Researchers identify 10 ‘friendly wasps’

Extensive exploratory surveys to discover the "friendly wasps" that are natural enemies of leafminers (LMs) (harmful insects that infest vegetables and ornamental crops) were conducted for the first time in the Philippine highlands of the Cordilleras, one of the regions mainly engaged in commercial vegetable production.

The survey is significant for its effort to eradicate the pests through natural means while simultaneously preventing the use of chemical insecticides/pesticides that are poisonous to humans and environment.

Researchers led by Dr. Ravindra C. Joshi, senior research fellow of the Department of Agriculture-Philippine Rice Research Institute (DA-PhilRice), Muñoz Science City, Nueva Ecija, conducted the survey. One of its team members is Dr. Elizabeth A. Verzola, regional executive director and chairperson, Potato Leaf Miner Task Force, DA-Regional Field-Unit Cordillera Administrative Region) DA-RFU-CAR.

"Friendly wasps" is the name they call the insects that serve as "natural emies" of harmful insects such as the leafminers. They are also referred to as "parasitoids" or parasites if they feed or "parasitize" on their enemy insect parasites to prevent them from developing into adults and multiplying.

From thier intensive sampling of infested leaves, the team observed that 10 species of friendly wasps attack LMs. These wasps are very small and not easily visible to the naked eye so that their role to periodically suppress LMs and the extent of their damage is usually underestimated by farmers.

This observation was reported to the Philippine Council for Agriculture, Forestry and Natural Resources Research and Development (PCARRD), a sectoral council of the Department of Science and Technology (DOST) based in Los Baños, Laguna.

From the samples collected by the researchers, Dr. John Lasalle of the Commonwealth Scientific Industrial Research Corporation, Australia, identified and listed the friendly wasps that fight off leafminers and provided information for each of them.

The friendly wasps identified were as follows: a) Asecodes delucchii (Boucek) – recently found in Southeast Asia, b) Cirruspilus ambiguus (Walker) – widespread throughout the Palearctic Realm and North Africa, c) Diglyphus isaea (Walker) – widespread throughout the Palearctic Realm and North Africa, d) Hemiptarsenus varicornis (Girault) – most common in Southeast Asia, e) Neochrysocharis formosa (Westwood) – common in Southeast Asia, f) Neochrysocharis okazakii Kamijo – known in Japan, China South to Indonesia, g) Pnigalio katonis (Ishii) - an asian parasitoid, h) Quadrastichus liriomyzae (Hansson and La Salle) - recently described coming from Taiwan, i) Opius species and j) Opius species 2

The most predominant among these friendly wasps is the Diglyphus Isaea (Walker) collected from LM-infested leaves in the Cordilleras. Their presence in large number in this place is puzzling to the researchers. The researchers believed that they were either introduced there through LM-infested host plants or mass released as adults.

Dr. LaSalle explained further that friendly wasps could have been naturally numerous in the Cordillera but with farmers in the area using broad-spectrum insecticides to protect their plants from pests, the wasps could have been eliminated resulting to the outbreak of LMs.

Meanwhile, Dr. Joshi’s research team will continue to look for predators that kill LMs while continuing to study the friendly wasps for the other characteristics such as, at what stage of LMs life cycle do they attact and what LM species do they prefer to attact; their spatial, temporal and seasonal dynamics; species composition and competition; and crop preferences. – S&T Media Service