Low-external Input Rice Production - Chapter 3 - Pest/Weed Control

Major rice insect pests, their natural enemies and economic threshold levels

There are about 800 species of insects in the ricefields. Of these, about 100 species attack rice and the rest are all friendly insects. Out of the 100 pest species, only 7 are major pests in Philippine rice farms.

There is a new strategy of controlling these major pests in rice. This method is based on ecologically sound practices in reducing pest populations and is called Integrated Pest Management (IPM). IPM is a pest management system that, in the context of the associated environment and the population dynamics of the pest species, utilizes all suitable techniques and methods. This is done in a manner that maintains the pest population at levels below those causing economic injury.

By thoroughly understanding a given crop, its pests and other elements of the agroecosystem, IPM tries to maximize natural pest control factors and minimize the need for outside measures like chemical pesticides. IPM explicitly means:

· use of chemicals based on need

· utilization of economic threshold levels

· use of resistant varieties

· knowledge of cultural practices

· enhancement of biological agents

IPM can help farmers increase profits and reduce health hazards and pest outbreaks by maintaining the pest-natural enemy relationship in the field. In maintaining such relationships, insecticide use is "need-based". In practice, the farmer has to know the Economic Threshold Level (ETL) for a particular pest. ETL refers to the pest population level where control measures are needed.

The information in this paper is designed as a quick guide for identifying major pests of rice and their natural enemies and to help determine the economic threshold level for each pest.

RICE BUG (L. oratorius)

· ECONOMIC THRESHOLD LEVEL (ETL)

10 bugs in 20 hills

· SAMPLING METHOD

Sample early in the morning or late in the afternoon from 20 randomly chosen hills from flowering to hard dough stage. Sample twice a week.

· INSECTICIDE

Monocrotophos EC
Nuvacron USC

· DOSAGE (kg ai/ha)

0.4 each

· METHOD OF APPLICATION

Spray in the morning

NATURAL ENEMIES

Parasites

Predators

Pest

Host plants

Susceptible stage

Symptoms

WHORL MAGGOT (Hydrellia philippina)

· ECONOMIC THRESHOLD LEVEL (ETL)

a. 2 eggs/hill
b. 5% whorl maggot - damaged leaves + 5% leaves damaged by chewing insects at 5 DAT

· SAMPLING METHOD

20 random hills/ricefield at 5 and 8 days after transplanting

· INSECTICIDE

Monocrotophos EC

· DOSAGE (kg ai/ha)

0.4

· METHOD OF APPLICATION

Spray when threshold is reached

NATURAL ENEMIES

Parasites

Predators

Pest

Host plants

Susceptible stage

Symptoms

STEMBORER (Scirpophaga incertulas)

· ECONOMIC THRESHOLD LEVEL (ETL)

75 deadhearts in 20 hills or 2 adults or 2 egg-masses/m²

· SAMPLING METHOD

20 random hills/ricefield from tillering to panicle initiation stage

· INSECTICIDE

Chlorpyrifos EC

· DOSAGE (kg al/ha)

0.4

· METHOD OF APPLICATION

Spray when larva hatch

· DAMAGE

Larvae feed on leaves and leaf sheaths

NATURAL ENEMIES

Parasites

Predators

Pest

Host plants

Susceptible stage

Symptoms

GREEN LEAFHOPPER (N. Virescens)

· ECONOMIC THRESHOLD LEVEL (ETL)

1 hooper/tiller

· SAMPLING METHOD

20 random hills/ricefield 1 to 10 weeks after transplanting

· INSECTICIDE

BPMC WP

· DOSAGE (kg al/ha)

0.4

· METHOD OF APPLICATION

Spray when older nymphs are present

· DAMAGE

Drief leaf tips and leaf margins orange discoloration

NATURAL ENEMIES

Parasites

Predators

Pest

Host plants

Susceptible stage

Symptoms

CASEWORM (Nymphula depunctalis)

· ECONOMIC THRESHOLD LEVEL (ETL)

50% of the leaves are damaged. Combine the damage caused by other leaffeeding pests with that of caseworm.

· SAMPLING METHOD

20 random hills/ricefield at 2 to 6 weeks after transplanting

· INSECTICIDE

Carbaryl

· DOSAGE (kg al/ha)

0.5

· METHOD OF APPLICATION

Spot treatment

NATURAL ENEMIES

Parasites

Predators

Pest

Host plants

Susceptible stage

Symptoms

BROWN PLANTHOPPER (N. Lugens)

· ECONOMIC THRESHOLD LEVEL (ETL)

1 hopper/tiller

· SAMPLING METHOD

20 random hills/ricefield 2 to 10 weeks after transplanting

· INSECTICIDE

BPMC WP
Buprofesin WP

· DOSAGE (kg al/ha)

0.4 each

· METHOD OF APPLICATION

Spray when other nymphs are present.

NATURAL ENEMIES

Parasites

Predators

Pest

Host plants

Susceptible stage

Symptoms

LEAFFOLDER (Cnaphalocrosis medinalis)

· ECONOMIC THRESHOLD

LEVEL (ETL)

a. 15% of leaves are damaged before Panicle initiation.
b. 5% of leaves are damaged after panicle initiation stage.

· SAMPLING METHOD

20 random hills/ricefield at 2 to 6 weeks after transplanting watch for months

· INSECTICIDE

Monocrotophos EC

· DOSAGE (kg al/ha)

0.4

· METHOD OF APPLICATION

Spot treatment

Parasites

Predators

Pest

Host plants

Susceptible stage

Symptoms

CULTURAL MANAGEMENT PRACTICES FOR PEST CONTROL IN RICE

A cultural practice is any farm operation that will make the environment less favorable for pests to develop or multiply but which still favors rice production.

Rice ecosystems are fundamentally very stable systems but can be disrupted by inputs such as pesticides and inorganic fertilizers. There are few key pests in rice. Therefore, cultural practices, when used together with pest-resistant rice varieties, will provide adequate defense against most rice insects and diseases.

Cultural practices for rice pest management include the following:

SYNCHRONIZED PLANTING:

Since the massive introduction of rice intensification programs in the 1960s when shortduration modern rice varieties were introduced, there was room for planting rice three times a year or even five times in two years. Due to socioeconomic factors (labor shortages, market prices), staggered rice planting (i.e., non-synchronized) became unavoidable. This situation is ideal for continuous development of pests. Staggered planting with short idle intervals stimulates the build-up of BPH populations and may result in serious outbreaks of the rice dwarf virus, BPH, RTV (transmitted by GLH) and WBPH. Rice gall midge and the rice stink bug also became more serious in Indonesia because of staggered planting.

In staggered rice patterns, the generations of the pests are overlapping. There is no clear-cut fallow period (i.e., for soil preparation) between the two rice seasons. In this situation, any rice pest will build up continuously. On the other hand, in the synchronized patterns, there is a fallow period between the two rice seasons for about one month. This is the time for simultaneous soil preparation (irrigating field, deep plowing under the stubbles [ratoons] and sanitation). Most rice pests will then be destroyed.

CROP ROTATION AND INTERCROPPING (DIVERSITY):

Rotating rice with non-rice crops helps to break up the life cycle of both insects and pathogens. Continuous planting with no time for the soil to rest not only depletes its fertility but also enables pests to survive better. Intercropping (planting a second crop between rice, as in upland areas) will also reduce the spread of insects and diseases especially if the crop is very different in architecture from rice. During the growing of short maturity non-rice crops, there is no chance for rice pests to develop and they are gradually brought under control in areas where synchrony and crop rotation are strictly followed.

SANITATION:

Sanitation aims to remove all breeding or hibernating sites and sources of food of the insect or survival sites for the pathogen.

The survival stages of the rice stemborer, BPH and GLH in the ratoons are all destroyed by plowing under or burning stubble, ratoons and straw. Grasses on the dikes and surrounding areas may also be removed or cut short to disrupt the life cycles of stink bugs and the green leafhopper. In rice, intensive cultivation and wet weather do not permit drying and burning of the straw.

Straw burning is not always advisable because it destroys most of the arthropod populations that play an important role in decomposing plant remains. It also eliminates the available nitrogen in the plant remains. Nutrient loss by leaching is also much higher after burning.

When the rice plant is somewhat older, weed sanitation in the field is, of course, needed. Weedy fields may make the microclimate more favorable for insect pests than clean fields. Clean weeding may not be always advantageous for certain species of natural enemies because there may not be any shelter left for them. For example, spiders require some shelter to survive during the period between two rice crops and this may be provided by having weeds on the bunds. With respect to BPH, the sanitation program may be limited to only destroying the rice stubbles and ratoons because other grasses are not real host plants for the insect.

Fish and ducks have been successfully used in several countries to control sheath blight and insects/weeds, respectively.

FERTILIZER MANAGEMENT:

The population of many pests, such as certain aphid species, BPH, spider mites, blast, bacterial blight and sheath blight are significantly more abundant with increased nitrogen levels. The rice stemborer Chilo suppressalis and the gall midge have also been found to be significantly more abundant in fields treated with high rates of nitrogen. High nitrogen causes the rice plant canopy to become very thick. Although high nitrogen generally favors pests, it is not advisable to use fertilizers at lower than the recommended dosage, i.e., to sacrifice high yield for expected pest control. BPHresistant varieties have commonly been selected in high fertilizer environments and integrating such varieties with synchrony, rotation and other control tactics should achieve both high yield and BPH control. Unbalanced nutrients favor some diseases, e.g., low phosphate levels result in higher levels of brown spot disease.

WATER MANAGEMENT:

Water may influence the abundance of some pest species. BPH problems are known to increase when irrigated rice cultivation replaced dry rice cultivation. In Japan, insects are abundant in the humid lowlands and rice fields with standing water have been found to encourage the multiplication of BPH. In Indonesia, BPH prefers irrigated rice to upland rice. The problems are more serious in plots continuously flooded or with standing water. The green leafhopper Nephotettix virescens also seems to favor fields with stagnant water and specially those with intermittent rain as well.

Good water management should therefore help control certain rice pests. Draining the fields for about two days suppressed BPH outbreaks in Malaysia. In the Philippines, farmers withhold irrigation and plants are spread apart every few rows to help dry out the fields for BPH control. To effectively control the rice water weevil, fields are drained at the proper time and irrigation is stopped for a predetermined period. Draining the water level in rice fields destroys the eggs of BPH laid in the leaf sheaths. Deep irrigation in the morning followed by the addition of a certain amount of kerosene to water gives good control of BPH. In Indonesia, it is a common practice to raise the irrigation water level to control BPH; sand or sawdust containing 0.25 l kerosene for every 100 m is then broadcast on the raised water level and the plants are shaken.

PLANT SPACING:

The spacing of rice plants in a field is believed to influence the abundance of certain rice pests. Close spacing may rapidly increase the BPH population. Close spacing results in a more shaded, cooler and more humid microenvironment, which makes it less favorable for the development of the natural enemies of BPH. Both GLH and WBPH may also increase in closely spaced rice plants. In direct-seeded rice where spacing is much closer than transplanted rice, these pests may become more severe. Close spacing also intensifies the severity of rice diseases such as sheath blight.

Spacing should be such that it allows some sunshine to penetrate into the basal portions of the rice plants. Solar and ultraviolet radiation restrain BPH increase. More air flow also makes the micro environment less humid and may also help the natural enemies develop. The distance between rice plants depends on the variety. Modern rice varieties with high tillering capacity may be planted further apart than those with less or moderate tillering capacity. Common spacing between rice plants is 20 x 20 cm or 25 x 20 cm.

KEY:

BPH -- Brown Planthopper
GLH -- Green Leafhopper
WBPH -- White-backed Planthopper
SB -- Stemborer
ShB -- Sheath Blight

Pesticide poisoning

The most common routes of pesticide poisoning are:

Breathing into the lungs

Skin contact

1. Skin contact -- by spilling or splashing pesticides on clothes or directly on skin. Dry materials can also be absorbed.

Wrists, armpits, neck, groin and feet are areas of the body that absorb pesticides more quickly than others. Cuts and scrapes also allow more pesticide to enter more easily.

2. Breathing into the lungs -- Dusts, sprays or fumes can enter the system by being breathed into the lungs. Poor ventilation indoor allows greater exposure.

3. Oral/Swallowing -- Pesticides are absorbed well through the mouth, stomach and intestine. Pesticides can be accidentally taken in by people who eat or smoke while applying pesticides or when improperly stored in food containers.

4. Eye contact -- Pesticides absorption and local damage can occur with eye contamination.

FIRST AID:

In Case of Skin Contact with Pesticide

1. Take off any contaminated clothing.

2. Wash skin with lots of soap and water. 

Do Not Touch the Pesticide Again or Handle Contaminated Clothing.

In Case of Eye Contact with Pesticide

1. Hold eyelids open and wash with gentle stream of cool, clean, free-flowing water.

2. If with contact lenses, remove them,

3. Continue rinsing eyes for at least 15 minutes.

4. See physician. 

In Case of Breathing in (Inhalation of) a Pesticide

1. Remove person from exposure to pesticide.

2. If conscious, place person in a sitting position with head and shoulders elevated.

3. If unconscious, give artificial respiration and call for medical assistance. 

In Case of Oral Contact or Swallowing a Pesticide

A. Induction of vomiting only if

1. patient is conscious

2. pesticide is moderately to extremely toxic. 

Induce vomiting using the following procedure

1. Sit or stand-up patient.

2. Give 1 to 2 glasses of water.

3. Tickle back of the patient's throat using a bland instrument (spoon handle). Use 2 fingers of the other hand to force the patient's cheek between his teeth.

4. Return patient to lying position-turned towards the left, neck extended. 

General Management

1. Keep patient calm and at rest.

2. Keep close observation of breathing and state of consciousness.

3. Place patient in proper position.

3.1 Place patient on his left side with head lower than the rest of the body by 15 to 30 degrees.

3.2 Keep patient comfortable but not hot and sweating or cold and chilly. Maintain a normal temperature. 

BREATHING:

If Breathing Stops

1. Pull chin forward to avoid tongue dropping to back of throat.

2. Roll patient on his back, keeping chin pulled forward and head back. Remove any vomitus or secretions from the mouth using a clean cloth.

3. Pinch patient's nose and blow into his mouth through a piece of cloth or handkerchief following your normal breathing rate. Alternatively, close his mouth and blow into his nose.

Make sure patient's chest is expanding with each flow. Continue until normal breathing takes place.

If Convulsion Occurs

· Insert padded gag between the teeth to prevent the patient from biting his tongue.

· Prevent further injury by placing a cushion or pad under his head and prevent him from falling. 

Tips to Induce Vomiting

4 egg whites for children 

8 egg whites for adults.

Efficient and safe use of pesticides

Pesticides are still widely used pest control agents against a variety of pests in rice. There are specific pesticide groups which control specific pest problems. There are insecticides to control insects, herbicides for weeds, fungicides for fungi, rodenticides for rodents, etc.

Despite their popularity, improper and careless usage of pesticides has resulted to undesirable effects on people, livestock, non-target organisms and the environment in the rice field. Accidents have also resulted during their use, transport and storage.

To avoid these adverse effects, the following tips should be followed in using pesticides:

THINGS TO REMEMBER BEFORE MIXING:

1. Read the label carefully. The label contains necessary information relevant on how the product must be used and what to do in case of poisoning.

Read the label carefully

THINGS TO REMEMBER DURING MIXING:

1. Wear gloves, safety glasses and/or masks/respirators and mix pesticides outside the house.

2. When mixing liquid concentrates with water, it is always advisable to place pesticide into the sprayer tank first before mixing with water.

Caution: If acid is used, it must be poured into the water during the preparation of the solution. Do not pour water into the acid because an explosion could result.

3. Immediately after mixing, close pesticide container tightly and keep it in a safe area not easily reached by small children.

THINGS TO REMEMBER DURING APPLICATION: 

1. Never smoke or eat during the spraying operation.

2. Wear protective clothing, such as long-sleeved shirts, pants and respirators when spraying.

Never smoke or eat during the spraying operation

3. Spray pesticide diagonal to the direction of the wind not against it.

4. Do not spray during windy days.

5. Limit spray application to 3 to 4 hours only.

Do not spray during windy days

THINGS TO REMEMBER AFTER APPLICATION:

1. Wash all exposed body parts twice with soap and water; a bath would be more advisable. An alkaline soap (Perla) should be used in taking a bath, stay away from sources of drinking water.

2. Wash all contaminated clothings thoroughly with soap and plenty of water. Separate them from ordinary family laundry.

3. Do not dispose excess pesticides nor wash the sprayers in waterways (irrigation, canals, streams, rivers). Do not burn containers.

4. Dispose empty pesticide containers by burying them in suitable pits that prevent pesticide leakage into the groundwater or other bodies of water. Never burn paper packages and plastics.

Wash all exposed body parts

Low-cost control methods for golden snails (kuhol)

INTRODUCTION:

The golden snail, commonly known as kuhol (Pomacea caniculata), was originally introduced in the Philippines as a source of protein for the family. However, it has become one of the most destructive pests of lowland rice. Kuhol usually feeds on the succulent parts of the rice plant, causing stunted growth and eventual destruction of the rice plant.

Kuhol belongs to the snail family (Pelidae) that lives only in or close to fresh water in swamps and rivers in South America. When kuhol was commercially introduced into the Philippines, its possible escape was not anticipated. The natural predators of the kuhol in South America do not exist in the Philippines. Therefore, there has been no natural check against growth and reproduction.

Between 25-500 eggs, depending on breeder size, are laid in oval-shaped clusters. Eggs are laid early in the morning and evening on standing crops, along dikes and on any object sticking up above the water surface. One kuhol can produce up to 200-300 eggs/week or 1,000-1,200 eggs/month, with 80% hatchability.

Kuhol can breathe underwater like fish or in the open air. When ricefields are drained, kuhol burrows into the moist mud, digging deeper as the dry season progresses. It can sleep hidden in dry soil for over 6 months then awaken overnight when the soil is flooded.

The kuhol is a voracious plant eater. It feeds on a wide range of plants such as Azolla, duck weed, water hyacinth, rice seedlings and other succulent leafy plants and vegetables. In irrigated ricefields, the rice is most vulnerable to the kuhol during the first 2 weeks of establishment for transplanted rice and during the first 4 weeks for direct-seeded rice.

To save the rice plant from this pest, farmers tend to use commercial/chemical snail killers which are not only hazardous to human, fish and animal health, but also alter the environment and add to the farmers' expenses. Some of the chemicals used to control snails have recently been banned. (Integrated Kuhol Management, DA/FAD, 1989).

DIFFERENT CONTROL STRATEGIES FOR KUHOL:

A. BEFORE TRANSPLANTING RICE

1. Several weeks before transplanting, allow ducks to roam around the paddy field. Ducks will feed on the eggs and smaller snails.

Allow ducks to roam around the paddy field

2. Hand-pick all the larger snails not eaten by the ducks. Crush them with a mortar end pestle and feed them to the ducks. The snail meet end shells are excellent sources of protein and calcium for laying ducks.

Hand-pick all the larger snails

B. AFTER TRANSPLANTING RICE

1. Install a wire mesh screen in the water runways to prevent the eggs and adult snails from entering the paddy field during irrigation.*

Install a wire mesh screen

2. Maintain shallow water (2-3 cm) during the first 15 days after transplanting to minimize damage. One month after transplanting, allow ducks to roam the paddy field and consume the remaining eggs and snails.

Maintain shallow water

3. Construct depressed strips in the paddy where wafer will be retained when the field is drained. The snails will migrate and collect in these lateral depressions and can then be collected.

Construct depressed strips

C. PLACEMENT OF STAKES

1. Snails prefer to climb above the water level to lay their eggs.

2. Collect stakes 0.5-0.75 m long and 2 cm in diameter. Arrange them 0.5 m from the rice paddy dikes, 2-4 m apart The kuhol will lay their eggs on these stakes.

Collect stakes 0.5-0.75 m long

3. Gather the eggs, crush them and feed them to ducks, chickens and pigs.

Gather the eggs and feed them to ducks, chickens and pigs

D. RICE HULL

1. Separate coarse hulls from the fine ones with a sieve.

2. After a rain, evenly spread a 1-2 cm layer of rice hulls in the ricefield. The hulls will affect the digestive system of the snails, causing them to starve and die. Three or four days after spreading the hulls, collect the dead snails.

Separate hulls

Spread hulls

E. EAT KUHOL

The kuhol first introduced as a high protein food for human consumption, has a high nutritive value. A bite-size snail contains the following:

Food energy	83.0 calories
Protein	12.2 gm
Fat	0.4 gm
Carbohydrates	5.5 gm
Ash	3.2
Phosphorous	61.0 mg
Sodium	0.4 mg
Potassium	17.0 mg
Riboflavin	12.0 mg
Niacin	1.8 mg

The kuhol also contains vitamin C, zinc, copper, manganese, magnesium and iodine. (Integrated Kuhol Management, DA/FAD, 1989).

RECIPES:

TORTANG KUHOL

1 saucer cooked ground kuhol

1 tbsp. chopped onion leaves

1 tbsp. chopped tomatoes

1 tbsp. chopped onions

1 tbsp. crushed garlic

2 tbsp. cooking oil

1/2 tsp. salt

1 whole egg beaten

1 tbsp. all-purpose flour 

Put salt on kuhol then saute with garlic, onions and tomatoes. Remove from pan and mix sauted ingredients with beaten egg. Coat the mixture with flour and fry. Serve hot.

GINATAANG KUHOL

2 saucers cooked kuhol shelled

2 cups coconut milk

1 tbsp. crushed garlic

1 tbsp. chopped onions

1 tbsp. chopped tomatoes

1 pc. ginger

2 tbsp. achuete

2 tbsp. cooking oil 

Saute garlic, ginger, onions and tomatoes in hot cooking oil. Add cooked kuhol to sauted mixture. Stir in coconut milk and achuete. Boil until oil comes out. Serve hot.

Note: Snails should not be eaten by humans or livestock including ducks if collected from rice paddies which have been sprayed with chemicals.

Easy ''do-it-yourself'' snail collector

Golden snail (Pomacea caniculata), a serious rice pest, can now be locally controlled at a bargain by using a do-it-yourself method of scoop and scrape snail collecting device called salaan collector.

Instead of bending or- stooping hundred of times to collect snails, the multipurpose snail picker, with its long handle, can now reach distant crawling snails and clusters of eggs, without tiresome bending.

With this simple and inexpensive picker, one can collect and dispatch snails by the thousands while they are still in egg clusters. This device, with its scorpion-shaped plate attachment, enables one to scrape eggs from walls and host plants without damaging them.

A. Snail collecting

B. Scraping eggs on walls

C. Scraping eggs on plants

HOW TO MAKE A "SALAAN" SNAIL COLLECTOR

Materials Needed:

1 pc 1 in x 1 in x 6 ft wood or bamboo pole

1 pc 2 1/2 in x 3 1/2 in gauge 20 or 22 galvanized sheet (This is roof gutter sheet gauge)

1 pc 1-2 mm mesh coconut strainer (salaan)

3 pcs 1/8 in x 3/4 in length self tapping screw

3 pcs 1/8 in x 1/2 in cap screw 

Procedure:

1. Paste the pattern below onto gauge 22 sheet metal.

2. Cut sheet metal with snip.

3. Drill hole with 1/8 in diameter puncher.

4. Bend metal to shape.

5. Plane sharp edges of 1 in x 1 in x 6 ft wood to make round for greater comfort.

6. Screw salaan with wood handle.

7. Assemble finished scorpion-shaped plate into salaan.

Note: For the scorpion plate, tin can materials may be used although life span of the plate

will be shorter.

How to make a "salaan" snail collector

Makabuhay, a natural pesticide for lowland rice

RESEARCH FINDINGS SHOW THAT:

· The application of chopped Makabahay is as effective as the use of chemical pesticides in reducing deadhearts and white heads due to striped stemborer attack and in reducing the green and brown leafhopper populations.

· The aqueous extract of Makabuhay (50 9/125 ml water) is toxic to green leafhopper when applied to rice seedlings by root-soaking 24 hrs before transplanting or by spraying it to the seedlings. These treatments are comparable to root-soaking in chemical pesticides.

· The submerged chopped Makabuhay stem is toxic to the rice green leafhopper.

· The combination of aqueous Makabuhay extract root soaking and broadcasting of chopped vine is as effective as the recommended chemical pesticide seedling treatment followed by spraying with chemical pesticides 25 days after transplanting.

· Broadcasting of ground Makabuhay vine (0.25 kg/sq.m) on rice seedbed 10 days after sowing is as effective as broadcasting with chemical pesticides.

Sc. Name: Tinospora rumphii Local Names: Makabuhay (Tag., Bik., Ilk.); Manunggal (Ilonggo); Abukay (Ilk.). Palayawan (Waray) 

PREPARATION AND USAGE:

Root soaking

1. Chop the vine into small pieces and pound it with the use of a mortar and pestle.

2. Add 1 liter water for every 200 9 crushed Makabuhay vine. Thoroughly stir the mixture, then soak the rice seedlings overnight before transplanting.

Ten to 15 kg of chopped vine are sufficient to treat seedlings needed to plant 1 hectare. 

IMMERSION 

1. Cut the Makabuhay vines to approximately 1 ft lengths.

2. Tie both ends of the cut vines onto bamboo stakes as shown in the diagram.

3. Drive the stakes into the ground along water inlets.

4. You can also put 1 liter chopped Makabuhay vines inside a fish net bag and place the bag along the wafer inlets. Replace the Makabuhay every 2 weeks. Check the bag regularly for accumulation of mud or other debris.

Tie both ends of the cut vines

Put 1 liter chopped Makabuhay vines inside a fish net bag

Low-cost insect trap

The light trap is an inexpensive tool used in monitoring insect pest populations and helping reduce their numbers. Light traps were used by many farmers before the introduction of modern rice varieties when chemical pesticides were still not generally available. The light trap can also be used in fishponds or rice- fish paddies to attract insects upon which the fish can feed. As pesticides became more common and were used to prevent damage to crop, light traps became less important.

Today, however, chemical pesticides are recommended only as a last resort because of their high environmental, health and economic costs. Therefore, pest management practices today require a greater knowledge in pest identification and a system of monitoring insect populations.

LANTERN DESIGNS:

Lanterns can easily be made from locally available materials like empty glass jars (mayonnaise jars) as illustrated below. The lantern costs from P50 (design A) to P15 (design C). It uses about P1 to P2 worth of kerosene per night and produces a bright white light.

Lantern designs

LOCATING THE INSECT TRAP:

The lantern is attached to a frame (tripod) of either bamboo or wood and is hanged above the rice crop. The frame has a platform that supports a basin of water just below the lantern. Adding some cooking oil to the water can make the insects immobile upon falling into the water.

In rice-fish fields, hang the lantern over the water in the trench at a height which is just above the dike. At that height, the light is easily seen by insects flying just above the crop canopy.

Locating the insect trap

USING THE LANTERN:

The lantern should be lit as soon as it gets dark (when insects are most attracted to light) for 24 hours. In cases where the field is far from the house, the lantern should be filled with just enough kerosene to burn for 2 hours. The lantern should be visited daily and the insects identified and counted.

NOTE:

· If the light trap is primarily intended to reduce the insect population, more than one trap is advisable.

· If the light trap is intended to monitor insect population for forecasting, 1-2 traps/ha. is enough. Check with the local technician.

Pests	Local Name	Time When Most Attracted
Scarab beetle	Uwang, salagubang, salaginto	New moon
Cricket (Gryllotalpa orientalis)	Subong	Full moon
Caseworm (Nymphula depunctalis)	Paruparong gabi	New moon
Green semliooper (Naranga aenescens)	Paruparong gabi (berdeng uod)	New moon
(Rivula atimeta)	Mabalahibong berdeng uod	New moon
Gallmidge (Orseolia oryzae)		Full moon
Armyworm (Mythimma separate)		New moon
Cutworm (Spodoptera litura)
(Spodoptera mauritia)
Stemborers:
Striped (Chilo suppressalis)
Yellow (Scirpophaga incertulas)	Aksip	New moon
Pink (Sesamia inferers)
White (Scirpophaga innotata)
Brown planthopper (Nilaparvata lugers)	Ngusong kabayo	Full moon
Whitebacked planthopper (Sogatella furcifera)
Green leafhopper (Nephotettix virescens)
(Nephotettix nigropictus)	Berdeng ngusong kabayo	Full moon
(Nephotettix malayanus)

The above is compiled from researches conducted by the Entomology Department of IRRI, Los Ba Laguna, Philippines.

Weed management

Weed management

REASONS FOR WEED MANAGEMENT:

1. Weeds reduce yield by competing with the crop for sunlight, moisture and soil nutrients.

2. Fertilizer application in weedy fields may prove wasteful because weeds absorb the fertilizer (especially N) more effectively than the crop.

3. Weeds may serve as alternate hosts for crop pests. 

LOW-COST WEED MANAGEMENT PRACTICES:

There are many ways to manage weeds in ricelands at little cost without having to resort to the use of herbicides. The key to low-cost weed management and high yield is prevention. Preventing weeds from growing is cheaper and easier than removing them. Some simple methods of prevention include: (1) thorough land preparation; (2) using weed-free seed or seedlings; (3) employing shade and mulch to slow down weed growth; (4) crop rotation; and (5) good water management (for lowland rice).

1. Land preparation. Good land preparation gives the crop a chance to grow ahead of the weeds. This reduces competition during the very sensitive seedling stage. Moreover, by the time the weeds start to emerge, the plants have grown tall enough to shade them out, further preventing their growth.

2. Weed-free seed and seedlings. If planting material is not kept free of weeds (or weed seeds) then the crop will have a competitor from the start of growth. In the Philippines, transplanting weeds with rice seedlings is causing losses of 16-23%. (See technology sheets on Rice Seed Production.)

3. Shading/mulching. "Let plants do the work for you." Keep a cover of economic plants on the field to shade out weeds.

· Select taller varieties of the crop to be grown.

· Increase the planting density to reduce weed competition.

· Use Azolla to effectively shade out grasses, sedges and small broadleaf weeds in (lowland rice). Use of Azolla alone can reduce weed dry matter production by 50-60%.

· Residues from the previous crop can be applied as mulch to deter weed growth (aside from conserving water and improving soil fertility).

· In fallow periods, a good stand of green manure will shade out most weeds, preventing them from setting seed.

Select taller varieties of the crop

Increase the planting density

4. Crop rotation can considerably reduce weeds. Weed population is lower when planting rice after an upland crop like mung bean or cowpea rather than when it is preceded by another rice crop. The radical differences in cultural practices between upland and lowland crops result in different species of weeds with each system. By rotating crops, weeds have less chance to establish, keeping their population down.

With continuous monocropping, weeds associated with the crop have a chance to establish themselves and increase their populations.

In areas where crop rotation cannot be practiced, levels of weed control have in the first crop affect weed population in the second. Good weed control in the first crop means fewer weeds in the second.

Another way to inexpensively control weeds is to have livestock do it for you. Both ducks and fish consume large numbers of weeds.

Most crops do not have to be kept weed-free for the duration of their growth, especially so when labor is scarce or expensive. The number of weedings can be reduced by comparing the recommended weed-free period and the time that critical competition begins between the crop and the weeds. This varies with crops and different cultural methods. For example, transplanted rice is supposed to be kept weed-free for the first 30-days after planting. However, the period when weed competition will actually reduce yields does not begin until 25-30 days after transplanting, so weeding can be reduced to one time only, that time between 20-30 days after transplanting.

Weed free period in rice crop

WEEDS ARE NOT ALWAYS BAD FOR FARMERS:

· Some weeds can be used as additional forage for livestock.

· Other weeds can be returned to the soil to increase OM.

· Allowing weeds to grow in some paddy dikes provides shelter to many beneficial insects where they stay throughout the dry season and help keep pest populations down once rice planting begins.

Weed control in lowland rice

With no weed control measures, an average of 34% yield loss is expected in transplanted lowland rice and 45% in direct-seeded rainfed lowland rice.

COMMON WEED CONTROL METHODS:

· Land preparation
· Hand weeding
· Mechanical weeding (use of push-type rotary weeders)
· Flooding (keeping the field flooded for a period of time to control most weeds)
· Use of herbicides
· Use of azolla

General comparison of selected weed control measures

MECHANICAL WEEDER VS. PRE-EMERGENCE WEEDICIDES

If on-farm labor is unavailable and must be hired, the use of mechanical weeders will involved higher costs compared to the use of weedicides. However, the net returns will be higher if farm family labor is used to utilize mechanical weeders.

The following case study (based on farm records) compares the two methods:

	Weeder	Pre-Emergence Herbicide
1. Area planted	1/2 ha.	1/2 ha.
2. Variety	IR 42	IR 42
3. Crop period/duration	Aug. 4	Nov. 18,1987
4. # Cavans harvested @50 kg/cay.	42	38
5. Gross Value of harvest @P3.5/kg	P7,350	P6,650
6. Cost
a. Labor for marking rows for transplanting @P40/ha.	20	20
b. Depreciation cost of weeder*	50	-
c. Cost of 1/41iterweedicide (Machete)	-	50
d. Labor for mechanical weeding (5 man days @P35)	175	-
e. Labor for spraying	-	8.75
(1/4 man days @P35)
f. Additional handweeding (2 man days @P35)	70	70
g. Total cost of weed control	P315.00	P148.75
7.Gross returns less cost of weed control	P7,035.00	P6,501.25

Above case also illustrates that a more effective weed control scheme is one that involves a combination of two or more weed control methods.

* Assuming a weeder costs P300 and can last for six cropping seasons.

Water management for weed control in rice

Flooding rice paddies was one of the first tools developed by farmers to control weeds in rice. On farms with reliable irrigation, water. management is also one of the most effective and lowest cost methods of controlling weeds. Even for farms in rainfed or semi-irrigated areas where the need to conserve water limits the ability to manipulate water levels, water management is still an important tool in weed control.

Water management for weed control in rice

1. At land preparation

Keep the paddy field flooded after harrowing to kill weeds and to hasten decomposition. Water level should be high enough to submerge all weeds.

2. At final levelling

Final levelling eliminates any high spots in the field. Weed seeds in these high spots would be able to germinate because they would be above the water level.

In areas with good irrigation, final levelling should be done in saturated soil but with no standing water.

In rainfed or semi-irrigated areas, conserve water by maintaining water levels at 3 cm.

Final levelling should be done 1 day before transplanting.

3. At transplanting

Irrigated: The puddled, levelled field should not have standing water. This facilitates straight-line transplanting because the lines can easily be seen and assures that the seedlings will establish good root-soil contact and quickly begin to grow.

Rainfed: Paddies should be drained to facilitate transplanting unless no rain is expected -- in which case some water should be maintained in the paddies.

4. Transplanting to tillering

Paddies should be flooded 1-3 days after transplanting to prevent weed seeds from germinating. The time to flood is determined by presence or absence of Azolla (Flood 1 day after transplanting if Azolla is being used.) and establishment of the seedlings.

Water level should be 2 cm initially and increased gradually to 10 cm as the rice plants grow.

5. After maximum tillering to post-flowering

Once maximum tillering stage is over, weeds have no effect on rice yield. Continuous flooding or submergence of the field is desirable but not necessary. Water depth may vary from 3-10 cm if there is sufficient irrigation water. Where irrigation water is scarce, the objective should be to maintain at least a saturated soil once crop canopy is full enough to shade out weeds.

Using ducks for low-cost weed management

The use of ducks can complement other weed management practices in rice paddies where straight row planting is used. When the crop reaches 20 cm in height (approximately 25 days after transplanting) until the booting stage, the ducks can be allowed into the rice paddy without damaging the crop. Forty to fifty (40-50) adult ducks feeding for 3 hours a day for 3 consecutive days can weed a 1,000 sq.m area. Any species can be used but Mallard ducks (Anas platyrhynchos) are most recommended because they are more active and have light and narrow bodies.

PROCEDURE

1. Irrigate the field to a depth of 3 cm (ducks will not enter the rice paddy field without water). To encourage them to enter, broadcast a handful of rough rice into the paddy.

Irrigate the field

2. The constant dabbling or feeding and trampling by the web-footed ducks make the soil soft and muddy and inhibit the growth of weeds and at the same time incorporate weeds growing in between the rows of rice.

Dabbling

3. Broadleaf weeds and sedges are eaten by the ducks. Insects (e.g. moths or stemborers, hoppers, mole crickets, etc.) and golden snails which are found at the base of the rice crop are also eaten, thereby reducing pest populations.