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Papaya mealybug, biocontrol, Muscat (report)

December 2011. An article in the Oman Daily Observer, entitled Hope in sight for papaya farmers elicited comments from members. The articvle is presented below.

A member from Cambodia who grows Jatropha asked for more details, and a member from India said that the mealybug was also causing problems in Kerala State, even though insecticides were used against it. After the introduction of the encyrtid parasitoid, Acerophagous papayae in December 2010 the infestation was brought under control.

As a follow up after a request for more information on the biocontrol of the mealybug, the following papers were cited, 1) Meyerdirk DE, Muniappan R, Warkentin R, Bamba J, Reddy GVP (2004) Bological cntrol of the papaya mealybug Paracoccus marginatus (Hemiptera: Pseudococcidae) in Guam. Plant Protection Quarterly 19(3):110-114 (www.wptrc.org/userfiles/file/PPQ-2004.pdf); 2) Muniappan R, Meyerdirk DE, Sengebau FM, Berringer DD, Reddy GVP (2006) Classical biological control of the papaya mealybug, Paracoccus marginatus (Hemiptera: Pseudococcidae) in the Republic of Palau. Florida Entomologist 89(2):212-217 (xa.yimg.com/kq/groups/1487661/1660654339/name/Papaya+mealybug-Florida+Entomologist.pdf).

These papers record the result from introducing three parasitoids: Anagyrus loecki Noyes, Pseudleptomastix mexicana Noyes and Schauff, and Acerophagus papayae Noyes and Schauff. Interestingly, attempts to introduce these three from Puerto Rico to Thailand were not successful, but local natural enemies consistang mainly of predaceous coccinellids brought the infestation to a level where it is no longer of economic importance. A summary of the thesis is here.

Other crops were also said to be affected by the mealybug, inlcuding mulberry (Morus spp.) and Plumeria.

Hope in sight for papaya farmers

Hope in sight for papaya farmers

Sun, 13 November 2011

By Kaushalendra Singh – MUSCAT ??? Hope is in the air and slowly papaya farmers in Salalah are getting back to business after the Directorate of Agricultural and Livestock Research Stations in Salalah decided to take help from international scientists to tackle the menace of mealybug. Soon after the identification of the problem, the directorate is ready with several thousand papaya seedlings to be distributed among the farmers.

???As of now we are ready with 20,000 new seedlings and by the end of this year we have a distribution target of 100,000 papaya seedlings among the farmers of Salalah,??? said Abdulaziz Mansoor Ghalib al Shanfari, Director of Agricultural and Livestock Research Stations, Dhofar. The papaya mealybug attacked Salalah papaya farms in the last quarter of 2010 and in the beginning of 2011 and caused heavy loss to papaya growers.

As the menace spreads, farmers lost hope and scaled down on papaya cultivation, the official said. Many farmers decided to cut down all the papaya plants, which caused steep hike in the price of Salalah papaya in the local market. The papaya mealybug has affected papaya farming spread over 130 hectares of land in general and not less than 400 farms in particular in whole of the Dhofar Governorate. The agriculture scientists were tackling the issue by spraying pesticides which were not proving to be very effective.
Finally, R Muniappan, an expert from Virginia Polytechnic Institute and State University, or Virginia Tech, identified the menace during his visit to Salalah in the last week of October. Muniappan is part of the pest management team from Virginia Tech which is involved in such activities worldwide. He along with other agriculture scientists is working out a solution to clear the farms from papaya mealybug and restore farmers??? confidence in papaya farming.

In an interview with Observer, Muniappan said: ???Though the damage due to the papaya mealybug was quite extensive, the authorities in the Sultanate took early and timely step by inviting experts to tackle the problem. Spray of pesticides is not at all a solution in such cases as the Mealybugs cover vast area by travelling in the air and affecting plants which come in their contact.

???The papaya mealybug or paracoccus marginatus is a polyphagous pest, with hosts recorded from 22 plant families including economic and weedy plants. Heavy infestations of the mealybug on papaya have been noted along the veins and the midribs of the older leaves and all areas of the tender leaves and fruits.

???Severely affected older leaves turn yellow and dry up. Tender leaves become crinkled. Terminal shoots become bunched and distorted. Heavy mealybug populations produce a large volume of honey dew which causes black sooty mould to cover the infected fruits and vegetation,??? he said.

Commenting on the solution Muniappan said: ???The solution lies in biological control of the pest. A tiny insect or parasitoid, which preys on the pest, is released to control the pest. In case of Salalah papaya, we did not release any parasitoid but they were found in the air. Since the problem has been identified, the solution can be worked out easily.???