Greenhouse - INSV and Thrips

Thrips are the vector of Impatiens Necrotic Spot Virus (INSV) in the greenhouse. The following is more information.

INSV is a Topsovirus vectored exclusively by thrips. There is no cure or treatment for INSV. When INSV is diagnosed it is recommended that the plants be discarded and to begin a rigorous program for controlling the thrips population. Thrips should be prevented from entering greenhouses by monitoring new shipments of plants. Do not grow ornamental plants and vegetable plants in the same greenhouse. Also, remove all plant debris on benches and floors.
Remember the soil under greenhouse benches is where thrips work through their developmental stages. In empty greenhouses, close vents and keep the house heated and empty for a week or more between crops to stimulate development of thrips pupae in the soil and eliminate emerging adults. Use an insecticide to knock down emerging adults. Weeds serve as a reservoir of both INSV and Tomato spotted wilt virus (TSWV): eliminate weeds in and around the greenhouse.

Biological controls for thrips include predacious mites (Hypoaspis species, Amblyseius cucumeris), beneficial nematodes (Thripinema nicklewoodii, Steinernema feltiae), entomopathogenic fungi (Beauveria bassiana), or predacious bugs (Orius insidiosus). Biological control should not be used when either INSV or Tomato spotted wilt virus (TSWV) is already present in the greenhouse and should be part of an IPM program. Recommendations for insecticides are available in the New England Floriculture Management Guide.

Information from the current edition of the New England Greenhouse Update
http://www.negreenhouseupdate.info/greenhouse_update/index.php

Greenhouse - Impatiens Necrotic Spot Virus INSV

Impatiens Necrotic Spot Virus is one of the most common viruses in greenhouses. It is spread by thrips. The following are lists of plants that are susceptible to this virus.






INSV on Fuschia.

Tables from "Symptoms and management strategies for impatiens necrotic spot virus" by Mary Hausbeck,Plant Pathology in the March 3, 2006 edition of the Michigan State University Greenhouse Alert newsletter.

Greenhouse - More on New Guinea Impatiens: Pest Issues

The following is additional information on New Guinea Impatiens insect and disease control from the University of Maryland.

Diseases to watch for:

- Pythium- root and stem rot. Symptoms include stunting, yellowing, wilting, and soft brown roots. Development promoted by over-irrigation and over-fertilization.
- Botrytis- look for the fuzzy gray spores on senescing flowers and dead plant material. Requires film of water on plant surfaces for several hours to germinate.
- Rhizoctonia- can cause root rot and stem cankers. It is called “web blight” when the mycelium grows on aboveground plant parts causing them to “melt down”

Foliar Leaf Spots

- Alternaria- fungal disease which requires a film of water and moist conditions for infection and sporulation.
- Myrothecium- attacks injured or stressed plant tissues and causes necrotic lesions with dark rings, often on the leaf margin. Green/black spores on white sporodochia are characteristic of this disease.

Virus – Tospovirus

- INSV (impatiens necrotic spot virus) some leaves show dark spots and rings, while others can have mosaic symptoms. If virus transmission is going on in the greenhouse, the tolerance level for thrips drops to almost zero. Monitor for thrips using sticky cards.

Thrips control: rotate between materials. Pedestal controls larvae of thrips. Pylon at the high rate of 10-15 oz/100 gallons works. Conserve can be one of the choices, but don’t just rely on this chemical for solving all of your thrips problems. Fortunately the suppliers are doing a better job of cleaning up tospovirus and we are seeing less and less of it. Still stay alert and look for the symptoms on plants. If you see it show up in your greenhouse immediately rogue out the infested plants.

Mites

Examine the undersides of foliage for mites. We usually see mites injuring New Guineas grown in the hottest parts of the greenhouse, especially hanging baskets and plants on south walls. Control: Akari, Avid, Floramite, Pylon, Judo, horticultural oil.

Information from the March 28, 2008 edition of the Greenhouse TPM/IPM Weekly Report
from the University of Maryland Cooperative Extension http://ipmnet.umd.edu/08Mar28G.pdf

Greenhouse - INSV and TSWV Viruses

INSV and TSWV are two common viruses that attack greenhouse plants in Delaware. The following is an article on this subject.

Greenhouse growers are gearing up for production of bedding plants and perennials for spring sale. Production of these transplants may involve propagation of possibly infected overwintering stock or movement of plugs, transplants and sometimes plant diseases long distances. Diseases caused by impatiens necrotic spot virus and tomato spotted wilt virus are important causes of losses in greenhouse ornamentals. Although the virus and thrips (the disease vector) are common, growers can avoid crop losses by aggressively controlling thrips and the viruses it spreads. Impatiens Necrotic Spot Virus (INSV) and Tomato Spotted Wilt Virus (TSWV) are two different but closely related viruses causing similar symptoms.

The most common and dramatic problems of greenhouse ornamentals in Delaware have been due to INSV. This virus is usually the one causing disease symptoms on impatiens, New Guinea impatiens, begonias, petunias snapdragons, cyclamen, cineraria and gloxinia. Both viruses are transmitted from plant to plant by western flower thrips. An adult thrips can infect a plant with virus after feeding for only 30 minutes. TSWV is very damaging to tobacco, tomatoes, and peppers, but it also attacks some ornamentals, most often dahlias imported from overseas, and chrysanthemums and (rarely) ivy geraniums. Both viruses have a very wide host range and both are vectored by western flower thrips.

Virus Disease Symptoms. TSWV/INSV causes a wide variety of symptoms including wilting, stem death, stunting, yellowing, poor flowering; and sunken spots, etches, or ring spots on leaves. Symptoms are not very specific or consistent, and merely tell the grower that there is something wrong with the plant. Many other diseases and plant problems can cause symptoms that resemble TSWV/INSV. Virus symptoms may depend on time of year, type of plant, age of plant, plant physiological state, growing conditions at the time of infection, and strain of virus. In the UD Plant Disease Diagnostic Laboratory, positive diagnosis is made by testing infected plant tissue with an ELISA test based on a chemical reaction to the virus proteins. Separate tests are used to look for both TSWV and INSV because a plant may have either or both viruses.

Managing INSV and TSWV in greenhouse ornamentals.

Inspect incoming plant material for signs of thrips feeding injury, or for symptoms indicative of TSWV or INSV infection. Most plant materials coming from suppliers are not guaranteed to be disease free; thus your inspections are most important. Insist on good thrips control from your plant suppliers.

Isolate incoming plants from all other plants in the greenhouse until certain they are free of the viruses.

Separate cutting crops from seedlings. The disease frequently enters the greenhouse within vegetatively propagated plant material. Hanging baskets of infected cutting crops over seedlings can lead to bedding plant losses, since the young seedlings are highly susceptible.

Immediately discard plants showing distinctive TSWV/INSV symptoms. Early destruction of a few infected plants may prevent an epidemic through all the susceptible plants in the greenhouse. If in doubt, throw them out. Infected plants cannot be cured.

Do not vegetatively propagate infected plants. The virus can still be maintained in a crop through vegetative propagation even in the absence of western flower thrips.

Plants may act as reservoirs of the virus. Flowering pot plant crops such as cyclamen can serve to carry the disease over from the fall to the following bedding plant season, as might weeds left under the benches. Eliminate weeds in and near the greenhouse which may harbor thrips and/or the virus.

Consider using petunia plants as indicators to monitor for TSWV/INSV and thrips feeding injuries; 'Calypso', 'Super Blue Magic' or Summer Madness' petunias may all be used as indicators of TSWV/INSV. Use a yellow (NON-sticky) card to help attract the thrips to the petunias.

Losses have been greatest with gloxinia, double flowered impatiens, New Guinea impatiens, begonia and cyclamen crops. Be particularly careful to keep these crops isolated from potential sources of virus.

Be aware that vegetable and tobacco transplants are also susceptible to these viruses and can serve as reservoirs of infection.

Perennial plant growers need to aggressively attack TSWV and western flower thrips in both greenhouse and outdoor plantings, and must be aware that plants originating from greenhouse production but now planted outdoors may carry the virus. Even if the thrips do not overwinter in DE, vegetatively propagating infected plants will maintain and spread the virus. Garden center operators must also be aware of the biology of TSWV and western flower thrips, especially if they keep herbaceous plants all year. Many perennials are susceptible to the virus and attractive to thrips. An infected perennial will retain the virus until that plant dies.

Adapted from "INSV AND TSWV ARE THREATS TO GREENHOUSE ORNAMENTAL PRODUCTION" By John Hartman in the Feb 12, 2007 edition of the Kentucky Pest News from the College of Agriculture at the University of Kentucky.

Greenhouse - Impatiens Necrotic Spot Virus, INSV

INSV, Impatiens Necrotic Spot Virus attacks many greenhouse plants including impatiens, New Guinea Impatiens, Double Impatiens, and Tuberous Begonia. I have had it diagnosed in Kent County greenhouses on many occasions. It is commonly brought in on propagation material and can be spread by thrips in the greenhouse. To manage INSV you need to reject any suspicious plant materials that come in, exclude thrips, and have a good thrips control program.

INSV on impatiens, New Guinea impatiens, Alstromeria, tuberous begonia and Cineraria. Photos from NC State University and University of Connecticut Extension.

Greenhouse - Test Strips Available for INSV

Impatiens Necrotic Spot Virus is a problem disease in greenhouses. In the past, samples had to be sent to a laboratory for testing. Now, growers can buy test kits that can be done on site with immediate results. Information is below.

Test Kits for INSV and other diseases are available from Agdia company in Elkhart, Indiana.

Go to http://www.agdia.com/immunostrip/

Their homepage is http://www.agdia.com/

You can get 5 test strip kit for $50 and a 25 test strip kit for $97.50.

The following is a description of the strips.

Agdia ImmunoStrips™Agdia’s ImmunoStrips™ are the first easy-to-use, economical plant diagnostic tests for use by greenhouse and field growers. ImmunoStrips™ are grower friendly and provide an effective way to detect the major viruses and bacteria in ornamental flowers and vegetables.

The tests are reliable, accurate, quick, simple, easy-to-read and economical.

ImmunoStrip™ Kits come complete with test strips, sample buffer and instructions.

Use Agdia ImmunoStrips™ to:

• Check the health of your incoming plants
• Monitor disease as part of your scouting program
• Protect healthy plants from infection
• Assure plant health quality before your plants are shippedto customers

Tests available for the following diseases:
Calibrachoa Mottle Virus (CbMV)
Cucumber Mosaic Virus (CMV)
Impatiens Necrotic Spot Virus (INSV)
Pepino Mosaic Virus (PepMV)
Ralstonia solanacearum (Rs)
Squash Mosaic Virus (SqMV)
The ImmunoStrip™ Comb (TSWV, INSV, CMV, TMV)
The ImmunoStrip™ Dual Strip (TSWV, INSV)
Tobacco Mosaic Virus (TMV)
Tomato Spotted Wilt Virus (TSWV)
Xanthomonas campestris pv. pelargonii (Xcp)

Tests will be available soon for:
Clavibacter michiganensis subsp. michiganensis (Cmm)
Potyvirus Group Zucchini Yellow Mosaic Virus (ZYMV)