Pulse Crop Virus Disease Incidents

VANCOUVER - Feb 3/06 - SNS -- Three virus diseases were reported in leguminous food crops such as peas, beans, chickpeas and lentils during the last half of 2005, according to Pro-MED, a program of the International Society for Infectious Diseases.

Bean pod mottle virus (BPMV) caused significant crop losses in soybean. It is spread primarily by the bean leaf beetle _Cerotoma trifurcata_ and other beetle species. Yields from infected plants are lowered by 10-40%, grain quality is reduced both in oil and protein, seed germination is lower, and delayed maturation results in "green stem." BPMV spreads in the North American region.

The fact that BPMV has been reported in Iran suggests that BPMV-infected seed may have been used for planting soybean in Iran.

The 2nd virus disease, Southern bean mosaic virus (SBMV) and its various strains, can cause severe mosaic symptoms in bean (_Phaseolus vulgaris_) and other important leguminous food crops. SBMV is transmitted by beetles (_Ceratoma trifurcata_ and _Epilachna variestis_) and can also be transmitted by seed (3-7%) in _Vigna unguiculata_ cv. Early Wilt Resistant Ramshorn.

It has been reported from Africa, North America, South and Central America, and France. SBMV probably entered Iran via infected seed. Disease management involves managing the bean leaf beetle. Growers should consider a later planting of soybean, especially if BPMV was a yield-limiting factor in previous years. Late planting can result in an increased risk of soybean aphid activity at a sensitive growth stage.

The 3rd disease, Tobacco streak, (TSV), infects Blackgram (_Vigna mungo_), and other important pulse crops in India, Nepal, Bangladesh and Myanmar. During the kharif season (a strong southwest land wind during the monsoon), a new disease was observed in the majority of the blackgram-growing areas of India.

Alternate hosts may also play role in disease epidemiology, since TSV infects many widely distributed weeds. TSV infects a wide range of hosts in India. It is transmitted by _Frankliniella occidentalis_ and _Thrips tabaci_; _Thysanoptera_ (possibly by allowing virus particles from the surface of infected pollen to enter through feeding wounds). TSV is readily transmitted via seed at high levels in bean. Disease management depends mainly on planting virus-free seed.