**7. References**

400 Herbicides – Properties, Synthesis and Control of Weeds

A field experiment was conducted during two growing seasons 2003/2004 and 2004/2005 in three locations in Tadla region to evaluate the effectiveness of some herbicides treatments. The main and important herbicides homologated on sugar beet and registered in Morocco such as ethofumesat, desmedipham, phenmedipham, metamitron, triflusulfuron methyl and

Tramat combi (Ethofumesate + lenacil) applied post sowing preemergence provided good efficacy (90 % and more) and protected then the crop for a long period more than 2 months. Generally when applied post emergence, herbicides ethofumesate, metamitron, triflusulfuron methyl, phenmedipham, desmedioham and lenacil achieved good efficacy in tank mixtures than applied individually alone because they are complementarily in eliminating maximum weed species. So, this must be taken in consideration in a weed chemical management program. These herbicide treatments allow to crop to grow without weed competitiveness nearly until the end of the critical period and are often followed by a

In Morocco, sugar beet is an important strategic crop. It is planted from September through June - July. Yield obtained by farmers, averaging 50 T/ha, is significantly below the request potential that would be 90 to 100 T/ha. Many factors contribute to low sugar beet production. Poor stand establishment, inadequate weed control, inadequate insect control and inadequate nitrogen fertilization are the main causes of low tonnage and poor quality

This paper presents the main results of investigations and experiments conducted in Tadla region to improve the weed management program by identifying mains weed species encountered in sugar beet field, studiying the effect of weeds on sugar beet growth and estimating yield losses and determining the critical period of weed control and evaluating

One hundred twenty six (126) fields of sugar beet were surveyed by stratified sampling in Tadla region (Center of Morocco). In total, 144 weed species belonging to 30 botanical families were recorded. Six among them asteraceae, poaceae, fabaceae, brassicaceae, apiaceae and caryophyllaceae account 81 species (56,1% of total species). Dicotyledonous (81,9%), annuals (82,6%) and the Mediterranean floristic element (56,2%) were predominant and characterized the weed flora. The agronomic study made it possible to distinguish 24 species and volunteer wheat causing appreciable problems to the crop. Statistical analysis

To determine the critical period of weed control in sugar beet, an experiment was conducted and consisting of 16 treatments. Weed free treatments included the removal of weeds at 4, 7, 9, 11, 13, 17 and 21 weeks after emergence (WAE) of sugar beet. In weed infested treatments, weeds were allowed to interfere with sugar beet crop 4, 7, 9, 11, 13, 17 and 21 weeks after emergence sugar beet crop. Weed infestation reduced root yield in all treatments. The presence of weeds during the entire growing season decreased root yield by 97.6 % and 68.9 % in 2003 and 2004, respectively. Based on 10 % permissible decrease in root yield, weeding

using soil-climatic factors allowed distinguishing four ecologic groups.

lenacil were experimented individualy alone or in tank mixtures.

mechanical cultivation or a hand hoeing.

**5. General conclusion** 

sugar beet in Morocco.

herbicide treatments.

**4.4 Conclusion** 


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**22** 

*1,3,4México 2Colombia* 

**Adverse Effects of Herbicides** 

*1Departamento de Química, Centro de Ciencias Básicas, Universidad Autónoma de Aguascalientes, Aguascalientes, 2Limnología Básica y Experimental, Instituto de Biología,* 

*Instituto Tecnológico de Boca del Río, Boca del Rio, Veracruz,* 

*3División de Estudios de Posgrado e Investigación.* 

*Autónoma de Aguascalientes, Aguascalientes,* 

*Universidad de Antioquia, Medellín,* 

Roberto Rico-Martínez1, Juan Carlos Arias-Almeida2, Ignacio Alejandro Pérez-Legaspi3, Jesús Alvarado-Flores1 and José Luis Retes-Pruneda4

*4Departamento de Ingeniería Bioquímica, Centro de Ciencias Básicas, Universidad* 

The use of herbicides to control weeds is a part of agricultural management throughout the world. Unfortunately, the indiscriminate use of these herbicides may have impacts on nontarget organisms (Sarma et al., 2001; Nwani et al., 2010). The long persistence of many herbicides in freshwater suggests that they are capable of producing adverse effects on freshwater zooplankton. Dalapon persist in water for 2 to 3 days, paraquat and diquat persist more than dalapon, and 2,4-D amine salt persist for 4 to 6 weeks; chlorthiamid breaks down into dichlobenil that stays for three months in water. On the other hand, terbutryne and diuron persist for more than three months in the water. These periods of time in the water show that most herbicides will cause serious adverse effects in the populations of freshwater zooplankton (Newbold, 1975). The herbicide n-chloridazon (n-CLZ) is degraded to desphenyl-chloridazon (DPC). This transformation product is more toxic than n-CLZ, and can last more than 98 days in surface water. Maximum concentrations of 7.4 μg/L DPC have been found in Germany (Buttiglieri et al., 2009). Atrazine (2-chloro-4-ethylamino-6 isopropylamino-*s*-triazine) is one of the most commonly used herbicides found in the rural environments, easily transported and one of the most detected pesticides in streams, rivers, ponds, reservoirs and ground waters (Battaglin et al., 2003; Battaglin et al., 2008). It has a hydrolysis half-life of 30 days and relatively high water solubility (32 mg/L), which aids in its infiltration into ground water. Atrazine concentrations of 20 to 700 μg/L in runoff surface waters have been reported (Nwani et al., 2010). Table 1 show some physicochemical properties of herbicides which are used to determine the toxic effects on freshwater

zooplankton, as well as lethal values of some of these herbicides.

**1. Introduction** 

**on Freshwater Zooplankton** 

