European and Mediterranean Plant Protection Organization s9
EUROPEAN AND MEDITERRANEAN PLANT PROTECTION ORGANIZATION
97/6436
P PR Point 3.1
PRA prepared by France for impatiens necrotic spot tospovirus (INSV)
1 Virus
Species impatiens necrotic spot tospovirus (INSV)
Genus tospovirus
Family bunyaviridae
Tomato spotted wilt tospovirus (TSWV) was considered for several years as the only member of the genus tospovirus. More recently, new species have been described and four groups were defined:
· I which includes TSWV
· II which includes tomato chlorotic spot virus (TCSV) and groundnut ring spot virus (GRSV)
· III which includes INSV
· IV which includes (still to be confirmed) groundnut bud necrosis virus (GBNV), peanut bud necrosis virus (PBNV) and watermelon silver mottle virus (WSMV).
INSV is mainly transmitted by the thrips Frankliniella occidentalis, but also by another species which is present in the United States, Frankliniella fusca.
2 Does the virus occur in the European Union
Yes.
3 EU status
Not listed.
4 EPPO status
Not listed.
5 Host plants
Many herbaceous species are host plants for INSV, including ornamental species and to a lesser extent vegetable species.
Ornamental species
Species Family
Aconitum carmichaeli Ranunculaceae
Alstroemeria sp. Amaryllidaceae
Anemone sp. Ranunculaceae
Antirrhinum majus Scrophulariaceae
Begonia x hiemalis Begoniaceae
Callistephus chinensis Compositae
Cineraria cruenta Compositae
Columnea sp. Gesneriaceae
Cyclamen persicum Primulaceae
Eustoma grandiflora Gentianaceae
Eustoma russellianum Gentianaceae
Fatsia japonica Araliaceae
Gerbera sp. Compositae
Gladiolus sp. Iridaceae
Impatiens x novae-guinea Balsamidaceae
Limonium sinuatum Plumbaginaceae
Lobelia sp. Campanulaceae
Pittosporum tobira Pittosporaceae
Ranunculus asiaticus Ranunculaceae
Sinningia speciosa Gesneriaceae
Zantedeschia aethiopica Araceae
Vegetable crops
Species Family
Cichorium endivia Compositae
Lactuca sativa Compositae
Ocimum basilicum Labiatae
Valerianella olitora Valerianaceae
INSV is often considered as occurring strictly on ornamentals under protected cultivation. As shown above, it also attacks in a few cases vegetable crops in the field outdoors.
6 Present geographical distribution
INSV is reported from US and from western Europe, including France, the Netherlands, Italy and Spain. In most cases, it is nevertheless restricted to areas with intensive cropping of ornamentals under protected conditions.
7 Possibility of spread to other EU regions
Possibilities of spread exist as the virus is mainly present under controlled conditions which favour both the development of host plants and of the main vector species Frankliniella occidentalis.
Pathways at risk:
- Ornamentals imported from third countries for consumers or growers. Such imports are numerous and concern a large number of plant species which are liable to carry the virus and its vector. Most commodities are introduced by air transport, and Paris airports are the main point of entry for France.
- Movement of ornamental plants from contaminated nurseries within the EU for consumers but mainly for growers. Such exchanges are numerous and also concern a large number of plant species.
The spread of the virus will most probably be due more to exchanges of plants rather than to natural spread of the virus.
8 Damage
8.1 Symptoms
Various symptoms can be observed: necrosis, malformation, formation of yellow rings, flower or leaf break, yellowing (widespread or not) on the foliage, stunting. Symptoms vary for a given plant species. However, as for many other viruses, symptoms are expressed only after a latent period, whose duration is difficult to determine and which immediately follows inoculation by the vector. Symptomatic plants (both ornamentals or vegetables) cannot be marketed. Symptoms caused by INSV cannot be distinguished from those of TSWV, either by their appearance, or by their severity.
8.2 Economical impact
The immediate loss is obvious (see 8.1). If a grower uses a contaminated lot, it obliges him to a continuous monitoring of his crops, as the vector is frequent under protected conditions: in most cases, it has sufficient time to transmit the virus from contaminated plants before those are detected and eliminated. The grower therefore must:
- apply prophylactic measures: detection and removal of infected plants. Monitoring of thrips populations
- apply chemical control: due to the high multiplication rate of the virus, treatments must be frequent (at 3-5 day intervals)
Introduction therefore give rise to two kinds of costs:
- financial costs: plants removed, labour cost of monitoring, plant protection products
- environmental costs: consequences of chemical treatments
Those costs are the same as for the introduction of TSWV.
9 Possible measures
9.1 At import
Surveillance of imports. However, visual inspection is not sufficient because of possible latent infections. As for TSWV, controls by ELISA can be envisaged and both viruses can be detected jointly.
9.2 Within the EU
Surveillance of nurseries. The arrival of a contaminated lot in a nursery is a serious event which often leads to the brutal introduction of a large virus inoculum. The continuous control of nurseries provides a certain level of guarantee for plant health. This control should be based on direct surveillance of plants by visual inspection or laboratory testing but it should also be verified that all preventive measures are taken to avoid the spread of tospoviruses:
- sticky traps or plant traps to detect the arrival of thrips;
- insecticide applications at (at least) 15 day intervals with alternation of active ingredients;
- continuous surveillance of the crop and destruction of the first infected plants by incineration.
10 Conclusion
When European quarantine lists were drawn up, they only considered TSWV, which at that time grouped several strains. One of those strains was since shown to be a separate virus, different from TSWV, and was named INSV. One should then consider whether it should be added to the quarantine lists.
INSV shares many common features with TSWV:
- wide geographical distribution, although slightly more limited;
- same main vector;
- large host range, even if it is slightly more narrow than for TSWV;
- very similar type and severity of symptoms;
- same detection methods in the laboratory.
For these reasons, INSV should be submitted in the EU to the same regulatory measures as TSWV.
11 References
De Avila A.C., De Haan P., Kitajima E.W., Kormelink R., Resende R. De O., Goldbach, R.W., Peters, D. (1992) Characterisation of a distinct isolate of tomato spotted wilt virus from Impatiens sp. in the Netherlands. J. Phytopathology 134,133-151
Llamas-Bousquet N., Allex D., Berling A. (1993) Importance of tomato spotted wilt virus on vegetable and ornamental crops in France. Premier colloque italo-français de phytopathologie, Alghero (Sardinia, Italy).
Mumford R.A., Baker I., Wood K. R. (1996) The biology of tospoviruses. Ann. Appl. Biol. 128, 159-183
Vicchi V., Bellardi M. G. (1997) Impatiens necrotic spot tospovirus (INSV) infecting ornamental and vegetable crops in Italy. 10th Congress of the Mediterranean Phytopathological Union. Montpellier (France)
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