Geographical distribution of principal cereal weeds in setif high plains.

The invasion of the wheat and barley cultures by weeds remains among the major problems of agriculture in Algeria considering the importance of yield tosses caused by these species. The cereal yields average is less than 700 kg ha(-1). The main purpose of this work was to obtain informations on geographical distribution of principal cereal weeds in the setif high plains. Two bioclimatic areas may be distinguished in this region, the semi-arid in the south and the sub-humid in the north. One hundred ten fields of cereals were surveyed by stratified sampling. In each field the level of infestation was scored on a homogeneous surface. The weediness of the species was estimated on the basis of the frequency and average of abundance. The results indicate thirty four important species. This harmful flora was characterized by the prevalence of annual and brod leaved weeds. The study of the geographical distribution cards of these species shows three groups: species related to the northern zone, species related to the southern zone and species common to both zone. The knowledge of the geographical distribution of principal weeds is an essential element for any plan of integrated weed management.

Study of the effect of Ammoides pusilla (Brot.) Breist, essential oil against Pseudomonas sp.

The economic losses caused by plant pathogens, the development of genetic resistance to applied pesticides by major pathogenic bacteria and public concerns about the use of synthetic chemicals on food and environment, increased interest in the search of alternative safe methods to control diseases spreading. Biological control with plant extracts has emerged as a promising option. The present study was carried out to determine the effect of Ammoides pusilla essential oil on the growth of two pathogenic bacteria, Pseudomonas syringae pv. syringae and Pseudomonas syringae pv. mosprunorum Three essential oil treatments, 1/2 v/v, 1/5 v/v and 1/10 v/v concentrations, were tested onto these bacteria, using the agar diffusion test. The results showed that 1/2 v/v concentration treatment completely inhibited Pseudomonas syringae pv. mosprunorum growth and produced a 35 mm diameter inhibition zone for Pseudomonas syringae pu. syringae. 1/5 v/v essential oil concentration produced inhibition zones of 19 and 17 mm diameter for Pseudomonas syringae pv. syringae and Pseudormonas syringae pv. mosprunorum respetively, while 1/10 v/v essential oil concentration gave inhibition plates of 11 and 12 mm diameter for both stains in the order cited. In in vitro culture essential oil gave promising results suggesting that future studies should be carried out and focus on determining appropriate formulation of this bio-molecule to be use as a bio-control agent.