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The botanical family Solanaceae includes several important vegetable
crops such as tomatoes, potatoes, eggplants, and peppers. These
crops share a number of insect and disease pests, so any crop
rotation plan should consider all crops grown from this family.
Aphids (Primarily the Green
Peach aphid, Myzus
persicae, and the Potato aphid, Macrosiphum
euphorbiae)
Aphids are small, soft-bodied insects View
photo 4.1 that suck nutrients
from plant tissues and form colonies on the undersides of leaves
and often in or around flowers. Several different species of aphids
attack potato, tomato, eggplant and pepper. In hot dry weather,
populations can increase rapidly causing leaves to wilt and twist.
In most organic systems, aphids are rarely a lasting problem because
predator and parasite populations keep the aphid population in
check. However, there is often a lag period between when aphid
populations first arrive and when their natural enemies build up,
so regular examination of the plants is needed. Some aphids transmit
viruses, which are particularly devastating in seed potato production.
Cultural Control:
- Encourage beneficial insects.
It is most important to limit use of broad spectrum insecticides
such as rotenone or pyrethrum because these kill predators
and parasites, and may cause the aphid populations to flare up.
Leaving or creating beneficial insect habitat and food sources
will help.
- Use virus resistant cultivars.
- Control overwintering weeds and inspect overwintered and
imported plants in greenhouses since they are often the source
of initial infestation of spring transplants.
Materials Approved for Organic
Production:
- Soap: If aphid populations are high, control
may be needed. Ensure coverage of the parts of the plant
where aphids live, especially the undersides of leaves. In recent
studies, soaps have been ineffective against green peach aphid.
Other studies we examined indicated 5 good, 1 fair, and 2 poor
results against other aphid species.
- Rotenone is recommended in the older literature (check with
certifier on approval status of formulated products, as none
are currently OMRI listed).
- Neem products can provide some control. Based on a limited
number of studies, neem products gave good control of turnip
aphid (2 studies); fair (4) to poor (3) control of green peach
aphid; and mostly good control of other aphids (2 good, 2 fair,
1 poor). Please see the neem chapter for a discussion of the
different types of neem products.
- Summer oils (2 fair and 3 poor results) will provide some
control.
- Kaolin clay (currently not labeled for aphids on these crops)
and
plant and mineral oils may be effective.
Colorado potato beetle (Leptinotarsa
decemlineata)
Colorado potato beetles (CPB) overwinter as adults View
photo 4.2,
hibernating in the soil near where previous host crops were grown.
They emerge in the spring and primarily crawl to new hosts where
they feed and lay eggs View
photo 4.3. The resulting larvae View
photo 4.4 and successive generations can quickly defoliate
a crop. The CPB prefers potatoes and eggplants but can also be
a problem on tomatoes and peppers.
Cultural Control:
- Crop rotation out of susceptible
crops is the first line of defense since CPB only feeds on
solanaceous plants. Control of solanaceous weeds such as horse
nettle is important.
- A barrier trench lined with plastic between the old field
and new field of host crops will catch many crawling adults and
trap them. This will reduce the overall population, but supplemental
control may still be required.
- If young potato plants are infested, rapidly moving a flame
from a propane torch over the top of the plant has been shown
to kill the overwintered adult CPB that tend to feed at the top
of the plant. Although this may singe the plant tissue, if done
carefully there will be no long-term damage to the plant. Suction
devices can also be used.
- Mulch crops with straw or hay before adults arrive. This
will significantly reduce and delay CPB pressure.
- For plantings less than two acres, hand-picking may be practical
if the CPB pressure is low.
- Trap cropping is effective, using a potato variety such
as ‘Superior’ that
grows well in cool weather. Plant the trap crop between last year’s
and this year’s fields (near CPB overwintering sites),
and destroy by flaming when adult CPB numbers on the trap crop
are high.
Materials Approved for Organic Production:
- Spinosad: Recent studies showed 12 good and 2 fair results.
- Neem products: Recent studies showed 1 good and 2 fair results.
Generally, neem is slow-acting, but it reduces overall damage
and numbers of large larvae. Please see the neem chapter for
a discussion of the different types of neem products.
- Beauveria bassiana: Recent studies showed 1 good,
1 fair, and 5 poor results.
- Bt tenebrionis (also called Bt san diego)
- currently there are no approved formulations
European corn borer (Ostrinia
nubilalis)
The European corn borer has over 200 host plants and is primarily
a pest of corn, but pepper and eggplant are also relatively common
hosts and tomato and potato somewhat less so. In the spring adults
lay their eggs on plants and the emerging larvae bore into stalks
View
photo 4.5 or fruits. The larvae usually enter the fruit under
the calyx or sometimes directly through the side and feed inside.
Secondary rotting of infested fruit is common.
Cultural Control:
- Crop rotation is only of limited value because the adults can
easily fly between fields.
- Some pepper varieties differ in their susceptibility, but
there are no truly resistant varieties.
- Effectiveness of spray materials can be increased by timing
sprays using information from pheromone traps regarding peak
activity periods. Check with county extension for any available
IPM forecasting services.
Materials Approved for Organic Production:
- Bt kurstaki: No recent studies on peppers; however,
Bt can be effective but has a very short residual protection.
- Spinosad: Recent studies: 3 good, 1 poor result on this crop.
Flea beetles (Potato
Flea Beetle - Epitrix cucumeris, Tobacco
Flea Beetle - Epitrix hirtipennis, Palestriped
Flea Beetle - Systena
blanda, and Eggplant Flea Beetle -
Epitrix fuscula)
Flea beetles View
photo 4.6 are common pests of potatoes, tomatoes
and eggplants when the crops are young. Their feeding causes
small holes in the leaves. Under light insect pressure and good
growing conditions, seedlings and transplants will grow out of
the damage. Eggplant is especially attractive to flea beetles
and small transplants may need protection. The species of flea
beetles that attack the Solanaceae are not the same as those
that attack brassica crops or sweet corn. This is important when
considering your crop rotation.
Cultural Control:
Row covers work well but can
be expensive. Crops under row covers usually produce earlier yields.
Materials Approved for Organic Production:
The studies below were mostly conducted on flea beetle pests of
other crops, particularly brassicas. Results may be different
on flea beetle pests of solanaceous crops.
- Rotenone: Growers have noted good control with rotenone
(currently, no rotenone products are on the OMRI approved list).
- Spinosad: Research trials have indicated that spinosad can
be effective, though results are variable. (3 fair and 2 poor
results).
- Neem products are similarly effective (2 fair, 2 poor results).
Please see the neem chapter for a discussion of the different
types of neem products.
- Capsaicin gives some control (45% in one study). The product,
Miller’s Hot Sauce™ is OMRI-approved and labeled
for use on crop plants as a mammal repellant. If so used, it
will also reduce flea beetle damage.
- Pyrethrum: Pyganic™ has shown variable results (4
fair, 2 poor) even with high rates.
- Kaolin clay (Surround™). Recent trials have shown
three poor results.
Note: Since flea beetles can re-colonize rapidly, especially on
sunny days, frequent treatment with any material may be required.
It is advisable to treat all susceptible plants in the field to
reduce influx from untreated areas.
Hornworm (tobacco, Manduca
sexta, and tomato, Manduca
quinquemaculata)
These large green caterpillars View
photo 4.7 are more common in warmer
climates but do turn up sometimes, including in hoophouses and
greenhouses. They can consume considerable leaf tissue.
Cultural Control:
Scouting and hand picking the larvae works well because they are
usually in small numbers. The caterpillars are well camouflaged;
look for the large droppings beneath plants.
Materials Approved for Organic Production:
- Bt
kurstaki: There is a lack of research data, however
growers report successful use.
- Spinosad: One recent study showed good control.
Potato leafhopper (Empoasca
fabae)
Potato leafhoppers View
photo 4.8 do not overwinter in the Northeast
but “leap frog” their way up from southern areas
each summer, arriving in very large numbers some years, and small
numbers in others.
The potato leafhopper favors alfalfa, beans, strawberries and
potatoes. It is a serious pest of potatoes, as both adults and
larvae suck plant juices. Their feeding causes curling, stunting
and dwarfing accompanied by a yellowing, browning or blighting
of the foliage known as “hopperburn” or tipburn because
the damage is first seen at the leaf tips working inwards. When
significant “hopperburn” is seen, your crop has already
lost yield, so be sure to scout your field early.
Cultural Control:
- Crop rotation will not help control leafhoppers since they do
not overwinter in the Northeast and because the pest can move
large distances.
- Some varieties are more tolerant and these include ‘Elba’, ‘Green
Mountain’, some russets, ‘Snowden’, ‘Ontario’,
and ‘Katahdin’. ‘Red Norland’ is very
susceptible. More information may be found in seed catalogues
or through your local extension office.
- Scouting and early detection are important because population
levels vary greatly from year to year, and successful control
must start early.
Materials Approved for Organic Production:
- Pyrethrum (recent trials have shown 1 good result).
- Neem products: One recent study showed fair control. Please
see the neem chapter for a discussion of the different
types of neem products.
- Spinosad: Entrust® is not effective against this pest.
Tarnished plant bug (Lygus
lineolaris)
The tarnished plant bug (TPB) is a sucking insect View
photo 4.9 that
feeds on flowers and buds of eggplant, pepper and tomato causing
flower drop, which greatly reduces yield in some years.
Cultural Control:
- Do not mow legume hay fields
surrounding crops just prior to or during flowering of solanaceous
crops because that will drive the TPB into the crops.
- Floating row covers work well to protect buds and flowers
on young plants and can greatly increase early yield but may
not be practical for mid-summer use.
- Practice good weed control, since TPB seems to be more of
a problem in weedy areas.
Materials Approved for Organic Production:
There are no proven effective organic insecticides for TPB, although
pyrethrums will reduce the overall populations. Neem products
are recommended for trial.
Diseases caused by bacteria
Bacterial canker (Clavibacter
michiganensis subsp. michiganensis),
bacterial speck (Pseudomonas
syringae pv. tomato) and bacterial
spot (Xanthomonas campestris pv. vesicatoria) are all quite common
and are all managed the same way.
Canker is most common on tomato but can occur on pepper as well.
The first symptoms may include wilting, browning at the margin
of the leaflet, and leaflet curling. Later symptoms include brown
stem cankers that frequently crack open, and spots on the fruit.
The fruit lesions have a dark brown center surrounded by a white
ring, with a characteristic “birds-eye” appearance
View
photo 4.10.
Speck is found only on tomato. Small black lesions (1/8 inch)
with a yellow halo appear on leaves, and black raised lesions or
dots appear on fruit View
photo 4.11.
Spot occurs on both tomato and pepper. Symptoms can appear on
leaves, stems, and fruit View
photo 4.12. Lesions begin as water-soaked
spots that become brown and may have an irregular shape View
photo 4.13. Infected leaves eventually turn yellow and drop
off the plant.
Cultural Control:
- Plant disease-free seed.
Hot water seed treatment at 122°F
for 25 minutes is recommended for tomato seed. For pepper seed,
hot water treatment at 125°F for 30 minutes is recommended.
Strictly follow time and temperature recommendations to minimize
damage to seed germination and vigor. Hot water treatment can
also eliminate fungal pathogens on the seed. Chlorine treatment
of seed is also effective and may be permitted, check with
the certification agent. Use one part household bleach to 4
parts water plus a half teaspoon of surfactant per gallon of
solution, agitate seed for one minute, then rinse in running
water for 5 minutes. Dry seed thoroughly.
- Pepper varieties that are resistant to bacterial spot are
available (see Cornell 2004) .
- If growing and using transplants, all greenhouse materials
should be cleaned and sterilized prior to use. The spread of
bacterial diseases in the greenhouse is common.
- If trellising or caging tomatoes, stakes and cages should
either be new or cleaned and disinfected. Sodium hypochlorite
at 0.5% (12x dilution of household bleach) is effective, and
must be followed by rinsing, and proper disposal of solution.
Hydrogen peroxide is also permitted.
- If pruning tomatoes, disinfect tools or gloves regularly
to minimize spread of bacteria from infected plants.
- Use a 3-year crop rotation away from tomato and pepper.
- Because bacterial diseases can spread by splashing water,
avoid overhead irrigation.
- Avoid working in the crop when it is wet.
- Compost may contain organisms that are antagonistic to the
pathogen.
Materials Approved for Organic Production:
Copper compounds. Recent studies showed 2 fair and 1 poor result.
Common scab (potato)
Common scab is a disease of potatoes that results in corky lesions
on the surface of the tuber View
photo 4.14. It is caused by the
filamentous bacterium Streptomyces scabies. The pathogen
can survive in the soil for many years.
Cultural Control:
- Plant scab free potato seed.
- Rotate with crops that are not hosts (hosts include beets,
carrots, turnip, radish and parsnip). Good rotation crops are
sweet corn and green manures such as rye, millet and oats. Avoid
plow down crops of legumes, especially red clover immediately
before potatoes.
- Use resistant cultivars (see Cornell 2004).
- Maintain pH below 5.5, although this is usually not suited
for diversified vegetable growers since it is detrimental to
the other crops in the rotation.
- Maintain good soil moisture, especially at tuber initiation.
Materials Approved for Organic Production:
- Applying sulfur in the row when planting is suggested, but
unproven.
- Biologicals such as Trichoderma are recommended for grower
testing.
Anthracnose (tomato)
Anthracnose is a common disease of ripe tomato fruit, caused by
the fungal pathogen Colletotrichum coccodes. Symptoms
begin as small, sunken, water saturated lesions. Black fungal
structures develop and are visible within the lesion View
photo 4.15. While
symptoms appear only on ripe fruit, infection can occur on both
green and ripe fruit.
Cultural Control:
- Use a 3-year crop rotation
away from potato, tomato and pepper.
- Mulching can reduce the severity of infection.
- Avoid overhead irrigation or use it such that fruit wetness
is minimized.
- Plant disease-free seed. Hot water seed treatment at 122°F
for 25 minutes is recommended for tomato seed.
- Stake or cage plants so fruit is not in contact with the
soil.
- Compost may contain organisms that are antagonistic to the
pathogen.
Materials Approved for Organic Production:
Copper products showed 1 poor result in recent studies.
Black scurf (potato)
Black scurf is a fungal disease (Rhizoctonia solani) of
potato that can delay emergence and reduce yield. More commonly,
however, the disease results in a high percentage of tubers with
black rough structures on the surface that reduce marketability
View
photo 4.16. These are asexual reproductive structures called
sclerotia. These sclerotia can survive for years in the soil and
infect susceptible crops in future seasons. While R. solani is
uncommon on tomato, pepper and eggplant, the pathogen has a very
broad host range including many vegetables.
Cultural Control:
- Use seed tubers free of
sclerotia.
- Use a 3-year or longer crop rotation
including a grass or cereal green manure such as sudex (sorghum-sudan
grass hybrid) or Japanese millet the year before potatoes.
- Promote
quick emergence by planting in warm soil, covering seed pieces
with no more than 2 inches of soil and hilling up later.
Also, avoid wet soil at planting time.
- Plow down Brassica green manures
that contain high levels of glucosinolates, e.g., ‘Pacific gold’ oriental mustard
and ‘Idagold’ mustard.
Materials Approved for Organic Production:
Trichoderma (RootShield®) has shown variable results.
Early blight (potato, tomato)
Early blight is caused by two fungi (Alternaria solani and Alternaria
tomatophila) that are a serious problem in tomatoes and
potatoes but rarely effects peppers and eggplants. All of the
above-ground portions of the plant can be affected throughout
the growing season. The disease starts on the lower leaves with
small circular spots that have a target appearance of concentric
rings View
photo 4.17. Leaves develop yellow blighted areas and later
the tomato fruit may rot on the stem end. Potato tubers can also
become infected, but this is quite rare. The pathogen can overwinter
in the soil on diseased plant residues.
Cultural Control:
- Use crop rotations of at
least 3 years to non-hosts (away from tomato, potato and
eggplant).
- Provide optimum growing conditions and fertility. Stressed
plants (including drought) are more susceptible to early blight.
- Stake or cage plants to keep fruit and foliage away from
soil.
- Drip irrigation is preferred, or overhead irrigation starting
before dawn, so that the plants are dry early in the day. The
key is to keep the period of leaf wetness to a minimum.
- Mulching helps to prevent splashing of spores from soil
up to lower leaves.
- Indeterminate tomato and late-maturing potato varieties
are usually more resistant/tolerant to early blight.
- Early blight can be seed-borne, so buy from a reliable supplier.
Hot water seed treatment at 122°F for 25 minutes is recommended
to control early blight on tomato seed. See chlorine treatment
procedures under bacterial diseases.
- Disinfect stakes or cages
with an approved product each season before using. Sodium
hypochlorite at 0.5% (12x dilution of household bleach) is effective,
and must be followed by rinsing, and proper disposal of solution.
Hydrogen peroxide is also permitted.
Materials Approved for Organic Production:
- Copper products showed one good and one poor result in recent
studies.
- A Trichoderma harzanium product, PlantShield HC®, used
as a drench at planting, showed fair to good results in NYS
on tomatoes over three seasons.
Gray mold (greenhouse tomato)
Gray mold, caused by the fungus Botrytis cinerea, can
occur wherever tomatoes are grown but is primarily a problem in
greenhouse production. The disease can affect all aboveground parts
of the tomato. Lesions can form on leaves, stem, petiole and senescent
petals frequently causing blossom drop or infected fruit View
photo 4.18. Lesions
on leaflets progressively expand to include the petiole and eventually
the whole leaf is killed. Infected tissue develops a gray fuzzy
mold growth, which can give off clouds of spores when shaken.
Cultural Control:
Since gray mold has a very wide
range of hosts, the spores are difficult to avoid. Controlling
the disease involves managing the environment in the greenhouse
to make it less favorable for disease spread. Reduce leaf wetness
to a minimum and maximize ventilation. High calcium levels in the
soil that result in a calcium to phosphorus ratio of 2 or higher
in the leaf petiole aids in reducing susceptibility of tomato plants.
Materials Approved for Organic Production:
Copper
may be effective. Begin application before the canopy becomes dense.
Late blight (potato, tomato)
Late blight View
photo 4.19 is caused by a fungus-like pathogen (Phytophthora
infestans) and is a serious disease of both potato and tomato,
and is infamous as the cause of the Irish potato famine. It can
quickly defoliate plants and cause fruit rot in tomato and tuber
rot in potato. Spores are carried long distances in the wind
and the disease can spread rapidly. The pathogen overwinters
only in living plant debris, most commonly on seed potatoes or
unharvested and cull potatoes in the Northeast. Imported solanaceous
transplants including tomato and petunia may harbor late blight.
Cultural Control:
- Destroy cull potatoes and control potato volunteers in all
fields.
- Use drip irrigation rather than overhead in order to keep
the foliage dry. Alternatively, overhead irrigate early in the
morning before dawn so the plants are dry early in the day. The
key factor is to keep the period of leaf wetness to a minimum.
Materials Approved for Organic Production:
Copper
products give fair to good control but must be applied often and
thoroughly.
Leaf mold (greenhouse tomato)
Leaf mold, caused by Fulvia fulva, is primarily a disease
in greenhouse production in the northeast. It is a disease that
is usually only a problem under highly humid conditions. The initial
symptoms are light green to yellowish spots on the upper surface
of the leaf View
photo 4.20 with a dark green mold on the undersurface
of each spot View
photo 4.21. Later the spots coalesce and the leaves
wither and drop from the plant. Usually, only the foliage is
affected. The older leaves are affected first and so if the disease
comes in late in the season it does not affect yield. If it strikes
early the loss of foliage will reduce yield. In severe outbreaks
blossoms, petioles and fruit may be affected.
Cultural Control:
Sanitation is important.
After harvest remove all crop residue. Once the crop residue
is removed the production area should be steamed for at least six
hours. Minimizing periods of leaf wetness reduces the severity
of leaf mold. Avoid wetting leaves by overhead irrigation or
dripping condensation. Maintain good ventilation.
Materials Approved for Organic Production:
None
known.
Phytophthora
blight (pepper)
Phytophthora blight, caused by Phytophthora capsici, is
a serious problem of peppers in warmer parts of the Northeast.
Plants collapse and fruit will rot where they touch the ground
View
photo 4.22. Fruit lesions develop as dark, water-soaked areas
that spread and become coated with the white spores of the pathogen.
P. capsici overwinters in the soil.
Cultural Control:
- Crop rotation away from a host
plant for 4-5 years. Note that peppers, tomatoes, eggplants,
cucurbits, lima beans and snap beans are all hosts for this pathogen.
- Use raised beds and ensure good soil drainage.
- Maintain good soil structure to avoid poor drainage and standing
water in the field.
Materials Approved for Organic Production:
No
control materials are effective against Phytophthora blight.
Septoria leaf
spot (tomato)
Septoria leaf spot is a fungal disease (Septoria lycopersici)
of tomato that behaves in a manner similar to early blight. Initial
symptoms include peppering of lower leaves first with small circular
spots with a dark brown margin View
photo 4.23. Rapid defoliation
can occur under optimal conditions View
photo 4.24. The fungus is
spread by splashing water, insects, equipment or field workers.
Cultural Control:
- Since this is often seed-borne,
be sure to buy seed and/or transplants from reputable sources.
- Space plants to promote air circulation, which will help keep
leaves dry.
Materials Approved for Organic Production:
Copper
products showed one good and one poor result in recent trials.
Verticillium
wilt (eggplant, tomato)
Verticillium wilt can be a serious problem in eggplant and some
tomato varieties. This disease can be caused by either of two
fungal pathogens, Verticillium albo-atrum or Verticillium
dahliae.
Infected plants exhibit leaves that turn yellowish and portions
of the plant collapse View
photo 4.25. Most modern tomato varieties
are resistant, but many heirlooms are not. On potatoes the disease
is called “early dying.”
Cultural Control:
- Avoid other host crops before
eggplant or tomatoes in the rotation including; tomatoes,
eggplant, potatoes, peppers and strawberries.
- Plant resistant varieties (see Cornell 2004).
- Compost may contain organisms that are antagonistic to the
pathogen.
Materials Approved for Organic Production:
No
control materials are effective against Verticillium wilt
White mold (tomato, pepper, eggplant)
White mold is a fungal disease caused by Sclerotina sclerotiorum,
which has a very wide host range including tomatoes, eggplants,
peppers, beans, carrots, lettuce, cole crops and many weeds.
Early symptoms are water-soaked lesions and a firm rotting of
stem tissue. Later these lesions become covered with a pure white
fungal growth and black sclerotia can be found on and in the
diseased tissue View
photo 4.26. All of the tissue above the lesion
dies, so entire branches of the plant will wilt and then die.
This disease is most common on heavy soils with poor drainage.
Cultural Control:
- Use raised beds and tiles to improve drainage if necessary.
- Rotation is difficult because so many crops and weeds are hosts
and the sclerotia are very long-lived in the soil. Four years
of sweet corn or other cereal is recommended for infested fields.
- Avoid excessive irrigation.
- Avoid overcrowding and weeds that maintain moisture in the
crop canopy. Good airflow is essential to control white mold.
Materials Approved for Organic Production:
Coniothyrium
minitans (Contans®) is a beneficial fungus that
can be applied to the soil to reduce survival of sclerotia.
It should be applied after a crop infected with white mold
or before a susceptible crop is planted in an infested field.
References
Cornell 2004. Reiners, S., Petzoldt, C. H., and Hoffmann, M. P.
eds. Cornell Pest Management Guidelines for Vegetables 2004.
Cornell Cooperative Extension Publication. Chapter 19, Eggplant;
Chapter 23, Peppers;Chapter 24, Potatoes; Chapter 27, Tomatoes.http://www.nysaes.cornell.edu/recommends/ |