Some Aspects of Biology of Leucinodes Orbonalis Guenee (Lepidoptera: Pyralidae), Feeding Behaviour of Larval Instars on Fresh Solanum Spp. Substrates (Solanaceae)

The fruits of Solanum spp. (Solanaceae) are attacked by several pests, including the species Leucinodes orbonalis Guenee (Lepidoptera: Pyralidae) which is the most dangerous agronomically, causing enormous damage of up to 70% in our country. Life history of Leucinodes orbonalis was studied on different species/varieties of Solanum spp. ( S. aethiopicum var. zong, S. aethiopicum var. jakatu, S. melongena var. F1 African beauty and S. tuberosum var. local) at Laboratory of Zoology of the University of Yaounde I at 28±1.44°C, 48±10.07% RH and 929±3.27mb/hPa. Fresh fruits of different species/varieties were obtained in an experimental field set up at the Higher Teacher Training College. Data on development period of immature stage and growth larval parameters were collected. Development stages consist of an egg, five larval instars (from S1 to S5), pupa and adult on fresh fruits of Solanum spp. The average length, the average width and the average weight of the larvae after each stage did not vary significantly from one substrate to another (p≥0.05). Thus, the respective average lengths, widths and weights of the body were 3.5mm, 0.5mm and 3.25mg at S1; 8.12mm, 1.4mm and 10.87mg at S2; 11.0mm, 1.76mm and 17.12mg at S3; 13.37mm, 2.22mm and 29.93mg at S4; 15.87mm, 2.71mm and 59.56mg at S5; 14.03mm, 5.62mm and 57.56mg at the cocoon stage. The average diameter of the head capsules of the larvae did not vary from one substrate to another for all the larval stages (p≥0.05) with 0.42mm at S1, 0.76mm at S2 (with an increase of 0.34 from S1 to S2); 1.13mm at S3 (with increase of 0.37 from S2 to S3); 1.46 at S4 (with increase of 0.33 from S3 to S4) and 1.56mm at S5 (with increase of 0.19 from S4 to S5). Body length, abdomen width and wingspan in females did not vary between substrates (p≥0.05) with mean values of 12.45mm, 2.95mm and 20.25mm respectively. For males, body length and wingspan showed significant variations depending on the substrates (F=10.87; df=3; p=0.003 for length; F=6.03; df=3; p=0.01 for the wingspan) with 11.08mm on the variety F1 african b and 9.61mm on the zong then 18.83mm on the F1 variety and 17.33mm on the zong. The average width (cumulative substrates) was 2.12mm. At cumulative substrates, Body length, abdomen width and wingspan respectively were higher in females compared to males (with 12.45mm, 2.95mm and 20.25mm for females and 10.23mm, 2.12mm and 18.12mm for males). The duration of development from one larval stage to another and from the cocoon stage to the adult stage did not vary from one substrate to another. The average duration of development from the egg stage to S1 was 4.51 days. That of S1 to S2, from S2 to S3, from S3 to S4, from S4 to S5, from S5 to the cocoon stage was respectively 1.00 days, 1.15 days, 1.44 days, 2.28 days, 3.33 days and 11.75 days. The average duration of larval development (from S1 to the cocoon stage) was 9.21 days and the total average duration of development from the egg stage to the adult stage was 25.47 days.