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The Population Dynamics of Helicoverpa Assulta (Guenee) and Helicoverpa Armigera (Hubner) and their Natural Enemies on Tobacco (Nicotiana tabacum L.) in Jember, East Java, Indonesia
Dissertation Abstract:
A study on the population dynamics of Helicoverpa armigera and Helicoverpa assulta and their natural enemies on tobacco was conducted in Jember, East Java, Indonesia, from January 1993 to March 1994 to determine the spatial and temporal distribution of H. armigera, species composition of the genus Helicoverpa in tobacco, and alternate host and their natural enemies.
The occurrence of H. armigera coincided with the presence of tobacco in the field. The highest number of moth caught in the pheromone traps was observed in South Jember. The distribution of H. armigera was clumped both spatially and temporally.
In the tobacco field, the proportion of H. armigera in South Jember was higher than in Central and North Jember while H. assulta was more abundant in Central and North Jember.
Four parasitoids were found in the tobacco areas in Jember, twotachinids (Carcelia sp. and Palexorista sp.), and two ichneumonids (Enicospilus sp. and Campoletis sp.). A nuclear polyhedrosis virus was the most frequent pathogen recorded on tobacco budworm throughout the study.
In cigar tobacco, the population of Helicoverpa spp. egg started to rise at four weeks after transplanting (WAT) and increased until it reached a peak at eight WAT. Larvae were observed in the first WAT and reached the peak at 10 WAT. The peak population of pupae and aduIts occurred during the reproductive stage of tobacco.
In flue-cured tobacco, the egg and larval population of Helicoverpa spp. had two peaks. The pupa and adult populations were very low throughout the growth stage of the plants.
In cigar and flue-cured tobacco, the mirid bug Cyrtopeltis tenuis (Reuter) and Rhinicoris fuscipes (F.) were the most potent natural enemies of tobacco budworm. Among the pathogens, NPV infection was the most frequently encountered in the field.
Two population tables of Helicoverpa spp. were constructed on cigar tobacco. Both population tables indicated that the highest percentage mortality was on the egg stage due to predation and infertility. Trend index of both population tables were positive.
In cigar tobacco, there was a positive correlation between H. armigera male moth captured by artificial pheromone trap with egg and larval density. Positive correlation was also found between H. assulta virgin female trap with egg and larval counts. In flue-cured tobacco, positive correlation was observed between H. armigera and H. assulta male moth trapped by artificial pheromone and virgin female H. assulta and the number of eggs observed in the field.
In the laboratory studies, female moth of H. armigera preferred to oviposit on corn, while female moth of H. assulta preferred to oviposit on P. angulata. First-instar, third-instar, and fifth-instar larvae of H. armigera preferred to feed on corn than other hosts. The first-instar larva of H. assulta preferred tobacco and P. angulata than other hosts, while the third-instar of H. assulta larva preferred corn and P. angulata.