Sooty Mould on Okra/ Ladyfinger

Sooty mould (Cercospora abelmoschi) is the black mould grow on the honey or plant sap left by plant sucking insects like aphids and leafhoppers. It is not harmful to the plant, large colonization cause reducing photosynthesis process and weakening the plants, make it vulnerable to insects attack. Besides, it is good indicator of infestation of plant sucking insects that may carry the virus. Okra plants that infected by virus will be stunted and leaves became rosy.

Sooty mould almost colonized the whole leaf of okra

Amrasca biguttula favour the okra and hopping on the leaves. It is easily recognized by its two dots on the back of wings. They stay underside of leaves and feed on plant saps at all stages of life cycle. Complete life cycles of A.biguttula is 1 month, eggs hatch in 1 week and nymphs comprises 5 instars, which emerge as adult in 1 week time. Adult has 2.5 weeks of lifespan. Lessenta (fipronil + imidacloprid) from Bayer at 3g/ 16L pump could reduce the population to certain level, but not during the pest outbreak. Besides, Plenum 50WG (pymetrozine) at 5g/ 16L pump  from Syngenta has good control on leafhopper as well. Neonicotinoids such as imidacloprid (Confidor) and dinotefuran (Oshin 20WP) as well as Clothianidin (Dantotsu) at 5-10 g/ml definitely could bring the population below threshold level too.
 

Adult and nymphs of A.biguttula stayed undersides of leaves

 

Armyworm (Spodoptera exigua) on Chilli

Armyworm could be very destructive at the early stage of planting and fruiting stage. It is easily recognized with two rows of pale yellow line along the side body. They are green when young and turn dark brown when matured. Their size around 3-4cm long. Young leaves on the early stage tend to attract pest attack that will consequently delay fruiting and lower yield. Some of them may hide in the flower and feed on flower as well. Larval stage (1 month) actively feed on plant's plant, it infests eggplant and tomato also.Weaken plants are prone to secondary pathogens attacks due to wounds caused by worms.

S.exigua feeding on the leaves

 

Few armyworms larvae sharing the same silk casing

 

 

With the application of the insecticides such as Steward EC (Indoxacarb 15.84%), Regent 50 SC (fipronil 5%) and Prevathon (chlorantraniliprole 5%) could have great control on this pest.

 

BACTERIAL SOFT ROT (Xanthomonas campestris pv. vesicatoria) ON CHILLI LEAVES

Perhaps this disease is less common being spotted in Malaysia, but it spread very fast during outbreak especially on intermittent of rainy and hot days. Usually the pathogens attack on the immature plant, causing defoliation.

Water-soaked soft rotting on the leaves margins, lesions became opaque like scalded by insects or dropped off.

Early symptoms showed with multiple greasy grey spots.



There is no BACTERICIDES in the current market. The only treatment available is using the copper based fungicides like tribasic copper sulphate (Cuproxat) with 1.5-2ml/L of water or copper hydroxide (Parasol) with 0.5-1g/L of water. Copper will disrupt the enzyme activity in the bacterial cells with exchange of magnesium and calcium ion, in turn accumulation causes cell ruptures.

Sanitizer e.g.SPOREKILL is highly recommended to add into spraying programme with copper fungicide to sterilize the leaves surfaces. It enhances the performance of fungicides with one time job killing the bacteria and other pathogens, while fungicides will play the residual role on the latter part.

 

One of the most concerning issue among farmers are copper fungicides are not safe and cause plants yellowing. However, with the careful steps followed, plants are usually safe from phytotoxicity. There are 3 precautious steps need to take note that pH, moisture and type of copper will determine how much of copper ion will be released on the leaves. Excessive of copper ion released if using ACIDIC water.

 

Second, copper deposited on leaves once applied and gradually release the copper when there is moisture like morning dew or raining. Too much of moisture like raining will release high concentration of copper.

 

Third, using fixed copper like copper hydroxide and tribasic copper sulphate instead of copper sulphate pentahydrate, which is less soluble and prolong the protection on the leaves. Solubility of copper: copper sulphate pentahydrate > copper hydroxide > tribasic copper sulphate. Hence, tribasic copper sulphate is recommended, it release 50% of the copper ion for shock treatment while another 50% will stay on plant surface to provide protection.

 

To be noted that copper fungicides are mainly play the protection function. During the disease outbreak, it is too LATE to be applied and treatment became limited. BRING THE RAINCOAT BEFORE IT RAINS.

Leaffolder on RICE (Cnaphalocrosis medinalis)

LIFE CYCLE:
Leaf rollers complete a full life cycle in a month.

DAMAGE:
-Scalding the leaf surface and became whitish streaks on leaf blades.
-Fold the leaf tips on the larva stage and feed the leaf tissues.
-Pest outbreak in short time if no action of control taken, infestation the whole field in just few days time.
-Larva stage is actively feeding on the leaves tissues during tillering to booting stage and they will spin the web to make the upper leaves into longitudinally folded.
-Larva is naturally favour to feed on young rice plants, especially those with high Nitrogen fertilized.

Heavily infested by leaffolders during active tillering stage

Infestation of leaffolders on hardening stage

Older leaves is folded like spikes

Larva Stage of leaffolder

Adult of leaffolder

CHEMICAL CONTROL:
-In general, most of the insecticides in the rice market can have good control on leaf rollers. e.g. buprofenzin (Applaud), cartap (Padan), acephate.
-Imidacloprid (Nuprid, Confidor), thiamethoxam (Actara) and dichlorvos (CH dichlorvos 42) have broad-spectrum control on planthopper, leafrollers as well as stem borer.

 Additional info:

http://www.scribd.com/doc/209942573/Integrated-pest-management-of-leaf-folder-Cnaphalocrocis-medinalis-Guen-in-rice
http://www.cropscience.bayer.com/Crop-Compendium/Pests-Diseases-Weeds/Pests/Cnaphalocrocis-medinalis.aspx
http://www.fintrac.com/cpanelx_pu/cambodia/12_13_5906_Technical-Bulletin-44-Rice-Leaffolder-English%20revised.pdf
http://www.knowledgebank.irri.org/decision-tools/rice-doctor/rice-doctor-fact-sheets/item/rice-leaffolder?category_id=345

Tomato Bacterial Wilt

Tomato bacterial wilt is a very destructive disease in green house planting in Cameron Highlands, caused by Ralstonia solanacearum, soil-borne pathogens. Harvesting could be ended after the first harvest, usually 2 months after transplanting. Disease getting severe after first harvest and start spreading from plant to plant, probably because harvesting tools used as the vector transmitting the inoculums. Healthy tomato plants in Cameron commonly can harvest up to 6 months.

 

Bacteria infection causing blockage of the vascular system, preventing water and nutrient transportation, symptoms started with wilting WITHOUT ANY LESIONS, followed with canker stretching over the basal stem, near the soil line. The canker symptom could be confusing with Botrytis cinerea, but its infection can be observed on leaves, fruit peduncle as well as stem. Fruits produced are small and inferior.

 

To differentiate the bacterial from fungal infection, cross cut the basal stem and dip into a glass of water, bacteria ooze will stream out from the stem.

 

Canker symptom appear on the basal stem.
 

Plants died off and fruits awaiting last harvest.

 

Great loss caused by the TBW.



 

 

 

Papaya Dieback Disease

Papaya (Carica papaya) dieback disease WITH NO EFFECTIVE CHEMICAL CONTROL

was discovered firstly in Java Island in 1913. Disease is caused by Erwinia papayae, which can survive in soil for 2 weeks as transient soil inhabitant and believed spread by human activity, birds or insects.

Symptoms:

1. Leaves
Water-soaked necrotic leaves from leaf tips to leaf vein.

Water soaked necrotic lesion
 

2. Shoot
Water-soaked lesions appear at the leaves stalk base and shoot, as well as the crown.

Advanced state of disease infection

3. Fruit
Started with sunken black spots which enlarges gradually.

Circular dark green lesion coalesces.