Weeds - this plant vegetation which seriously hampered agricultural crops.Weeds are easily propagated.These plants are poisonous weeds, they are on all continents, but no benefit from them.

Not all weeds were originally established.For example, if a sunflower, which does not apply to weeds, showering their seeds, then some of them will germinate in the spring and will clog the crops of cultivated plants.Most often this winter crops, which are sown in this place behind sunflower.

Weeds, species whose number has already exceeded several thousand, causing serious damage to the agricultural sector, and the harm that is diverse.They absorb water from the soil in large numbers, their roots are poisoning the soil emit harmful substances.Consuming a lot of water, they are distinguished by rapid growth, respectively, deprived of light crop plants, thus reducing the yield.Sometimes even the crops are dying.

severe losses at harvest results in the presence of climbing weeds such as field bindweed, or Polygonum convolvulaceae.Under their weight happens lodging of crops, which means that cleaning them is difficult - and will remain part of the harvest in the fields.

suffer from weeds (creeping thistle, sow-thistle, etc.) And harvesting machines, grass clogged their parts, which leads to poor performance.This can reduce weeds and the quality of the harvest.This is due to the increase in seed and grain moisture at harvest enters the juicy parts of the weeds.

impossible not to mention another trouble.Sometimes the fall in grain seeds of poisonous weeds, and then it leads to the poisoning of animals, and sometimes humans.Weeds can reduce the yield and nutritional value, and sometimes even to displace farmland fodder grass varieties.Weeds that lead to silting of channels for irrigation, in addition, decrease their throughput.And even in the hot season, they become the source of fire.Especially dangerous abundance of weed becomes a so-called right of way oil or gas pipelines.

Classification of weeds produced by several criteria: the locus, especially reproduction, distribution and renewal.

The peculiarities of breeding, there are three biological groups: perennial and 2 groups maloletnika (seed and vegetative).The group includes maloletnikov seed plant breeding, propagating and resumed using the seed, or the fruit of the seed germ.They come in both annual and biennial.

Weeds-annuals are divided into subgroups.In the subgroup of early spring, which are the major pest for early spring crops, quinoa, oat, hemp.For the subgroup of late spring, clogging millet and actively hinder the development of late spring, are weeds, whose name foxtail, amaranth, and others. The subgroup of winter weeds is well tolerated winter plodonosya a year, this group of major damage to the plant causes winter crops.For the subgroup of wintering include shepherd's purse, Yakut field.

Biennial weeds live for two years: the first year of life appear vegetative organs of the seed, and the plant dies and bears fruit in the second year of life.

separate group of parasitic weeds, they include dodder, broomrape, zubchatki later or rattle large.Dodder clings to the stem of alfalfa, clover or other plants, roots of broomrape powered by tomatoes, alfalfa or tobacco, and the last two weed plants are semiparasites.