Growth and Spray Retention of Wild Oat and Flax in Relation to Herbicidal Selectivity*

Abstract

Summary. The growth of wild oat (Avena fatua L.) was accompanied by an increase in the amount of spray retained per plant and per unit weight of plant, probably because the projected area (plan view) increased as the plant became larger. Flax (Linum usitatissimum L.) retained a fairly constant volume of spray per plant from the 8‐leaf to the 35–40‐leaf stages, so that the spray retained per unit plant weight decreased considerably as the plants grew. This was related to the decrease in projected area as a proportion of the whole. There was also a difference in retentivity between the cotyledons and true leaves; the cotyledons retained ten to twenty times more spray per unit weight. These results suggest that maximum selectivity would be achieved by spraying at an advanced stage of growth. Wild oat at the 3‐leaf stage retained more than half the aqueous spray in the two leaf axils, while flax retained most on the cotyledons. Distribution was shown to be a probable reason for selectivity. Addition of a surfactant greatly increased retention by both species, but although the effect of a spray on wild oat might thereby be increased, under certain conditions injury to flax might be increased and the margin of selectivity reduced. Croissance et retention des bouillies herbicides par la folle‐avoine et le lin en rapport avec la sélectivité

Effect of ammonium sulphate and related salts on the phytotoxicity of dichlorprop and other herbicides used for broadleaved weed control in cereals

“…The greater activity of dichlorprop salt without surfactant shown in Table 7 may have practical advantages, in improving selectivity between 5. media and cereals. When surfactant is omitted, spray retention on leaves of cereals and grasses generally is poor (Hibbitt, 1969).…”

Spray retention, foliar penetration, translocation and selectivity of asulam in wild oats and flax

“…Thus only the top few leaves receive most of the spray solution. Furthermore, al the leaf stage used in these experiments the true leaves, which are very water repellent, retain a little spray but the cotyledons, which arc readily wetted, become increasingly shielded (Hibbitt. 1969).…”

“…docks (Catchpole & Hibbitt, 1972) and bracken (Veerasekaran et at.. 1977) have shown that translocation of '•*C occurs primarily according to a "source to sink" pattern with accumulation of radioactivity in metabolically active sinks. Hibbitt (1969) reported that the differential selectivity of asulam between wild oats and flax was due to a dificrence in spray distribution pattern on the plants.…”

The influence of climatic conditions around the time of spraying isoproturon on the subsequent injury to barley

“…The treatments on 7 October 1985 were made in very light rain which may have redistributed the herbicide into the leaf bases which are potent sites for pesticide entry into plants (Robertson & Kirkwood, 1983). The target presented by the plant's habit may also influence both retention (Hibbit, 1969) and any redistribution and in this case (7 October 1985), the more erect younger plants showed a much greater weight reduction than the older plants. Since isoproturon can be washed through the alkathene beads when plants are watered with a spray boom (Martin & Blair, unpublished) this may have occurred in the light rain on 7 October 1985, although it is not thought to be a major factor.…”