Slow adoption by farmers in Western Australia of new wheat cultivars led us to propose that their grain yield advantage over the old cultivars may not be evident under the traditional agronomic practices used in the State. The experiments, including both tall (rht) and semi-dwarf (Rht) commercial cultivars, were sown from early to mid-May, up to early July at five locations each year in the central wheatbelt of southwestern Australia in 1986, 1987 and 1988. Semi-dwarf outyielded tall cultivars more when sown in May (0.65 t ha-l) than in early June (0.35 t ha-1) and did not outyield them at later sowings. It is postulated that the yield advantage of the semidwarfs is dependent on early sowing. The yield advantage of the semi-dwarfs was related to greater ear and kernel numbers. The relative reduction in kernel size with later sowing was greater in the semi-dwarfs than in the tall cultivars. The semi-dwarfs had larger harvest indices at the May sowings but the talk equalled or exceeded them at the sowings in June. We concluded that the semi-dwarfs used in our experiments were more sensitive to the stresses associated with later sowing in this environment than the tall cultivars. The optimum flowering period for the study area over the three seasons was 7 to 29 September. However, there was considerable variation from season to season, and we concluded that an adequate definition of the optimum flowering period should be based on time-of-sowing experiments over a range of seasons.

Average commercial wheat yields in the southern, high rainfall area of Western Australia have seldom exceeded 1.5 t/ha and wheat is not widely grown. However, the average annual rainfall and length of growing season (>400 mm and >6 months) are conducive to much larger yields. Thirteen factorial experiments with mid and long season cultivars (Aroona and Osprey), 2 levels of applied nitrogen (N) (40 and 80 kg N/ha), 2 seed rates (50 and 100 kg/ha) and with or without fungicide were conducted at 8 sites over 2 seasons. The experiment was done to investigate combinations of cultivar and agronomic practices suitable for increased wheat production in long season environments in Western Australia. Largest grain yields (>4 t/ha) were obtained where wheat followed a grass-free break crop, and the mid season cultivar was used with 80 kg N/ha and 100 kg/ha of seed. Increases due to cultivar and seed rate were more consistent than those due to N, and increases from application of fungicide were less consistent. It is suggested that the optimal wheat production 'package' will include sowing in May in rotation with a grass-free break crop, seed rate of about 100 kg/ha and, when all other factors are optimal, N rates of over 40 kg/ha. The greatest yield increases were associated with the sites where wheat followed a grass-free crop. Increases due to other factors were relatively smaller. Hectolitre weight and percentage of small grain (<2 mm) often reached levels that would have entailed downgrading in commercial deliveries. However, in the most productive crops where root and leaf diseases were minimal, these quality parameters were seldom deficient and grain protein contents exceeded 10% at yields of up to 4 t/ha.

Coptotermes Wasmann is one of the most important genera of wood-destroying insect pests, both in its native and introduced countries. Pyrethroids are among the most widely used insecticides in wood preservation around the world. Consequently, they have often been evaluated against different species of Coptotermes. However, because various test methods have been used between countries, comparing results is problematic. These field trials, using a single aboveground method of exposure, assessed a range of retentions of two pyrethroids (bifenthrin and permethrin) in Pinus radiata D. Don sapwood against two species of Coptotermes in three countries to provide directly comparable results. Coptotermes acinaciformis (Froggatt) in Australia consumed the most nontreated wood, followed by Coptotermes formosanus Shiraki in China, then C. formosanus in the United States, although these data were not significantly different. Both termite species demonstrated a dose-response to wood treated with the two pyrethroids; less wood was consumed as retention increased. Overall, C. acinaciformis consumed relatively little of the treated wood. In comparison, C. formosanus consumed 20-90% of the wood treated at the lowest retentions of the pyrethroids evaluated. Results indicated that C. acinaciformis was more sensitive to pyrethroid toxicity/repellency compared with C. formosanus. Factors that may have influenced the results are discussed. However, using a single aboveground method of exposure across three countries, that suited both species of Coptotermes, made it possible to determine unambiguously the actual differences between the species in their tolerances to the two pyrethroid insecticides.

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