Research & Development Center Bajo

Causal Organism

Fungus:

a)      Sexual state - Magnaporthe grisea (Hebert) Barr

b)      Asexual state Pyricularia grisea (Cooke) Saccardo

Rice Blast Spores (photo courtesy of Rice Blast Genomics Project)

Parts affected

·         Leaf blades

·         Stem nodes

·         Panicles

Rice Blast life cycle (photo courtesy of IRRI)

Symptoms

On leaf blades

·         Presence of lesions (wounds) on the leaves

·         New lesion (wound) colour is white to gray-green with darker green borders

·         Older lesions are whitish to gray with necrotic (burned) borders

·         Lesions on younger leaves are less than 1cm long while in older leaves are larger (2cm and above)

Leaf blast (photo courtesy of IRRI)

On stem nodes

·         Infected nodes have blackened appearance

·         Culm breaks easily at infected nodes.

Neck blast (photo courtesy of NPPC)

On panicles

·         few, no seeds, or white heads when neck is infected or rotten

Panicle Blast (photo courtesy of The American Phytopathological Society)

Control Measures

1.      Cultural Control

·         Use disease-free seeds. Never use seeds from a blast-infected field since the fungus can be transmitted through seeds.

·         Raise seedlings on a wet bed, as dry nurseries generally favour blast.

·         Do not apply too much manure or fertilizer as high Nitrogen will increase the susceptibility of paddy to blast.

·         Avoid high density planting. Maintain at least 20 cm planting distance.

·         Farmers in the same area should transplant at the same time.

·         Do not leave the fields dry after transplanting. Paddy is more resistant to blast when grown under proper water management.

·         Burn infected straw and stubble in the field.

2.      Varietal Control

·         Use resistant varieties like Bajo Kaap, Chumroo, No. 11, and IR64.

3.      Chemical Control

Seed treatment:

·         Soak seeds in water for 24 hours.

·         Treat the seeds with Tricyclazole at 3 g/kg of seed.

·         Germinate the seeds for 24-48 hours before sowing.

Field Spraying:

·         Monitor rice nurseries/field regularly for blast infection.

·         If there are blast symptoms on the leaves, spray early on with Tricyclazole at 1 g/litre of water.

Causal Organism

Insect:

a)      Yellow stem borer (YSB) Scirpophaga incertulas (Walker)

b)      White stem borer (WSB) S. innotata (Walker)

c)      Striped stem borer (SSB) Chilo suppressalis (Walker)

d)     Gold-fringed stem borer C. auricilius Dudgeon

e)      Dark-headed stem borer C. polychrysus (Meyrick)

f)       Pink stem borer Sesamia inferens (Walker)

YSB, SSB,

Dark-headed SB &

 Pink stem borer

(photo courtesy

of www.doae.go.th )

Parts affected

·         Tillers

·         Panicles

Symptoms

On tillers

·         Central tiller dries and dies during vegetative stage.

·         Dried/dead tillers can be easily pulled from the base.

·         Small holes on stems and tillers.

·         Faeces or excretion of the larvae inside the affected stems.

Dead tiller/heart (photo courtesy of IRRI)

On panicles

·         Panicles are unfilled, empty or chalk-like.

Whitehead at reproductive stage (photo courtesy of IRRI)

Control Measures

1.   Cultural Control

·         Harvest the crop at ground level to remove the larvae in stubble. Remove and destroy stubble and volunteer rice – these are rice plants that grow on its own from seeds left in the field.

2.   Chemical Control

·         Do not spray chemical as it alters the natural predators’ ecology.

Causal Organism

Bog Pond Weed or  Shochum

(Potamogeton distinctus A. Benn.)

Flowering Shochum  (photo courtesy of NPPC)

Effect on rice

·         Reduces yield up to 35%

·         Competes with nutrients and space.

Shochum growing vigorously along with rice (photo courtesy of RNRRC, Bajo)

Control Measures

1.   Low weed (grass & sedge) pressure

·         Do hand weeding at least two times (20 and 40 days after transplanting [WAT]). If hand weeding is to be done, keep in mind to closely space the plants and do the first weeding not later than 30 days after transplanting [DAT].

2. High weed (grass & sedge)  pressure

·         Use line planting and rotary weeding. If line planted, do two rotary weedings at 20 and 40 DAT.

4.      Low

      Shochum  

      pressure

·         If there is no or little Shochum but weed pressure is expected to be high, apply Butachlor at 12-16 kg per acre 3-6 DAT. Do not use Butachlor in areas heavily infested with Shochum.

5.      High Shochum pressure

·         Do intensive hand weeding 3-4 times thoroughly at 2, 4 and 6 WAT, by removing and destroying the weeded Shochum biomass.

·         Pull out the roots/turions and dispose the weeds in a pit away from the field.

·         To minimize Shochum problem, adopt cultural methods like increased tillage, deep ploughing, and restricting the physical movement of plant parts from one field to another.

·         Since weeding is laborious and the use of herbicides is not environment-friendly, use indirect complementary weed control methods like good land preparation, proper water management, and use of weed-free seedbeds and seeds.

Causal Organism

Fungus:

Phytophthora capsici Leonian

Spores of  Phytophthora capsici (photo courtesy of Michigan State University)

Parts affected

·         Leaves

·         Stems

·         Fruits

·         Roots

Symptoms

On leaves

·         Lesions (wounds) are circular and water-soaked initially and become greyish brown as the disease advances.

·         Infected leaves are usually “half-moon shaped”.

·         Leaves wilt and die.

Water-soaked lesions on leaves caused by P. capsici (photo courtesy of NPPC)

On stems

·         Dark lesion girdles the base of the stem and may expand on the stem restricting the upward movement of nutrients and water from roots.

·         Stem girdling results in sudden wilting of the plant.

Black stem lesion caused by P. capsici (photo courtesy of NPPC)

On fruits

·         Starts as “small, water-soaked, dull green spot” that rapidly spreads to the whole length of the pod under favourable conditions.

·         Infected fruit shrivel but remain attached to the plant.

Fruit rot caused by P. capsici (photo courtesy of NPPC)

On roots

·         Root rots and hence restricts the movement of water and nutrients to other parts of plant.

Root and crown rot caused by P. capsici (photo courtesy of NPPC)

Control Measures

1.   Cultural Control

·         Select a site that has not been used for chilli cultivation.

·         Avoid water-logged fields.

·         Follow crop rotation with non-solanaceous crops such as cabbage, cauliflowers, broccoli etc.

·         Sterilise the soil by burning straw/mulching materials.

·         Use healthy seeds and seedlings. Never buy from weekend markets.

·         Raise and transplant seedlings on a raised bed at least 30 cm high and 1 m wide to ensure that moisture does not collect at the base of the plants.

·         Avoid planting too densely; maintain 30 cm row-to-row and 20 cm plant-to-plant distance.

·         Maintain the height of the bed and drain water throughout the cropping season.

·         Drain out standing water from the field immediately after rainfall.

·         Rogue out any infected plants and burn the plants.

2.   Chemical Control

Seed treatment:

·         For 500 g chilli seeds, dissolve 2.5 g Copper Oxychloride and 2 g Ridomil in 500 ml water. Mix the solution thoroughly.

·         Soak the seeds for 10-15 minutes. Leave overnight and air dry in a shade.

Seedling treatment:

·         Prepare fungicide solution by dissolving 2.5 g Copper Oxychloride and 2 g Ridomil in 1 litre water.

·         Dip seedlings for 10-15 minutes with the roots fully immersed in the solution.

Foliar Spray:

a)    Under low rainfall condition

·         1st Spray- Use Ridomil at 2 g/litre of water within two weeks of transplanting. Observe waiting period of at least seven weeks before harvesting.

·         2nd Spray- Use Copper Oxychloride at 2.5g/litre of water 14 days after 1st spray

·         3rd Spray- Use Copper Oxychloride at 2.5g/litre of water 10-14 days after the 2nd spray

b)   Under heavy rainfall condition

·         1st Spray – Use Ridomil at 2 g/litre of water within 10 days of transplanting.

·         2nd Spray – Use Ridomil at 2 g/litre of water 15 days after the 1st spray. Observe waiting period of at least seven weeks after the last spray before harvesting.

·         3rd Spray – Use Copper Oxychloride at 2.5 g/litre of water 14 days after 2nd spray.

·         4th Spray – Use Copper Oxychloride at 2.5 g/litre of water 10-14 days after 3rd spray.

Causal Organism

Insect:

Agrotis segetum (Denis and Schiffermüller)

Cutworm caterpillar (photo courtesy of NPPC)

Parts affected

·         Stems

Symptoms

On stems

·         Stem of seedlings above the ground level is cut though.

·         Leaves of cabbage seedlings are cut off.

·         Below ground the caterpillar also feeds on crops like potato, turnip and turnip.

Cabbage seedling damaged by cutworm (photo courtesy of NPPC)

Control Measures

1.   Cultural Control

·         Dig out and expose pupae and larvae to the sun and natural enemies.

·         Clean the field and remove weeds to reduce larvae population in the soil. Weeds serve as host for cutworm to lay eggs and supply food for the larvae.

·         Mulch chilli plots with Artemisia, a shrub, locally known as Khempa, Mayreng-ma, Titepathi to prevent build-up of cutworm population.

2.  Mechanical  Control

·         Collect and manually remove the larvae from the affected fields.

·         Dig the soil around the affected plants to expose and kill the larvae.

3.   Natural Control

·         Protect birds like Hoopoes as they feed on cutworms.

4.   Chemical Control

·         Dip seedlings in Chlorpyrifos solution (4 ml/litre water) before transplanting.

·         In case of severe infestation, spray with Chlorpyrifos at 4 ml/litre water.

Causal Organism

Fungus:

Phytophthora infestans

Sporangia of P. infestans
 (left) and Oospores of Phytophthora infestans (photo courtesy of Cornell University)

Parts affected

·         Leaves

·         Tubers

Symptoms

On leaves

·         Small light to dark green water soaked spots with a chlorotic halo.

·         Lesions become bigger rapidly and turn brown or purplish black.

·         Affected leaves covered by a cotton-like white mouldy growth on the underside of the leaf or stem.

·         Infected leaves die with a few days.

Late blight lesion on potato leaf (photo courtesy of Cornell University)

On tubers

·         Infected tubers show irregular and slightly depressed areas of brown to purplish skin.

·         Tubers may rot completely due to secondary infections.

Late blight tuber rot (photo courtesy of The Pennsylvania StateUniversity)

Control Measures

1.   Cultural Control

·         Select a site that has not been used for potato cultivation.

·         Avoid water-logged fields.

·         Follow crop rotation with non-solanaceous crops such as cabbage, cauliflowers, broccoli etc.

·         Use certified healthy seeds preferably from Druk Seed Corporation (DSC).

·         Sort out infected tubers during seed selection.

2.   Chemical Control

Foliar Spray:

·         Monitor potato field for late blight symptoms.

·         Spray immediately on emergence of first disease symptoms. Use Mancozeb at 2 g/litre water followed by a second spray, if needed, with Copper Oxychloride at 5 g/litre water. During rainfall, use sticker (e.g. Sandovit) with the chemical.

Weeds

a)    Crab Grass (Digitaria ciliaris),

b)   Helpsi, Shido (Persicaria runcinata, P. nepalinsi)

c)    Jagyouma, Jasasuju (Galingsoga parviflora)

d)   Pig Weed (Amaranthus spp.)

e)    Lambsquarters/Fat Hen (Chenopodium spp.)

f)    Bermuda grass (Cynodon dactylon)

g)   Nutsedge/Nutgrass (Cyperus rotundus)

Effect on potato

·         Reduces yield by as much as 50-60%

·         Competes with nutrient, water, and light

·         Damages tubers

Control Measures

1.  Mechanical Control

·         Plough or use power tiller to control established annual and perennial weeds.

·         Clear and remove roots/rhizomes of perennial weeds manually.

2.   Physical Control

·         Do first weeding and ridging as soon as the potato emerges (4 weeks) or sooner if weed growth is heavy.

3.   Chemical Control

·         Before the potatoes emerge, spray Metribuzin (Sencor) at 1 g/litre water. During rainy condition, use a suitable sticker (e. g. Sandovit).

·         Supplement chemical application with hand weeding.

Causal Organism

Insect:

Potato Tuber Moth, Phthorimaea operculella (Zeller)

Close-up view of potato tuber moth (photo courtesy of NPPC)

Parts affected

·         Tubers

·         Leaf Veins

·         Petioles

·         Stem

Damage Symptoms

On tubers

·         Presence of galleries inside infested tubers when cut open

Infested tubers (photo courtesy of NPPC)

On leaf veins, petioles, and stem

·         Tunnelling of the above parts

·         Wilting of the plant

Potato leaf showing signs of damage caused by the
PTM (photo courtesy of  the Virtual Museum of Canada)

Control Measures

1.   Cultural Control

·         Do deep planting (at 10 cm deep) with frequent hilling-up of the soil to reduce field infestation.

2.  Sanitation

·         Use only healthy tubers as seed.

·         Clean storage conditions. Clean the walls and the floor of the store properly and dispose off old leftover potatoes to reduce infestation.

·         Store potatoes in a cool area as low temperature limits the development of the pest.

3.   Natural Control

·         Natural enemies like parasitoids may play an important role in keeping this pest in check. Avoid improper and indiscriminate use of chemicals to encourage the presence of natural enemies.

4.   Resistant Variety

·         Use resistant varieties like Desiree to reduce infestation.

5.      Chemical Control

Field:

·         Apply either Cypermethrin (1 ml/2 litres water) or Chlorpyrifos (4 ml/litre of water) when pest appears in the field.

·         For severe infestation, spray with Chlorpyrifos at 4ml/litre of water.

Store:

·         Mix Fenvalerate dust with the infested tubers at 100 g/100 kg potato).

Causal Organism

Fungus:

Phytophthora infestans

Sporangia of P. infestans (left) and Oospores of Phytophthora infestans (photo courtesy of Cornell University)

Parts affected

·         Leaves

·         Stems

·         Fruits

Symptoms

On leaves

·         Pale green, water-soaked spots, often beginning at leaf tips or edges.

·         Lesions/wounds of 1-2 mm diameter are visible on leaves after 3-4 days of infection.

·         Lesions/wounds have a brown dead centre, surrounded by host tissue that has died and appears either water soaked, grey-green, or yellowed.

Tomato leaves with late blight lesions (photo courtesy of T.A. Zitter, Cornell University, Ithaca, NY)

On fruits

·         Large, firm, brown, leathery-appearing lesions/wounds, often concentrate on the sides or upper fruit surfaces.

·         Abundant white mould growth on the lesions.

·         Rotting of entire fruit if secondary soft-rot bacteria gains entry in the wounds resulting in a slimy, wet rot of the entire fruit.

Phytophthora blight of tomato

(photo courtesy T.A. Zitter, Cornell University, Ithaca, NY)

On stems

·         Infected stems appear brown to black.

Infected tomato plants with lesions on stems and foliage
 (photo courtesy T.A. Zitter, Cornell University, Ithaca, NY)

Control Measures

1.   Cultural Control

·         Select a site that has not been used for tomato cultivation before.

·         Avoid water-logged fields.

·         Follow crop rotation with non-solanaceous crops such as such as cabbage, cauliflowers, broccoli etc.

·         Use certified healthy seeds preferably from Druk Seed Corporation (DSC).

·         Sort out infected tubers during seed selection.

2.   Chemical Control

Foliar Spray:

·         Monitor potato field for late blight symptoms.

·         Spray immediately on emergence of first disease symptoms with Mancozeb at 2 g/litre water followed by a second spray, if needed, with Copper oxychloride at 5 g/litre water. During rainfall, use sticker (e.g. Sandovit) with the chemical.

Causal Organism

Bacteria:

Xanthomonas campestris pv. juglandis

Parts affected

·         Nuts

·         Shoots

Symptoms

On shoots

·         Black lesions, and leaves show irregular lesions on blade.

A shoot infected with walnut blight (photo courtesy of University of California)

On Nuts

·         Black, slightly sunken lesions at the flower end (end blight) when young;

·         More lesions develop on the sides of the nut as it matures (side blight).

Blight infection on side of young walnut (photo courtesy of University of California)

Control Measures

1.   Chemical Control

·         Spray Copper oxychloride at 5 g/litre water when the first nutlet/pistillate flower emerge. In areas with heavy rainfall, spray 7-10 days after first spray. Use sticker (Sandovit) when spraying chemical during rainy periods.

(Source: http://www.ipm.ucdavis.edu/PMG/r881100111.html)

Causal Organism

Insect:

Red-spotted Longhorn Beetle Batocera rufomaculata (De Geer)

An adult Red-spotted Longhorn Beetle (photo courtesy of NPPC)

Parts affected

·         Branches

·         Bark

Damage Symptoms

On branches

·         Presence of “ring barks”.

·         Damage of growing tips and branches.

On bark

·         Presence of cuts on the barks.

·         Excretion of fluid after oviposition (laying of eggs).

·         Presence of tunnels.

·         Large quantities of saw dust like frass removed out of feeding holes.

·         Presence of exit holes.

Control Measures

1. Preventive

·         Do timely weeding and bush clearing, basin making, and other proper orchard management practices.

·         For small trees, maintain only one trunk so that it is easy to check for infestations later.

·         Collect adult beetles in April-June. Put them in a closed jar and exposed to the sun.

2.Curative

·         Regularly monitor the trunk base for tiny wet or swollen spots. Scrape the bark open with a small knife and kill the small larvae.

·         Remove weeds around the trunk to easily monitor infestations.

·         Poke the entry holes of the beetles with an iron wire to kill the older larvae. Plug the holes with petrol-soaked cotton or inject the holes with petrol. Close the hole with mud preferably mixed with cow dung. Monitor the treated trees for fresh frass (saw dust-like wood powder produced as a result of the beetle’s feeding) and repeat the treatment if frass is still produced.

3. Sanitation

·      Remove and burn heavily-infested unproductive trees.

·      Destroy dead trees as they can serve as breeding place for the beetle