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How to prevent and treat atrophy of young buds on dendrobium orchids

Young buds shrink, rot and fall off very early. Big buds have brown spots, flower buds are deformed, discolored, the buds that bloom have damage on the petals, manifesting very similar to gray mold on flowers ...

Those are symptoms in orchids Denrobium when harmed by the larvae of the fly Contarinia maculipennis.


Recently, in some Dendro orchid gardens in Ho Chi Minh City, there is a phenomenon of falling buds. It is often seen that the young buds shrink, rot and fall off very early. The big buds have brown spots, flower buds are deformed, discolored, and the buds that hatch out have damage on the petals, and the expression is very similar to gray mold on flowers. This phenomenon causes serious harm to flowers of all ages from newly sprouted buds on flower buds to mature flowers, causing big losses for orchids. Gardeners have used a variety of medications but have not seen any reduction in the damage.

Bud loss disease, atrophy of young buds on dendro orchids
Young bud atrophy and falling on Dendro orchids

Through observation, investigation and research in the garden we found the damage caused by the larvae of a species of flies. This is demonstrated by breaking off some damaged flower buds found inside some small white or yellow maggots, when touching these small maggots can pop a few centimeters away, each infected bud can Contains 5-30 maggots. Want to be sure you can put a few flower buds in a nylon bag so that a few hours later you will see the maggots come out a lot in the nylon bag.

Harmful agent

The maggots found in Dendro orchid buds are Contarinia maculipennis's larvae, a flower-damaging fly species now found on many crops such as orchids, hibiscus, jasmine, tomatoes, eggplant, potatoes, melons and on some other ornamental plants. This damaging fly was first found in the early 1900s in Hawaii. Reports of harm on Dendro orchids first appeared in Florida (USA) in 1992.

In Ho Chi Minh City, according to incomplete statistics, this species of flies was first recorded in 2003, since then they have continued to cause harm in orchid gardens and appear throughout the year. A special feature is that this type of fly is only harmful on Dendro orchids, other orchids even though planted in the same garden or close together do not see infection.

This insect habit

In order to find the right control method, we need to understand the habits and life cycle of this insect.

An adult has an outward appearance more like a mosquito than a fly. They are very small: about 2mm in length, twice as long as the body. Live 4 days. The fly's life cycle is from infancy to adulthood from 21–32 days depending on temperature and environmental conditions.

Female flies lay eggs on the heads of flower buds, eggs are creamy white visible to the naked eye, eggs hatch within a day, larvae after hatching deep into flower buds, they feed on tissues of flower buds. causing deformation, discoloration on buds and petals, when damaging on young buds, they also drop flower buds.

Buds and petals, after being damaged, often break down or grow gray mold, making it easy to mistake the flowers are suffering from gray mold.

Newly hatched larvae are white when older are yellow, larvae live in flower buds for 5-7 days, at this time the larvae can snap a few centimeters away in the air, this is a feature to distinguish them from larvae of other species. The habit of flicking a few centimeters away helps them to leave the flower buds deep into the ground.

After leaving the flower buds, they will pupate in the wet soil, stay in the soil from 14 to 21 days, the final stage of the nymph will turn from yellow to brown and come up close. the ground to become an adult. They usually appear in the evening.

Flies and their larvae adapt to environmental changes very well, female flies lay eggs on the tips of flower buds where the larvae can easily get into the flower buds they also often choose young flower buds for larvae. there is enough food and a good environment to grow up. When bud conditions change such as drought or damage, the larvae will leave the bud earlier than necessary and pupate time in the soil is longer than normal and the fly matures. the wall is also smaller in size than the well-conditioned fly.

The fly density will also decrease rapidly when the ambient temperature falls below 18 ° C.

In temperate countries, cold winters often do not see them appear.

Consider the entire life cycle of flies from infancy to adulthood from 21 to 32 days depending on temperature and environmental conditions. In the process, the larval stage is the stage of flower bud destruction, causing the greatest losses, although this stage lasts only 5-7 days. It is also important that the insecticides have no effect on the larvae because they are protected by the thick flower bud tissue. According to our testing, some of the endosperm drugs also kill the larvae, but the effect is very low.

Currently there are no reports of natural enemies on this fly. Adults can be caught in spider webs, ants can eat pupae in the soil.

The method of using chemical drugs with very low results, for effective control, needs to combine many measures

Control measures

Because flies appear all year round and with high temperatures like in Ho Chi Minh City, the life cycle of flies will be short, control needs to be done regularly and persistently to bring good results. To do:

Discard all infected flower buds and flower buds in a nylon bag and burn them within the same day, do not dump them in a landfill, this action is simple but very important to quickly reduce the density of larvae. In the garden, take care when cutting off, put it in a non-handle bag from one place to another to allow the larvae to jump to the ground.

Spread seed medicine on the ground below the orchid: drugs can use Diaphos 10H, Sago Super 3G, Chicken Nug 4G, ... when spraying water to absorb the drug evenly on the ground to kill pupae in the soil. Because the flies overlap, it is necessary to pay attention to spray the drug every 10-15 days to kill the pupae.

Spraying insecticide on adult flies: Adult flies appear and lay eggs in the evening after sun off, so spraying at this time is effective. The commonly used drugs: Sec Saigon 25EC, Dragon 585EC, ... when sprayed with SK Enpray 99EC mineral oil or adhesives, this is important because adult flies have long wings that are easily susceptible to adhesives or oil. mineral, increase eradication effect.

It takes persistence and continuity to follow the schedule, the new fly density gradually decreases.

Stemming from passion, perseverance and hard work, after 23 years of research and research on orchid growing techniques, I have accumulated a lot of experience in propagating and cultivating forest orchids effectively.