Pulse Crop Update - 2nd May 2014
Pea aphids are present at low levels in pea and bean crops following a mild winter and spring. Several aphid-transmitted viruses are associated with infested crops, affecting both yield and quality, especially if aphids are present before flowering. Virus symptoms may not be apparent until the onset of flowering - and control of early aphids is essential to prevent virus transmission. Products containing pirimicarb (field beans, combining and vining peas, green beans) or thiacloprid (combining and vining peas) will give good control of aphids.
Pea and bean weevil
Pea and bean weevil activity continues to be high and continuous due to the warm, dry weather. High levels of damage are being recorded in all pea and bean crops, and emerging spring crops are at high risk. Sprays should be applied as soon as leaf-notching is seen. There are a number of pyrethroid products available for use in peas and beans for weevil control, and a second application will be necessary 10 to 14 days after the first, where damage is severe.
Field thrips Damage also remains high and products used for weevil control will control thrips. Symptoms include yellow translucent spots on the leaf surface and puckered, leathery leaves. In most cases, crops should grow away from damage if weather remains warm.
Bruchids are present in crops, although winter and spring beans are not yet at the correct growth stage for spray applications. Winter beans are at the first flower growth stage and may be setting pods in the next week or two. Crops should be sprayed when temperature has reached 20°C for two consecutive days and when crops have set first pods (when 50% pods on the bottom trusses are 2cm long).
Ascochyta fabae (leaf and pod spot) in field beans
Ascochyta fabae (leaf and pod spot) has been observed in some crops of winter beans. The first sign of infection appears as small, discrete lesions on the leaves of newly emerged beans. The lesions are greyish-brown, circular to oval in shape and often develop a lighter grey centre. Lesions may follow the leaf veins. There may be small, dark pin-point sized pycnidia in the centre of the lesion.
The disease can be spread by rain-splashed spores over the surface of the plant and to surrounding plants. Harvested seed may be blemished and infected with the disease, causing it to be unsuitable for use for human consumption or as seed. Products containing azoxystrobin can be useful in reducing both foliar infection and seed infection in the harvested produce.
Downy Mildew in beans
Winter beans are developing medium levels of downy mildew as conditions have remained favourable, with cool humid weather prevailing. If conditions become warm and dry following early infection, disease development stops and the plants are able to produce new healthy growth.
In cases where 25% or more plants are infected in winter or spring beans, sprays including the active ingredient metalaxyl-M will give good control of downy mildew.
The current forecast is for low to moderate risk of infection.
Post-emergence herbicide applications in beans and peas
Bentazone is the only active ingredient available in beans. Bentazone and MCPB are options in peas. Known herbicide-sensitive varieties are noted on the label - newer varieties that do not appear on the label cope well. Sensitivity scores are based on full-rate applications. At the more commonly used half rate of bentazone, with the option of a second application in beans, few crop sensitivity issues are reported. It is important to check that there is adequate leaf wax on peas as both bentazone and MCPB are mainly contact materials.
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