CURRENT STATUS OF INSECTS
AND DISEASES IN WILD,
CULTIVATED ORCHID SPECIES AND COUNTERMEASERES IN VIETNAM |
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Dr. Lam Quang Du, Prof. Tran Duy Quy et al,
Institute of Agricultural Genetics, Hanoi, Vietnam.
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| Vietnam belongs to sub-tropical
and tropical region, where species of orchids are very diverse ( app.
125 genera and 800 species compared to 750 genera and 25000 species
in the world). Recently, orchids are being exploited and cultivated
in natural forest, households, and private companies. Mostly, there
has few effect of breeding towarding the creation of new varieties
possess nice colour or big flower, resistant to pests and diseases
and so on. Many kinds of pests and diseases for orchid are available
in natural condition. Moreover, increasingly, in Vietnam, different
orchids are been being imported from some other countries as: China,
Taiwan, Korea, Thailand, America and so on. That’s why many new pests
and diseases in orchid present also in Vietnam. |
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| 1. |
Some pests and diseases for orchid
in Vietnam |
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| Viruses |
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| Viruses infection are quite
common for orchid in Vietnam. Once infected, the whole of a plant
becomes infected. It is weakened but does not die, and may be relatively
symptom-free. They involve various degree of leaf discoloration, often
with yellow or black mottling or pitting, or streaked patterns. Viruses
can cause color and shape abnormalities in in flowers. Some of viruses
for orchid in Vietnam may be Cymbidium Mosaic virus (CyMV), Tobacco
Mosaic virus (Orchids type, and Odontoglossum Ring Spot virus (ORSV). |
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| Fungal and Bacterial
diseases |
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Mostly, fungal and bacterial
diseases cause some forms of rot, or discoloration and spotting of
flowers or leaves. The common symptoms that are attributable to fungal
and bacterial attack are rotting, where the plant tissues become discolored,
then streaks or spots of discoloration on leaves or flowers. In Vietnam
condition, we usually remove the affected parts of orchids by cutting
back to clear tissue; then spray or paint cut surfaces with bactericide
and fungicide, and dispose completely of infected materials.
Fungicides as: Physan and Streptomycin Sulphate (agricultural antibiotic),
1% Copper Sulphate solution, Captan, Thiram, Zineb, Etridiazole, Metalaxyl
or Natriphene can be used to control infections. In many cases, infected
plants were removed immediately, as infection spreads rapidly in collection. |
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| Pests |
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In Vietnam, a wide range
of pests, most of which are insects, can damage orchids. Apart from
snails, cockroaches or beetle larvae that actually feed on the plant
or their flowers. Other pests such as: aphids, mites, thrips that
may infect the plant that it becomes seriously debilitated or even
killed. The commonest problems are mites, thrips, and scale insects.
Damage activities and countermeasures of them as following:
Scale insects: they cause infections of tiny brown scales covering
plant leaves and stems. Dimethoate or Triazophos can be used for effective
control.
Mites: red spider mites and false spider mites attack the leaves and
stems, sucking the sap. They particularly accumulate on the surface
of leaves. Amitaz, Diazinon, Dimethoate and Propagite can be used
effectively for mite control.
Mealy Bugs: the bodies of mealy bugs form a white powdery mass around
stems. Malathion can be used for effective protection.
Beetles: beetle larvas eat flowers or root tips. Pesticides as: Trichlorfon,
Dimethoate or Diazinon can be used for effective control.
Cockroaches: they eat the green tips of roots. Diazinon or Malathion
can be used for effective control.
Thrips: they cause failure of the flower buds or distortion of flower
or white streaks. Dimethoate, Diazinon and Trizophos can be used for
control. |
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| 2. |
Some fungicides, bactericide, and pesticides using for orchid in some places of Vietnam: |
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| Recently, most of pesticides, which are being used in Vietnam to be imported from oversea as China, Japan, the United State of American, etc. Some of them are tested and guided in detailed for use as following: |
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| Names Concentration |
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| Names |
Concentration |
| Dimethoate |
1-2
ml/l |
| Fenpropathrin |
2-3
ml/l |
| Endosufan |
1,5 –3
ml/l |
| Topsin-M |
1 kg/
500 l water/ha |
| Zincopper |
2-3
kg/ 500 l water/ha |
| Daconil
500SC |
2.3-3
kg/ 500 l water/ha |
| Kocide |
2-4
kg/ 500 l water/ha |
| Sumi-eight
12.5wp |
0.4-0.8
kg/ 500 l water/ha |
| Zeneb |
1-1.5
kg/ 500 l water/ha |
| Dursban
50W |
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| Diazinon
50W |
- |
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It’s necessary to have molecular pathology techniques to test virus infection at very early stage. It is Enzyme Linked Immune-Absorbent Assay (ELISA) or others. - In many cases, the use of fungicides, bactericide, and pesticides had not been controlled. It should be controlled carefully by authorities. |
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Pests and diseases of the imported orchids from oversea have to be controlled carefully. |
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Fungticides possess different compositions and effectiveness varies with different fungy. So, different fungticides should be used at alternate application. |
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Furthermore, selection of new orchids with good resistant to pests and diseases should be performed. |
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