The Paddy Disease In Tropical Asia

Published Date: 02 Nov 2017

Introduction

Paddy disease in Tropical Asia

5-6

Common disease in Malaysia

Bacteria blight

7

Blast

9

Tungro disease

11

Stem nematode

13

Economic important

15

Conclusion

16

References

17

LIST of TABLE and FIGURE

TABLE

PAGE

2.1

Bacterial causal agent

5

2.2

Fungi causal agent

5

2.3

Virus causal agent

6

2.4

Nematode causal agent

6

FIGURE

PAGE

1.1

Paddy morphology

4

3.1

Symptom of bacterial blight

8

3.2

Microscopic view of Xanthomonas oryzae

8

3.3

Symptom of blast disease

10

3.4

Microscopic view of Pyricularia oryzae

10

3.5

Symptom of tungro disease

12

3.6

Nephotettix impicticeps

12

3.7

Microscopic view of Rice Tungro Spherical Virus

12

3.8

Symptom of stem nematode

14

3.9

Microscopic view of Ditylenchus angustus

14

INTRODUCTION

Table 1.0: Paddy classificationScientific classification

Nature

Plant

Unranked

Plantae

Unranked

Monocots

Unranked

Poales

Family

Poaceae

Genus

Oryza

Species

O. sativa

Binomial name

Oryza sativa

Figure 1.0: Paddy morphology

Paddy is one of the commodity crops in Malaysia. It is widely planted in Peninsular Malaysia particularly in north region which is includes Perlis, Kedah and Terengganu and a few area in Selangor and south of Malaysia. This happened due to the favorable condition for paddy cultivation which are there is a lot of swampy area and the average annual rainfall exceeds 3500mm as well as reinforcement by the prolonged summer. There are two type of paddy planted in Malaysia which are wet rice, also known as paddy rice and upland rice.

Paddy was found planted in Malaysia at Cha Cave and Cave Tiger from the Neolithic Age between 6000 and 4000 years ago. The upland paddy used to be planted in Malaysia before the introduction of the paddy rice. The upland paddy have low yield due to old practices which less fertilizer application and the seed is less good. Paddy have similar problem as happened to other commodity crop which are favorable to be damage by pest.

PADDY DISEASE in TROPICAL ASIA

Causal agent: Bacteria

Disease

Pathogen

Bacterial blight

Xanthomonas oryzae pv. Oryzae

Bacterial leaf streak

Xanthomonas oryzae pv. Oryzicola

Foot rot

Erwinia chrysanthemi

Grain rot

Burkhoderia glumae

Sheath brown rot

Pseudomonas fuscovaginae

Table 2.1: Paddy common disease in Tropical Asia cause by bacteria

Causal agent: Fungi

Disease

Pathogen

Blast

Pyricularia oryzae

Magnaporthe grisea (teleomorph)

Brown spot

Cochilobolus miyabeanus

Bipolaris oryzae (anamorph)

Black kernel

Curvularia lunata

Cochilobolus lunatas (teleomorph)

Downy mildew

Sclerophthora macrospora

Sheath blight

Rhizoctonia solani (anamorph)

Sheath rot

Sarocladium oryzae

Stem rot

Sclerotium oryzae (synanamorph)

Table 2.2: Paddy common disease in Tropical Asia cause by fungi

Causal agent: Virus

Disease

Virus

Vector

Grassy stunt

Rice Grassy Stunt Virus (RGSV)

Nilaparvata lugens

Tungro

Rice Tungro Spherical Virus (RTSV)

Nephotettix impicticeps

Nephotettix apicalis

Recillia dorsalis

Yellow dwarf

Rice Dwarf Virus (RDV)

Nephotettix cincticeps

Nephotettix impicticeps

Nephotettix apicalis

Table 2.3: Paddy common disease in Tropical Asia cause by virus

Causal agent: Nematode

Disease

Pathogen

Stem nematode

Ditylenchus angustus

Root nematode

Hirschmaniella oryzae

Root-knot

Meloidogyne spp.

Crimp nematode

Aphelenchoides besseyi

Table 2.4: Paddy common disease in Tropical Asia cause by bacteria

COMMON PADDY DISEASE IN MALAYSIA

Bacterial Blight disease

Causal agent : Bacteria

Xanthomonas oryzae

Infection : Xanthomonas oryzae live in the seed and dead plants and move from plant to plant easily through water from irrigation or other abiotic factor. The bacteria infest into plant through natural opening like stomata or crack on roots and through wounded area. The bacteria then grown within the plants and infects the plant leaf veins as well as the xylem causing blockage and plant wilting. Bacteria transmit from the leaf lesions by wind or rain, especially when the strong storms occur and cause wounds to plants.

Symptom(s) : Usually an entire leaf becomes straw yellow due to death of the leaf tissue. The elongated lesion with wavy margins starts to form one or both edge of the leaf and gradually extend and kill the entire leaf. When the lesions spread quickly the leaf tissue will rapidly wilt. Bacterial substance produced may be observed in the morning as milky dew drops on young lesions.

Control method(s) : Controlling should be done as early as nursery stage by avoiding flooding because it wills easier the bacteria to spread. The use of more resistant cultivar also would be an alternative to this disease. Besides, we should avoid excess application of fertilizer especially nitrogen (N) and the chemical application would be the last solution

Figure 3.2: Microscopic view of Xanthomonas oryzae

Figure 3.1: Symptom of bacterial blight

Blast disease

Causal agent : Fungi

Pyricularia oryzae

Magnaporthe grisea (teleomorph)

Infection : This fungus known as Pyricularia oryzae infect as a spore which produced lesions or spot on parts of the paddy such as leaf, leaf collar, panicle, culm and culm nodes. By using the structure called an appressorium, this fungus penetrates the plant then produce spore in the infected rice plant to be dispersed as conidiospores. The cycle repeated as the fungus overwintered the plant.

Symptom(s) : Spots or lesions on leaves, nodes, the panicle base and branches, and on grains, but seldom on the leaf sheath. The center of the spots usually grey and the margin, brown or red brown. The shape, size and colour of the spots vary, however, depending upon the age of the spot, the degree of the susceptibility of the rice cultivar and the environmental conditions. The spots normally begin as small, water-soaked, white, grey or blue dots and it is rapidly enlarge under moist condition.

Control method(s) : This fungal causal disease can be control by manipulating the cropping system. We have to avoid cultivating in different season, because the disease will spread to our field when there is no host in other area. Besides, we also can use more resistant cultivar such as Teptep and Carreon and the chemical would be the last alternative for this disease.

Figure 3.4: Microscopic view of Pyricularia oryzae

Figure 3.3: Symptom of blast disease

Tungro disease (Penyakit Merah)

Causal agent : Virus

Rice Tungro Bacilliform Virus (RTBV)

Nephotettix impicticeps (vector)

Infection : Normally only a portion of a field population of Nephotettix impicticeps is able to transmit this RTBV. The transmission of this virus is 50-8-% of total paddy population. N. impicticeps acquires the virus by feeding plant sap on the infected plant, it can transmit the RTBV immediately after feeding. Virus attaches to the cell of plant host, and then they inject their contents into the nucleus cell which change the host plant metabolism to reproduce new viruses. This birus only replicate inside the phloem cells in infected host plant.

Symptom(s) : Infected rice plant normally stunted and the number of tillers is lightly reduced. The leaves are yellow, slightly rolled outward and somewhat spirally twisted. The plant becomes stunted through a shortening of both the leaf sheath and leaf blade. The limited elongation of the new leaf sheath, the unfolded leaf is sometimes elapsed by the outer leaf sheath. The degree of stunting varies among rice varieties and reduction in plant height decrease with increasing plant age at the time of infection.

Control method(s) : A well sanitation practice is needed to control this disease. The residue that can be the habitat for Nephotettix impicticeps must be thrown away and the infected plant must be destroyed. Then the use of more resistant cultivar is much more recommended such as Bengawan, Intan, FB 24 and etc to withstand this disease. Chemical application would be the last option.

Figure 3.7: Microscopic view of Rice Tungro Bacilliform Virus (RTSV)

Figure 3.6: Nephotettix impicticeps

Figure 3.5: Symptom of tungro disease

Stem Nematode (Ufra Disease)

Causal agent : Nematode

Ditylenchus angustus

Infection : Infection takes place when there is a favorable humidity. They climb up the stems and attack the growing tissues. They enter the bud and can find their way into the inner potions by working their way between the folds. They do not penetrate bodily through the tissue, but protrude their stylets, which are inserted into the epidermal cells and suck the plant sap.

Symptom(s) : In the seedling stage, the chlorosis happened, followed by withering and death (Padwick, 1950 recite by OU, 1985). The symptom in paddy field may be observed as early as 2 month after planting and may varies based on nematode activities, the leaf are twisted and in some cases the basal portion of leaf become wrinkled, followed by whitish-green discoloration and death.

Control method(s) : Flood the filed when there is no paddy to exhibit the growth of the nematodes in soil. Removal of the destructed stem by nematode is necessary to avoid the nematode move to other plant. The use or more resistant cultivar like Khao-tah-oo and Khao-tah-haeng are recommended and the use of chemical like sunfuran 5G, edfuran 5G and fowafuran 5G would be the last option

Figure 3.9: Microscopic view of Ditylenchus angustus

Figure 3.8: Symptom of stem nematodes

ECONOMIC IMPORTANT

As we all know paddy is one of the commodities crop in Malaysia and there must be some study should be done to ensure this industry will long last. Paddy was planted almost 700,000 hectares which produced almost 4000kg per for each hectare in 2010. Just like other commodity crop, paddy also susceptible to be infected by diseases. There is a lot of study done out there in related to disease of paddy. They are study on controlling methods, disease cycle, abiotic and biotic that could bring the favorable condition of pathogen to spread and infest. All of these studies are done in order to sustain the paddy industry which important in contributing in Malaysian GDP.

(Source: Department of Agriculture, Malaysia)

In 1985, paddy industry contribute around 0.9% of Malaysia GDP and 4.7% of agricultural value added but this statistic start to decline recently due to management problem relating to paddy cultivation and rice production (Lopez, (Unknown). One of the problems is disease that brings huge effect to economic of paddy industry. Disease such blast and rust, bacterial blight and stem rot are the most dangerous disease that gives economic damage to paddy. It destroys the rice grain which is an interested part to be harvest. Decrease in yield will eventually effect the decrease in profit for sure, thus will lower the productivity. Study should be done to overcome every single problem faced in this industry for sustainable paddy industry.

CONCLUSION

As conclusion, it is important for us to study and understand well the common disease of paddy in order to support and to develop a sustainable paddy industry in Malaysia. There are many small holders which cultivated paddy in Malaysia. Some of them don’t have a proper knowledge and understanding on the disease. Without true understanding on the common disease like bacterial blight, blast, tungro and stem nematode as well as the basic information of the disease cycle, we cannot predict and calculate the risk of the disease to infest on our cultivation area. Well spread of one of this disease to the above economic injury level will cause the crop to be abundant. At this level the controlling action does not effective anymore.

Therefore we should understand well the disease because some of the disease does not alone but it transmitted by the vector. In other word, sometime we don’t need to control disease, but by only control the possible vector of the disease, we can save the crop. Some of the diseases are naturally born like, soil born (nematode) and air born (bacteria), so we need to take an alternative action such as making a soil treatment by applying some effective microorganism (EM) that can help us in controlling the nematodes inside the soil. Beside of using the chemical as the controlling methods, we can use some of the natural enemy of the disease causal agent and it will bring an effective cost management.