Microbial populations and respiratory activity are reported for topsoils (0-10 cm) of 15 cm diameter cores (depth 50 cm) of 10 pasture soils representative of soils of North Island, New Zealand, after 15 months' irrigation with either municipal tapwater or unchlorinated sewage effiuent from a biological filtration plant. Respiratory activity in the unamended soil was low, with respiratory quotient (R.O.) less than 1. Addition of glucose produced about a four-fold increase in CO? production and the R.O. rose to 1. Total microbial populations were similar. There were few bacterial spores but more actinomycetes. Gram-negative bacteria comprised only a small proportion of the population. Coliform counts, both total and faecal, were low. A wide range of organisms were present; the moat numerous, other than bacteria and fungi, were flagellates, amoebae, and solitary green algae. Representatives of the fauna found in the filtration plant were recovered from the effiuent irrigated soils. All measurements showed greater oifferences among the different soils studied than between the two irrigation treatments.

A method is described for rearing two introduced parasitoids; Cotesia kazak (Telenga) (Hymenoptera: Braconidae) on Helicoverpa spp. (Lepidoptera: Noctuidae) and Hyposoter didymator Thunberg (Hymenoptera: Ichneumonidae) on cluster caterpillar, Spodoptera litura (F.) (Lepidoptera: Noctuidae).It facilitates the production of large numbers of parasitoids for field release.A number of species of noctuids are considered to be major pests of agriculture in Western Australia. In response to this problem several species of hymenopteran parasitoids have been introduced and reared for field release. This paper describes the methods employed in mass rearing two of the species; Cotesia kuzak (Telenga) ( = Apanteles kazak Telenga 1949), using Helicoverpa armigera (Hiibner) and H. punctigera (Wallengren) as hosts, and Hyposoter didymator Thunberg on Spodoptera litura (F.). Our procedures were adapted from those of Carl (1977Carl ( , 1978. Singh et al. (1982) and Michael et al. (1984) to allow for large-scale production. General rearing proceduresHosts and parasitoids were both reared in a quarantine insectary. The host colonies were developed from field-collected adults, while pupae imported from Switzerland (C. kuzak) and Greece (H. didymator) initiated the parasitoid colonies. Larvae of the host species were laboratory reared on an artificial diet similar to that described by Shorey and Hale (1%5), but based on soybean, bran, wheatgerm and yeast.Room temperature was 15°C. except for two periods of the day (0500-0830 and 1500-2000 h) when it was 25 "C to encourage oviposition. Natural light was supplemented by fluorescent lighting to provide 15 h light. Relative humidity was 70 & 15%. Rearing of Cotesia kazakWe presented 100 Helicoverpa larvae (late first and second instar) to five female and five male C. kazak ( > 2 d old) in 2 L plastic bottles with a mesh base (Fig. 1). The bottles were positioned on their sides with the mesh end facing the light and contained two pieces of host diet (5 mm') and two pieces of folded greaseproof paper (as larval retreats). Five thin streaks of honey were scraped onto the mesh window as food for the wasps. The insects remained in the jar for 24 h, after which the parasitoids were removed to perspex holding cages supplied with honey. Transfer of adult C. kazuk was achieved using a vacuum pump.FIG. I-Diagram of set-up used for facilitating oviposition of host larvae by C. kazak.Host larvae were allowed to develop to third instar, at which time they were moved (using a fine paintbrush) to 2 L plastic boxes with mesh inserts in their lids. Each box was supplied with two pieces of host diet and two coloured paper napkins. Parasitoid pupae were conspicuous on the coloured background and could be cut away with scissors, while those on the surfaces of the container were levered off by fingernail without mortality. Pupae were placed in paper cups inside perspex cages where they emerged 12-20 d after oviposition, or up to 180 d later under diapause-inducing conditions (< 12 h light). Unparas...

Three different weed control treatments were applied every 3 weeks for 6 years to plots of Levin mottled silt loam previously under grass. The treatments were (i) spraying with a proprietary herbicide mixture containing equal parts of paraquat and diquat (0.3 kg total a.i./ha), (ii) spraying, plus hoeing to 1.5 em depth, and (iii) spraying, plus forking to 25 em depth. A mown grassed strip served as control. Soil density and aggregate stability were reduced by the treatments. Few large soil animals were present in any of the plots. The abundance and diversity of nematodes were reduced in the treatment plots; numbers declined significantly with soil depth only. in the grassed-strip and uncultivated plots, which had a vegetative cover of mosses and liverworts. A typical grassland microflora persisted in the treatment plots, although some bacterial groups, such as clostridia, were reduced in number. Soil from the treatment plots had lower organic C content and pH values, oxygen uptakes, carbon dioxide production, and dehydrogenase activity than soil from the grassed strip; dehydrogenase activity was significantly correlated with oxygen uptakes, and decreased significantly with soil depth. In general, the removal of the grass vegetative cover and the continued application of paraquat-diquat had most influence on the properties examined, and the additional weed control treatments had little effect.

A sequence of four soils derived from schist, and ranging from 900 to 5.000 ft above sea level, has been studied bacteriologically in association with biochemical measurements. The two soils at lower altitudes were of semi-arid to subhumid moisture regimes and weakly acid to near neutral. but the two upland soils were of the humid moisture regime and strongly acid.Of the isolates studied. 75% were Gram-negative, about one-half of them possessing carotenoid pigments. The non-pigmented Gramnegative rods included a large group of non-motile, slow-growing, psychrophilic bacteria that have not been recorded previously from these soils and have been clas~ified as Acinetobacter. Spore-forming bacteria constituted 9%, and pleomorphic bacteria 14% of the isolates.Fungal plate counts, streptomyces, and spore-forming bacteria tended to decrease with increasing altitude, but Gram-negative bacteria became increasingly numerous.The rhizosphere of Poa colensoi appeared to have higher populations than those of Festuca novaezelandiae or Chionochloa rigida.Growth tests showed Gram-negative soil taxa to be generally more tolerant of low temperatures and acid conditions than pleomorphic, Gram-positive, or spore-forming taxa, but there was considerable variation, particularly with the Bacillus species. The variation with B. megaterillm isolates suggested that the range of temperature or pH within which population growth took place was related to the soil environment from which it was sampled.