Detailed Explanation of Key Points for Pest and Disease Control in Phalaenopsis Orchids

Diseases: Phalaenopsis orchids are native to trees in tropical rainforests, where they not only grow vigorously but also rarely suffer from disease infestations. The most important disease is blight, which is caused by a fungus that invades the leaf tissue of the plant, divides and multiplies within the tissue, and destroys the cells of the tissue. This fungus divides and multiplies at an astonishing rate, and in just twenty-four hours, it is enough to destroy a healthy plant.

The fungi that can infect Phalaenopsis plants include (1) Phytophthora Palmivora (2) Phytophthora Parasitica. These two fungi are most rampant in the hot, humid summer season, and all Phalaenopsis plants suffer the most damage during this period. Therefore, the importance of the cultivation environment has been repeatedly emphasized above. Generally, when a diseased plant infected by fungi can first be observed with the naked eye, it already shows dark green, light-transmitting small spots. These spots spread very quickly. If this condition is found on a Phalaenopsis, the affected part must immediately be removed with a knife or scissors, and the area removed needs to be about 10 mm wider than the perimeter of the spot on all sides, to prevent a small amount of fungus that has already invaded healthy tissue but cannot yet be distinguished with the naked eye. Therefore, the removed portion must include some surrounding healthy tissue. The blade of the knife or scissors used for removal must be disinfected with 75% alcohol before and after use, and the wound should also be wiped and coated with alcohol, because alcohol can cauterize the cells on the wound surface and can also eliminate any bacteria attached to the wound. After the wound is coated with alcohol, on the second or third day a layer of white cambium can be seen after cauterization and drying. This indicates that the damaged wound is no longer a problem and will no longer be invaded and harmed by external bacteria.

In a plant body infected by fungi, the epidermis of the affected area ruptures and exudes water when lightly touched by hand, and it carries a fishy odor. If the fungus infects the leaf core area, this Phalaenopsis must immediately have the infected area cut away to save its life. If it is not noticed or not taken seriously, then this Phalaenopsis may be beyond saving. For common varieties, there may be no need to regret it, but for famous varieties, it is truly a case of losing more than gaining. Although a plant whose growing point has been cut away may not necessarily have its side shoots survive completely, as long as the wound after cutting is immediately coated with 75% alcohol, the chance of side shoots growing is generally over seventy percent. However, after cutting away the affected part, the water supply must be reduced to the minimum, and the affected plant should be placed in a place with weaker light to facilitate the growth of its side shoots. After the affected area is cut away, it must be properly disposed of to prevent the fungus from spreading. It is best to burn it with fire or soak it in disinfectant. Of course, burning is the most economical and trouble-free method.

Although experiments have shown that the roots cannot be directly infected by fungi, infection can spread from the leaves or stem to the roots. Under suitable conditions, in a whole pot of community seedlings, as long as one small seedling is infected and not dealt with, within two or three days all the small seedlings in the entire pot will be attacked by the fungus and all die. Therefore, orchid growers who use large community pots are advised to pay attention to this drawback.

2. Pests (including animal and mechanical damage):

The most common Phalaenopsis pests are the following several types, but if insect-proof netting can be added outside greenhouse windows, preventing some pests in advance will, it is believed, be very effective. Prevention is better than cure. For example, some larger pests such as katydids, locusts, and snails cannot invade.

1. Scale insects: There are many kinds of scale insects with differing shapes. Most scale insects harm Phalaenopsis, and all of them use piercing-sucking mouthparts to pierce into leaf tissue and suck out its nutrients. Therefore, plants harmed by scale insects become weak in body and their leaves turn yellow and wither. If not controlled, the plant will ultimately decline and die as a result.

Any scale insect can be controlled with a 1000-fold dilution of 50% Dimethoate emulsifiable concentrate, an 800-fold dilution of 50% Malathion emulsifiable concentrate, and by adding 1.2% premium summer oil per liter.

Scale insects can all secrete honeydew, so wherever there are scale insects, there are ants, and ants will also transport their eggs to healthy plants, causing them to settle and secrete honeydew for the ants to feed on. If you see ants busily working on a plant, you need to pay attention to whether scale insects have invaded, and ants can also spread bacterial blight, so immediately use Miendike powder to kill them.

2. Aphids: These include the barley aphid Sitiobion granarium (Kirby), the sorghum aphid Longiunguis sacchari (Zehntner), the bean aphid Aphis laburni (Kaltenbach), the corn aphid Rhopalosiphum maidis (Fitch), and others. Their control methods are the same as for scale insects, so they will not be repeated here.

3. Locusts: These include the Taiwan grasshopper Chondracris rosea (DeGeer), the striped soil locust Patanga succincta (L.), the small locust Oxya intricata (Stal), and others. They can bite and eat leaves and damage the Phalaenopsis plant body, but their degree of harm is not great, because with current greenhouse equipment, it is sufficient to prevent locusts from invading. If this pest occurs, a 1000-fold dilution of Miendike can be applied, or they can be caught and removed by hand.

4. Moth larvae: This pest occurs in early spring. Any moth may lay eggs on Phalaenopsis leaves, and hatch small larvae that gnaw on the leaves. Therefore, in early spring, pyrethrum extract should be applied for control. If Phalaenopsis leaves are seen being gnawed by some unknown insect, appropriate measures must immediately be taken: find the insects by hand and crush them to death, or spray insecticide for control. Generally, pyrethrum extract or synthetic pyrethrum extract can be chosen as the insecticide, to reduce the chance of harm to the human body from insecticides.

5. Mollusks: There are many kinds of mollusks, but snails alone give growers headaches. Whenever traces of snails or mollusks large or small are seen, metaldehyde must immediately be applied to lure and kill them, so as to avoid harm to the plants. The African giant snail in particular has a very large appetite and can gnaw through several small seedlings in one night, causing no small damage. Therefore, growers need to constantly pay attention to what is happening in the greenhouse and seek countermeasures to control any pest. During the rainy season, apply metaldehyde in all areas of the garden once every month.

For all insecticides, attention must be paid to their safety for the human body when using them, and there is no need to believe some unfounded suggestions or recommendations. However, as long as an insecticide can be used for environmental sanitation, it can be bought and applied as an insecticide for Phalaenopsis. This point very much needs to be brought to the attention of orchid growers: by no means should medication be used carelessly. The insecticides to be applied can be purchased at specialty pesticide stores, and detailed questions about medication safety should be carefully asked. Do not pretend to be an expert when you are not, for in the end the one who gets hurt is yourself.