Successfully cultivating 'pure carving' of the worms

Caterpillars are the most serious pests on cruciferous vegetables in all countries. Vietnamese researchers have experimented in importing and developing D.semiclausum bees to kill silkworm in Da Lat vegetables.

Because Vietnam lacks important natural enemies, caterpillars - exotic worms spread more quickly, devastating vegetable growing areas, especially cruciferous vegetables (about 6,000 ha) in Da Lat-Lam Dong.

Sponsored by the Food and Agriculture Organization of the United Nations (FAO), the Plant Protection Department has imported a number of natural enemies, including 500 D. semiclausum Hellén bee pods from Malaysia's Cameron Highlands to Da. Lat to feed.

Because it was the first time to experiment in Vietnam, Lam Dong Plant Protection Department had to research for many years. From the initial 500 cocoons, scientists have cultivated, developed thousands of bees and released the vegetables of Da Lat to kill worms.

D. semiclausum bees are black (when mature), 5 - 5,5 mm long; cylindrical cocoons, 4.5 to 5 mm long, rounded at both ends and gray-brown in color. This is not a common honey bee but similar to the silkworm pupa that parasitic on the caterpillar larva and destroy it.

Ong D. semiclausum

'Because of its temperate origin, D. semiclausum bee is very suitable for ecoregions with temperatures of 20 - 250C like Da Lat and has now established populations in key vegetable areas such as Cam Ly and Nam Ho, Bach Dang, Thai Phien . The parasitic ability of D. semiclausum bees in large vegetable gardens: After mating, adult female bees will lay eggs in the larvae; Bee larvae grow in the caterpillar and use insecticides as food . A female bee can parasitize, destroy from 33 to 63 worms, some kill to 117 deep ' - Deputy Director of Lam Dong Plant Protection Department Nguyen Van Son said.

However, the scientists recommend that D. semiclausum bees be stable and sustainable to limit the density of silk moths that need to be reduced by spraying insecticide because no less than 65% of bee larvae die when exposed. chemical drugs .

Results of field surveys using biological control measures (almost no chemical spraying) showed that the parasite ratio of D. semiclausum was 37.8% on average, where the highest was 52, 5% and no field does not detect parasitic bees.

However, in the field of farmers' fields, due to the use of many chemical agents (some households use mixed types and spray a dozen times / crop to eliminate silkworms), the parasitic ratio of D. semiclausum bee only average 9.1%, the highest is 22.23% and up to 3 fields do not detect parasitic bees.

The prevention of silkworm by D. semiclausum bee has many advantages: Improving the quality of commercial vegetables (without pesticide residues), safe for users, not causing environmental pollution while the initial cost private investment decreased from 5 to 10 million VND / ha / crop compared to chemical spraying, so the Department of Plant Protection has recommended to apply widely to the neighboring districts of Da Lat city.

The Plant Protection Department is also preparing a document to report to the Scientific Council of the Ministry of Agriculture and Rural Development requesting the recognition of scientific and technical progress for the research on bee keeping and parasitic research in Da Lat.

The silkworm (Plutella xylostella Lin) was first discovered in 1746 and only 10 years later was resistant to DDT, BHC pesticides . A series of new pesticides were put into use but not 'racing' ' floating with the speed of drug resistance of silkworms. By 1974, scientists recommended that if only chemical drugs were used, about 60% of the world's farmers could not control pest.