Population dynamics of rice leaffolders (Lepidoptera: Pyralidae) and their natural enemies in irrigated rice in the Philippines

Abstract

Populations of rice leaffolders and their natural enemies were studied in eight crops of irrigated rice in Laguna Province, the Philippines. The rice leaffolder complex consisted of three species: Cnaphalocrocis medinalis (Guenée), Marasmia patnalis Bradley and M. exigua Butler. Leaffolder population dynamics were characterized by an egg peak at maximum tillering and a broad larval peak around booting stage. Peak densities ranged from 0.2 to 2.0 larvae per hill. Most larvae originated from immigrant moths and there was no substantial second generation. The seasonal percentage egg parasitism by Trichogramma sp. ranged from 0 to 27%, and percentage larval parasitism from 14 to 56%. The braconid Macrocentrus philippinensis Ashmead was the most commonly reared larval parasitoid. Forty natural enemy taxa that may attack rice leaffolders were identified from suction and sweepnet samples: 24 predator taxa and 16 parasitoid taxa. The estimated survival rates from leaffolder egg to larval stages and between larval stages showed large variation between rice crops, but were not clearly correlated with observed levels of parasitism, natural enemy abundance, or natural enemy to leaffolder ratios. It is suggested that the generally low densities of rice leaffolders in Philippine transplanted rice are caused by their ovipositional preference for crops at the maximum tillering stage, allowing for only one generation, and by high immature mortality caused by the abundant and diverse complex of natural enemies.

Assessment of the egg parasitoid guild of rice leaf folder, Cnaphalocrocis medinalis (Guenee): a search for biocontrol agents

“…This finding agrees with a result of a similar study by De Kraker et al (1999), in irrigated rice in the Laguna Province, the Philippines. The same study reported egg parasitism of C. medinalis by Trichogramma to be 0 -27 %.…”

“…This approach requires the identification of locally available egg parasitoids. In some countries, the egg parasitoid guild of RLF has been characterised (De Kraker et al, 1999). In Sri Lanka the larval and pupal parasitoids have been identified (Rajapakse, 1990) This study was conducted with the following objectives.…”

Survey of Parasitoids and Predator on Asiatic Pennywort Farms in Thailand

“…Three coccinellid predators namely, B. suturalis, S. parcesetosum and C. transversalis were observed in mungbean and urdbean during July to September [22]. In the paddy filed, C. longipennis had a minor role in control insect pest [23,24].…”

Modification and Application of a Leaf Blower-vac for Field Sampling of Arthropods

“…The method is not suitable for sampling highly mobile flying insects, such as predatory Odonata or larger hymenopterous parasitoids. As with any sampling method, the combination of the blower-vac with other methods, such as sweep net sampling or destructive harvesting of plants, can provide a more complete and balanced assessment of the arthropod community 26 .…”