Diseases and Insect Pest Management

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Diseases and Insect Pest Management

Barley is exposed to various diseases and insect pests responsible for heavy reduction in yield and quality Though barley is attacked by many pathogens but few are economically important in India which need attention through resistance breeding or chemical control In India stripe rust yellow rust Puccinia striiformis fsp hordeii and leaf rust brown rust Puccinia hordei are major problems in NWPZ while in NEPZ leaf rust and leaf blights are common In NH Zone stripe rust and powdery mildew are serious problems In recent years stripe rust has become the most damaging cereal rust in cool climate across international locations Yadav 2003 Barley stripe rust has the potential to greatly affect the barley industry in India due to the races with shorter life cycles capable of producing more urediniospores and adapted to warm temperature Stripe rust appears early in season that other two rusts Symptoms include yellow orange pustules develop on leaves and eventually grow together forming stripes The orange pustules contain spores that reinfect barley Losses to stem rust black rust Puccinia graminis tritici in barley have been very rare in many areas because the disease occurs in late season Leaf rust develops rapidly between 15 and 22oC in the presence of free moisture

During earlier days the Helmithosporium leaf blights were considered as a minor disease as most of barley was under rainfed cultivation in dry areas but due to change in climate and cropping patterns and adoption of new technologies the disease levels of leaf blight have increased The spot blotch Bipolaris sorokiniana is gaining importance in regions where the day temperature increases during March Initial leaf infections in the field result from airborne conidia produced either on wild grasses or on plant residue in or above the soil Extended periods of warm of 20oc 16hrs moist weather are conducive to epidemic development Yield losses of 1020 may occur when environmental conditions are favourable for 12 weeks after plants have headed losses may be as high as 2030 when favourable conditions persist for 34 weeks Singh 2004

In case of malt barley cultivation application of more fertilizers under irrigated condition results in more foliage growth favoring build up of pathogens In late sown barley the vegetative stage coincides with warm and humid conditions during February and March which provides good spread of blights In recent years leaf blights assumed an important yield limiting factor in barley cultivation causing very heavy losses The net blotch Pyrenophora teres is also recorded in NEPZ occasionally Severe infection kills leaves prematurely and mainly causes reduced seed weight It may also reduce number of ears and number of grains per ear Yield reductions of 20 to 30 per cent can occur and grain quality may also be affected Powdery mildew Erysiphe graminis f sp Hordei development is optimal at temperatures between 15 and 22oC and is markedly retarded above 25oC Barley is most susceptible during periods of rapid growth Dense stands of susceptible cultivars heavy nitrogen fertilization high humidity and low temperatures favours disease development

The loose smut Ustilago tritici infected heads emerge as a mass of dark brown powdery spores replacing the entire head of plants with little development of floral bracts and awns Smutted heads often emerge earlier than healthy heads Spores are dislodged and scattered by wind when the delicate membranes surrounding them break The pathogen survives from one season to the next only as dormant mycelium within the embryo of infected barley seed and the seed treatment with systemic fungicide Carboxin eradicates the pathogen The covered smut Ustilago hordei infected heads remain intact until harvest and the disease is externally seed borne

Among insect pests barley foliar aphid Rhopalosiphum maydis can cause damage early in the season and yield loss through direct feeding damage Heavy infestations can cause a reduct

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