Crops > Roots & tubers > Cassava > Parasitoids, cassava mealybug, Thailand

Crops > Roots & tubers > Cassava > Parasitoids, cassava mealybug, Thailand

Crops Roots & tubersCassavaParasitoids, cassava mealybug, Thailand

Parasitoids, cassava mealybug

July 2010. A member from Thailand was concerned about the introduction of a parasitoid to that country from Benin, Africa for the control of a mealybug attacking cassava. The story appeared in The Bangkok Post.

The following response was sent by a member:

???I would like to point out that David Rayong (the writer of the article) is not comparing apples with apples in his critique. Toads are generalist predators, so it was hardly surprising that they impacted all sorts of non-target organisms in Australia, rather than the pests they were intended to control. For this reason, it is now widely recognized that vertebrate predators are not suitable for insect biological control. Parasitoid wasps, on the other hand, are almost always highly specific in their choice of host. Of course David Rayong is correct that rigorous testing should have been carried out to assess the likely impact on native fauna before any releases took place.

???If the parasitoids being discussed were introduced to Thailand to control the Neotropical cassava mealybug, Phenacoccus manihoti, I know that the pest mealybug was authoritatively identified (by me) before the biological control work commenced. That is the first, essential, step in a biological control programme.

???Recent introductions of neotropical mealybugs to Thailand include three species of Phenacoccus ??? P manihoti, P madeirensis and P solenopsis. Only one native member of Phenacoccus has been recorded from Thailand so far ??? P. vetiveriae, which feeds on grasses like Vetiveria. Any introduced Neotropical wasp parasitoid of a Neotropical species of Phenacoccus is unlikely to find many native species of mealybug that it would be capable of attacking, much less any other organisms.

???The likely control agent to have been introduced (Epidinocarsis lopezi (De Santis), Hymenoptera: Encyrtidae) originated from South America, not Africa, and has proved highly effective against P manihoti in equatorial Africa over many years.???

Later (March 2011), FAO announced that it was launching a new IPM initiative in Asian countries to limit the spread of Phenacoccus manihoti, the Cassava pink mealybug). It will be done under the decade old vegetable IPM programme. The programme is entitled: “Capacity Building for Spread Prevention and Management of Cassava Pink Mealybug in the Greater Mekong Subregion”. Work will involve mass rearing of In addition, nations in the region that are currently free of the pest will be aided in mass rearing the mealybug parasite Anagyrus lopezi as a key biocontrol agent.