finals

34問 • 1年前

問題一覧

DEFOLIATORS

Whorl maggot (Hydrellia philippina Ferino), Rice caseworm (Parapoynx stagnalis), Leaffolder (Herpetogramma hipponalis), Cutworm (Agrotis ipsilon), Army worm (Mythimna unipuncta)

SAP SUCKERS

1. Green Leafhoppers (GLH)- Nephotettix virescens, Brown planthopper (Nilaparvata lugens) , Whitebacked planthopper ( Sogatella furcifera ) , Rice Black Bug (Scotinophara coarctata)

STEM BORERS

Yellow stem borer (Scirpophaga incertulas), White stem borer (Scirpophaga innotata) , Striped stem borer (Chilo suppressalis)

flies; adult flies are grayish; 2mm long, 1/3 size of housefly a. Destructive stage – maggot or larva b. Susceptible stage of plant – seeding to early tillering stage c. Characteristic damage – distortions on the sides of emerging leaves due to larval feeding before leaves unfold. d. Life cycle – 4 weeks

Whorl maggot (Hydrellia philippina Ferino)

- moth; white; 6mm long a. Destructive stage – larva b. Susceptible stage of plant – seeding to early tillering c. Characteristic damage – ladder-like appearance of white or green portions; leaf tips appear as if cut by scissors; presence of larval cases attached to the plant or floating on the water d. Life cycle – 35 days

Rice caseworm (Parapoynx stagnalis)

- moth; light brown with horizontal black markings on wings, attracted to shady areas. a. Destructive stage – larva b. Susceptible stage of plant – tillering to flowering c. Characteristic damage – longitudinal white and transparent streaks on leaf blades caused by removal of leaf tissues by larval feeding; leaf blade folded into tubular structures d. Life cycle – 25-35 days

Leaffolder (Herpetogramma hipponalis)

- moth; color of larva varies with color of leaves where they feed; cutworm larva has prominent black spots on thorax; curls into C-shaped when disturbed; pupates in the soil, feeds also on grasses. a. Destructive stage – larva/caterpillar b. Susceptible stage of plant – seeding to panicle stage c. Characteristic damage – young larva eats the leaves; older cutworm larva may eat the whole plant; armyworm larva may cut panicles; feed also on grasses d. Life cycle – 34-42 days

Cutworm (Agrotis ipsilon) and Army worm (Mythimna unipuncta)

– nymphs are green and adults are bright green with variable black markings on the wings; suck plant sap and transmit the rice tungro virus; found mostly on leaves or upper portion of plant. a. Destructive stage – nymphs and adults b. Susceptible stage of plant – seedling to tillering c. Characteristic damage – vector of tungro virus d. Life cycle – 22-26 days

Green Leafhoppers (GLH)- Nephotettix virescens

- adults are brown, short- or long-winged; 2.5-3 mm long; nymphs are whitish; found at the base of plant; transmits grassy stunt and rugged stunt virus. a. Destructive stage – nymphs and adults b. Susceptible stage of plant – early tillering to flowering c. Characteristic damage – wilting and eventually death resulting in hopperburn due to excessive feeding; the drying of plants progresses in a circular manner d. Life cycle - 20-24 days

Brown planthopper (Nilaparvata lugens)

- nymphs are white to a strongly mottled dark gray or black and white; adults have white strip on their back; females are short-winged and males are long-winged. a. Destructive stage – nymphs and adults b. Susceptible stage of plant – tillering to flowering c. Characteristic damage – heavy infestations may cause outer leaves of a hill to show burn symptoms but rarely causes hopperburn d. Life cycle – 19-24 days

Whitebacked planthopper ( Sogatella furcifera )

nymphs are grayish to black, adults are black and are weak fliers but can be transported over long distances by wind, ships, or other means of transportation; strongly attached to light. a. Destructive stage – nymphs and adults b. Susceptible stage of plant – vegetative stage onwards c. Characteristic damage – at the vegetative stage, central leaf may roll resembling a deadheart; dead panicles or whiteheads; heavy infestation results in bugburn d. Life cycle – 26-37 days

Rice Black Bug (Scotinophara coarctata)

- female moth is straw colored, with very distinct black spot on each forewing; larva with hairless yellowish body; eggs laid on the upper surface of leaf in oval batches and covered with mat of anal hairs of female moth.

Yellow stem borer (Scirpophaga incertulas)

- moth is white and no black spot on wings; larva like YSB but white in color; eggs similar to YSB.

White stem borer (Scirpophaga innotata)

moth straw color to light brown with silvery scales and a row of black dots at the tip of forewings; larva with five longitudinal purplish brown stripes; eggs are scale-like, laid near the base of leaf, not covered with hair. a. Destructive stage – larva b. Susceptible stage of plant – seedling to panicle stages c. Characteristic damage – deadheart at tillering stage and whiteheads at reproductive stage d. Life cycle – 30-45 days

Striped stem borer (Chilo suppressalis)

Whorl Maggot and caseworm

1. Drain the field since the adults of whorl maggots are attracted to fields with standing water and to kill caseworm larvae. , 2. Conserve and enhance natural enemies as a biological control method. , 3. Practice synchronous planting.

Leaffolder

1. Avoid excessive use of fertilizer. , 2. Conserve and enhance natural enemies as a biological control method. , 3. After careful evaluation on the severity of damage on the flag leaves, insecticide application may be considered. , 4. Practice synchronous plant

Cutworm and armyworm

1. Maximize natural/biological control. Eggs and larvae are attacked by several species of parasitoids and predators. , 2. Keep fields free of weeds to remove alternate hosts. , 3. If population is high especially at early instars, insecticides application may be needed., 4. Practice synchronous planting.

Brown planthoppers

1. Plant resistant varieties. , 2. Practice synchronous planting. , 3. Maximize natural control. Eggs, nymphs and adults are attacked by several species of parasitoids and predators. Several species of fungi also infect the nymphs and adults. , 4. If population becomes high, insecticide application may be needed especially in hybrid rice seed production.

Whitebacked planthoppers

1. Practice synchronous planting. , 2. Maximize biological control. Eggs, nymphs and adults are attacked by several species of parasitoids and predators. Several species of fungi also infect the nymphs and adults. , 3. If population becomes high, insecticide application may be needed especially in hybrid rice seed production.

Green Leafhoppers

1. Plant resistant varieties., 2. Practice synchronous planting. , 3. Maximize natural/biological control. Eggs, nymphs, and adults are attacked by several species of parasitoids and predators. Several species of fungi also infect the nymphs and adults. , 4. Chemical control. Th ae use of insecticides is not necessary when tungro infected plants are not present around the area, and if tungro infection occurs after 45 days after transplanting. , 5. Spray application based on tungro symptoms will be too late and unnecessary because the hoppers would have transmitted the virus about 7-14 days earlier. Hence, in areas where tungro is endemic, do not wait for symptoms to appear. , 6. Spray appropriate insecticides as soon as green leafhoppers are observed.

Rice Black Bug

1. Practice synchronous planting. , 2. Grow tolerant varieties. , 3. Avoid alternate hosts like gabi, corn, and several species of weeds. , 4. Biological control – conserve naturally occurring parasitoids and predators; nymphs and adults are infected with Metarhizium fungus. , 5. In case of heavy infestation, chemical control may be necessary.

Stem borer

1. Practice synchronous planting. , 2. Know the peak of stem borer population in your locality and schedule transplanting to avoid it.

is a type of pest control which involves the action of natural enemies or beneficial organisms.

Biological control

where man does not actively manipulate natural enemies or applied biological control which involves the use and management of natural enemies by man.

natural biological control

CHARACTERISTICS OF AN IDEAL NATURAL ENEMY

Density dependent , Exceptional searcher and has a high reproductive capacity

their effects increase with increasing host density and decrease with decreasing host population.

Density dependent

able to find the host or prey at very low densities and keep it there.

Exceptional searcher and has a high reproductive capacity

GROUPS OF NATURAL ENEMIES:

PREDATORS, PARASITOIDS/PARASITES, PATHOGENS, BACTERIA

PATHOGENS

Microorganisms naturally occurring as control agents;, Fungi, Viruses

Important control agents for caterpillar populations. The most important are the Nuclear polyhedrosis and Branulosis viruses.

Viruses

Important organism for leafhoppers and planthoppers control;

Fungi

BT means

Bacillus thuringiensis

PATHOGENS

Virus diseases, Fungus diseases

PREDATORS

Lady Beetles, Ground beetles, Crickets, Grasshopper, Water Bugs, Damselflies and Dragonflies , Earwigs

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