Impatiens Necrotic Spot Virus (INSV), a plant virus identified in Impatien plants. However it infects many other species both ornamental and agricultural. INSV is spread rapidly over long distances by the western flower thrip (Frankliniella occidentalis) as they feed on infected plants and then move to healthy ones. The virus produces symptoms that range from necrotic spots on leaves and stems, stunting growth with wilting, to overall plant decline. INSV therefore represents a crucial threat for gardeners, farmers and horticulturists as severe infections can cause major yield losses and impair plant quality.
What are these viruses?
Impatiens necrotic spot virus (INSV), a member of the Tospovirus genus, has been identified as one several plant infecting viruses with marked influence on agriculture and horticulture. Although tospoviruses, including Tomato Spotted Wilt Virus (TSWV) and INSV consist of enveloped sphere particles with a negative-sense RNA segmented genome. Thrips, small insects that feed on plant tissues, mostly transmit these viruses and become feeding sites for the viral particles as they pick up infected then carry them to new healthy plants. Tospoviruses are highly polyphagous, affecting numerous ornamental and essential crops. Because symptoms of Vm and Vi include dead leaf margins, stunted growth (Fig. 1), wilting, ring spots that may result in large economic yield losses as well reduced plant quality.
Symptoms of Impatiens Necrotic Spot Virus (INSV)
Impatiens Necrotic Spot Virus (INSV) can create a litany of symptoms that negatively impacts the health and aesthetics of infected plants. Depending on the plant species and environmental conditions, these symptoms may differ but are usually as follows;
- Necrotic Spots: Dead areas that are dark in color. These lesions, initially small in diameter, can increase in size resulting in extensive tissue damage. If your plants have been struck by rust, the necrotic spots can coalesce to create tiny droughts in plant tissue (which limit photosynthesis) and in so doing significantly disrupt plant energy.
- Poor Growth: Infected plants do not grow as well and may look smaller and less robust than healthy ones. The stunting from this action can impact the plants growth overall, while also making for a low yielding plant. New growth can be especially impacted, with the most severe stunting in young shoots and leaves.
- Wilting: Affected plants may fail to be able to maintain turgor pressure in their leaves and stems, causing them to wilt. This wilting may be present with enough water but the result of internal damage from the virus. Wilting could be an indication of infection systemic; until the spread everywhere on all parts of it.
- Ring Spots: Circular discolored areas or necrotic regions on the leaves. Ring spots are a classic symptom of tospovirus infections and can be helpful in diagnosing INSV. Ring spots, any size and with or without chlorotic (yellow) halos
- Leaf Distortion: Leaf twisting, curling or abnormal shape. This deviation can in turn impact the extent of the photosynthesis and robustness of the plant. Leaves with these distorted growth may be abnormally small or have an abnormal mature shape.
- Flower abnormalities: Discoloration, deformity and stunting of flowersIn ornamental plants. This could result in flower petal streaking, deformed flowers and lack of bloom as well.
- General Decline: In more severe cases, plants can experience a decline in overall vigor characterized by reduced yields and quality fruit that eventually leads to death. This could be seen as a slow enfeeblement of the plant with leaves getting yellow or brown and dropping off prematurely.
- Stems Lesions: Streaks or lesions, which can eventually encircle the stem causing girdling that blocks the flow of water and nutrient dams legislatures. These lesions can cause fractures and structural weakness.
- Fruit symptoms: Fruit symptoms arise in crops like tomatoes and peppers, single or grouped lesions on the surface around picking time. Contaminated fruit show sunken spots that make them not fit for marketing.
- Secondary Infections: Plants weakened by INSV are more susceptible to secondary infections with bacteria and fungi. These are opportunistic pathogens that can worsen plant decline and increase the complexity of management efforts.
Early detection and control of INSV are important to prevent large-scale losses, as the health of both ornamental plants and field crops could be affected by it. Control measures can include monitoring and managing thrip populations, removing infected plants for destruction, or cultural practices to lower the risk of infection and spread.
Management of Impatiens Necrotic Spot Virus (INSV)
Strategies to control Impatiens Necrotic Spot Virus (INSV) are summed up as Integrated strategies to avoid infecting the plants or reduce it, thereby minimizing its effects also on other crops. Some of the best management practices include;
- Thrip Management: Management of INSV In thrip (Frankliniella occidentalis) is considered as the major vectors for transmission of this virus, controlling thrip population becomes very important. This can be done with insecticides like systemic treatments or contact solutions. Predators like mites (Amblyseius rubra or A. cucumeris) can also significantly reduce the number of thrips around your plants.
- Cultural Practices: The incidence of INSV infection can be reduced by adopting good cultural practices. Such practices include weeding to remove weeds which can also harbor thrips, planting at recommended spacing for good air circulation around plant foliage and not overhead irrigating since the wet conditions may help keep this insect thriving.
- Sanitation: Remove and destroy infected plants, so the virus doesn’t spread to healthy plants. Clean any tools and equipment that you use in infected areas to prevent the spread.
- Resistant Varieties: Similarly to PLRV, varieties should be tolerant (but this is not always available). Search for tospovirus resistant or tolerant cultivars.
- Monitoring and Early Detection: Monitor plants at regular intervals for INSV occurrence. Recognizing symptoms early allows immediate action, such as removing affected plants to prevent the disease from spreading.
- Chemical Treatments: Severe outbreaks may require chemical treatments to control the thrip populations and thus reduce viral transmission. Directions on the label must be followed and environmental precautions should not be glared over.
- Crop Rotation: This can break the virus cycle and be especially effective in agricultural settings because non-host crops will reduce incidence as a reservoir of specific viruses (soil or plant debris).
- Education and Awareness: Raise awareness amongst gardeners, farmers or horticulturists on the symptoms of INSV pest vectors importance educating in preventive measures that can stop an outbreak before it starts to minimize economic losses.
When control measures are applied in concert, growers can manage INSV and preserve the beauty of their ornamental crops as well sustain productivity for most agricultural ventures against this virus. Regular monitoring, swift actions and integrated pest management (IPM) strategies are the cornerstones of effective INSV prevention.
