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

Insect pest control and yield patterns in Central Queensland cotton crops

During 1957-1960, six field trials were carried out mainly to investigate the status of Heliothis armigera (Hubn.) as a pest of cotton under a variety of agronomic conditions. Heavy fertilizer dressings and hormone applications were used to increase the potential yields of seed cotton per acre in both rain-grown and irrigated crops. Early-season control of H. armigera is shown to exert the same influence under all agronomic conditions encountered, i.e. higher early-pick yields with no increase in total yields. In two trials in which severe infestations. of Pectinophora scutigera Hold. were experienced, DDT applications resulted in considerably increased yields. Results of one trial indicated that relatively small populations of leaf-eating insects during the early and major square and boll production period can depress yields. Fertilizer is shown to have potential value in irrigated cotton, but the use of alpha naphthalene acetic acid sprays did not increase 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

Cotton pest control trials in northern and south-western Queensland

In 1959 two cotton pest trials were carried out in northern Queensland and during 1959-60 four in south-western Queensland. All trials were in irrigated crops. One involved fruit-form removal, three covered the effects of insecticide applications on yields, and two were screening trials for kills of Earias huegeli Rogen. In two of the insecticide trials fruit-form production studies were also made. The trial concerned with fruit-form removal indicated that early season loss of fruit forms did not adversely affect yields in irrigated cotton in northern Queensland. Yield trial results showed that reasonable commercial control of the major pest species, E. huegeli and H eliothis annigera (Huhn.) in northern Queensland and E. huegeli and H. punctigera Wallengr. in the south-west, is possible by using DDT and endrin. The screening trials proved that of the materials tested, "Telodrin" is the only one likely to improve commercial control of E. huegeli. Fruit-form production studies proved that although insecticides give considerable yield increases, the basic problem in both areas is the inability of the cotton varieties in use to produce regularly under current cultural conditions the fruit forms necessary for high potential yield

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