No abstract

No abstract

Total deposits and their distribution on bush and dwarf hedgerow apple trees, sprayed at the late dormant and full foliage stages with a copper fungicide by five different methods, were estimated by colorimetric determination of the acid‐extracted copper from all the tree parts, and for comparison purposes were converted to equivalent volumes retained. The bush trees were sprayed by hand lance (4500 litresha‐1), by automatic nozzle mast sprayer (2250 litres ha−1), by conventional air‐blast sprayer at medium volume (1125 litres ha−1) and low volume (560 litres ha−1), and by hand‐directed ultra‐low‐volume (ULVH) fan‐assisted spinning‐disc sprayer (6 litres ha−1). The hedgerow trees were sprayed by conventional air‐blast sprayer at low volume (560 litres ha−1) and by an experimental tractor‐mounted ultra‐low‐volume air‐blast sprayer (45 litres ha−1). At the late dormant stage, the bush trees retained only 9–22 % of the total spray applied by all methods, except that those sprayed by the hand‐directed ULVH sprayer retained 57%. At the full foliage stage, when most of the spray was deposited on the leaves, retention for all methods of application was 22–37%. The hedgerow trees at late dormancy retained 6% of the spray applied in low volume and 10% of that by tractor‐mounted ultra‐low‐volume methods, but at full foliage, retention was 25 and 63 %, respectively. On both types of tree the proportions of the spray deposited on the tree components were related to the surface areas of those components.

No abstract

Spray deposit assessments were made on the leaf surfaces in the top, middle and base zones of intensively grown dessert apple trees sprayed by a conventional high volume automatic mast method applying 2250 litres/ha, an experimental low and ulfralow volume tractor mist blower, applying 225 litres/ha at normal dilution, 45 litres/ha at five times normal concentration or 22.5 litres/ha at ten times normal concentration, and a modified proprietary hand‐directed fan‐disc sprayer applying 225 or 22.5 litres/ha. Fluorescent tracer assessments showed that the high volume method gave heavy cover on upper and lower surfaces of the leaves in all zones, the tractor mist method gave lighter but uniform cover and the fan‐disc sprayer gave sparse cover on the upper surfaces at the top and on the lower surfaces at the base zone. The hand‐directed low and ultralow volume methods, applying one‐tenth of the amounts of copper fungicide/ha, gave deposit levels 5–30 % of those of the high volume method and the tractor mist applications gave 0.8–5.2%. The corresponding captan deposits from 5–6 applications were 12–50% and 10–20%: residual deposits from the ultralow volume applications of the concentrated captan were greater than the low volume applications of the same quantities in dilute form. In general, the order of pest and disease control obtained by the three methods was high volume automatic, fan‐disc and experimental mist, and this was related to the order of deposit levels: the order of control by the three volume rates was 2250, 225 and 22.5 litres/ha, and this could be related to the degree of spray cover.