Pest, Insects, Agri-Crop

WAYS OF CONTROLLING INSECT PESTS:

In controlling insect pests, use of chemicals should always be the last recourse. Visit the farm regularly to detect presence of insect pests. If negligible apply natural ways of controlling either biological or organic method. A combination of the methods below should be considered:

1. Biological control – done by promoting the existence of natural enemies of rice insect pests. These natural enemies can be grouped into:
1. spiders which eat any insect pests they can catch
2. insect predators which eat many kinds of pests
3. insect parasites which eat only one or a few kinds of pests, pathogens/organisms which infect different kinds of pests
2. Using pest resistant varieties – by incorporating insect resistance genes in the high yielding varieties of rice like the new varieties offered by the DA and other government agencies.
3. Cultural and chemical controls for insect pests of rice with their nature of attack and damage are shown and discussed below.

          There are about 100 species of insects that infest the rice plant. However, only 15 of these are of major significance and are regularly occurring. Some of the most destructive insects are: rice whorl maggot, rice caseworm, common army worm, cutworms, rice stemborer, rice leaf folder, green leafhopper, brown planthopper and  the newly  discovered black bugs in some parts of the country.

Major Insect Pests

1. Rice whorl maggot (Hydrellia philippinia) Local name: ngilaw ti pagay, ngilaw ti taltalon (Iloc.), langaw-bukid (Tag.)
             The adult fly is dull-grayish. It is attracted to newly transplanted rice with standing water. Eggs are laid singly on either surface of the leaf. Incubation ranges from 2 - 4 days. The newly hatched maggots migrate to the unopened central leaves where the larvae feed on the inner margins of developing leaves. As the leaves expand, the damaged areas become very visible. Pupation takes place outside the feeding stalk and lasts for 7-10 days. Egg to adult stages normally extends 26-28 days. Infestation generally occurs from seedling to maximum tillering stage.

2. Rice caseworm (Nymphula depuntalis) Local name:  kutalo (Iloc.).
             The adult moth is white with wings that are marked with a few light brown to black specks and 2 - 3 dull brownish yellow bands located below the margin (Figure 27). Eggs are laid in 1 or 2 adjacent rows in the lower surface of the leaves or on the leaf sheath near the water surface. After 2-4 days, eggs hatch into pale cream minute larvae.
             The caseworm derives its name from the larva’s habit of wrapping itself in a section of a leaf and attaching itself to the rice plant. It feeds on the upper portion of the leaf. The larva undergoes five instars. It changes its leafcase after each morning.

3. Common armyworm (Mythimna separate Walker). Local name: arabas (Iloc.)
             Armyworm infestation occurs sporadically. Outbreaks are characterized by the sudden appearance of larvae in immense numbers causing severe damage before they are detected.
             The adult is nocturnal and appears to be pale brick red to brown. It has a hairy body covered with dark specks and patches. The eggs are laid in clusters between the leaf sheath and the stem. They hatch from 7 to 9 days.

4. Cutworm (Spodoptera litura). Local names: tariptip (Qui.) arabas (Cag.)
             It is a polyphagus insect that feeds on many plant species. It is also a very common pest of various agricultural crops.
             The forewings of the adult insects are purple-brown with numerous spots and light colored lines with hindwings. Larvae are brown-black and thoracic segments have 1 to 2 dark specks near the base of the legs. The eggs are round with ridge surface, pearly white, and laid in clusters of 300 covered with short brownish hair on either surface of the leaf. Adults come out during night time. This insect usually attacks rice plants at the seedling stage.
5. Rice stemborers. Local name: rusok (Cag.)
             Considered the most serious pest of rice, stemborers are of regular occurrence and of wide distribution. They reduce tillers even on resistant varieties and are difficult to control with insecticides. This pest occurs in all rice environments and are generally abundant toward the end of the rainy season. They infest rice plants from seedling stage to maturity. Their damage to the rice plants results in deadhearts when the central leaf whorl is affected and white head when base of the panicles are severed (Figure below).
             The adult of most stemborer species are positively strong fliers. They mate in the evening.

6.                 6. Riceleaffolder (Cnaphalacrocis medinalis) Local name: balbalkot, igges nga aglukot ti bulong (Iloc.).
          Leaffolders have increased in importance in areas where rice is heavily fertilized and planted during the dry and wet seasons.
          The adults have shiny light brown wings and dark broad margins and 2-3 vertical dark stripes. The larvae are long, yellowish green with brown head. The eggs are oval, yellowish-white and laid of rows of 10-12 each, arranged linearly along the midrib of either surface of the leaves. They attack rice plants from seedling to flowering stages

7.           7. Greenleafhoppers (Nephotettix spp) Local name: berde a sepsep (Iloc.), berdeng ngusong kabayo (Tag.).
          The green leafhoppers (Figure below) generally feed on the leaves and upper parts of the plants. They are vectors of virus organisms causing tungro and yellow dwarf diseases. Oviposition occurs 2 - 3 days after emergence. Egg masses are laid on the upper surface of the leaf blade or leaf sheath. Incubation takes 7 - 8 days. The nymphs undergo 5 instars in 14-19 days before they become adults. They attack rice plants from seedling to booting stages.

8. Brown planthoppers (Nilaparvata lugens) Local name: kolor kape a sepsep (Iloc.).
             The brown planthopper (Figure 11) infests the lower parts of the plants. Brown planthoppers are of two kinds: the winged and wingless types. Both winged and wingless hoppers transmit grassy stunt but the wingless type causes direct damage known as “hopper burn.” This is characterized by gradual yellowing followed by sudden drying of the plants forming circular patches in the fields.
9. Rice bugs (Leptocorisa oratorious) Local name: dangaw (Iloc.)
             This pest is a major problem where rice is grown continuously and rice in all its stages of growth. Both nymphs and adults are distinguished by their peculiar bug odor. They are phototropic and remain active during early morning and when sunlight is weak.

When to apply insecticides

Growth stage	Insect pests	Spray insecticide when
Seedling	·   Caseworm ·   Army worm ·   Cutworm	·   50% of the leaves damaged
Vegetative	·   Whorl maggot	·   15% whorl maggot-damaged leaves + 5% leaves damaged chewing insects at 5 DAT
	·   Green leafhopper ·   Brown leafhopper	·   None in the areas with RTV ·   20 hoppers/hill or 1 hopper/tiller
	·   Stemborer ·   Leaffolder	·   More than 20% dead heart or 1% white head ·   30% of leaves damaged or cut
	·   Caseworm	·   30% of leaves damaged or cut
After panicle initiation	·   Brown planthopper	·   20 hopper/hill or 1 hopper/tiller
	·   Green leafhopper	·   None in the areas with RTV