O B S E R V A T I O N S O N C O N T R O L O F P I S T I A S T R A T I O T E S L I N N . I N F I S H P O N D S B Y

" G R A M O X O N E "

BY S. PATNAIK (Central Inland Fisheries Research Substation, Cuttaek, India)

Received May 24, 1971

(Communicated by Dr. B. S. Bhimachar, F.A.~.)

A~STRACT

An account is given of the yard and field trials conducted at Cuttack which showed that 'Gramoxone' (20~ paraquat) at 0" 1 to 0-2 kg/ha. (a.i.) gave complete control of Pistia stratiotes in one to two weeks' time. The cost of clearance by the weedicide worked out to Rs. 64--93/ha as against Rs. 168-178/ha. for manual clearance. Treatment in instalments is re- commended to avoid oxygen depletion due to rotting of treated weed mass and consequent fish mortality.

INTRODUCTION

THE water lettuce, Pistia stratiotes Linn., is widely distributed in inland freshwaters, especially along the coasts of India. Some aspects of its morpho- logy, taxonomy, ecology and distribution of the plant have been studied by Arber (1920), Biswas and Calder (1955), Subramanyam (1962), Mitra (1966), Singh et al. (1967) and Philipose etal. (1970). Among the publica- tions on control of water lettuce besides other water weeds in India and Ceylon, the work of Parija (1934), Thomas and Srinivasan (1949), Dassana- yake and Chow (1954), Singh (1962), Ramachandran and Ramaprabhu (1968), Philipose (1968) and Misra and Das (1969) are worthy of mention. Con- siderable work has been done on paraquat in U.S.A. and U.K. (Blackburn, 1968; Brian, 1966; Parker, 1966). Weldon etal. (1963) stated that 1.2 kg./ha, of paraquat was effective for the control of water lettuce. Lawrence etal. (1963) reported that paraquat is non-toxic to fish at concentrations even much greater than what is recommended for aquatic weed control. Investigations on the use of 'Gramoxone ' (20% paraquat), against Pistia stratiotes undertaken at Cuttack, Orissa, during 1967-70 and the observations on its efficacy and economics are given in the present paper. ' Gramoxone '

15

i6 S. PATNAIK

a product marketed by I.C.I. (India), is a bipyridylium herbicide containing 20 per cent of paraquat ion.

EXPERIMENTAL DETAILS AND RESULTS

Yard experiments.--Four series of experiments were conducted and the results are given in Table I. Fresh Pistia plants were collected and grown in earthen pots (surface area 0.166 sq.m.). After a week when the plants were well established the calculated quantity of the weedicide was sprayed by a small hand sprayer keeping two replicates for each rate tried and for untreated controls. In all cases the plants lost their natural colour and started wilting 4-5 hours after spraying. The leaves gradually turned from yellow to brown and later whitish and the disintegration of the plants began by the fourth or fifth day. The affected plants rotted and floated as a pulpy mass before sinking. During this process the dissolved oxygen (D.O.) of the water ranged from traces to 0"62 ppm. The entire process of death and disintegration in the first and second experiments conducted during winter (December and February) took 14 and 9 days respectively, whereas, in the third and fourth experiments conducted during summer (May) it took 7-8 days only. In the fourth experiment addition of a 0.1 per cent solution of a detergent (Surf) gave comparatively better results. The slightly quicker decomposition in the third and fourth experiments could be due to com- paratively higher temperature and humidity in summer (Table I) as also reported by Brian (1966).

Field experiments.--The field experiments were carried out in 6 ponds at Cuttack ranging from 0.13-0.46 ha. which were choked with Pistia. The results are presented in Table II. The weed infestation was divided with rope into plots of 10 m. breadth for convenience of thorough spraying from both sides.

In trial 1, spraying of the entire pond at the rate of 0.3 kg./ha. (a.i.) was done with a knapsack sprayer having cone jet nozzle, from the rear end of a small tin boat (2 m length) dragged through the infestation. Rotting of the plants started seven days after spraying. Some dead specimens of the fishes Barbus ticto and Mystus vittatus were observed floating while other fishes and some murrels were observed at the surface possibly due to a sudden fall of D.O. to almost nil. The D.O. increased to 1.4 ppm. by the thirteenth day and no further mortality of fish was observed. After two weeks all the dead weeds settled to the bottom. As seen from Table II, above 97 per cent. clearance was achieved. As a result of disintegration of the weed the phosphate level of water increased from 0.4ppm. to 0"85 ppm.

Control o f Pistia stratiotes Linn. in Fish Ponds by Gramoxone 17

TABLE I

Effect o f different rates (active ingredient) o f ' Gramoxone ' on Pistia stratiotcs in yard trials

Rate of weedicide

(~-i.) in

kg.lha.

Eapt. No. I; dated 22-12-1967 Expt. No. 2; dated 27-2-1968

t Percentage

(by wt.)

Temp. and

humidity Remarks

Rate of Percentage weedicide ~ , Temp.

(a i.) l~i~l and in (by wt.) ~.umidity

kg./ha.

Remarks

0"5

0"6

1.0

1.0

1 ' 4

1"4

2.0

2.0

Nil

Nil

0.05

0.05

0"1

0"1

0.15

0.15

0 .2

0"2

Nil

Nil

I00

100

t00

100

100

100

100

100

Nil

Nil

Expt. No.

60.(

88.7

95./

95.(

99 .~

99.~

I00

I00

Nil

Nil

, o

28°C.

36~

a .

3, Dated

~4.5oc.

85%

= .

D O

b @

Complete d ecay in 14 days

do.

do.

do,

do.

do.

do.

do.

In control no decay

do,

4 -5-1970

Decay in 8 days

do.

do.

do.

do,

do.

do.

do.

In contIol no decay

do.

0.2

0.2

0 .3

0.3

0 .4

0.4

0 .5

0.5

Nil

Nil

0.02

0.02

0.05

0.05

0.1

0.1

0.15

0'15

Nil

Nil

98.8

99.2

L00

L00

L00

L00

t0O

[00

Nil

Nil

98.5

97-5

99.5

~9.0

100

100

I00

100

Nit

Nil

31°C.

525

Complete decay in 9 days

do.

do.

do.

do.

do.

do.

do.

In control no decay

do.

Expt. No. 4, dated 25-5-1970

.. Detergent added 0.1 ~ , decay in 7 days

Decay in 8 days 33.5oc.

905 Detergent added 0" 1 • , decay in 7 days

Decay in 8 days

Detergent added 0 , 1 ~ . plete decay in 7 days

Complete decay in 8 days

c o m "

Deterger, t added 0. I • , complete decay in 7 days

Complete decay in 8 days

Detergent added 0 .1g ' , control no decay

In control no decay

B 2

18 S. PATNAIK

In trial 2, spraying was done at 0.2 kg./ha. (a.i.) with a knapsack power sprayer (Aspee Bolo). The D.O. on the fifth day was only 0.5 ppm. but no fish mortality was observed probably because of the fact that only half the water area was covered with Pistia, the rest being free from weeds. At the end of the experiment fishes like Cyprinus carpio, Channa striatus and Notopterus notopterus were netted out in healthy condition. Above 93 per cent clearance was attained (Table II).

In trial 3, spraying was done at 0.2 kg./ha. (a.i.) with hand operated sprayer as in trial 1. The weeds started disintegrating by the sixth day and on the seventh day the carps Labeo rohita, Carla catla and Cirrhina mrigala, which were present in large numbers were observed in distress from late night till 9-00 A.M. the next day. The D.O. was observed to be 0.8, 1.4, 2.8 and 1.0 ppm. at 6.00 A.M., 12 NOON, 6"00 P.M. and 10"00r.M. respectively(Table 1i). This condition continued for four days. Clearance of 97.5 per cent. of the weed was achieved.

In trial 4, the treatment was done at 0.15 kg./ha. (a.i.) with the aid of a stirrup pump sprayer having long polythene tubing for reaching the interior of infestation while the weedicide solution was pumped from the shore. Though there was heavy rain six hours after spraying, the majority of the treated weeds were observed settling down seven days after the treat- ment. The D.O. fell to traces, but no fish mortality was observed as was the case in trial 2. When the pond was clear of the weed, fishes like C. striatus, N. notopterus and C. carpio were netted out in healthy condi- tion. In this case above 97 per cent clearance was attained (Table II).

In trial 5, spraying was done as in trial 4 with the aid of a stirrup pump sprayer at 0.1 kg./ha. (a.i.). On the sixth day after spraying the plants were observed decaying. The D.O. was observed to be 0.6 ppm. but no mortality of the fishes present, viz., Hypophthalmichthys molitrix, Ctenopharyngodon idella, C. carpio., L. rohita and C. mrigala occurred as in the above case. 99 per cent clearance was achieved (Table II).

In trial 6, weedicide was sprayed at 0.05 kg./ha. (a.i.) with the aid of a stirrup pump sprayer as in trial 4. The sixth day after spraying the affected plants started disintegrating. The D.O. was found to be 0.8 ppm. and no distress of fishes was observed although fishes like L. rohita, C. carla, C. mrigala were present. In this case only 76 per cent. clearance was achieved (Table II) though with the same rate 99 per cent. clearance was achieved in the yard trials.

Control of Pistia stratiotes Linn. in Fish Ponds by Gramoxone 19

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= ~ . #o ~ ~0~ ~

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20 S. PATNAIK

Effective rate.--From the results of yard experiments (Table I) the rates, i.e., 0"02 kg./ha, to 2 kg./ha. (a.i.) effected satisfactory kill (above 90~) of Pistia. In the field trials, however, satisfactory clearance was achieved with the rates 0.1, 0.15, 0.2 and 0.3 kg./ha. (a.i.) The dilutions used during the field trials were 450-500 l./ha. (Table II). These proved satisfactory. It may be emphasized that an effective coverage of the plots is essential to achieve satisfactory results. Addition of a 0-1 per cent. detergent (Surf) solution seemed to enhance the rate of kill in trial 5 (Table II).

Economics--In India the age old practice of clearance of weeds by manual labour is becoming increasingly expensive and hence uneconomical. The possibility of quick re-infestation of the weeds is also greatest in manual methods. It is for these reasons that gradually chemical methods of weed control have become very popular. Philipose (1963) reported cost of single manual clearance of Pistia as Rs. 75.00/ha. at the prevailing rate Rs. 1.50 for six man hours. Dassanayake and Chow (1959)reported manual clearance cost of the plant in Ceylon as Rs. 300/ha. as against Rs. 40-50 with 'phenoxylene-30' mixed with 'Teepol' . in two field clearances (0-29 and 0.07 ha.) by manual labour during the present investi- gation the cost worked out to Rs. 178 and 185/ha. (at Rs. 3.00 per 6 man hours) compared to only Rs. 64-93/ha. with 'Gramoxone ' in six trials. The details of cost per hectare are as follows:

Cost of weedicide (Gramoxone) 0.5-1-0 kg. .. Labour charges for 13 to 16 men days ..

(at Rs. 3 per man day of 6 hrs.) Detergent and other incidental charges ..

Rs. Rs. 20 -- 40 39 - - 48

5 5

TOTAL . . 6 4 - - 9 3

Though there are reports of effective kill of Pistia by other chemicals viz., Taficide-80 and Simazine, the economics of the operation has not l:een worked out.

CONCLUSIONS

Field treatment rates of 0,1 to 0,2 kg./ha. (a.i.) of the weedicide ' Gramoxone' with a dilution of 450 I. water/ha, and addition of a 0., 1 pel~ e0nt. d-~terg~nt can ~iv0 effective clearance of P(stia ¢~tratiotes,

Control of Pistia stratiote~ Linn. in Fish Ponds by Gramoxone 21

When the weed starts rotting by the action of the weedicide, the dis- solved oxygen of water usually drops to very low values (below 0.5 ppm.) which could cause fish mortality. Hence it is desirable to treat small areas at intervals when the vegetation is dense instead of treating the entire area at a time to avoid fish kill.

An important management procedure after the chemical clearance is to remove stray unaffected plants, and regenerating plant residues which may later threaten to reinfest the water body by rapid vegetative growth,

ACKNOWLEDGEMENT

I extend my deep gratitude to Dr. V. G. Jhingran, Director, for his keen interest in the study. Grateful acknowledgement is made to Dr. M. T. Philipose for encouragement and critically going through the manuscript, to Shri V. Ramachandran for giving valuable suggestions during the course of this work and going through the manuscript. I am also thankful to Shri S. B. Singh for valuable suggestions in preparation of this paper and to Shri K. M. Das ['or analysing water samples.

REFERENCES

Arber, A. ..

Biswas, K. and Calder, C.C. ..

Blackburn, R. D.

Brian, R. C.

Dassanayake, W. L. P. and Chow, C. Y.

Lawrence, J. M., Funderbmk, H. H., Blackburn, R. D. and Beasley, P. G.

Misra, G. and Das, N. ..

Water Plants, Cambridge University Press, London, 1920, p. 436.

Handbook of Common Water and Marsh Plants o f India and Burma, New Delhi, Manager of Publications, 1955, p. 140.

"Weed control in fish ponds in the United States," In Pillay, T. V. R. (Ed.), Proe. WorM Symp. on Warm Water Pond Fish Cult. F.A.O. Fish Rep. (44), 1968, 5, 1-17.

"The bipyridylium quaternary salts. The effect of atmos- pheric and soil humidity on the uptake and movement of diquat and paraquat in plants," Weed Res., t966, 6, 292-303.

"The control of Pistia s'ratiotes in Ceylon by means of herbicides," Ann. trcp. Med. Parasit., 1954, 48, 129-34.

"The status of diquat and paraquat as aqautic herbicides," Proc. Conf Stheast. Ass. Game Commrs., 1963, 16, 157-63.

"Studies on the control of aquatic weeds of Orissa. Res- ponse of Pistia stratiotes L., Spirodela polyrhiza Sch[eid and Ipomoea aquatica Forsk. to hormone herbicides," Hyacinth Control J., 1969, 8, 40-41.

22 S. PATNAIK

Mitra~ E.

Parija, P.

Parker, C.

Philipose, M. T.

Philipose, M. T., Ramachandran, V., Singh, S. B. and Rama- prabhu, T.

Ramaehandran, V. and Ramaprbhu, T.

Singh, S. B.

~ , Ramaprabhu, T. and Janardhan; K. V.

.. "Contributions to our knowledge of Indian freshwater plants. 5. On the morphology, reproduction and autecology of Pistia stratiotes Linn.," J. Asiatic Soc. Beng., 1966, 8, 115-35.

.. "Physiological investigations on water hyacinth (Eichhornia crassipes) in Orissa with notes on some other aquatic weeds," Indian J. Argic. Sci., 1934, 4, 399--429.

.. "Influence of water hardness on the phytotoxicity of para. quat," Nature, Lond., 1906, 212, 1465-66.

.. "Making fish ponds weed free," Indian Livestock, 1963, 1, 20-21, 34-36.

.. "Present trends in the control of weeds in fish cultural waters of Asia and the Far East," In Piltay, T. V. R. (Ed.), Proc. World Syrup. on Warm Water Pond Fish Cult.) F.A.O. Fish Rep. (44), 1968, 5, 26-52.

"Some observations on the weeds of cultivable freshwaters in Orissa," J. Inld. Fish. Soc. India, 1970, 2, 61-84.

Subramanyam, K. ..

Thomas, K. M. and Srinivasan, A. R.

Weldon, L. W., Blackburn, R.D. "Studies on control of water lettuce," and Seaman, D.E. Control Conf., 1963, 16, 356.

"Investigations on aquatic weed control with special reference to the use of chemicals," In Pillay, T. V. R. (Ed.), Proc World Syrup. On Warm-water Pond Fish Cult. F.A.O. Fish Rep. (44), 1968, 5, 92-108.

"Control of some emergent and floating water weeds by Taficide-80," Proc. Indian Sci. Congr., 1962, 49, 107, I l l Abstr.

"Observations on the phenology and reproductive capacity of some freshwater weeds in Orissa with suggestions for their control," Proc. nat. Acad. Sci. India, 1963, 37B, 148-160.

Aquatic Angisoperms, C.S.I.R., New Delhi, 1962, p. 190.

"Weed Killers," Indian Fmg., 1949, 10, 101-6.

Proc. Sth. Weed