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This article was published in 1977
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Some Field Aspects of D.D.T. Residues in Cattle in the Namoi Valley

J.A. Macfarlane, B.V.Sc., Veterinary Inspector, Narrabri/Pilliga Pastures Protection Boards

INTRODUCTION

The successful emergence of the cotton industry in the Namoi Valley since 1962, along with the demise of that industry in the M.I.A. and Ord River has led to the situation where 52% of the cotton grown in Australia is grown in the Namoi Valley (and supplies about 70% of Australia's raw cotton requirements). The introduction of the Stock (Chemical Residues) Act has highlighted some of the consequences associated with the cotton industry.

Prior to the introduction of the Act, livestock levels monitored by the Commonwealth Department of Primary Industries sampling at Wallangarra abattoir, had indicated that high levels of Pesticides (specifically D.D.T.) were present in cattle coming from the Namoi Valley cotton area.

Firstly it would be pertinent to look at the Namoi 'Valley' and some appropriate aspects of the cotton industry.

THE NAMOI VALLEY

Map 1. Illustrates the part of the Namoi Valley under consideration.

Map 2. Gives the detail of the cotton, grazing and mixed areas of the cotton area.

The Namoi actually ceases to run in a 'valley' west of Narrabri, as it leaves the Nandewar foothills at this point and runs onto the North West black soil plains.

The reason why grazing and irrigation are carried out in this region is illustrated best by some slides of the area. Clearly, low lying river flats, billabongs and adjoining river gullies, heavily timbered with River Gums (E. camaldulensis) are excellent for grazing country and useless for other purposes.

THE COTTON INDUSTRY

1. Development of the Industry:

Keepit Dam - headwater storage on the Namoi was completed in 1956 and contains adequate storage (216 x 106m³) approximately to irrigate 28,000 hectares. Shortly afterwards the Narrabri Agricultural Research Station was opened and initial cotton trials were established by Hungarian plant breeder, Nick Derara.

The possibilities of commercial cotton growing, as unearthed by these trials, encouraged two Americans to try commercial cotton growing.

26 hectares (65 acres) gave an acceptable yield of 2.4 bales/ha in 1961 and acreages increased yearly until full capacity of 22,000 ha was reached in 1973. The 1977 area is estimated at 17,760 ha.

At this time commercial cotton growing ceased on the Ord, as insect control had become impossible.

2. Cotton Pests and D.D.T. Usage:

The successful growing of cotton depends on a large number of factors, not the least of which is successful insect control.

This was illustrated by the failure of cotton growing in the Ord. In the last year of commercial cotton growing in that area, growers were not able to control the common bollworm despite spraying 125 kg. of D.D.T. per ha, of cotton (about 1 cwt. per acre during the season). Clearly it is not possible to rely entirely on pesticides for pest control.

The Bollworms (Heliothis spp.) are the most damaging pests of cotton. Heliothis spp. are also well known as the maize, tomato, lucerne and linseed caterpillar, the tobacco budworm and the corn earworm.

It attacks a wide range of horticultural, field and vegetable crops, as well as many weeds. (Because of this, and because D.D.T. is the recommended spray, residue problems may occur in association with any of the above crops).

There are two species of economic importance: H. punctigera (native budworm) and H. armigera (cotton bollworm). They are very similar in most respects (life cycle etc.) and their caterpillars are indistinguishable.

The current recommended spray for Heliothis attack in cotton is D.D.T. (details of which follow). H. armigera has been partially resistant to D.D.T. and other chlorinated hydrocarbons since 1972/73.

D.D.T.

It is not within the scope of this paper to include any discussion of the bio-chemistry of D.D.T. or its analysis.

As far as I can ascertain, the following facts may be correct and may apply:—

D.D.T. breaks down to D.D.D. and D.D.E. Consequently half life studies are complicated by the fact each analogue may vary.

Half life in soil: 3 - 20 years. It persists longer when cultivated into the soil, as loss from deposits on the surface of undisturbed soil is high.

Half life in cattle: variable, but usually stated at about 12 weeks. Heavily lactating cows increase the excretion rate considerably.

Fattening of the cattle can reduce the levels of D.D.T. and its analogues, presumably by a dilution effect.

THE CURRENT SITUATION WITH REGARD TO D.D.I. USAGE

D.D.T. usage has decreased in the last two years. There are 3 reasons:— Firstly, farming management has changed so that whereas cotton crop followed cotton crop, now a rotation of cotton - wheat fallow system is followed. This was initiated mainly for Verticullum Wilt control, but also affects a degree of control of Heliothis spp. Heliothis pupates in the ground and overwinters in this state. Thus a large number are destroyed in this alternate cropping system.

On the other hand late sorghum crops remain a major overwintering source of Heliothis, although this area is down this year. Secondly, the number of sprays has been reduced as a result of research work at the Agricultural Research Station. This research has indicated that spraying in the past was not only unnecessary, but harmful in many cases (killing beneficial insects). Improved crop scouting techniques have allowed more judicious use of D.D.T. sprays. Thirdly, since 1973 (considered the worst year) conditions have been unfavourable for pests (bi-annual flooding).

Most common usage currently is the spray known as 'Hercophene'. It is a mixture of D.D.T. and chlorcam (Toxaphene) containing 1.25kg active ingredient D.D.T./ha and 2.55 kg/ha chlorcam. This spray works reasonably well against both species of Heliothis. 12-16 sprays are applied per year.

STOCK (CHEMICAL RESIDUES ACT (1975).

1). Effect on D.D.T. Usage:

The effect of this Act has been to bring 'Good Agricultural Practice' to a reality in the cotton fields area. Fortunately this has also been aided by the following facts -

(i) D.D.T. sprays have been reduced and

(ii) wheat is planted immediately upon completion of the cotton harvest, and there is not the area of cotton stubble to graze as was the case in yearly cotton cropping schemes.

2). On Grazing Management.

Obviously grazing on cotton stubble has ceased and the habit of grazing cattle in areas of 'waste' land within irrigated areas has also ceased (i.e. land surrounding prepared fields, canals, storages and the like).

However, as illustrated earlier, cotton fields are adjoined by large areas of country suitable only for grazing. This consists of low lying river flats, billabongs, etc., which is not suitable for irrigation.

Further, there are holdings within the cotton area where only grazing and dry land farming is practiced. This also applies to all farms on the edge of the cotton area.

The system currently adopted for grazing in this area is to spread cattle in areas away from D.D.T. contaminated areas and only use country adjacent to the cotton fields for short term fattening. It is not possible to say how successful this will be in the long term.

Sheep would be a disaster as they eat closer to the ground and therefore probably would ingest more pesticide. The area is burr ridden (24D is not used, it kills cotton) and they are not known for their ability to swim (the Namoi River has taken to flooding bi-annually).

SOURCES OF RESIDUES (50% of M.R.L. AND ABOVE

Summary of trace backs (using Tail Tags) - Table 1.

CATTLE OWNERS WHO ARE:	Total No.	Tracebacks
CATTLE OWNERS WHO ARE:	Total No.	5.0 ppm	2.5 - 5.O ppm
(Narrabri P.P. Bd.)
1. Cotton Farmers	25	9	5
2. Adjoining cotton farms	32	7	18
3. Others	600	2	0
(Pilliga P.P. Bd.)
1. Cotton Farmers	13	4	3
2. Adjoining cotton farms	10	0	4
3. Others	250	1	0

FOR DETAILS SEE APPENDIX 1.

ACTUAL SOURCE OF RESIDUE

Prior to the introduction of the Act, spray was applied liberally to, and beyond, the edges of cotton to ensure a full coverage. There is no question that at this time grazing land and cattle would have been sprayed directly. Consequently D.D.T. (and analogue) residues would have arisen from direct intake either by absorption or licking of the coat after spraying

Secondly, at this time cotton crop followed cotton crop and in between cattle were grazed on cotton stubble and D.D.T.(and analogue) residues arose by ingestion of heavily contaminated pasture and earth.

Consequent upon the Act, these practices have virtually ceased and the source of residue would be:

1. Spray drift - probably the main source of D.D.T. Residues can arise either by direct contact with spray droplets (and subsequent absorption) or by ingestion of pasture and earth contaminated by spray drift.

2. Ingestion of previously contaminated soil in areas where D.D.T is no longer used. This especially is significant in low-lying areas which since the recent floods are no longer used for cotton and are now being used for grazing.

3. Grazing land contaminated by 'Tail Water'. Flood irrigation has as part of its management the draining off of excess water (called 'tailwater'). Some of this water is returned to the river, but mostly it is spread out onto surrounding pasture land. In drier times these areas provide a large proportion of feed available to cattle. The amount of D.D.T. in this water is very variable. D.D.T. is very insoluble and consequently the amount of D.D.T. is probably related to the amount of sediment contained within the water. If for example heavy rain occurs during irrigation, this excess water must be removed quickly and it would be very dirty.

THE FUTURE

Undoubtably the research work being undertaken in this field will lead to a fuller understanding of the epidemiology/pathogenesis of this problem.

The amount of research is staggering, but not surprising considering the amount of discussion D.D.T. has received on a world level.

Two local programmes might be mentioned:—

Firstly, a study is being made in the area by the Department in collaboration with the State Pollution Control Commission. The Departmental effort is being co-ordinated by the Director, Pesticides and Environmental Studies and includes the Division of Animal Industry and the Chemistry and Entomology Branches of the Biological and Chemical Research Institute, Rydalmere. Other bodies involved are the Fisheries Branch, National Parks and Wildlife Service and Water Resources Commission.

Secondly, integrated pest control programmes are being developed; these combine managerial, cultural, mechanical, biological, as well as chemical control methods. The C.S.I.R.O. and N.S.W. Department of Agriculture are currently working along these lines in the Heliothis field.

On a world wide basis all pesticide production companies are constantly searching for new pesticides. All I know about that subject is that two groups of pesticides that are alternatives to D.D.T. are relatively close to availability.

One chemical (Chlordimeform) was in fact released but voluntarily withdrawn following unfavourable experimental evidence in laboratory mice.

However, a similar chemical (Armitraz) is currently available and is being investigated.

The other group is the synthetic pyrethroids. A number of companies are developing chemicals in this group. How useful they will be against Heliothis I do not know, but I understand they may not be as useful as first anticipated.

Most cotton farmers (being familiar with the American scene) expect D.D.T. to be banned if and when an alternative becomes available. Cotton is currently grown successfully in America without D.D.T. and there is no reason to believe it should be any different here, given time.

D.D.T. is, in general, being phased out where practical.

APPENDIX No. 1.

SUMMARY OF INDIVIDUAL TRACEBACKS (D.D.T. only)

Legend:- No. : Abattoir Traceback Level : Description.

75/45/1	5.3 ppm	Cotton Farmer. Test results 0.75 - 2.00 ppm
2	8.00 ppm	Cotton Farmer. Test results 0.61 - 3.6 ppm
3	5.2 ppm	Cotton Farmer. Test results: i). 3/76 9.2 - 48 ppm. Av. 29.0 ppm (all D.D.E, & D.D.D., equal proportions. ii) 7/76 2.9 - 8.2 ppm Av. 5.5 ppm (nearly all D.D.E.) iii) 9/76 5.2 - 10 ppm Av. 7.4 ppm iv) 11/76 3.7 - 8.8 ppm. Av. 6.8 ppm (Cattle much better condition). v) 1/77 4.4 - 11 ppm Av. 8.7 ppm (spraying season, traces of D.D.T. in all samples at about 0.2 ppm level. D.D.D. levels rose markedly).
4	5.9 ppm	Cotton Farmer. i) 4/76 2.6 - 7.0 ppm Av. 4.0 ppm ii) 8/76 5.6 - 15.1 ppm Av. 9.1 ppm (about 2/3 D.D.E. 1/3 D.D.D. NO D.D.T. very poor condition). iii) 10/76 8.0 - 4.9 ppm Av. 5.7 ppm (better conditioned cattle). iv) 5.1 - 1.8 ppm Av. 3.6 ppm (all D.D.E. released from quarantine as spraying season was about to start).
76/45/1	6.1 ppm	Adjoins cotton farms. i) 6/76 2.3 - 9.5 ppm Av. 5.1 ppm (mostly D.D.E., but traces D.D.D. & D.D.T). ii) 9/76 3.1 - 6.2 ppm Av. 4.1 ppm (virtually all D.D.E.) iii) 11/76 2.1 - 8.7 ppm Av. 4.8 ppm (higher components D.D.D. Traces D.D.T. Owner in hospital).
2	14.0 ppm	Owner leases land on cotton farm not used for cotton growing. 1) 9/76 44-4.1 ppm Av. 17.3 ppm (all components D.D.T. / D.D.D. / D.D.E. ratio 1:2:4). ii) 2/77 49 - 10 ppm Av. 22.4 ppm (D.D.D. component the highest - increased av. from 5.5. - 12.5 ppm.) Cattle running on old cotton country abandoned due to flooding and adjacent cotton.
3	10.0 ppm	Nowhere near cotton. Occasional buyer of cattle for fattening in Narrabri Yards. Test 0.06 - 0.011 ppm Subsequent traceback of 3.1 ppm
4	7.3 ppm	Cotton Farmer. Test result 2.4 - 5.3 ppm Av. 3.5 ppm
5	12.0 ppm	Cotton Farmer i). 10/76 1.6 - 9.00 ppm Av. 5.0 ppm (5 vealers below level, 5 cows over the limit). ii) 1/77 4.5 - 8.3 ppm Av. 6.6 ppm (spraying season. The 9.0 ppm cow of last test died (?))
6	7.8 ppm	Adjoins Cotton Farms. Test result 3.9 - 5.9 ppm Av. 4.4 ppm
7	24.0 ppm	Cotton Farmer. All cattle sold, cattle running adjacent to and on cotton prior to introduction of Act.
8	32.0 ppm	Cotton Farmer. All cattle sold.
9	6.3, 8.5., 9.4., 7.5., 5.1., 7.05 ppm	Cotton Farmer. Test result 0.43 - 10.0 Av. 4.9 ppm
10	8.0 ppm	Cotton Farmer. Test result 0.71 - 3.2 ppm
	This is a typical case of the current management system. Cattle are bred on farms away from the area and vealers, steers or whatever, are fattened in the cotton area. These are then all sold at once. In these cases the tested cattle obviously are different from those from which the beast of residue 8.0 ppm represents.
77/45/1	8.7 ppm	Adjoins cotton farms. (All cattle sold, new lot coming for fattening.)
76/45/1	6.6 ppm	Cotton Farmer. All cattle sold/farm sold.
2	7.4 ppm	Cotton Farmer. Test result 4.2 - 30 ppm Av. 14.0 ppm Mostly D.D.E., but higher % levels of D.D.D. in higher readings.
3	12.0 ppm	Farmer some miles from cotton. Test result 0.9 - 3.6 ppm Reason for 12.0 ppm obscure. Cotton was grown there 1974 and before.
76/47/4	5.7 ppm	Cotton Farmer. Test result 0.7 - 3.9 ppm
Miscellaneous
i)	7.6., 5.9., 11.0 ppm	Deceased Estate. Agisted on TSR's and farms in cotton areas.
ii)	20 ppm	Victorian owner. Cattle on TSR's in cotton area during drought - all sold.
iii)	Await Action: 9.7 ppm 10.9 ppm	Owner adjoins cotton farms. Cattle buyer - not near cotton area.