May 23, 2017

Louisiana greenhouse tomatoes are under attack

Tomato russet mite and tomato yellow leaf curl are attacking greenhouse-grown tomatoes in Louisiana.

Tomato russet mites have cigar-shaped bodies with two pairs of legs and cannot be seen without the aid of a microscope, said LSU AgCenter “Plant Doctor” Raj Singh.

“These tiny mites have piercing-sucking mouthparts, and they feed on all above-ground plant parts, including leaves, petioles, stem and fruits,” Singh said.

Both adults and immatures are capable of causing considerable damage from their feeding behavior. Tomato leaves turn brown and paper-like and dry out. Stems, petioles and fruit display bronzing or “russeting.”

Initially, the symptoms appear towards the base of the plants and later move upwards. These symptoms are easily confused with diseases, nutrient deficiencies and other abiotic disorders, Singh said.

Management of tomato russet mites relies on good sanitation and cultural practices, use of miticides and control of weed host plants.

“Tomato yellow curl virus has also been reported in greenhouse tomato production. It is a plant virus that’s transmitted by whiteflies,” he said. “Symptoms on the leaves include yellowing of the tissues between the veins, upward or downward curling of the leaf margins and an overall reduction in their size.”

Plants severely stunt when infected at an early stage, but only new growth is affected when older plants are affected. Newer infections cause leaves to curl downward, and older infections cause leaves to curl upward.

Both adult whitefly and their immature stages can transmit tomato yellow leaf curl virus. The virus does not multiply within the whitefly and is not passed from one generation to the next.

However, whitefly nymphs feeding on an infected plant that has the virus will retain it as they go through successive molts, Singh said.

– Johnny Morgan, Louisiana State University