Life history of two braconid parasitoids of rice leaffolder in the laboratory

Guo Yu-jie, K. L. Heong, and R. P. Basilio, Entomology Division, IRRI

Two braconids, Cardiochiles philippinensis (Fig. la) and Macrocentrus philippinensis (Fig. lb), are the dominant parasitoids of leaffolder Cnaphalocrocis medinalis larvae in the Philippines. We studied their life history under 26 ± 3°C temperature and 75 ±10% relative humidity. Newly emerged parasitoid adults were paired and placed in an oviposition cage (23 cm in diameter x 60 cm high) with 20 3rd-instar larvae of C. medinalis on potted plants. Host larvae were replaced daily until the parasitoid died.

Parasitized larvae were reared on potted rice plants for 7 days, then transferred individually into test tubes (16 mm in diameter x 150 mm high). Fresh rice leaves were provided every other day until pupation. Ten replications for species were used.

The life cycle of C. philippinensis feeding on the 3rd-instar larvae of C. medinalis was 22.7 days; and that of M. philippinensis was 29.4 days. The difference was due mainly to adult longevity (see table). C. philippinensis had a shorter adult period, but its reproduction capacity was close to each that of M. philippinensis. This implies that C. philippinensis may be more efficient. M. philippinensis had a longer parasitism period than C. philippinensis (Fig. 2). Total number of larvae parasitized throughout the lifetime of a female was significantly less for C. philippinensis (16.7 ± 0.2) than for M. philippinensis (20.1 ± 1.1).

1. Females of parasitoid species Cardiochiles philippinensis (left) and Macrocentrus philippinensis (right).

2. Daily parasitization by Macrocentrus philippinensis (MP) and Cardiochiles philippinensis (CP) on 3rd-instar larvae of C. medinalis. Vertical bars show the standard error at 95% confidence.

Development of Cardiochiles philippinensis and Macrocentrus philippinensis feeding on 3rd-instar larvae of C. medinalis under laboratory conditions.

Developmental stage No. Duration a/ No. Duration a/

Egg - larva 16 9.5 ± 2.7 14 11.2 ± 2.4Pupa 16 7.2 ± 1.7 14 6.6 ± 1.2Adult 10 5.9 ± 0.3 10 11.5 ± 1.8

Total 22.7 ± 3.8 29.4 ± 3.2a/ Expressed in mean days with standard error at 95% confidence.

C. philippinensis M. philippinensis

Guo Yu-jie, Heong KL, Basilio RP. 1991. Life history of two braconid parasitoids of rice leaffolder in the laboratory. International Rice Research Newsletter 16 (2) 22-23.