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Understanding and controlling Tomato Brown Rugose Fruit Virus

Tomato Brown Rugose Fruit Virus (ToBRFV) is an emerging virus in greenhouse tomato production worldwide. The virus was first identified in Israel a few years ago and has since been found in Europe, Asia, Mexico, and the US.  The pathogen is known to be present in greenhouse tomatoes in Mexico, and has occasionally been found in field tomatoes grown there (UMASS); it has also been found on imported fruit in FL (Also see VGN story below). An outbreak was reported (and contained) in CA in early 2019 but, unfortunately, the virus was found in greenhouse tomato production in New Jersey this past fall.

ToBRFV is more severe on young tomato plants and can result in 30-70% yield loss (UFL). Foliar symptoms of ToBRFV on tomato and pepper include deformed, crinkled leaves, mosaic, mottling, flecking, chlorosis, and/or necrosis (see images). Fruit symptoms include discoloration and rough brown patches or ringspots. Irregular fruit shape and maturation patterns may also occur. Browning of the veins in the fruit calyx in the early stages of fruit ripening may also be observed. Symptom expression can vary widely among tomato cultivars (UMASS); while some green fruit may be infected but remain asymptomatic until the fruit starts to ripen.

ToBRFV is a member of the tobamovirus family along with tobacco mosaic (TMV), tomato mosaic (ToMV), and tomato mottle mosaic (ToMMV). ToBRFV is especially worrisome for tomato growers because it has overcome the Tm-22 gene that confers resistance to tobamoviruses in many tomato cultivars. Like TMV, ToBRFV is very stable and easily transmitted by mechanical means; in a highly managed crop such as greenhouse tomatoes, this means that human activity is the primary vector. The virus may also be transmitted mechanically by bumble bees employed to pollinate greenhouse crops. The virus can be seedborne and research indicates that it is associated with the seed coat, not the embryo. This means that treatments such as hot water or steam should be effective in removing the virus from seed (UMASS).

Management practices for ToBRFV include planting of disease free seed and seedlings, scouting plants regularly for symptoms, and isolating symptomatic plants. Disinfect tools and workers’ hands frequently. Recent research has demonstrated that the most effective disinfectants include 10% bleach, 50% Lysol, and 20% nonfat dry milk (UMASS). Currently, no commercial tomato varieties are tolerant to ToBRFV. Peppers with tolerance to TMV and pepper mild mottle virus (PMMoV) have shown some tolerance (MSU). ToBRFV’s high stability allows it to stay infectious in the soil, in plant debris and on stakes for long periods—up to 20 years. There are reports of spread by bumble bee pollinators in greenhouse situations. However, there are no reports of plant-to-plant transmission by aphids, leafhoppers or white flies (MSU).

There are no sprays that can be applied that are effective in helping to reduce the virus’s spread. Seed and transplant production are the most critical steps since contamination at these steps may create a risk of further contamination (MSU). A number of County Offices have the equipment for doing the hot water seed treatment method. Please contact your county agent for more information. Importantly, as a note, there is very limited to no information on infested seed sources, with only a few greenhouse tomato cultivars with known problems.

Recommended actions include (from MSU):

  • Start with certified clean or treated seed from a reputable dealer. Do not purchase seed from unverified sources, especially if they come from known restricted areas.
  • Have greenhouse workers wash and sterilize hands and tools often.
  • Supply single-use gloves that are discarded between greenhouse ranges.
  • Provide protective clothing that stays in that greenhouse range or that is well washed before going to another range.
  • Dispose of symptomatic plants and plants within 5 feet of infected plants. Also, dispose of plants, strings, trays and media through incineration—DO NOT spread it out on your fields (or reuse it for other crops in the greenhouse)!
  • Monitor movement of equipment and workers between fields. Thoroughly wash equipment and possibly have workers bring a change of clothes.
  • Rogue and incinerate symptomatic plants and conduct any daily activity last in that greenhouse followed by good sanitation.

On November 15, 2019, USDA/APHIS issued an emergency federal order that calls for pre-export testing of tomato and pepper propagative material (plants, seeds, grafts, and cuttings) and fruit produced in any country where ToBRFV has been detected; to date, this list includes Israel, Jordan, Turkey, Greece, Italy, the United Kingdom, the Netherlands, China, and Mexico. Countries where ToBRFV has not been reported may state this fact by providing a letter from the nation’s plant protection organization: propagative material and fruit exported to the USA will then be exempt from the testing requirement. Tomato and pepper fruit from Canada will also be subject to inspection prior to export, because Canada imports these crops from Mexico and re-exports them to the US. US Customs and Border Protection will also increase inspections at U.S. ports of entry to ensure imported tomato and pepper fruit from Mexico, Israel, the Netherlands, and Canada are free from symptoms of ToBRFV. (UMASS, USDA)

The NJDA, in cooperation with USDA APHIS PPQ, has been assisting affected NJ tomato producers in identifying critical control points and implementing the best management practices necessary to reduce the threat of introducing Tomato Brown Rugose Fruit Virus (ToBRFV) into future production. Tomato growers in New Jersey who suspect ToBRFV are encouraged to contact their county agent and the NJDA Division of Plant Industry. The NJDA is working with USDA APHIS PPQ to establishing testing protocols and will facilitate the screening of suspect plants.

Source: Rutgers University (Andy Wyenandt)


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