THE DISTRIBUTION AND RECOVERY OF AERIAL ULTRA‐LOW VOLUME SPRAYS FOR CONTROLLING NYMPHS OF THE AUSTRALIAN PLAGUE LOCUST, CHORTOICETES TERMINIFERA WALKER

Abstract

Field trials were conducted to determine the effect of a number of factors on the distribution and recovery of ULV spray droplets, emitted from a light aircraft equipped with Micronair rotary cage atomisers for the control of Australian plague locust nymphs [Chortoicetes terminijera (Walker)]. Spray deposits were sampled with small oil-sensitive papers attached to pasture vegetation, and were analysed with a Quantimet 720 Image Analyser for droplet number and volume densities.Results indicated that volume recovery was 6 times higher in a strong (3-5 m/s) than in a light ( < I m/s) wind, and about 3 times higher with a 50" Micronair blade angle and thus a relatively coarse droplet spectrum (volume median diameter ca 120 pm) than with a 25' setting (ca 70 pm). Aircraft flying height (either 3 or 10 m) had little influence on average recovery, though the greater altitude gave a slightly more uniform spray distribution.Subsequent trials applying fenitrothion 128% w/v at 0.3 L/ha against C . terminijera nymphal infestations confirmed the effectiveness of spraying in a strong wind using the 50' blade setting; nearly 100% mortality was recorded and treated areas were cleared of nymphal bands in 2 d. Control was unsatisfactory in the light wind trial, despite a higher applied dosage of 0.38 L/ha.

THE ACQUISITION OF AERIAL U.L.V. SPRAYS BY AUSTRALIAN PLAGUE LOCUST NYMPHS, CHORTOICETES TERMINIFERA (WALKER)

“…The trials have indicated that with the present technique of aerial nymphal control (Nguyen and Watt 1981), the vegetation cover in the treated area may need to be considered in the conduct of spray operations because of its effect on insecticide acquisition by the nymphs.…”

“…Technical fenitrothion I .28 kg L-I was applied by a Cessna 185 aircraft equipped with 2 Micronair AU.3000 atomisers. The Micronair fan blades were set at 50' as in normal control operations (Nguyen and Watt 1981). Application was made at a speed of ca 190 km h-I and from a height of ca 5 m. Applied dosages were generally less than the recommended 0.3 L ha-' (0.38 kg ha-l a.i.)…”

“…Five spray sensitive cards 75 x 50 mm (CFl, ClBA Geigy, Switzerland) were placed on the round within the selected hopper band, to sample settling droplets. Deposits were later analysed on a buantimet 720 Image Analysing Computer for the average spray volume density (Nguyen and Watt 1981).…”

Fenitrothion, an organophosphorous insecticide, impairs locomotory function and alters body temperatures in Sminthopsis macroura (Gould 1845) without reducing metabolic rates during running endurance and thermogenic performance tests

“…Our selected dose of 90 mg kg −1 fenitrothion is ecologically realistic based on our knowledge that S. macroura can consume up to 100% of its body mass daily while gorge feeding and that locusts may contain residue values of up to 80 mg kg −1 fenitrothion after locust control operations . The dose selected for the present study is 3‐fold higher than previous research that found oxygen consumption rate to be unaffected by fenitrothion during both peak thermogenesis and exercise in a closely related species, S. crassicaudata .…”

The Simulated Spraying of a Low Flying Locust Swarm

“…Estimates have been made of the amount of insecticide acquired by both flying and settled locusts following aerial application at right angles to a light wind, using MicronaiP rotary cage atomisers (Symmons and Nguyen 1980; N. T. Nguyen unpublished data). The results used here are for a large atomiser blade angle since that produces a much higher recovery on settled targets (Nguyen 1979) as well as a greater collection by fliers (Symmons and Nguyen 1980). Curves have been fitted to allow the amount collected inpg/g of body weight, to be calculated for any time interval between the release of the spray and collection by the insect (Fig.…”