10 ‘friendly wasps’ attacking leafminers discovered

Ten species of "friendly wasps" that attack the destructive leafminers (LM) in the Cordilleras have been discovered.

The wasps, commonly referred to in the science world as "national enemies" or "parasitoids" or "parasites", were found during extensive exploratory surveys conducted for the first time in the Northern Luzon highlands.

The survey team was headed by Dr. Ravinda Joshi, senior research fellow of the Department of Agriculture-Philippine Rice Research Institute (Da-PhilRice). Members were Dr. Elizabeth Verzola, regional executive director and chairperson, Potato Leaf Miner Task Force, DA-Regional Field Unit-Cordillera Administrative Region (DA-RFU-CAR); and Nicasio Baucas, Agriculturist II, DA-RFU-CAR.

The "friendly wasps" were identified by Dr. John LaSalle of the Commonwealth Scientific and Industrial Research Organization (CSIRO) of Australia, one of the very few specialists in the world who has thoroughly studied species of "friendly wasps" attacking leaf miners.

Samples of the wasps gathered by the survey team were sent to Dr. LaSalle.

The Australian scientist named the species as follows:

• Aescodes delucchii (Boucek), found recently in Southeast Asia.

• Cirrospilus ambiuguus Hansson & LaSalle, found in Taiwan, Africa, and recently in Southeast Asia.

• Digluphus isaea (Walker), widespread throughout the Palearctic realm and North Africa.

• Hemiptarsenus varicornis (Girault), most common in Southeast Asia.

• Neochrysocharis Formosa (Westwood), common in Southeast Asia.

• Neochrysocharis okazakii Kamijo, known in Japan, China (South), and Indonesia.

• Pnigalio katonis (Ishii), an Asian parasitoid.

• Quadrastichus liriomyzae Hansson & LaSalle, recently described from Taiwan.

• Opius species 1.

• Opius species 2.

"Diglyphus isaea is the most predominant ‘friendly wasp’ reared from leafminer leaves in the Cordilleras. Their high occurrence in the region is quite puzzling; unless they were either introduced with LM-infested host plants or mass-released as adults," the survey team stated in a report, quoting Dr. LaSalle.

He also explained that naturally-occurring "friendly wasps" killing leafminers are numerous in the Cordilleras, but unfortunately, with applications of broad-spectrum insecticides, often made to control other species of bad insects (thrips, aphids, and mites), farmers eliminate "friendly wasps" and this results in outbreaks of leafminers.

In the future, Dr. Joshi’s team will also look closely for predators that would capture and kill leafminer fly (LMF) and those that would prey on LMs.

He said the "friendly wasps" already identified in the Cordilleras will be studied in-depth to determine the LM species and stage attacked; their spatial, temporal, and seasonal dynamics; species composition and competition; and crop preferences.

"This knowledge will help farmers to preserve ‘friendly wasps’ and cut on unnecessary cost to control LMs damage on potato, celery, cutflowers, and other economically important crops in the Cordilleras," the survey team concluded. – Rudy Fernandez