A handbbok on Weed Control in Rice.pdf

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Chapter 5 Principal rice herbicides Herbicides play an important role in integrated weed management in rice. Early-season weed competition significantly reduces rice grain yield, and preemergence herbicide treatments are widely used. But most weed seeds germinate over a long time, and preemergence herbicides, with their relatively short residual life, may not control weeds long enough to opti- mize rice yields. Then, postemergence herbicides may be needed along with other control measures. Moreover, any one herbicide may not control all the weeds present in a ricefield. Herbicide mixtures are used to obtain a wider range of weed control. Herbicide mixtures, rotations, and sequences Mixing herbicides and spraying them simultaneously increases the range of weed control. Using herbicide mixtures can also save time and reduce application costs. A broadleaf herbicide and a grass herbicide are often mixed together (e.g., bensulfuron + butachlor). Residual and foliar contact herbicides may be combined (e.g., thiobencarb + 2,4-D). Herbicides that may be combined often are sold as formulated products. When these are not available, two or more herbicides may be mixed in the spray tank at the time of application- a tank-mix combination. Combina- tions must be selected carefully and comply with manufacturers’ recommendations to avoid product incompatibility. Herbicide classification and uses The herbicides commonly used for weed control in rice are described here. Table 5.1 lists the weeds controlled by the herbicides. Details on their use are discussed in Chapters 6-9. Every effort has been made to ensure that the information presented is correct (Roberts 1982, Swarbrick 1984, Attwood 1985, Chemical and Pharma- ceutical Press 1986, Thomson 1986, Worthing 1987). But because herbicide activity varies from locality to locality, only general recommendations are given. Specific recommendations should be obtained from weed special- ists in the reader’s locality. Most herbicides are organic com- pounds. Herbicides are considered ideal if they are toxicologically safe, selective to rice, cost-effective, effective on weeds, and have no lasting adverse effects on the environment. Herbicides may be classified, for convenience, by method and timing of application. Or they may be classified by chemical group, which also gives an indication about how the herbicide may be used. Anilides Anilides are used to control germinating annual weeds, especially grasses. They often are most active as surface preemergence treatments. The primary mechanism of action is through inter- ference with nucleic acid and protein synthesis. Butachlor, pretilachlor, and propanil are examples of this group. Butuchlor. Butachlor is absorbed primarily through germinating shoots and secondarily through roots. Its mode of action is inhibition of protein synthesis. It is used at 2-3 kg ai/ha for preemergence control of most annual grasses at the 1- to 2-leaf stages and of certain broadleaf weeds, and can be applied postemergence. For trans- planted rice, it is applied 3-7 d after transplanting. For direct seeded rice, it is applied 10-12 d after emergence. Principal herbicides 65
Table 5.1. Susceptibilitles a of important rice weeds to common rice herbicides (treatment at recommended doses and application times). Herbicide Weed Acanthospennum hispidum Aeschynomene viginica Ageratum conyzoides Altemanthera sessilis Amaranthus spinosus Ammannia coccinea Bidens pilosa Brachiaria mutica Commelina benghalensis Cynodon dactylon Cyperus difformis Cyperus esculentus Cyperus iria Dactyloctenium aegyptium Digitaria sanguinalis Echinochloa colona Echinochloa crus-galli Echinochloa glabrescens Eclipta alba Eichhornia crassipes Eleusine indica Eleocharis acicularis Euphorbia hirta Fimbristylis miliacea lmperata cylindrica Ipomoea aquatica Ischaemum rugosum Leersia hexandra Leptochloa chinensis Ludwigia octovalvis Marsilea minuta Monochoria vaginalis Nymphaea stellata Cyperus rotundus S R S S R S S S S S S S S S S S R S R S S S MS R R R R R S R S S R R R R S S S MR S S R S MS S R MR MR MR MS S R S MR R S S S R R R S MS S R S S S S MR S S S R R S R S S S S S R S S R S S S S S S R R S S S s R S S S S R S MS S S S R S R MS S S S S S S S R MR R S MS S R R R R R R S S R MS S R S R R R S S S R R R R R R R S R MS R R R R S S S S S R R S R R MR R S S S R MR R R R S S R MR R S S S S MR MR MR MR S S R R S S R S S S S S S S S S S S MS MS S S S S S S S S S S S S S S S S S S S S S S R R S MS R R R R R R S S R MS S R R R R S S S S R MS MR S R S S S S S MS R R S MR MS S S S MR R MR R MS S R S S S S S MR S R S S S S S S S R S R S S R R S S S S S S S S S R S R S S S S S S S S S S MR MR R S S S R S S S S S S MS S S S S R MR S S S S S R S R R R S R S R S S S S S R S MR S R S R S S S R R R R R R R R S R S R S S S R R S R R R S S S S S S S S S S R S S S S R R R S R S R S MR S S S MR MS S S R S MR S S MS MS MR MR MR S S S MR MS R MS R R R MR MR R S R S R R S S S S MR S S R S R MS MR S MS MS S S S R R R R R R R R R R R S R R R R R R R R S
Page 1 and 2:
1991 P.O. Box 933, 1099 Manila, Phi
Page 3 and 4:
Foreword Farmers everywhere search
Page 5 and 6:
Contents FOREWORD PREFACE 1 S IGNIF
Page 7 and 8:
Table 1.3. Weeds as secondary hosts
Page 9 and 10:
horizontal leaves. Tall plants have
Page 11 and 12:
Chapter 2 Rice weeds of worldwide i
Page 13 and 14:
Lowland rice weeds ASTERACEAE (Comp
Page 15 and 16: Lowland rice weeds / CYPERACEAE (se
Page 17 and 18: Lowland rice weeds / CYPERACEAE (se
Page 19 and 20: Lowland rice weeds / ONAGRACEAE (ev
Page 21 and 22: Mature plant Inflorescence Seed, ma
Page 23 and 24: Lowland rice weeds/POACEAE (grass f
Page 25 and 26: Lowland rice weeds / POACEAE (grass
Page 27 and 28: Lowland rice weeds / PONTEDERIACEAE
Page 29 and 30: Upland rice weeds AIZOACEAE (carpet
Page 31 and 32: Upland rice weeds / ASTERACEAE (sun
Page 33 and 34: Upland rice weeds / CYPERACEAE (sed
Page 35 and 36: Upland rice weeds / POACEAE (grass
Page 41 and 42: Upland rice weeds / PORTULACACEAE (
Page 43 and 44: Deepwater weeds / CONVOLVULACEAE (m
Page 45 and 46: Wetland tillage is common in most t
Page 47 and 48: leaf size), with the resultant shad
Page 49 and 50: Economics of control The economic b
Page 51 and 52: Chapter 4 Principles of herbicide u
Page 53 and 54: Preemergence herbicide application
Page 55 and 56: and behavior in the crop environmen
Page 57 and 58: Table 4.1. Meanings of signal words
Page 59 and 60: 4.3 Controlled-droplet applicators
Page 61 and 62: amount after spraying is 8 liters,
Page 63 and 64: The decision to spray should be mad
Page 65: farmers, however, should wear cloth
Page 69 and 70: Propanil can be used at 3-4 kg ai/h
Page 71 and 72: Thiocarbamates Thiocarbamates are a
Page 73 and 74: Quinclorac. Quinclorac is a chino-
Page 75 and 76: Planting method Transplanting into
Page 77 and 78: Direct seeded on puddled soil In di
Page 79 and 80: Table 6.2. Herbicides suitable for
Page 81 and 82: 6.4 Rice growth stages when herbici
Page 83 and 84: Fertilizer Incorporating N and P fe
Page 85 and 86: Nurseries Seedling nurseries should
Page 87 and 88: Land preparation Leveling the puddl
Page 89 and 90: Land preparation Land preparation s
Page 91 and 92: Chapter 8 Weed control in upland ri
Page 93 and 94: Hand weeding The weed-free period r
Page 95 and 96: Chapter 9 Weed control in deepwater
Page 97 and 98: Hand weeding Hand weeding is the mo
Page 99 and 100: Chapter 10 Management of some diffi
Page 101 and 102: Wild rices The important wild rices
Page 103 and 104: Herbicides For effective control of
Page 105 and 106: IRRI-International Rice Research In
Page 107 and 108: B. Conversion table for granular fo
Page 109 and 110: Index A Absorption of herbicide, 50
Page 111 and 112: in deepwater and floating rice, 96
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