Oilseed rape weeds

Linseed has a lower nitrogen requirement than oilseed rape, so it could be grown satisfactorily in organic systems, but again no specialist market is available. It is also a crop that is difficult to keep weed free. 

Forcella, F. (1987). Herbicide-resistant crops Yield penalties and weed thresholds for oilseed rape (Brassica napus L.). Weed Res., 27 31-34. 

Uses herbicide to control post-emergent wild oats, wild millets, and other annual grass weeds in wheat, barley, rye, red fescue, and broadleaf weeds in crops such as soybeans, sugar cane, fodder beet, flax, legumes, oilseed rape, sunflowers, clover, lucerne, groundnuts, brassicas, carrots, celery, beet root, parsnips, lettuce, spinach, potatoes, tomatoes, fennel, alliums, herbs, etc. 

Chemical Name 4-(dipropylamino)-3,5-dinitrobenzene-sulfonamide 3,5-dinitro-lV, A -dipropylsulfanilamide Uses herbicide for pre-emergence control of many annual grasses and broadleaf weeds in cotton, fruit trees, vines, nut trees, soybeans, groundnuts, oilseed rape, sunflowers, lucerne, peas, sweet potatoes, mint, ornamentals and also used in noncrop areas. 

Metazachlor is a selective preemergence herbicide active on a wide range of both broad-leaved and grass weeds. It can be used selectively in Brassica spp. crops including winter oilseed rape at a rate of 1-1.8 kg active ingredient/ha. 

Figure 1. Transfer of the triazine tolerant cytoplasm from a weed biotype to oilseed rape by backcrossing.

Most of the triazine tolerant weed biotypes Identified to date have economic relatives but few if any are as closely related to economic crops as the birds rape. To date, this cytoplasm has been transfered to oilseed rape, rutabaga and oriental mustard by several breeding groups. Partial cross-compatibi 1 ity with several other Brassica species including the cole crops, and other more distantly related species (eg, Diplotaxis and Raphanus species) may permit transfer by classical methods (perhaps assisted by embryo rescue techniques). Chloroplast or mitochondrial X nuclear Incompatibilities however, may limit this potential. As other triazine tolerant weed biotypes emerge, opportunities for transfer to closely related economic species by classical methods may evolve. 

Few studies have been carried out on a large scale to investigate the environmental impact of GM plants. Herbicide-resistant oilseed rape plants have been evaluated mainly to assess the gene flows within species or to weed species closely related to oilseed rape [8, 9]. Regarding the pollinating entomofauna only two studies have been achieved recently. 

Some important weed species ate in the same family as the crop plant, e.g. charlock in oilseed rape or fat hen in sugar beet. Weed control using herbicides is then often difficult as there is not enough selectivity in the herbicide activity to kill the weed without injuring the crop. 

Cleavers (Fig. 5.13a) is the most competitive weed in winter cereals and winter oilseed rape, more competitive than wild oats. It can be confused at the seedhng stage with ivy-leaved speedwell (Fig. 5.13a). Note that cleavers has a notched cotyledon and the cotyledons are not stalked. Cleavers germinates at fairly low temperatures mainly in the autumn and winter, with some in the spring. 

Not all brassicas affected. Several weeds are hosts to this aphid. Populations vary widely each year due to weather conditions. Threshold for treating winter oilseed rape is 13% plants infected before petal fall. 

Table 14.2 General table of weed susceptibility to some commonly used herbicides in oilseed rape, combinable peas and field beans... 

Perennial weeds should, if possible, be controlled by glyphosate applied preharvest in the previous cereal, oilseed rape, pea, or bean crop (the weeds must be green and actively growing), or by treatment in the autumn. 

Peas do not compete well with weeds and efficient weed control is essential to avoid yield loss. Pereimial weeds should be dealt with before planting and thistles, oilseed rape and groundkeeper potatoes can be a particular problem. Nettles and thistles can interfere with hand picking and, in machine-harvested crops, weeds can lead to crop rejection from the processor. Inter-row cultivations may be effective when the peas are between the second and fifth node growth stage. 

Cabbages can compete well with weeds due to their laige leaves but established perennial weeds shonld be controlled prior to transplanting or drilling. With the limited number of approved heibicides available many growers rely on mechanical methods of weed control (Fig. 17.4). Oilseed rape volunteers and potato groundkeepers can cause a problem in some crops. 

Established perermial weeds shottld be controlled prior to transplanting or drilhng. Oilseed rape volrmteers and potato groimdkeepers can cause a problem in some crops. 

The chloroacetamides alachlor, 2-chloro-N-(2,6-diethyl-phenyl) -N- (methoxymethyl) acetamide and metazachlor, 2-chloro-N-(2,6-dimethylphenyl)-N-(1H-pyrazol-1-ylmethyl) acetamide are selective pre-emergent or early post-emergent herbicides used to control annual grasses and many broad-leaved weeds in cotton, brassicas, maize, oilseed rape, peanuts, radish, soyabeans and sugarcane. 

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