Jpn. J. Trop. Agr. 37(1): 32-37, 1993

Integrated Weed Control in Plau-Noi (Croton sublyratus KURZ)

Plantation

Eisuke MATSUNAGA, Chatchal DOMETHONG and SekSan PHULSAWAT

Institute for Plant Biotechnology & Development Thai Sankyo Company Limited, Bangkok 10400, Thailand

Abstract In order to develop the most efficient system of weed control, experiments in integrated weed control combining mechanical and chemical control with the use of leguminous covers, were carried out in a large plantation of Plau-Noi trees (1,120 ha).

Glyphosate, N-(Phosphonomethyl) glycine is one of the most important herbicides for weed control in Plau-Noi

plantations. Although young Plau-Noi trees less than two years old can be damaged by the application of agricultural chemicals such as glyphosate, adult Plau-Noi trees more that 2 m high are not affected by such applications. Therefore, the following weed control program was designed and adopted.

Effective weed control in young Plau-Noi plantations consisted of integrated control including cutting, digging and plowing using farm implements, and weeding by utilizing the competitive growth between herbaceous weeds and cover crops. On the other hand, in adult Plau-Noi plantations chemical control consisting of the application of glyphosate at rates ranging from 1.4 to 3.3 kg a.i./ha. was adopted.Key words Calopogonium mucunoides, Croton sublyratus, Glyphosate, Integrated weed control

プ ラ ウ ノ イ 園 に お け る 雑 草 の 総 合 的 防 除 法 松 永 英 輔 ・チ ャチ ャイ ドメ ト ン ・セ ェ ー クサ ン プ ー ンサ ワ ッ ト タ

イ三 共 株 式 会 社 プ ラ ン トバ イ オ テ ク ノ ロ ジ ー開 発 研 究 所 バ ン コ ッ ク10400,タ イ

要 約 大規模 なプラウノイ園(1,120ha)に お ける効率的 ・経済的雑草防除法 を確立す るため,若 干の基礎試験 を実施 した.そ の結 果

は以下 の通 りであ った.

2年 生以下 のプラウノイ幼木園 における雑草防除法 は,雨 季の初期(1989年5月 下旬)に 畜力耕耘 と人力小器具 による機械的除草を

行い,そ の後 マメ科被覆作物,Calopogonium mucunoidesを 播種 ・栽培 して雑草 との競合 による耕種的除草を実施 した.

3年 生以上 のプ ラウノイ成木園 における雑草防除 は,雨 季の初期(1989年5月 下旬)か ら終期(1989年11月 下旬)に か けて以下の

よ うな処理を3回 繰 り返 した.一 般雑草が約20cmの 高 さに出揃 った頃,グ リフ ォセー トをヘクタールあたり1.4kg,さ らに防除困難

な雑草について は3.3kgを 茎葉処理 した.

以上の試験結果か ら,大 規模な プラウノイ成 木園における雑草防除法 と して,次 の ような総合的防除が最善 の方法 と思 われる.

初め に,雨 季に雑草が約20cmの 高 さに出揃 った頃,防 除剤によ る化学的除草 を実施 する.次 に再び雑草が約20cmの 高 さに出揃 っ

た頃,畜 力耕耘 と人力小器具 による機械的除草を実施 し,完 全 除草後 マメ科被覆作物を播種 ・栽培 して雑草 との競 合による耕種 的除草

を実施す る.最 後 に,乾 季 にプラウノイ樹の 自然発火の防止 も含 めて,畜 力耕耘 と人力小器具 によ る機械的除草を実施 する.

キー ワー ドCalopogonium macunoides,グ リフォセー ト,プ ラウノイ,総 合的防除

Introduction

In the course of studies on the identification of antipeptic ulcer substances of plant origin,

OGiso et al.7) found that an extract of the crude drug called Plau-Noi exhibited an anti-peptic

ulcer activity. Plau-Noi has been known to be

an antihelmintic and dermatological agent in traditional medicine in Thailand. We developed an economical method of cul-

tivation of Plau-Noi trees in Thailand for the manufacture of an antipeptic ulcer drug2-5).

As soon as the rainy season starts, many

weeds grow very rapidly, competing strongly with Plau-Noi trees for water, nutrients and light. Therefore, inadequate weed control is the main factor responsible for the decrease of the

production of Plau-Noi leaves and one of the major causes of the occurrence of diseases and insect pests. NODA et al.7) outlined the weed problems in Thailand and reported in the National Weed Science Research Institute Project. We were interested in implementing integrated weed control combining mechanical and chemical control with leguminous covers, since some authors reported that the control of weeds could be achieved by planting leguminousReceived January 30, 1992

MATSUNAGA, et al: Integrated Weed Control in Plau-Noi Plantation 33

cover crops.

This paper deals with the implementation of

integrated weed control consisting of the com-

bination of mechanical and chemical control

with the use of leguminous covers in Plau-Noi

plantations.

Materials and Methods

The experiment was conducted during a

period of two years from 1988 to 1989 in the Plau-Noi plantations of Prachuab Khiri Khan located about 325 km south from Bangkok.

Glyphosate is one of the most important her-bicides for weed control in the Plau-Noi planta-tions. However, depending on the age, Plau-Noi trees may sustain damage by the application of agricultural chemicals such as glyphosate. Therefore, we designed and adopted the follow-ing weed control program.1. Plantation of Plau-Noi trees less than two

years oldFarm implements, knife, hoe and ox-drawn

wooden plow were used to remove weeds and to dig up deep-rooted weeds from areas cover-ing 29.3, 24.3 and 46.1 ha, when the weeds sta-rted growing, after the first rain in the rainy season. After land preparation at the end of May, 1989, cover crops were seeded circularly at the foot of Plau-Noi trees. The cover crops sown consisted of the following leguminous species, Calopogonium mucunoides, Canavalia ensiformis, Cent rosema pubescens, Crotalaria juncea, C. paulinea, C. spectabilis, Indigofera spi-cata, Lablab purpureus, Mimosa invisa var in-ermis, Pueraria phaseoloides, Styzolobium deeri-ngianum and Stylosanthes hamata.

The work efficiency related to different kinds of mechanical control practices using farm implements was evaluated by calculating the labor per unit area and time.

The morphological characteristics of the twelve legume species used as cover crops were surveyed by observation with the naked eye. In addition disease and insect damage, tolerance to excess water, weed competition, soil adaptability, presence of leguminous bac-teria, palatability to livestock (cow), seed collc-tion and drought-resistance were also deter-mined based on the occurrence of diseases and incidence of insect outbreaks, normal growth and development of cover crops, degree of inhi-

bition of weed growth, soil fertility, number of

bacterial nodules, consumption of cover crops

by livestock, seed quality and quantity, and

wilting during the dry season respectively.

A randomized block design with two replica-

tions was used in this test. Plot size measured

1.5 •~ 10 m. Visual observations were made at

60 day intervals throughout the 6-month

period of study.

2. Plantation of Plau-Noi trees more than three

years old

The herbicide used in this field trial was

glyphosate (48% soluble concentrate). Weeds

were treated with aqueous solution at three

designated rates of 1.4, 2.2 and 3.3 kg a.i./ha.,

when they grew up a 20 cm height. The weeds

which survived after glyphosate treatment

were cut with a knife and hoe.

The tests were designed as randomized

blocks, replicated 2 times. Test plots measured

4 •~ 6 min twelve weed trials.

Weed control efficacy was evaluated by the

following formula: (fresh weight in untreated

area- fresh weight in treated area) •~ 100/fresh

weight in untreated area=weed control %.

The values were ranked from 0 to 5: where 0

= 0-10%;1=11-20%; 2=21-40%; 3=41-60%;

4=61-80%, and 5=81-100%.

Results and Discussion

Dominant or aggressive weeds in the Plau-Noi plantations were Amaranthus spinosus L, A. viridis L, Abutilon indicum SWEET, Brachiaria reptans L, Cenchrus echinatus L, Chloris barbata Sw., Cleome viscoa L, Commelina benghalensis L, C. diffusa BURM, Cyperus pilosus VAHL, C. rotun-dus L, Dactyloctenium aegyptiaeum WILLD, Digit-aria adscendens (H. B. K.) HENR, Echinochloa col-onum (L) LINK, E. crusgalli (L) BEAUV, Eleusine indica (L) GAERTN, Eupatorium odoratum L, Eu-

phorbia geniculata ORT, E. hirta L, Fimbristylis dichotomy (L) VAHL, Gomphrena celosioides MART, Hyptis suaveolens POIT, Imperata cylindr-ica (L) BEAUV, Jussiaea linfolia VAHL, Mimosa invisa MART, M, pudica L, Pennisetum pedicella-tum TRIN, Phaseolus lathyroides L, Physalis minima L, Sida acuta BURN, Tridax procumbens L and Vernonia cinerea (L) LESS.

To control these weeds, several trials were carried by implementing integrated weed con-trol combining mechanical and chemical con-

34 Jpn. J. Trop. AAr. 37(1) 1993

Table 1 Comparison of work efficiency related to different kinds of mechanical control practices in a plantation of Plau-Noi trees less than two years old in Prachuab Khiri Khan (1989)

Table 2 Comparison of weed control efficacy related to different kinds mechanical control practices in

a plantation of Plau-Noi trees less than two years old in Prachuab Khiri Khan (1989)

z The activity index 5 indicates 81-100% of weed control; index 4=61-80%; index 3=41-60%; index 2=21-40%; index 1=11-20%; and index 0 indicates the absence of effect.

y After land preparation by plow, the seeds of Calopogonium mucunoides were sown at the end of May, 1989.

trol with the use of leguminous covers. The results obtained were as follows.1. Plantation of Plau-Noi trees less than two

years oldAs shown in Tables 1 and 2, the mechanical

weed control method using a hoe and knife did not give satisfactory results, as compared with that using a plow. In a large area, this method did not actually enabled to control the weeds. The use of hoes only enabled to eradicate the weeds around the shade area of Plau-Noi trees and also the use of knives contributed to the control of the height of weeds which continued to grow and spread over a wide area (Fig. 1).

The mechanical weed control method using

plows was more effective from both the stand-points of weed control and soil improvement, as compared with the use of a hoe and knife. Especially, after land preparation, the green-cover enabled to control common weeds

(Tables 3 and 4). Calopogonium mucunoides, Mimosa invisa var. inermis (M. invisa with pri-ckles was not suitable for such a purpose) and Stylosanthes hamata were more effective in terms of weed competition, soil adaptability, presence of leguminous bacteria, tolerance to

Fig. 1 Two-year-old Plau-Noi field with mech-

anical weed control by the knife

excess water and seed production, as compared with other leguminous cover crops. Moreover, no disease and insect damage was observed in

these covers. Calopogonium mucunoides grew so fast that 4 to 5 months after seeding, the cover formed a dense and entangled canopy 50 cm

high and 150 cm wide.

Calopogonium mucunoides was found to be the best cover crop in the field of this planta-

tion. However, Mimosa invisa var. inermis and Stylosanthes hamata may be more suitable as

MATSUNAGA, et al: Integrated Weed Control in Plau-Noi Plantation 35

Table 3 Characteristics of twelve legume species used as cover crops in a plantation of Plau-Noi trees less than two years old (1989)

Table 4 Growth habit of twelve legume species used as cover crops in a plantation of Plau-Noi trees two years old (1989)

cover crops (in plantations of one or two-year-old Plau-Noi trees), since they did not become entangled over the Plau-Noi trees.2. Plantation of Plau-Noi trees more than three

years oldChemical weed control was an effective

method in the plantation of three-year-old Pla-u-Noi trees.

Among the twelve major weeds shown in Table 5, Cenchrus echinatus, Cyperus rotundus, Dactyloctenium aegyptiacum, Digitaria ad-scendens, D. sanguinalis, Eleusine indica, Eu-

36 Jpn. J. Trop. Agr. 37(1) 1993

Table 5 Effect of glyphosate treatments on the control of aggressive and dominant weeds in a plan-tation of Plau-Noi trees three years old (1988)

z Herbicidal activity index during the 1st 35 days after glyphosate treatment; index 5 indicates 81-100%, index 4=61-80%; index 3=41-60%; index 2=21-40%; index 1=11-20% and index 0 indicates the

absence of effect.

phorbia geniculata, E. hirta, Hyptis suaveolens, Imperata cylindrica and Pennisetum pedicella-tum were adequately controlled by 1.4 kg a.i./ha of glyphosate, unlike Commelina benghalensis. However, when the concentration of glyphos-ate increased to 3.3 kg. a.i./ha, the fresh shoot weight of Commelina benghalensis was reduced significantly.

Based on these results, effective weed control in a large plantation of Plau-Noi trees was as follows.1. Plantation of Plau-Noi trees less than two

years oldCultivation with ox-drawn wooden plow was

initiated in May, immediately after the first rain of the rainy season when the weeds sta-rted to grow. Hoes and knives were used with circular plowing around the trees where weeds were still present. Thereafter a cover crop, Cal-opogonium mucunoides, was sown in the field of the Plau-Noi plantation to control other common weeds by utilizing the competitive growth between them. Finally, plowing in No-vember was recommended to prevent fire out-breaks during the dry season.2. Plantation of Plau-Noi trees more than three

years oldFirstly, weeds were treated with an aqueous

solution of glyphosate at the rate of 1.4 kg a.i. /ha, when they grew up to a 20 cm height in May.

Secondly, the application of glyphosate at the rate of 1.4 kg a.i./ha two times in July and September was considered to be necessary to control completely the common weeds when-ever the weeds regrew up to a 20 cm height. When the deep-rooted weeds still remained they were treated again with glyphosate at the rate of 3.3 kg a.i./ha.

After these treatments the persistent weeds which survived were dug up with a hoe. Finally, plowing in November was recomme-

nded to prevent fire outbreaks during the dry season.

Acknowledgement

The authors would like to acknowledge the continuous guidance and encouragement of Dr. Takashi SATO, Professor Emeritus, Kobe Uni-versity. We are grateful to Dr. Shoji SHIGENAGA and Dr. Misako ITO, Kyoto University, and Dr. Akira OGISO, Sankyo Company Limited for their helpful suggestions and critical reading of the manuscript. Furthermore, we wish to thank Mr. Ananta LAOPHANICH and Mr. Iwao MIKURIYA, Thai Sankyo Company Limited for their support in this work.

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