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Ten commercial sugarcane cultivars were planted in 10 replicate plots in each of three field trials in southern Queensland, to evaluate their response to the sugarcane soldier fly Inopus rubriceps. Trials were monitored for three harvests. Numbers of soldier fly larvae differed slightly between cultivars, but probably not enough to prevent the development of damaging populations. Weights of larvae were the same on all cultivars, suggesting that antibiosis was not involved. The effect of soldier fly on performance of cultivars in each trial was examined by regression of number of ratoon shoots and subsequent number and weight of mature stalks and crop yield on larval density during summer−autumn within each crop class. Where statistically significant relationships were detected in ratoons, each increase in soldier fly density of 100 m−2 was associated with a yield reduction of 1.2−6.4 tonnes cane ha−1, or 3−8% of the expected yield of uninfested plants. In most analyses, the slopes of regressions were the same for all cultivars, indicating no differential response to soldier fly infestation among the cultivars tested.

Larvae of sugarcane soldier fly, Inopus rubriceps, pupated during autumn in sugarcane fields. Under conditions of moist soil and good cane growth, pupation occurred about 1 month later in northern and central Queensland than in southern Queensland and northern New South Wales, and this was related to soil temperature. the midpoint of the pupation period coincided with mean soil temperatures of 20-25° in each area. A laboratory experiment showed that pupation was inhibited at 25° and favoured by lower temperatures. the timing of pupation varied between years in one canefield in southern Queensland. Late pupation in 1991 was associated with small average size of larvae in early autumn and with dry soil conditions and poor cane growth. A high proportion of larvae failed to pupate before winter in this field in 1991. In normal years this carryover of larvae into winter was only about 10%. Male pupae were smaller than female pupae. Pupal weights were similar in each of the areas and years studied, but in some fields pupal weights declined with time during the pupation period.

Large differences in ratooning were observed between sugarcane clones in a variety trial that became infested with larvae of the sugarcane soldier fly Inopus rubriceps. To investigate this apparent resistance, pot experiments were carried out using two clones that responded differently in the trial. Soldier fly larvae reduced the number of ratoon shoots produced by both clones after harvest, with the commercial cultivar CP44–101 less affected than the experimental clone 81S595 under a range of growing conditions. This differential effect was consistent with field observations. The effect of soldier fly on plant growth prior to harvest was similar in both clones. Larval survival was independent of clone or larval density. The difference between the two clones appears due to a tolerance of soldier fly feeding by CP44–101. Pot experiments should be useful for screening commercial cultivars.

Larvae of the sugarcane soldier fly Inopus rubriceps fed on plants in the families Gramineae, Cruciferae, Cucurbitaceae (but not zucchini), Leguminosae, and Solanaceae in a pot experiment. Larvae grew faster under sugarcane, sorghum, legumes, and tomatoes than when crucifers, cucurbits, or capsicums were present. Plants with larger root systems were more favourable for growth. Larval growth was associated with increased survival. Fewer larvae may survive in fields between cropping cycles of sugarcane if ground is maintained as a bare fallow in comparison with a rotation with favourable host plants.

A survey of damage caused by Inopus rubriceps to sugarcane was carried out in the Millaquin-Qunaba mill area near Bundaberg. Damage was less frequent in first and second ratoon crops than in older ratoons. An effect of sugarcane varieties was evident, but damage levels were the same for the 3 main varieties in the district. No damage was recorded in fields treated with suSCon Blue (controlled-release chlorpyrifos granules) against canegrubs (Coleoptera: Scarabaeidae). Damage was more frequent in cane fields that had been replanted immediately after ploughout of the previous crop than in those that had an interval without cane. This interval could be a bare fallow or a rotation with a vegetable crop. Other factors including rotary hoeing, past use of dieldrin, and use of chlorpyrifos EC at planting were not shown to affect the frequency of damage.

Larvae of sugarcane soldier fly, Inopus rubriceps, began aggregating near sugarcane plants in troughs within 1 week of planting. By 6 weeks, almost 80% of larvae were found within 13 cm of the plants and only 5% were found 25-50 cm distant.

A method for extracting the sugarcane soldier fly (Inopus rubriceps (Macquart)) larvae, pupae and remains from canefield soils by suspension in moving water is presented. Vertical and lateral distribution of larvae and pupae in relation to sugarcane plants was studied.

Isolates of the entomopathogenic fungus Metarhizium anisopliae were bioassayed against larvae of Inopus rubriceps Where spore concentration was high (6.7 × 105-6.7 × 1 06 spores/g of soil) all isolates were pathogenic At lower concentration (6.7 × 104 sores/g soil), pathogenicity varied significantly between isolates, as did their ability to grow and sporulate on the larval cadaver followng internal colonisation There was variation in the campatibility of M. anisopliae isolates with pesticides used on sugarcane, but certain isolates were highly compatible. Although some of the isolates of M. anisopliae were highly pathogenic and highly compatible with the pesticides tested, strain improvement to enhance epizootic potential may be appropriate. M. anisopliae has the potential to be an effective biological control agent of I. rubriceps.

The distribution of the sugarcane soldier fly, Inopus rubriceps is mapped in its native Australia, as well as in the introduced range, New Zealand and California. Populations are discontinuous, and apparently determined by warm temperatures (> 12.8 °C mean annual temperature) and high rainfall (> 750 mm/yr in warm temperate or > 1000 mm/yr in subtropical/tropical regions). Larvae are found only in friable and free‐draining soils, largely alluvial or basaltic in origin. Populations in several widely separated areas of eastern and southern Australia are probably reproductively isolated, although distribution may have been more continuous in the past. Southeast Queensland and northern New South Wales is the geographical centre of the range in Australia. No related species of Inopus occur in this area, and climate is genial for I. rubriceps. The species has probably had a long evolutionary history in this region.

Altermetoponia flava. sp. n., is described from adults reared from larvae infesting sugar cane in the coastal area of Queensland.

A new species of diapriid, Neurogalesus militis, is described from Australia and is compared with N. rubripes Dodd and N. dissimilis Dodd. It was found as a parasite of the pasture soldier fly, Inopus rubriceps (Macquart), a serious pest of sugarcane in parts of eastern Australia.