Cereals seed rates

High seed rates can help reduce weed competition. In winter cereals drilling 500seeds/m compared with 200seeds/m can halve the weed biomass. In horticultural crops it is not always possible to plant high populations as this technique can affect crop quality and lead to poor marketable yields. 

Tillering capacity - some varieties tiller more freely than others and so their seed rate may be reduced. Winter cereals have more time to tiller than spring cereals and so fewer plants need to be established. 

The first ALS-resistant weeds were reported in 1987 when prickly lettuce (Mallory-Smith, 1990 Mallory-Smith et al, 1990b) and kochia (Primiani et al, 1990) control failures occurred in Idaho and Kansas, respectively, after 5 consecutive years of chlorsulfuron use. The kochia biotype proved to be cross-resistant to six other ALS-inhibitor herbicides, including sulfonylureas and imidazolinones. Within 5 years, sulfonylurea-resistant kochia had been identified at 832 sites in 11 states of the United States and in three Canadian provinces (Saari et al, 1994). ALS inhibitor-resistant kochia and Russian thistle have become widespread problems in cereal-producing regions of northwestern United States and Canada. The mobility of these tumble weeds as plants with mature seeds or pollen carried by wind has undoubtedly contributed to the rate at which resistance has spread. 

Pyrrolizidine alkaloids cause obstruction of the hepatic venous system and can lead to hepatic necrosis. Clinical manifestations include abdominal pain, ascites, hepatomegaly, and raised serum transaminases. The prognosis is often poor, death rates of 20-30% being reported. In an outbreak of veno-occlusive disease in the Sarguja district of India, probably caused by consumption of cereals mixed with Crotalaria seeds, 28 of 67 patients died (19). 

DNOC is used as its ammonium- or sodium salt, which are water-soluble. The salts are contact herbicides for the control of broad-leaved weeds in cereals, onion and garlic at rates of 3-5 kg active ingredient/ha. In emulsifiable concentrate formulation DNOC can be used for the preharvest desiccation of potatoes and leguminous seed crops (Worthing, 1979). 

Benazolin is a selective postemergence herbicide translocated in the phloem. Combined with phenoxy herbicides, such as MCPA and MCPB, 2,4-DB and 2,4-DP, it efficiently controls many broad-leaved weeds, particularly Stellaria media and Galium aparine, in undersown cereals and direct sown leys. Alone it is used against wild mustard, chickweed cleavers and oil seed rape at a rate of 0.9-2.S kg active ingredient/ha (Shafer and Stobbe, 1973a, Rea et al. 1976). Used in the form of its water-soluble sodium or potassium salt it is not adsorbed in the soil and is rapidly leached. 

As a seed treatment fluquinconazole protects cereal roots against take-all (Gaeu-mannomyces graminis) at the rate of 75 g-a.i. per 100 kg of seeds [77]. Systemic... 

Fipronil s high intrinsic activity against Dipterans allows its successful use as a seed treatment in several crops for control of root maggots. In cereals, fipronil provides excellent control of wireworm and wheat bulb fly (Delia coarctata) at rates of 50 g per 100-kg seed [8]. In leeks, seeds filmDelia antiqua) as well as thrips and onion moth [106, 107]. 

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