1. WEEDS of RICE & their MANAGEMENT
Part 1: Understanding the PalayCheck System

2. What are weeds? Rice in bermuda grass landscape
Bermuda grass in a corn field
Corn in a rice field
Weeds grow where they are not wanted.
Not all of them are good; not all are bad.
Ask the class which of the plants mentioned are weeds? Then process ideas by saying that weeds are plants that grow where they are not wanted.

3. Top 10 common rice weeds Antena, Telebisyon (Echinochloa crusgalli)
Antena, Telebisyon (Echinochloa glaberescens)
Palay maya (Leptochloa chinensis)
Pagpagay (Digitaria sp.)
Trigo (Ischaemum rugosum)

4. Top 10 common rice weeds 6. Sili-silihan (Sphenoclea zeylanica)
7. Malapako (Ludwigia octovalvis)
8. Gabi-gabihan (Monochoria vaginalis )
9. Payong-payungan (Cyperus iria)
10. Ubod-ubod (Fimbristylis miliacea)

5. Characteristics of rice weeds
They are persistent.
Prolific seed producers
Can perpetuate their own species
Efficient seed dispersal
Extensive seed reserve in soil (seed bank)
Dormancy

6. Weed seed reserve (seed bank)
In 1 m2 area at 0-15 cm depth =
80,407 weeds emerged
804,070,000 viable weed seeds per ha.
(Vega and Sierra, 1970)
Weed seeds planted in 1 m2 at 0-15 cm depth=
497,051 weeds emerged (Kim, 1986)
Study on 25-year viability of buried weed and crop seeds:
Highest % germination observed was in weed seeds and none on crops (Pancho, n.d.)

7. Weeds: Prolific seed producers
Weed species
Seeds / plant
Echinochloa crus-galli (antena)
40,000
Amaranthus spinosus
196,000
Bidens pilosa
6,000
Commelina benghalensis
25,000
Dactyloctenium aegyptium
66,000
Eleusine indica
41,200
Portulaca oleracea
10,000

8. Weeds are classified according to…
Life cycle
Annuals – complete life cycle in less than a year
Perennials –complete life cycle more than a year
Habitat
Upland –favor well-drained soil
Lowland –favor moist to saturated soil
Morphology
Broadleaf
Sedge
Grass
Ask the class which of the plants mentioned are weeds? Then process ideas by saying that weeds are plants that grow where they are not wanted.

9. Broadleaves Leaves are generally broad and flat
Usually dominate transplanted rice
Show real specimen and allow participants to observe. Ask them about their observations then process.

10. Sedges Triangular stems
Not as competitive as grasses but can reduce yields if they become dense
Show real specimen and allow participants to observe. Ask them about their observations then process.

11. Grasses Similar characteristics with rice
They don’t have ligules and/or auricles
Dominant and competitive
Example: Antena
Show real specimen and allow participants to observe. Ask them about their observations then process. L A

12. Why manage weeds? Compete with crops causing yield reduction
Harbor pest/alternate hosts
Affect quality of agricultural produce
Causes trouble in irrigation systems and roads
Ask the participants why farmers need to manage weeds?

13. Crop-Weed Competition
Interference – describes all effects caused by one plant on another plant (weeds to rice)
Competition
What will happen?

14. Crop-Weed Competition
Interference – all effects caused by one plant on another plant
Allelopathy – emission of chemicals by one plant that could affect the growth of another plant

15. Crop-Weed Competition
Critical period of competition – time when weeds are most likely to reduce crop growth and yield
1/3 -1/2 of the life cycle of the crop
Control at seedling stage to the closure of the canopy
Yield reduction: 40-96% across rice ecosystems

16. Crop-Weed Competition
Critical threshold level – maximum density of weeds which the crop can tolerate without causing significant yield/biomass reductions
Rice can tolerate below 25 weeds/m2 (Cyperus sp.)
(Echinochloa sp. or grasses) at 5/m2 caused 9% yield reduction

17. Current scenario
Shifts in crop establishment (transplanted to direct seeded) gave way for complex weed problems
Dominant weed species still prevalent but there are emerging important weeds like weedy rice.

18. Emerging weeds Ischaemum rugosum (saramollagrass)
Leptochloa chinensis (sprangletop)
Cyperus rotundus (purple nutsedge)
Hydrolea zeylanica
Weedy Rice (red rice)

19. Emerging important weed
Weedy Rice
More popularly known as RED RICE
Shattering, low tillering, taller than cultivated rice, long panicle, early growth and maturity
With or without awn, brown to reddish grains
Difficult to control

20. Cultivated rice varieties Weedy rice biotypes of Iloilo
[Screenhouse Experiment]
Cultivated rice varieties
Weedy rice biotypes of Iloilo

21. What farmers say and do Weeds ranked 1st or 2nd as problems
Weeds bring about concerns on costs, health, and environment (costs of herbicides)
Farmers generally use cultivation, water management, and herbicides to manage weeds depending on effectiveness and ease of use
Water management and availability is a concern

22. What farmers say and do Farmers generally use high seeding rates
Sources of weeds in paddies are outside their control
Farmers don’t know that some practices (e.g. repeated herbicide use) could cause weed shifts

23. What farmers say and do
Herbicides are the first line of defense and preferred method of weed control in DS rice (Butachlor/pretilachlor use is still common)
Herbicide application is dependent on weed density and observations on field monitoring (if less water, more herbicides)
Farmers are doubtful about herbicide efficacy (possible resistance?)

24. Herbicide Resistance (HR)
Inherited ability of a weed biotype to survive herbicide application to which the original population was susceptible
“superweeds”
Worlwide: 175 species in over 280,000 fields
Rice weeds: 30 species in all rice-growing areas
After a time

25. Herbicide resistance integrated approach is needed
complex due to difficulty in predicting which weed will become resistant and when will this situation happen
cannot be controlled by man but could be delayed
directly linked to herbicide program used, weed species present, and crop management practices employed
integrated approach is needed

26. Integrated Weed Management
Crop
Rotation
Land Preparation
Fallow
Management
Integrated Weed Management
Land Levelling
Clean
Equipment
Good Seed
Rogue
Weeds
Clean Nurseries
and Seedlings
Nutrient
Management
is the solution.
Variety
Selection
Direct Weed
Control
Clean Bunds
and Canals
Water
Management
Crop Stand
Crop Establishment
Method

27. Land Preparation Key IWM Components Follow PalayCheck recommendations
Clean bunds and nurseries
Plow under weeds and stubbles cm deep 3-4 weeks before transplanting or direct-seeding
Stale seedbed technique -plowing and repeated harrowing to effectively reduce weed seeds and tubers in the soil

28. Water management Key IWM Components Follow PalayCheck recommendations
Practice controlled or intermittent irrigation
At 7-10 DAT or 14 DAS, 2-5 cm water is introduced into paddy, water is allowed to drain and seep through the soil, leaving field saturated for 5-7 days
Another irrigation is done after, and repeated up to the 3rd cycle of irrigation which coincides with maximum tillering and panicle initiation

29. Weed Control Action Indicator (WCAI)
Key IWM Components
Weed Control Action Indicator (WCAI)
- decision making tool to aid farmers in deciding if another herbicide application or handweeding is needed based on weed cover and relative weed height

30. Weed Control Action Indicator (WCAI)
RWH = Ave height of weeds (regardless of spp. and growth stage)
Ave height of the crop
WC= aggregate weed cover by weeds as percent of total area
Control Options:
Control action is needed at 15 DAS if RWH >20% and WC>5%
Control action is needed at 30 DAS and 45 DAS if RWH >30% and WC >5%

31. Biological control After WCAI, decide: Ideal for small areas
Use of natural enemies (ducks, fish, etc.) to suppress growth or reduce weed population

32. Chemical control After WCAI, decide:
Choose most appropriate for weed problem; check herbicide claims
Butachlor+propanil effective, able to control emerged weeds, cheaper
One pre-emergence herbicide is usually recommended for direct-seeded rice

33. Other strategies
Use quality seeds to prevent using seeds mixed with weed seeds
Low seeding rate (40 kg/ha) can also help, but not higher
Drumseeder for better weeding in between rows
Ask ATs or experts to know which seeds have undergone technology demonstration or adaptability trial

34. Weed control action indicator (WCAI)
Chemical control
Good land preparation
Weed control action indicator (WCAI)
No significant yield loss due to weeds.
Biological control
Water management
IWM Components

35. What farmers say about IWM
[Taken from Nueva Ecija and Iloilo provinces after two years of IWM]
Better weed control
Increased yields
Higher profits
Local farmer groups adopted

36. Mrs. Leylani Juliano, Mrs. Anita Antonio, Mr. Edwin Martin
CREDITS
Instructional presentation designer: Ms. Ella Lois Bestil
Sources of technical content/reviewers of presentation:
Mrs. Leylani Juliano, Mrs. Anita Antonio, Mr. Edwin Martin
Note:
Adapted from a powerpoint presentation developed by: Mr. Glenn Ilar, Mrs. Marissa Bautista
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& build upon this presentation non-commercially. However, always use with acknowledgment.
Unless otherwise stated, the names listed are PhilRice staffers.
Produced in 2011.
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