1. Sampling Insect Pests, their Damage and Beneficial Organisms
Philippine Rice Self-Sufficiency Plan (PRSSP)
Sampling Insect Pests, their Damage and Beneficial Organisms

2. Overview
Sampling is done by collecting, counting or inspecting a small part of the population. It determines the trends in population of organisms.
The sampling should be done in a proper manner so that it would reflect the condition of the whole population. For example, the population of insect pests and the damage on the crop are generally randomly distributed that later aggregate into clumps. This maybe caused by the behavior of adult immigrants or by concentration of eggs laid on a plant before the insect moved to the next. Such situation is also pertinent in insect transmitted virus diseases.
Therefore, estimate of population density depends on taking enough samples and systematic random sampling from a field.It is important to remember that sampling is only an instrument to achieve a goal and not an end to itself
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3. Overview
There are two fundamental reasons for sampling; Research and Pest Management Decision-Making. Sampling for research purposes normally requires considerable time and effort and is costly. On the other hand, sampling for pest management is not as comprehensive and may also consider the conditions of the neighboring fields.
There is no universal sampling method but this is carried out by using a variety of techniques and devices depending on the objective of the work.
Effective pest surveillance and monitoring system can result to efficient timing of interventions and reduce cost of production. In addition, hazards on health and safety of farmers and the environment are reduced.
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4. Overview
Several kinds of traps are appropriate for sampling flying insects. Sticky traps intercept insects while on flight, however most traps depend on stimulus to the insects, e.g. light, color and sex pheromones (Carińo,1979).
Catches of brown planthopper (BPH) with light and sticky traps showed the same trend at the Experimental Farm of the International Rice Research Institute (IRRI,1975), and peak catches occurred at the same time as in the field (IRRI,1978).
Nagata and Masuda (1978) reported the efficiency of sticky boards for estimating BPH field populations in Japan and used for field sampling as part of surveillance for BPH in Maysia (Ooi,1982).
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5. Common Sampling Techniques and Devices for Pest Management Decision Making
Advantages
Involves a varying size sample. Good for comparing seasonal and yearly catches of insects.
Disadvantages
Catches are subject to changes in insect behavior. Do not catch non-flying insects.
Light trap
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6. Advantages Disadvantages
Fast method and economical. Good for sampling arthropods staying in the canopy of the plant
Disadvantages
Human error due to variability. Poor catch of arthropods at the base of the plant.
Sweep Net
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7. Tapping the plant
This is a sampling method that utilize a collecting pan with soap solution or oil with water to collect arthropods at the base and stem of the plant. After tapping, arthropods are identified and counted immediately in the field.
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8. Visual count Advantages Disadvantages
Economical (laborcosts) only and data recording can be done on field.
Disadvantages
Human error (Identification and only rough estimate of arthropod density are obtained.
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9. Sticky Trap Advantages Disadvantages
Economical, measures insect movement and colonization
Disadvantages
Caught insects are messy to handle and does not catch non flying insects
Benefits of timely application and right amount of irrigation water
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10. Yellow Pan Trap Advantages Disadvantages
Economical; measures insect migration, easy sorting and counting of samples.
Disadvantages
Attraction is due to colorstimulus; does not catch non-flying insects.
Benefits of timely application and right amount of irrigation water
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11. Suggested procedures and techniques for sampling insect pests, damage and natural enemies in rice ecosystem
Rice stem borers
Adults-light trap catches are used to determine seasonal abundance of the different species of stemborers. The flight activity of the striped stemborer, Chilosuppressalis can be measured by sex pheromone traps and generally more effective than light traps for pest management purposes.
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12. Egg mass density -count and record the number of egg masses on all leaves from hills selected randomly or systematically in a plot, hills depending on the objective of sampling.
Larvae and pupae –Hills are selected systematically or randomly and examine for signs of borer damage. Damaged or infested hills are removed from the paddy, the tillers counted, and all tillers dissected. Larvae of stem borers collected from the dissection are then counted and computed. Pupae of yellow and white stem borers are located at the base of the plant.
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13. Deadheart (DH)and whitehead(WH)-this damage due
to stemborers are normally presented in percentage. When
damage is presented, it is important to include the method
or formula when reporting stemborer damage.
The basic formula in calculating percent DH or WH :
No. of DH or WH
DH OR WH (%) = X 10
Total no. of tillers or panicles
The above method is commonly used for varietal screening programs. The standard formula used by ecologist for years and based on suggestion by statisticians is given below. The size of the sample is 25 randomly selected hills.
No. of damaged hills Damaged tillers or panicles
(in 25 hills) (in 25 hills)
DH or WH (%) = X X 100
Hills sampled Total tillers or panicles
(25 hills) (in 25 hills)
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14. Plant and leaf hoppers
Normally the nymph and adults are sampled at the same time in the field using the same techniques and devices.
Sweep net is probably the most common device for sampling leafhoppers in rice. It is easy and fast, usually sweeps per plot are made.
Mouth aspirator, visual count and suction machines are most commonly used for planthoppers. When studying migration and seasonal fluctuation of these insects, researchers use yellow pan, aerial nets and light traps.
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15. Rice leaffolders
Light trap and sex pheromone traps are used to monitor adults of rice leaffolders.
Since eggs are very small, larvae and damaged leaves in 10 randomly selected hills are usually sampled in the field.
Damaged leaves (%) and number of larvae per unit area are calculated.
For yield loss studies, the degree of damage from each leaf is counted.
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16. Ricebug
This insect is quite active and highly mobile when disturb, sampling of this insect is normally done early in the morning or late afternoon.
Nymphs and adults are counted on 25 randomly selected hills or in a 1m2. Sampling per unit area should be replicated at least 4 times.
Damaged When yield is not part of sampling, sweep net is usually used. Sampling are normally done taken from flowering to soft dough stages.

17. Rice Black Bug (RBB) Light trap (ordinary bulb)
To determine the presence or absence of RBB in the area or
To determine seasonal / yearly fluctuation on the population of RBB
The bugs are attracted to light trap from 2 days before full moon up to 3 days after full moon.
During high RBB population, high intensity light bulbs (super light) could be used to trap and kill the adults.
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18. For pest management decision-making:
Sample 25 randomly selected hills per field (in transplanted rice) or 25 quadrants (25cmx25cm in direct seeded rice) per farmers’ field. Sampling should be done by walking diagonally in the field. Count and record egg mass, nymphs and adults stages of RBB. Record crop growth stage; if possible record variety planted and pest management strategies implemented by the farmer in the field being sampled. If there are more than 5 RBB/hill, intervention is needed. Nymphs and adults are counted on 25 randomly selected hills or in a 1m2. Sampling per unit area should be replicated at least 4 times.
Sample 10 randomly selected fields per village to have a good estimate of RBB in the area.
Record also visible damage caused by RBB feeding like DH, WH and bug burn in severe cases.
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19. Predators Parasitoids
Count predators per unit area or hill. However, highly mobile predators like mired bug, and crickets Suction machines likeD-VAC, FARMCOP, and BLOW/VAC are efficient sampling devices for predators. Flooding a small area enclosed in metal frame is a good technique for sampling spiders during fallow and dry period in the field.
Parasitoids
Normally the pests or hosts of parasitoids are reared in the laboratory to determine percentage parasitism. For ecological studies, suction devices used for predators are also efficient for parasitoids.
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20. Larvae of detritivores, filters feeders and other aquatic larvae
The Blow/Vac and FARMCOP suction machine are the most appropriate devices for sampling aquatic insects in the rice field. In earlier studies, Blow/Vac suction machine gave a better estimate of aquatic larvae than FARMCOP.
Other insects
Visual count of insects in 10 or more scattered hills or sampling all hills in an area, usually 1m2 replicated several times is normally taken.
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21. End of presentation

22. Subject Matter Specialists
Mr. Gertrudo S. Arida, PhilRice
Ms. Josie Lynn Catindig, IRRI
Mr. Jorge Karganilla, BPI
Mr. Genaro S. Rillon, PhilRice
An Interagency collaborative effort in support to the DA’s Philippine Rice Self-Sufficiency Plan