Pesticides are widely used in agricultural production to prevent or control pests, diseases, weeds, and other plant pathogens in an effort to reduce or eliminate yield losses and maintain high product quality. Although pesticides are developed through very strict regulation processes to function with reasonable certainty and minimal impact on human health and the environment, serious concerns have been raised about health risks resulting from occupational exposure and from residues in food and drinking water. Occupational exposure to pesticides often occurs in the case of agricultural workers in open fields and greenhouses, workers in the pesticide industry, and exterminators of house pests. Exposure of the general population to pesticides occurs primarily through eating food and drinking water contaminated with pesticide residues, whereas substantial exposure can also occur in or around the home. Regarding the adverse effects on the environment (water, soil and air contamination from leaching, runoff, and spray drift, as well as the detrimental effects on wildlife, fish, plants, and other non-target organisms), many of these effects depend on the toxicity of the pesticide, the measures taken during its application, the dosage applied, the adsorption on soil colloids, the weather conditions prevailing after application, and how long the pesticide persists in the environment. Therefore, the risk assessment of the impact of pesticides either on human health or on the environment is not an easy and particularly accurate process because of differences in the periods and levels of exposure, the types of pesticides used (regarding toxicity and persistence), and the environmental characteristics of the areas where pesticides are usually applied. Also, the number of the criteria used and the method of their implementation to assess the adverse effects of pesticides on human health could affect risk assessment and would possibly affect the characterization of the already approved pesticides and the approval of the new compounds in the near future. Thus, new tools or techniques with greater reliability than those already existing are needed to predict the potential hazards of pesticides and thus contribute to reduction of the adverse effects on human health and the environment. On the other hand, the implementation of alternative cropping systems that are less dependent on pesticides, the development of new pesticides with novel modes of action and improved safety profiles, and the improvement of the already used pesticide formulations towards safer formulations (e.g., microcapsule suspensions) could reduce the adverse effects of farming and particularly the toxic effects of pesticides. In addition, the use of appropriate and well-maintained spraying equipment along with taking all precautions that are required in all stages of pesticide handling could minimize human exposure to pesticides and their potential adverse effects on the environment.

Field experiments were conducted to study the effect of three rye (Secale cereale L.) populations, six triticale (3Triticosecale Wittm.) cultivars, and two barley (Hordeum vulgare L.) cultivars, used as cover crops, on the emergence and growth of barnyardgrass [Echinochloa crus-galli (L.) P. Beauv.], bristly foxtail [Setaria verticillata (L.) P.Beauv.], and corn (Zea mays L.). Moreover, bioassay studies were conducted to assess allelopathic potential of the winter cereal extracts on both weed species and corn. All winter cereal extracts reduced barnyardgrass and bristly foxtail seed germination and growth, but none of them had any effect on corn. Bristly foxtail was affected more by all extracts than barnyardgrass, and growth of both weed species was reduced more by the extract of barley cultivar Athinaida. In field, 4 wk after corn planting, barnyardgrass and bristly foxtail emergence was reduced by 27 to 80% and 0 to 67%, respectively, in winter cereal mulched plots compared with that in winter cereal mulch-free plots. On the contrary, corn emergence was not affected by any cover crop mulch. At harvest, corn grain yield increased by 45% in no herbicide treated barley cultivar Athinaida mulched subplots as compared with that in respective mulch-free subplots. This corn yield in no herbicide treated Athinaida mulched subplots was similar with that obtained in respective herbicide-treated subplots. The results of this study suggest that some winter cereals such as barley cultivar Athinaida could be used as cover crop for annual grass weed suppression in corn and consequently to minimize herbicide applications. MATERIALS AND METHODS Laboratory Experiment Extract PreparationPlants of three rye populations originated from Albania, Germany, and Greece, as well as six triticale cultivars (Thisvi, K.

No abstract

Activity, adsorption, and mobility of emulsi®able concentrate (EC) and microencapsulated (ME) formulations of alachlor and acetochlor as well as of metolachlor, S-metolachlor, dimethenamid and¯ufenacet were studied. Petri-dish bioassay, based on root response of oats (Avena sativa L.), was used for their activity in sand and in a silty clay loam soil, and for determination of herbicide concentrations in soil solution (not adsorbed) and in column leachates of the adsorption and mobility studies respectively. Flufenacet and both acetochlor formulations showed the highest activity in both soils and ME-alachlor and metolachlor the lowest; the activity of dimethenamid, EC-alachlor and S-metolachlor was intermediate. Activity of both formulations of alachlor and acetochlor decreased with increasing organic matter content, but alachlor activity was reduced more than that of acetochlor. Lower amounts of dimethenamid and S-metolachlor were adsorbed by soil compared with the other herbicides and, consequently, greater amounts of these two herbicides were leached through that soil. None of the herbicides tested was detected below 30 cm. Less alachlor and acetochlor were biologically available in soil solution after their application as ME-formulations and, therefore, lower amounts of both ME-alachlor and ME-acetochlor were leached through the soil compared with those applied as EC-formulations.

Field experiments were carried out in northern Greece during 1994, 1995, and 1996 to study the effect of nitrogen fertilization on competition between sterile oat and wheat, barley, and triticale. Dry weight of all crops was not affected until early March by sterile oats (110 plants m−2), but wheat and triticale dry weight were significantly reduced by sterile oats competition after that time. Grain yield of both wheat and triticale was equally reduced by 61% due to the presence of sterile oats, whereas the reduction for barley grain yield was 9%. Nitrogen fertilization (150 kg N ha−1) slightly increased yield of all crops grown without weed competition compared to the control (0 kg N), whereas the same treatment increased sterile oats dry weight as well as its competitive ability against wheat and triticale. Split application of nitrogen (50 kg N ha−1 before planting and 100 kg N ha−1 in early March) caused a slightly higher increase in sterile oats dry weight compared to the control or one application (150 kg N ha−1) before planting, when grown with wheat and triticale. However, dry weight of sterile oats grown with barley was severely reduced by the interference of the crop. Total nitrogen content of all crop plants grown without sterile oats increased with nitrogen fertilization compared to the control. However, total nitrogen in crop plants grown with sterile oats was reduced compared to the weed-free control; percent reduction was greater in plants grown in plots treated with nitrogen than in the control. These results indicate that barley could be used for limiting sterile oats interference in areas where winter cereals are grown; time of nitrogen application could also be used for a slight reduction of sterile oats competitive ability against wheat or triticale.