WEEDS of RICE & their MANAGEMENT

1. WEEDS of RICE & their MANAGEMENT Part1: 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.

3. Top 10 common rice weeds • Antena, Telebisyon(Echinochloacrusgalli) • Antena, Telebisyon(Echinochloaglaberescens) • Palaymaya(Leptochloachinensis) • Pagpagay(Digitaria sp.) • Trigo(Ischaemumrugosum)

4. Top 10 common rice weeds 6. Sili-silihan(Sphenocleazeylanica) 7. Malapako(Ludwigiaoctovalvis) 8. Gabi-gabihan (Monochoriavaginalis ) 9. Payong-payungan(Cyperusiria) 10. Ubod-ubod(Fimbristylismiliacea)

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

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

9. Broadleaves • Leaves are generally broad and flat • Usually dominate transplanted rice

10. Sedges • Triangular stems • Not as competitive as grasses but can reduce yields if they become dense

11. Grasses • Similar characteristics with rice • They don’t have ligules and/or auricles • Dominant and competitive • Example: Antena 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

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

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

21. What farmers say and do • Weeds ranked 1st or 2ndas 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 • complexdue 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 LandPreparation Fallow Management LandLevelling 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. Key IWM Components Land Preparation • Follow PalayCheck recommendations • Clean bunds and nurseries • Plow under weeds and stubbles 10-15 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. Key IWM Components Water management • 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 - 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. After WCAI, decide: Biological control • Ideal for small areas • Use of natural enemies (ducks, fish, etc.) to suppress growth or reduce weed population

32. After WCAI, decide: Chemical control • 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. No significant yield loss due to weeds. Biological control Chemical control Good land preparation Water management Weed control action indicator (WCAI) 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. CREDITS Instructional presentation designer:Ms. Ella Lois Bestil Sources of technical content/reviewers of presentation: Mrs. LeylaniJuliano, Mrs. Anita Antonio, Mr. Edwin Martin Note: Adapted from a powerpoint presentation developed by:Mr. Glenn Ilar, Mrs. Marissa Bautista You may use, remix, tweak, For more information, visit: & build upon this presentation non-commercially. However, alwaysuse with acknowledgment. Unless otherwise stated, the names listed are PhilRice staffers. Produced in 2011. Text: 0920-911-1398