control but will also provide very good flea
beetle control.
Rescue Treatments:
permethrin (Ambush 3.2-12.8 fl oz 2EC/A or 4-8 fl oz Pounce 3.2EC/A)
esfenvalerate (Asana XL 5.8-9.6 fl oz 0.66EC/A)
disulfoton (Di-Syston 13.5-20.5 lb 15G/A [Broadcasted and incorporated before planting or applied in the seed furrow or in a band on each side of the seed furrow. An additional application may be sidedressed after plants become established.]
phosmet (Imidan 2 lb 50WP/A)
methomyl (Lannate--1.5-3 pt LV/A)
endosulfan (Thiodan l.33-2.67 pt 3EC/A)
oxamyl (Vydate L 1-4 pt 2L/A)
Alternative ControlsControl of early
spring weeds near potato fields and cultivation are used to reduce overwintering
and reservoir populations of flea beetles (5).
White grubs (Scarabidae)
Damage
and Life CycleWhite grubs are the larval stage of beetles in the
scarab family. They have a broad host range, feeding on over 200 species
of plants, including most vegetable crops (5). Females prefer to lay their
eggs in fields which have extensive weed growth during mid-summer (16).
Larvae hatch during late-summer and move through the soil where they feed
on developing tubers, leaving large, shallow, round holes. Since there
are no foliar symptoms of grub feeding, beetles may do extensive damage
to tubers before the grower is aware of a problem. Damage is usually worst
in fields previously planted in sod or pasture (5). White grubs feed and
develop as larvae for 1 to 4 years, depending upon the species (16).
Frequency of Occurrence
White grubs are a minor pest of potatoes
(14). Like wireworms, white grubs are most commonly found in fields where
the preceding crop was sod or other grasses (16). They thrive best in cool,
wet soils (9).
Management
Chemical Controls
No insecticides are labeled to control
grubs in potatoes. However, insecticides labeled for wireworm control provide
some degree of white grub suppression.
Weeds
Weeds cause economic loss in potatoes
in several ways. These include competition for nutrients, space, water
and light, which will reduce yields; and a reduction in the efficiency
of harvesting. Weeds may also act as reservoirs for insect pests and diseases.
Most weeds produce numerous seeds, many of which can remain in the soil
and increase weed populations for years. Therefore, proper weed management
is essential not only for this years crop, but for years to come (7)
Weed Management
Non-chemical Controls
Herbicides are used in conjunction
with cultivation and cultural control practices to achieve good weed control
in potatoes. Where possible, growers select cultivars that compete well
with weeds, and plant rows close together to discourage weed growth (5).
Weeds carried over from previous crops in the rotation are reduced through
use of certified seed for all crops in the rotation. The spread of weeds
from one field to another is minimized by cleaning farm equipment between
uses in different fields. Maintaining good weed control around field borders
and fence rows is important, as these are a potential source for insect
pests and disease as well as weed seeds. Growers do this by planting competitive
grasses at field borders and keeping these areas free of weeds. Well-planned
crop rotations are also an important strategy growers use to reduce weed
pressure (7). Cultivation is a critical part of weed management
in potatoes, but it must be done with great care to avoid damage to the
plants and yield loss. Fields must be cultivated while the target annual
weeds are small to achieve effective control (7).
Scouting
Fields are scouted to Identify the
weeds in each field and select recommended herbicides that control those
weeds (6). Scouting is done within 4 weeks of crop emergence to determine
the effectiveness of preplant incorporated and preemergent herbicides.
Scouting can determine if a postemergent product is needed, what products
should be used, and assure that the application is made while weeds are
still small and susceptible. Fields are scouted again 4 or 5 weeks before
vine kill to increase harvest efficiency and to plan weed control strategies
for the next cropping season (5).
Chemical Controls
I. Preplant Incorporated and Preemergent Herbicides
Preplant incorporated and preemergence
herbicide selection is based on the mixture of weeds present in the field,
soil type, and the percent of organic matter in the soil (6).
EPTC -- Growers apply 3 - 4.5
lb ai per acre (3.4 - 5.1 pt/A of Eptam 7E or 30 to 45 lb/A of Eptam l0G)
at one of three times: (1) immediately before planting and disking (this
treatment is used for early season control of nutsedge and other weeds,
but on plantings before April 1, it may reduce early vigor and yields slightly);
(2) immediately after drag off cultivation, incorporated into sod; (3)
just prior to the first or second cultivation (this treatment is best for
late-season control of nutsedge and other weeds). EPTC is not applied within
45 days of harvest. This herbicide primarily controls annual grasses, yellow
nutsedge, and a few broadleaf weeds (6).
Linuron -- Growers apply 0.4
- 1 lb ai per acre (0.8 - 2 lb/A Lorox 50DF) after planting or before potatoes
emerge, but after final drag-off and before grasses are 2 inches tall and
before broadleaf weeds are 6 inches tall. Linuron mainly controls broadleaf
weeds, and is tank-mixed at low rates with metolachlor or pendimethalin,
or used in addition to EPTC for preemergence annual grass control. Lower
rates of linuron are used if tank-mixed (6).
Metolachlor -- Growers apply
1.25 - 3 lbs ai per acre (1.25 - 3 pt/A of Dual 8E) before potatoes emerge,
but after final drag-off. This product will primarily control annual grasses.
Nutsedge control may be adequate if weed pressure is light. Metolachlor
is tank-mixed with linuron or metribuzin for broadleaf weed control (6).
Metribuzin -- Growers apply
0.38 - 0.5 lb ai per acre (0.5 - 0.66 lb/A of Sencor or Lexone 75DF or
comparable rates of liquid formulation) just prior to emergence. If drag-off
is practiced, then the application is made after drag-off. Metribuzin primarily
controls broadleaf weeds, and is tank-mixed with metolachlor or pendimethalin,
or used in addition to EPTC for preemergence annual grass control. Metribuzin
is not applied within 60 days of harvest (6).
Pendimethalin -- Growers apply
0.5-1.5 lbs ai per acre (1 to 3 pts/A of Prowl 4EC) before potatoes emerge.
Pendimethalin controls certain broadleaf weeds, including velvetleaf, and
early-season annual grasses, but does not control yellow nutsedge. This
product is combined with linuron to improve velvetleaf control, or with
linuron or metribuzin to improve the control of most other broadleaf weeds
(6).
II. Postemergence Herbicides
Growers apply postemergence herbicides
when crop and weeds are within the recommended size and/or leaf stage to
maximize weed control and minimize crop damage (6).
Rimsulfuron -- Growers apply 0.0156 lb ai per acre (1 oz/A of Matrix 25DF) soon after emergence to control many weeds including foxtail species, pigweed species, wild mustard, and wild radish. Common lambsquarter, common ragweed, jimsonweed, morningglory species, and yellow nutsedge may only be suppressed by rimsulfuron. This product is tank-mixed with reduced rates of metribuzin to increase the spectrum of weeds controlled. A second application 2 to 4 weeks after the initial spray is used to improve the suppression or control of common purslane and perennial weeds, such as field and hedge bindweed. Results tend to be most effective when used following a preemergence residual weed control program. To improve weed control, growers add nonionic surfactant to be 0.25 percent of the spray solution (1 quart per 100 gallons of spray solution). Growers do not exceed 2 ounces of Matrix 25DF per acre per year. Rimsulfuron is an ALS inhibitor and is always used in combination with other herbicides with different modes of action to prevent the development of resistant weed populations (6).
Metribuzin -- Growers apply
0.25 - 0.5 lb ai per acre (0.33 - 0.66 lb/A of Lexone or Sencor 75DF) before
weeds are 1 inch tall. Metribuzin mainly controls broadleaf weeds. It is
applied only if there have been at least three successive sunny days prior
to application. It is not used on red-skinned or early maturing, smooth,
white-skinned varieties. Treatment can cause some yellowing or minor burn
(6).
Sethoxydim -- Growers apply
0.2 - 0.4 lbs ai per acre (1 - 2 pts/A Poast 1.5EC with oil concentrate
added to be 1 percent of the spray solution) after emergence to control
annual grasses and certain perennial grasses. For best results, growers
treat annual grasses when they are actively growing and before tillers
are present. Control may be reduced if hot, dry weather or drought conditions
occur. Repeated applications may be needed to control certain perennial
grasses. Yellow nutsedge, wild onion, or broadleaf weeds will are not controlled
by sethoxydim. Growers do not tank-mix with or apply within 2 to 3 days
of any other pesticide unless labeled, as the risk of crop injury may be
increased, or reduced control of grasses may result. No more than 5 pints
per acre of Poast is applied during the growing season, and a minimum preharvest
interval of 30 days is observed (6).
III. Postharvest
Glyphosate - Growers apply 2
- 5 lbs ai per acre (2 - 5 qts/A of Roundup Ultra 4SC) in the fall after
harvest to control perennial grasses and broadleaf weeds, including quackgrass,
field bindweed, Canada thistle, and others. (Rate varies depending on the
weed population.) Application is delayed after harvest (but applied prior
to the first frost) to allow for adequate weed regrowth to intercept the
spray. Growers do not till or mow for 1 week after application (6).
Chemical
Control Issues for Herbicides
Table
2. Potato herbicides for grasses and sedges.
|
GRASSES
AND SEDGES
|
|||||||
| Herbicide | Barnyard-grass | Crabgrass,
Large |
Fall Panicum | Foxtail sp. | Goosegrass | Johnsongrass (seedling) | Yellow
nutsedge |
| Preemergence or Preplant Incorporated: | |||||||
| EPTC | G | G | G | G | G | G | N |
| Preemergence: | |||||||
| linduron | F | P/F | P | F | P/F | - | N |
| metolachlor | G | G | G | G | G | G | F/G |
| metribuzin | F | F | F | F | F | - | N |
| pendimethalin | G | G | G | G | - | G | N |
| Postemergence: | |||||||
| rimsulfuron | G | F | F/G | G | P | - | F |
| metribuzin | F | F | F | F | F | - | - |
| sethoxydim | N | N | N | N | N | N | N |
Herbicide performance is affected by weather, soil type, herbicide rate, weed pressure and other factors. These ratings indicate ONLY relative effectiveness in tests conducted by the University of Delaware, University of Maryland System, The Pennsylvania State University, Rutgers, The State University of New Jersey, and Virginia Polytechnic Institute and State University. Actual performance may be better or worse than indicated in this chart (*). (Table modified from 1999 Commercial Vegetable Production Recommendations, University of Maryland Cooperative Extension Bulletin 236)
Key: G = good
F = fair
P = poor
N = no control
I
= insufficient data
Table 3.
Potato herbicides for broadleaf weeds
|
GRASSES
AND SEDGES
|
|||||||||
| Herbicide | Carpet-weed | Cocklebur, Com. | Galinsoga,
Hairy |
Jimson-weed | Lambsqtr.,
Common |
Morning-
glory sp. |
Pig-weed sp. | Purslane,
Common |
Rag-weed,
Common |
| Preemergence or Preplant Incorporated: | |||||||||
| EPTC | G | P | N | P | F | F | G | G | P |
| Preemergence: | |||||||||
| linduron | G | P | G | P/F | G | P | G | G | F |
| metolachlor | F | N | G | N | P | N | G | F/G | N |
| metribuzin | G | F | G | F/G | G | F/P | F/G | F | G |
| pendimethalin | G | N | N | N | F/G | P | F/G | F/G | N |
| Postemergence: | |||||||||
| rimsulfuron | - | F/G | G | F | P/F | F/G | G | F/G | P |
| metribuzin | G | - | G | G | G | P | G | G | G |
| sethoxydim | |||||||||
Herbicide performance is affected by weather, soil type, herbicide rate, weed pressure and other factors. These ratings indicate ONLY relative effectiveness in tests conducted by the University of Delaware, University of Maryland System, The Pennsylvania State University, Rutgers, The State University of New Jersey, and Virginia Polytechnic Institute and State University. Actual performance may be better or worse than indicated in this chart (*). (Table modified from 1999 Commercial Vegetable Production Recommendations, University of Maryland Cooperative Extension Bulletin 236)
Key: G = good
F = fair
P = poor
N = no control
I = insufficient data
Vine Killing and Storage
Vine Killing
Potato vines must be killed prior to
harvest. Vine death signals an end to tuber growth and promotes the formation
of the outer skin. Timing is important. Tubers harvested too soon after
vine kill will be more prone to injury and early and late blight infection
during harvest. Tubers left in the ground too long after vine kill may
be damaged by frost or may have excessive Rhizoctinia sclerotia
on the tuber surface. For most cultivars, a period of 10 to 14 days after
vine kill is sufficient to allow tubers to mature (7).
The following desiccants are used for
vine killing (6):
Endothall - Growers apply 0.75
to 1 lbs per acre (1.5 - 2 qts/A of Desicate II), mixed with ammonium sulfate
and a surfactant, 10 to 14 days before harvest. Higher rates are applied
if vine growth is vigorous or if weather is cool and cloudy.
Diquat - Growers apply 0.25
lbs per acre (1 pt/A of Diquat 2SC in 20 to 100 gallons of water) with
a nonionic surfactant. Application is repeated after 5 days if needed.
Tubers are harvested 7 days post-treatment.
Paraquat - Growers apply 0.4
to 0.6 lb ai/A (1 to 2 pts/acre of Gramoxone Extra 2.5SC) with 50 to 100
gallons of water at least 3 days prior to harvest. Paraquat works well
on grassy fields, but is not used on vigorously growing vines if potatoes
will be stored or used for seed.
Storage Vines of potatoes going into
storage are killed 14 to 21 days before harvest. Tubers are maintained
at a temperature of 50o to 60oF for the first 2 to
3 weeks, to promote healing of cuts and bruises. After this, the storage
temperature for table stock or seed potatoes is lowered to 40oF.
If the potential for rot is high, the curing period is eliminated a storage
temperature of 45oF is used until the crop is sold (6).
Sprout inhibitors are applied directly
to tubers after cuts and bruises from harvesting have healed. Growers use
chlorpropham (Chloro IPC or Sprout-Nip) (6).
Contacts:
Subject matter contacts at the University of Delaware, College of Agriculture and Natural Resources:
Joanne Whalen
Bob Mulrooney
Mark Van Gessel
Ed Kee
TracyWootten
REFERENCES
(1)
Delaware Agricultural Statistics Summary. Vegetables for Fresh Market;
Delaware 1996 to 1998. http://www.nass.usda.gov/de/p1897.htm
(2)
Kee, Ed. POTATOES. University of Delaware Cooperative Extension. HG-30
8/96. http://bluehen.ags.udel.edu/deces/hg/hg-30.htm
(3)
Dively, Galen, Entomologist, University of Maryland, College Park. Personal
Communication. 1999.
(4) Vegetable and Agronomic Crop Budgets,
1995-1997. Extension Circular #152, revised. Delaware Cooperative Extension
Service. University of Delaware and Delaware State University. 1997.
(5) Potato Production in the Northeast:
A Guide to Integrated Pest Management. Hollingsworth, C.S., D.N. Ferro,
and W.M. Coli, eds. Department of Entomology, University of Massachusetts,
Cooperative Extension Service. 1986.
(6) 1999 Commercial Vegetable Production
Recommendations: Delaware Cooperative Extension Bulletin 137 (revised).
1999.
(7) Potato Health Management. Rowe,
R.C., ed. American Phytopathological Society. 1993
(8) Insect Pests of Tomato, Pepper
and Eggplant, Pest Management Aid no. 3. University of Maryland Cooperative
Extension Service, College Park, Maryland. 1986.
(9) Vegetable Insect Management with
Emphasis on the Midwest. Foster, R. and Flood, B., Eds. Meister Publishing
Company. 1995.
(10) Integrated Pest Management for
Potatoes in the Western United States. University of California, Division
of Agriculture and Natural Resources. Publication 3316. 1986.
(11) Bean and Pea Insect Pests 1, Pest
Management Aid no. 5. University of Maryland Cooperative Extension Service,
College Park, Maryland. 1986.
(12) Insect Pests of Sweet Corn I,
Pest Management Aid no. 2. University of Maryland Cooperative Extension
Service, College Park, Maryland. 1986.
(13) Maryland Blacklight Trap Program - Twenty Six Year Summary of Selected Pest
Periodic Flight Activity. Maryland Department of Agriculture, Anapolis,
Maryland. 1999. Courtesy of Dick Bean.
(15) Insect Pests of Sweet Corn I,
Pest Management Aid no. 1. University of Maryland Cooperative Extension
Service, College Park, Maryland. 1986.
(16) Northeast Sweet Corn Production
and Integrated Pest Management Manual. Adams, R.G. and Clark, J.C., eds.
University of Connecticut Cooperative Extension System. 1995.
Authors:
Joanne Whalen - INSECTS
Mark VanGessel - WEEDS
Susan Whitney - General Information
Portions of this crop profile were adapted from the draft potato crop profile written by Al Fournier, University of Maryland.