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Sunflower necrosis disease (Tobacco streak virus) Photo: Natalieisner · CC BY-SA 4.0 · source ↗

Sunflower necrosis disease (Tobacco streak virus)

Sunflower necrosis disease (SND) is caused by the Tobacco streak virus (TSV, genus Ilarvirus) and is responsible for episodic, large-scale yield losses across the sunflower-growing belts of Andhra Pradesh, Karnataka and Telangana. Documented by ICAR-IIOR (Hyderabad) and UAS Dharwad since the late 1990s, SND can flatten entire fields in epidemic seasons because it is transmitted by thrips moving in from nearby weeds and crop hosts.

Identification and symptoms

Early symptoms appear 25-40 days after sowing as small dark-brown necrotic spots and streaks on younger leaves and petioles. As the disease progresses, the necrosis extends along the stem and petioles, the growing point dies, and characteristic "stem girdling" causes the top of the plant to bend over. Heads that form on infected plants are deformed, with twisted ray florets, partially-filled seed and a sunken, blackened back. Plants infected at the seedling stage typically die without producing a head.

Hosts and lifecycle

The virus has a wide host range that includes sunflower (the highest-impact host), groundnut, cotton, soybean, marigold, Parthenium, Ageratum and many weeds. Transmission is by thrips (Frankliniella schultzei, Scirtothrips dorsalis and Thrips palmi) which acquire the virus from pollen of infected plants and inoculate susceptible plants while feeding. Mechanical transmission is also possible through sap. Parthenium and Ageratum growing on bunds and field margins are the principal weed reservoirs.

Damage and economic impact

In epidemic years, ICAR-IIOR has recorded incidence of 30-90 percent in southern Karnataka, Anantapur, Kurnool and Mahbubnagar sunflower fields, with yield losses ranging from 30 percent to total field loss. The disease devastated the Karnataka sunflower area in the late 1990s and early 2000s, contributing to the long-term decline in sunflower acreage in the region.

Management

  • Resistant/tolerant varieties: most popular hybrids - KBSH-44 (Kbsh 44 Sunflower), MSFH-17 (Msfh 17 Sunflower) - are susceptible. ICAR-IIOR DRSF 113, RHA-272 and ARM 243 are reported with field tolerance.
  • Weed sanitation: aggressive removal of Parthenium, Ageratum and Chrozophora from field bunds and surroundings is the single most effective cultural intervention.
  • Sowing date: avoid late-kharif sowing that coincides with peak thrips populations; sync sowing within a village so that thrips do not move from older to younger fields.
  • Border crops and barriers: a 2-3 row maize or sorghum border around the field reduces thrips ingress; intercropping sunflower with redgram or maize lowers incidence.
  • Thrips management: blue sticky traps at 10-15 per acre, imidacloprid 17.8 SL (0.3 ml/L) or thiamethoxam 25 WG (0.2 g/L) sprays at 20 and 35 DAS reduce vector populations. Rogue out infected plants in the first 30 days.

See also: KBSH-44 sunflower, MSFH-17 sunflower, Sunflower crop.

Sources

  1. Sunflower necrosis disease. ICAR-Indian Institute of Oilseeds Research, Hyderabad.
  2. Sunflower necrosis - epidemiology and management. University of Agricultural Sciences, Dharwad.