Supplementary funding was provided by the CRDC allowing three personnel ($1750 each, $5,250 total) from the pesticide chemistry group to attend the 8th International Congress on Pesticide Chemistry, held in Washington DC from July 4-9, 1994. Additional funding was provided by personal contributions (ca. 25%) and a University travel grant for postgraduate students. I.R. Kennedy also travelled to the Pasteur Institute in Paris, France in connection with a collaborative research program on nitrogen metabolism, with travel costs partly covered by an Austra1ian Research Council grant. Alice Lee, a CRDC Research Scholar working on the development of immunoassays for pesticides, also attended, funded separately

A large collection of microorganisms with over 2000 isolates has been established at the Australian Cotton Research Institute for the purpose of identifying potential bio-control agents and developing biological control methods for seedling diseases and Verticillium wilt. These isolates have been collected from within, on and around the roots of cotton plants collected from commercial crops in different cotton growing areas of New South Wales. The culture collection has been screened for in vitro antagonism against the pathogens that cause seedling diseases (Pythium sp., Rhizoctonia sp.), Verticillium wilt (Verticillium dahliae), black root rot (Thielaviopsis basicola), and bacterial stunt (Pseudomonas sp.) of cotton. About 29% of the culture collection inhibited the growth of one or more pathogens. A part of the culture collection was screened in in vivo glasshouse and growth chamber experiments for activity against the seedling disease pathogens and Verticillium dahliae. Several bacterial strains were found to be effective. Cotton seed inoculation with bacterial strains increased seedling survival by up to 80% (compared to the non-treated control). Some bacterial strains significantly reduced the incidence of Verticillium wilt. The proportion of plants with vascular symptoms ranged from 11-30% compared to 64-78% in the non-treated controls. Some bacterial strains which were effective in pot experiments significantly increased seedling survival in field experiments. The addition of nutrients to the inoculum and the use of combinations of bacterial strains as a means of enhancing biocontrol activity need to be investigated

The conference was held on the 23 - 27th of August, 1994 in Silsoe, UK. It reflected the broad spectrum where soil dynamics is applied, varying from the classic soil compaction studies, gantry systems, force predictions on tillage tools to ballistic penetration of stony soils. Researchers from the EEC, USA, , Canada, Japan, Israel and Australia were present. One oral paper, 'Stress paths under agricultural tyres' and one poster paper was presented, Controlled traffic, an Australian perspective'.

This report summarises the findings from the CRDC funded project "Managing soils to avoid compaction problems in cotton growing". The project ran from 1989/90 to 1991192. It had the principal aims of: * developing a management system for cotton growers that would minimize tillage requirements, and * avoiding current problems with soil compaction associat.ed with heavy machinery

Disease surveys in November and March of each season have been undertaken on a regular basis since 1983. The results of these surveys indicate the relative importance of those diseases which are present and provide an indication of the effects of various cultural and environmental factors on disease development. Disease surveys also present an ideal way to monitor the effects of disease control strategies as they are implemented. Verticillium wilt is the most widespread and important disease of cotton in Australia with the potential to reduce yields by 20-25% in some fields when weather conditions are favourable. Seedling disease is always present and effective control is important so that the costs and problems associated with replanting can be avoided. Mycorrhizas have been shown to be important in the early season growth of cotton in some areas. The purpose of these studies was to develop recommendations to growers for the more effective control of verticillium wilt and seedling diseases and to develop a better understanding of the importance of mycorrhizas so that cropping strategies to maximise early season growth of cotton seedlings can be developed. The increasing importance of Black root rot, the recent occurrence of Fusarium wilt and the significant epidemics of altemaria leaf spot in Pima cotton have also demanded attention.

OBJECTIVES: 1. To study sampling and control practices for mirlds in irrigated and dryland cotton. * development of more accurate sampling techniques *insecticide trials to improve control *development of economic thresholds 2. To assess the importance of local alternate hosts in producing populations of green mirids that attack cotton. * assess mirid invasion of cotton from nearby lucerne and safflower *assess whether mirids invade cotton on weather fronts from distant sources

The aim of this study was to complete the development of a mirid feeding bioassay to facilitate screening and characterization of proteinaceous toxins. The types of protein toxins that are available for screening influenced the assays that were developed. Acute toxins, such as the scorpion neurotoxin, can be assayed using adults and scoring for monality or paralysis. However, there is a very limited nwnber of these acute toxins available. Much more numerous and available are inhibitors of digestive enzymes, lectins and similar proteins that are likely to have a more subtle effect on mirid feeding, growth and development. Assessment of the deleterious effect of these proteins necessitated the development of a feeding bioassay using nymphs.

The aims of the CRDC project CSE 29C were: - to optimise the design of recombinant Helicoverpa viruses with increased insecticidal activity (Activities 1 and 2 of the overall program above), - to develop suitable large-scale production systems (Activity 4) and - to assess the potential impact recombinant viruses may have upon the environment (Activity 5). Timescales for the overall program are shown in Figure 1. Objectives for each year of the CRDC project

Vertosols are the main soil type on which cotton is grown in Australia. Eighty percent of irrigated cotton is grown in retained hill. However, from time to time the hills may need realignment which requires knocking dawn the old hills and fanning new furrows and hills. As a result, new hills can be relocated over old wheel tracks, causing a compacted zone beneath the hill in the root zone, thus impeding root growth. The very nature of the Vertosols lends themselves to self repair under repeated wet/dry .cycle. An attempt has been made in this study to investigate the effect of wet/dry cycles in repairing the structure of a compacted Vertosol from a commercial cotton farm in the Darling Downs of Queensland

A growth disorder of cotton ( Gossypium hirsutum) occurs in irrigated cracking clay soils in cotton growing regions of northern New South Wales. Observations of early season cotton growth were made at l 00 m intervals along transects in fields that showed gradients in severity. Ordination analysis of physical and chemical properties of the soil distinguished three groups of sites (A, B, and C) which corresponded to patterns of yield and early season growth. Early season growth and arbuscular mycorrhizal colonisation of cotton at group A and B sites was much slower than at group C sites. Group B sites showed a recovery of yield later in the season while group A sites did not. Group A and B soils had lower pH, finer texture and higher P, Zn, Mn and exchangeable Mg, K and Na than group C soils. Thus, paradoxically, the greatest stunting occurred in the more fertile soils with putatively more favourable pH for cotton growth. Shoot growth also decreased with increasing manganese availability, soil clay content and soil water holding capacity. The stunting of seedlings at an early stage was not consistent with some potential physical and chemical causes of stunting, including sodicity, compaction, manganese toxicity and waterlogging. Cotton had a high relative field mycorrhizal dependency in group C soil (up to 92% at six weeks after sowing). A series of bioassays in pots showed that slow mycorrhizal development in group A soils was not due to a reduction in the number of propagules of mycorrhizal fungi. Cotton was less dependent on mycorrhizal fungi in group A soils (15 to 20 % ), which partly accounted for the lower levels of colonisation, but the soil microflora also inhibited mycorrhizal development. Sterilisation of group A soils consistently eliminated root browning, a symptom of the disorder, and increased cotton growth in pots and in the field. This was despite the negative effects of sterilisation on P and Zn nutrition due to the elimination of mycorrhizal fungi. Fungi, viruses and nematodes were discounted as possible pathogens. Soil borne bacteria were shown to be causal because (i) cotton growth was increased by the application of streptomycin and penicillin, (ii) bacteria were observed in and streaming from browned cotton roots and (iii) bioassays showed that a species of fluorescent Pseudomonas isolated from cotton roots was pathogenic to cotton. Variation in cotton growth within fields could be accounted for by the additive effects of nonbiological and biological properties of the soil, including both beneficial and pathogenic microorganisms