DNA fingerprinting of ramets of breeding clones has revealed errors in labelling ramets used in a breeding arboretum, confirming the value of the technique in quality control.

The assays of progeny from controlled crosses without emasculation have shown that significant levels of selfed seed can occur. This needs to be tested across a number of females.

DrinnanJE@dpi.qld.gov.au,

(1) Determine the current nutritional status and corresponding yields of tea tree grown in Australia (North Queensland and Northern New South Wales).

(2) Determine some ballpark optimum fertiliser recommendations for tea tree.

(3) Improve the knowledge base of the Australian producers on the nutritional requirements of tea tree.

The affect of storage conditions on adverse events due to changes in component levels was evaluated by exposing oil to heat, light and air.

· To evaluate the ability of tea tree oil and its major components to cause skin sensitivity.

The prick test involves an immediate allergic reaction. It is the type of test used in the diagnosis of grass and dust-mite allergy amongst other things, and we tested these allergens as well as tea tree oil in order to determine if our volunteer population was more or less allergic than average. 

The patch test detects a delayed reaction that develops on the skin surface. It is used to diagnose allergic contact dermatitis, but sometimes causes an irritant reaction. There are some substances that commonly cause allergic dermatitis. 

We tested the volunteers to some of these in addition to tea tree oil in order to determine their overall reactivity in this type of test. Any volunteer who exhibited a reaction to tea tree oil was tested again with 100% oil, 10% oil and oil components.

The tests for immediate allergy indicated that while we had an overly reactive group of people, only 1.4% of people (3 of 219) displayed any reaction to tea tree oil, and reactions were to only 1 or 2 of 10 oils. 

The volunteers also appeared to be slightly more reactive to contact allergens than might be expected. A total of 52 of the 219 volunteers displayed some reaction to tea tree oil although, in a number of these people, this consisted only of a questionable reaction to 1 or 2 of the 10 oils. Secondary testing was performed on 33 volunteers. Results were classified as allergic contact dermatitis, mild or marked irritant contact dermatitis, indistinguishable between allergy and irritancy, or no response. 

The prevalence of allergy in the whole group was 2.9% up to a possible 4.8% if indistinguishable is included. To have an allergy requires a previous exposure to the substance being tested, and the levels of allergy amongst those who had previously used tea tree oil was 4.6% up to a possible 7.6% including the indistinguishable reactions. The prevalence of marked irritancy to 100% tea tree oil ranged from 2.4-4.3% (with or without the indistinguishable reactions), with any level of irritancy ranging from 7.2-10.1%. Irritant reactions are particularly concentration dependent, which means that many of these reactions should be avoidable if a lower concentration of oil is used. Very few reactions occurred in response to tea tree oil components, with a single mild response to each of 2 components, and 4 significant reactions to another component.

The Food and Drug Administration requires that the in vitro antimicrobial spectrum of compounds intended for use as a health-care antiseptic be determined. We therefore tested a range of normal and commensal isolates of the type found on skin. The result suggested that tea tree oil may be useful in removing transient skin flora while suppressing but maintaining resident flora.

Treatment of E. coli suspensions with tea tree oil or components resulted in significant reductions in optical density. These results suggested that the membrane was a site of action in E. coli. Other experiments showed that genetic material was being lost from bacterial cells through damage to the membrane. C. albicans cells were not lysed with terpinen-4-ol treatment and by electron microscopy, appeared unaltered. In contrast, E. coli cells appeared as empty "ghost" cells by electron microscopy. The appearance of terpinen-4-ol S. aureus also suggested damage to the cell membrane or wall. The original premise, that tea tree oil and/or its components act on the cell membrane or wall, was confirmed. While further evidence is required to corroborate these observations, the possibility that other sites of action may exist, must be considered.

There are now eighteen registered treatments with all but one being Pesticide Order treatments. In some cases, recommended treatments arising from this project are 80% cheaper that previously recommended treatments and exhibit little difference in weed control and safety. There was no detectable level of herbicide residue in oil samples from tea trees treated with some of the new recommended treatments.

A weeds identification and weed control booklet will transfer information gained from this project to relevant people and will be published in 1996.

Growers will possess better weed identification skills as a result of the advisory booklet and will be best advised to solve a particular weed problem.

Although considerable cost savings were made with new treatments (blanket applied), there are further savings and benefits if the practice of directed spraying was properly developed. This could allow the use of herbicides normally damaging to tea trees.

· correlating the incidence of Pyrgo in the field with weather parameters, and refining the maximum temperature threshold values for larval and egg survival to account for field observations and to improve predictive modelling;

· evaluating a monitoring procedure for detecting Pyrgo in the field; and

· screening selected insecticides and other chemicals for efficacy against Pyrgo in the laboratory and the field.

Insect problems are recognised and acknowledged by most growers, but little is known about the ecology of Pyrgo, and this has limited the development and implementation of appropriate control strategies. The industry has been promoted as being "clean and green", implying minimal or no use of insecticides, but this is belied by the substantial evidence (residues in the oil) showing that unregistered insecticides have been used on many crops. This is partly caused by the paucity of insecticides (only one is registered for use in NSW) legally available to growers, and there is clearly the need for a range of products to be available for use. 

If rational insect control strategies are to be developed and implemented for the industry, then it is important to have a better understanding of the ecology of the pests concerned. Once this is established, potential insecticide and other control measures can then be devised and evaluated.

Illegal use of non-registered insecticides is a potential "time bomb" that, if not addressed quickly, will seriously harm the industry. Several potential insecticide products have been evaluated and found to be more effective than the current permitted product, methomyl. Steps should be taken urgently to secure their registration for use on tea tree.

This project has highlighted the need for further research on control of mites and psyllids, and on the screening of insecticides to determine their potential for leaving residues in oil.

· To survey tea tree growers to establish the range of weed problems encountered, and the scope of current weed control techniques used in tea tree cultivation.

· To identify the mechanisms by which weeds inhibit the growth and oil production of established tea tree plantations.

· To define practical methods of weed control for plantation managers, which minimise the use of herbicides.

The extent to which weeds affect the regrowth of tea tree by competing for light, nutrients and water has not been quantified, but the industry perception is that it is a real but variable problem. It is postulated that weed problems are linked to loss of fine roots of tea tree following coppicing. In these situations, the tea tree plant has weakened competitive ability against rapidly growing annual weeds until regrowth has been well established. The use of herbicides, as is currently practiced, is seen as damaging to the image of the product (tea tree oil), by growers and potential consumers. A range of cultural practices additionally used by growers, could form the basis of a non-chemical system of weed control in plantations. 

This study seeks to evaluate these alternatives. The information gained should provide guidance on when weed control is required during the regrowth cycle, and what the method used must achieve if it is to be successfully adopted. 

Concurrently, other studies were undertaken to determine the effectiveness of various weed control strategies such as herbicide use (overall and strip treatments), cover crops, mowing, mechanical cultivation, and hand hoeing. These trials were undertaken at several localities over a three year period.

Two features of the regrowth cycle of tea tree are thought to be relevant to the crop’s competitiveness after harvest: the first, "coppice vigour" (the high relative growth rate of new shoots from the cut stump) increases the crop’s ability to compete for light; while the second, death of fine roots about halfway through the regrowth cycle, reduces the crop’s ability to compete for water and nutrients in the latter half of the regrowth cycle.

When all weed control strategies were compared, herbicides continued to provide the most effective control, while mechanical cultivation was the best of the non-chemical methods. Other strategies used by the industry may also be effective, but they need to be assessed against these two standards.

· To select and breed seed for economic gains in oil characteristics. Gains in yield and quality are considered essential if the Australian tea tree industry is to prosper against overseas competition and the downward pressure on oil prices.

A progeny trial of 204 families will be further tested for oil characteristics, superior trees selected and inferior trees culled to prevent them breeding with superior trees. The superior trees will grow on and flower to produce genetically improved seed. The coppicing ability of families grown at different sites will also be used to select superior families in the orchard.

The performance of families across two sites (family x site interaction) was reasonably consistent, indicating that it will be possible to select families with good general adaptability in a single breeding population, thus avoiding the extra cost of establishing multiple breeding populations in different environments. 

The best performing provenances were identified and seed from these areas will be released to the industry. The controlled pollinations in 1995 have produced seeds, indicating that the methodology used has potential.

Doran, J. C., Baker, G. R., Murtagh, G. J. Williams, E. R. and Morris, S. G. (1996). "Breeding and selection of Australian Tea Tree for improved oil yield and quality 1993 to 1996" Review Report for the Rural Industries Research And Development Corporation and the Australia Tea Tree Industry Association.

Doran, J. C., Baker, G. R., Murtagh, G. J. and Southwell, I. A. (1996). "Breeding and selection of Australian Tea Tree for improved oil yield and quality" Final Report for Rural Industries Research And Development Corporation.

· To increase the market demand for tea tree oil by measuring and documenting data on the skin irritancy and minimum inhibitory concentrations (MICs) of different grades of tea tree oil that might be required by regulatory bodies like the USFDA for monograph acceptance.

However, one factor hindering the broadening of the tea tree oil market base is that oil reach in cineole is considered to be of high skin irritancy and therefore not of a marketable standard.

More than 20 strains of bacteria were used to test numerous tea tree oils with varying levels of cineole concentration for antimicrobial activity.

This research shows clearly that there are no grounds for promoting low cineole oils other than for avoiding low terpinen-4-ol oils. If all buyers could be convinced of this, more tea tree oil could be offered for sale, providing a yield boost to many producers.

The results of the project should aid the marketing of tea tree oil. It documents: 1) the absence of skin irritancy for formulated preparations; 2) the non-allergenic nature of most tea tree oil constituents; 3) methods for the removal of some possible allergens; 4) a wider range of tea tree oil-susceptible microorganisns; 5) specific MIC values for a range of oils; and 6) enhanced MIC values for specific oils.

· To facilitate the rapid development of the knowledge base on the production of tea tree oil in the Mareeba Dimbulah Irrigation Area, Qld.

· To develop guidelines for irrigation scheduling for maximising oil yield and quality.

· To establish a gene pool of selected superior plants.

Irrigation scheduling guidelines have been developed. Mature trees use 0.8-1.0 times the pan evaporation rate which is equivalent to a total water requirement of I OML/ha/year or 7.5ML/ha/year when rainfall is subtracted.

Major factors influencing oil concentration and hence yields identified include genotype, time of year, nutrition, irrigation, and seedling vs coppice growth.