Parasitic wasps control cassava mealybugs

Pink mealybug is a dangerous pest on cassava plants, living in symbiosis with ants, causing damage to the tops, leaves and stems but living mainly in the top clusters.

Aphids lie hidden in leaf sheaths, under the leaves, cling to cassava stems and suck cassava nutrients, causing the cassava shoots to shrivel and the stems to develop crookedly.

Aphids have the ability to multiply rapidly in the field because they reproduce asexually, the number of eggs ranges from 300 - 500 eggs/female and adapt to hot temperature conditions, thriving in the dry season.

To prevent pink mealybugs, using chemical sprays is very ineffective, only 5% because the mealybugs live in hidden places on cassava plants. Furthermore, the mealybugs have a layer of wax and white powder covering their bodies, making the medicine not stick to their bodies. It is only recommended that people soak cassava cuttings with chemicals before planting.

Therefore, to effectively prevent it, many measures need to be applied, focusing on biological measures such as using natural enemies available in cassava fields for prevention.

In which, the parasitic wasp Anagyrus lopezi is a species originating from South America that has been raised and released into cassava fields by countries in the Mekong region such as Thailand, Laos, Cambodia... with high efficiency in preventing aphids, reaching over 80%.

Parasitic wasps lay eggs on aphids

Anagyrus lopezi wasp belongs to the Hymenoptera order, Encyrtidae family. It has a black body, size from 1.2 - 1.4 mm, males are smaller than females, the difference between males and females is that the entire antennae of the male is black, while the antennae of the female are alternating black and white.

Adult bees both suck aphids and use their stingers to lay eggs on the aphids' bodies. Every day, a female bee both sucks aphids and lays about 50 pink mealybug eggs. Male bees suck about 20-30 aphids per day.

Male bees mate before female bees. Bees are capable of parthenogenesis. If a female bee does not mate, she can still lay eggs, but those eggs will only hatch as male bees.

In cold weather conditions, parasitic wasps are inactive and they develop best at temperatures of 28 degrees Celsius. The wasps are active during the day and hide under cassava leaves at night.

To have a source of parasitic bees to release into the fields, first of all, the bees must be collected from the fields and brought to the room, the greenhouse to be raised with honey diluted 5 - 10% and pink mealybugs as prey. The mealybugs are raised on cassava cuttings and pumpkins that have reached the ripe stage but the color of the fruit is still green.

When the bees develop in large numbers, collect them in plastic bottles with a ratio of 1 male, 1 female and release them into the fields. Based on the severity of the cassava field being infected with pink mealybugs, release the bees. If the cassava area is lightly infected, release 300 - 600 pairs of bees/ha, if the infection is heavily infected, release 1,200 - 3,000 pairs of bees/ha.

When releasing bees into cassava fields, follow the wind direction, do not release bees when it is raining or about to rain, and release them early in the morning. Inform people not to spray chemicals in cassava growing areas where the parasitic wasp Anagyrus lopezi has been released.

After 9-10 days of releasing the bees, the bodies of the pink mealybugs will be found. The symptoms of the parasitized mealybug bodies are gray and have holes on the backs of the mealybugs for the wasps to emerge from.

According to NNVN