Insecticidal control of sorghum midge, Contarinia sorghicola (Coq.)

On the Darling Downs and in the Callide Valley during 1951-1956, 8 field trials were carried out using insecticides against sorghum midge, Contarinia sorghicola (Coq.). Trial results, and consequent commercial practice, demonstrate that spraying at flowering with DDT (1 lb/ac in not less than 15 gal) in well-grown crops is economically sound when midge populations exceed 6 females per head. When swarm populations are present the save is 50-60 per cent

Heliothis as a pest of cotton

Over the 10-year period 1948-1957, 13 trials with modern insecticides against Heliothis armigera (Hubn.) were conducted on both irrigated and rain-grown cotton in Central Queensland. Results from four of these trials show total yield increases after DDT applications which were successful in killing Heliothis armigera; the increase was economically significant in one instance only. During the 1955-56 season investigations were expanded to cover plant reaction to pest kills. Although goods kills of Heliothis and most other insects were obtained there was an increase in yields in the first pick but no differences among total yields. The killing of Heliothis caused the plants to hold larger percentages of early squares and bolls; later, however, fall from sprayed plants was sudden while that from unsprayed plants was gradual. Consequent replacement of squares and bolls was responsible for the levelling of total yields

Technical notes. Parasites of Sorghum midge, Contarinia sorghicola (Coq.), in Queensland

During the seven years' study period the highest percentage of parasites in any population sample was 24·2 based on total insects (parasites plus midge emerged and in diapause). The mean in late-maturing crops on the same basis was 14·1 per cent.: this level has little economic significance

Control of Thrips tabaci Lind. in onion crops in the Lockyer Valley

Thrips tabaci Lind. is normally present in bulb and seed onion crops in the Lockyer Valley, the major commercial onion district in Queensland. During 1951-55 an investigation of the pest status of this insect included 11 screening and field trials under irrigated conditions, using 14 insecticides. Thrips populations were reduced satisfactorily by several insecticides, but parallel yield increases were not obtained consistently. In irrigated plantings, unthrifty onion plants, rather than vigorous ones, carry large thrips populations, and are also more susceptible to thrips damage. Irrigation of onion crops in the Lockyer Valley, as carried out over the past decade, has in effect reduced the status of thrips as a pest, and has forestalled the benefits which might have been derived from the use of modern insecticides under the older dry farming conditions

Effects of fruit form removals on cotton yields in Central Queensland

During 1957-1959 four trials in both irrigated and rain-grown cotton were conducted in Central Queensland. Removals of all squares and bolls were carried out during eight weeks following the first burst of squaring, approximately three weeks after the appearance of the first squares. Removals during the first four weeks did not affect yields. Maturing of replacement squares following removals during the next four weeks was dependent on length of season and growing conditions. The effect of loss and damage among squares and bolls late in the season was demonstrated by an unusually severe Heliothis armigera (Hubn.) attack during March and the incidence of Pectinophora scutigera (Hold.) during 1958-59

Insecticidal control of Agrotis infusa (Boisd.) and Leucania unipuncta (Haw.) in field crops

Several species of cutworms and armyworms are recorded in Queensland, and some of these periodically infest crops in plague numbers. Such infestations by Agrotis infusa (Boisd.) and Leucania unipuncta (Haw.) were experienced during the spring of 1952 on the Darling Downs and in neighbouring districts. Field trials were carried out to determine the optimum DDT dosage for commercial control of both pests, and several insecticides were screened against A. infusa

Technical notes. Insecticidal control of Heliothis in linseed

Two species of Heliothis attack linseed in Queensland; Heliothis punctigera Wallengr. predominates in southern districts, and occurs in about equal numbers with H. armigera (Hubn.) on the Central Highlands. Three trials, with plot size of 1/100 ac, were carried through; two at Capella, Central Highlands, during 1957 and 1959, and one on the Darling Downs in 1958

Technical notes. Bag treatment to control pests of hooded sorghum

Head hooding with paper bags to prevent cross-pollination is an essential feature of sorghum breeding work. Conditions within these bags are ideal for the development of insects such as Heliothis armigera (Hubn.), Cryptoblabes sp. and Aphis maidis Fitch, and damage by these pests can be a limiting factor in the seed produced for plant-breeding purposes. Control trials using paper bags fully or partially impregnated with an insecticide by thorough wetting and then drying were carried out at the Biloela Regional Experiment Station during 1955, 1956 and 1958. The bags, made of brown Kraft paper double crown 37, were prepared during the week prior to hooding. Immediately after harvesting, infestation ratings of 0-5 (severe) were recorded for species on each head in trials where pest numbers were high. For the later trials a similar rating range for fungi was used and samples for germination testing were taken

Bionomics of sorghum midge (Contarinia sorghicola (Coq.)) in Queensland, with particular reference to diapause

During 1950-1957 investigations of sorghum midge (Contarinia sorghicola (Coq.) ) were made with respect to hosts, sorghum varietal susceptibilities, life history and seasonal populations, with particular reference to the factors influencing development from diapause

Technical notes. Destruction of sorghum midge in seed grain

During 1951-1953, experiments on eliminating the midge from sorghum seed consignments were carried out. Treatments were based on the BHC dusting of seed grain recommended for the control of insect pests of stored grain (McDougall 1951), and the commercial fumigation of grain with carbon bisulphide (Caldwell 1947). A 2 lb. glass jar was used as the unit, and treatments were replicated 10 times. The grain included large numbers of aborted spikelets containing diapause larvae. At examination a specified number of aborted spikelets were selected at random and dissected. During the earlier examinations many of the larvae subjected to fumigation were bleached but otherwise appeared normal: none of these recovered