Science and Technology News

Phenomenon "strange leaf-eating worm" in HCMC caused by Antheraea frithi moth

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Over the past few years, in Binh Duong and Ho Chi Minh City (HCMC), the strange phenomenon of leaf-eating worm has appeared, causing concern for people living in the area. To study this pest, the Southern Institute of Ecology sent its staff to collect worm samples in the area of My Phuoc - Tan Van and Pham Van Dong street to breed and conduct species identification. Initial results show that this is Antheraea, known as Tasar silkmoth (or Tasar silkworm), belonging to Saturniidae family, Lepidoptera.

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Locations of leaf-eating worm spots (Base map: Google Earth)

The moth is considered to be very difficult to classify, due to its polymorphic characteristics and many populations of the same sperately evolve species, creating subspecies. However, based on physical morphology, researchers have determined that this is Antheraea frithi Moore, 1859 (Wild tasar silkmoth), once recorded in Saigon ( Arora and Gupta, 1979) and several other areas in Vietnam. This species has a fairly wide distribution, from India stretching south of China, down to Java Island in Indonesia (Arora and Gupta, 1979; Paukstadt and Paukstadt, http://wildsilkmoth-indonesia.com/1fri_vis.html). )

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Males of Antheraea frithi Moore, 1859

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Females of the Antheraea frithi Moore, 1859

Antheraea is recorded mainly in natural forests. It has large size. Its wingspan is usually over 10cm. It is edible on a variety of plants, including the Dipterocarpaceae family, reported to have been attacked in recent times.

The natural enemies of Tasar silkmoth are quite diverse. The time from hatching eggs to the end of 5-year-old worms is about 30-45 days. It takes25-45 days from cocoons to Antheraea frithi. It can take longer if there are adverse weather conditions. The fact that worms are recorded more often around September to November (usually the end of the rainy season), so they will usually have two generations of blooming during the year, once around June-August in the rainy season and another again in early December to early dry season but with less quantity. After hatching into moths, they will mate and lay eggs on the host plant for the worm to continue a new life cycle.

According to Jollyand his co-workers (1976), species of the Antheraea make great contribution to the silk weaving industry in India and China and to other medical applications. Consequently, the wild Antheraea frithi and many other species of the the Antheraea have been studied for controlled farming in the wild, especially reforestation areas, contributing to environmental protection, creating more jobs and income for workers. Therefore, people should not be too worried because this is a species that, if controlled well, it will benefit humans and natural ecosystems.

However, the fact that they have appeared in large numbers recently is concerned issue. Researchers suspect that in the past, a few small populations exist scatteredly in un-reclaimed natural plots. During the development of the population, they often find more favorable places (the large number of host plants, less affected by natural predators), so they boom. Therefore, it is necessary to widely inform the people, in order to record additional data on the location and time of discovery so that it can propose effective measures and promptly control this situation in the future. Currently, scientists propose measures to deal with the following worm outbreak:

  • Most of the worms when becoming cocoon wrap 2-3 leaves around and then pull the silk and cover the body with a thick cocoon, so the treatment by spraying can only kill the worm, does not affect to the pupa. One more step is therefore needed to manually acquire these cocoons, to avoid the situation they are still capable of moth hatching and continue to mate to maintain populations.
  • In the future, when first discovering worms eating leaves, to limit spraying, we can treat as follows: wrap a cloth or plastic sheet around the base of the tree with a larger size than canopy, then shake the tree to let the worm fall. Then prune trees to remove caterpillars and butterfly nymphs still on the tree. Extend to nearby trees until there are no more worms falling after shaking the tree, then stop. This measure can take a lot of effort, but minimizes future population growth. The collected worms and nymphs can be destroyed, or buried as clean fertilizers, or evenly distributed to natural forests so that they can balance themselves in nature.

Translated by Tuyet Nhung
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