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Replicated field plot trials were carried out to evaluate the role of fish as biocontrol agents of insect pests of rice in the Philippines. Evidence from suction sampling, examination of fish gut contents, and rice plant damage assessment strongly suggest that Common Carp Cyprinus carpio (L.) and Nile Tilapia Oreochromis niloticus (L.) do significantly reduce the densities of stemboring moths and chironomid midges, while the abundance levels of other arthropods are not significantly affected. This impact by fish often was more important in the wet season when heavy rains and wind likely caused the arthropods to become dislodged from the plant and fall onto the water. Predation by fish was particularly evident during the first 45 days of the crop during the wet season when adult chironomid midge abundance was high. The fish gut content analysis revealed that all insect guilds are represented in the diet of both of the fish species regardless of whether the life-cycle of the arthropod prey is aquatic, semi-...

Rainfed wetland rice (RWR) had more species in common with irrigated wetland than dryland rice agroecosystems. Across ecosystems, higher pest densities and losses were recorded in RWR sites. We hypothesise that under low pressure from natural enemies, vegetative stage losses became particularly high due the combination of whorl maggot and caseworm damage combined with the physiological stress of transplanting shock. Both of these pest groups benefited from an expanded vegetative period common in RWR agroecosystems. Losses in older rice were probably due to stemborers. RWR is more prone to an array of physiological stresses than irrigated rice that we believe minimises crop compensation to accentuate insect losses. Chemical control is uneconomical mainly due to the low yield potential of RWR and the poor efficacy of applied insecticide.

In the Philippines most of the dryland rice pests are distinct from those of wetland culture. Partitioned-growth-stage yield loss studies revealed the highest losses in dryland rice were due to sown-seed and seedling pests (ants, field crickets, mole crickets, and termites) as well as root feeders (white grubs and root aphids) and early seedling pests (seedling maggot and flea beetle) more than the common foliar wetland pests. Losses (5–71%) were highest in the sites with the smallest rice area in which pests were concentrated and the poorest soils (which constrain yield compensation) along a continuum of dryland rice habitats. Crop management practices such as overseeding and fertility management can mitigate potential losses to a large degree. Therefore integrated crop management plays a central role in integrated pest management in dryland rice cultivation where the use of insecticides should be minimized for economic and environmental reasons.

Monthly plantings conducted over 4 years in a rainfed triple maize cropping system in southern Mindanao, Philippines, revealed the Asian corn borer (ACB) Ostrinia furnacalis (Guenee) as the most important insect pest. Of minor importance and being restricted to one crop stage were rice seedling maggot Atherigona oryzae Malloch, thrips Thrips palmi Karny and Megalurothrips usitatus (Bagnall), corn leafhopper Cicadulina bimaculata (Evans), corn earworm Helicoverpa armigera (Hubner), and corn leaf aphid Rhopalosiphum maidis (Fitch). Farmers escape damage from ACB, seedling maggot, and thrips by planting the first crop in April. Planting of the second crop should be shifted from August to September to avoid ACB damage. Pest damage was low during the third crop, thus planting time is not an important consideration. Additional information on ACB bionomics was revealed in the study. Mean egg mass size was 36 eggs (range 1 – 169). Oviposition was found to be positively correlated with cumulative rainfall...

Beneficial arthropods were monitored in monthly plantings over 4 years in a rainfed, triple-maize cropping system in southern Mindanao, Philippines. Generalist predators and two egg parasitoids of the Asian corn borer Ostrinia furnacalis (Guenee) (ACB) did not show significant differences in abundance with respect to calendar month of planting over 39 crops. Two species of Trichogramma (T. evanescens Westwood and T. chilonis Ishii) collectively parasitized 67% of ACB egg masses and 58% eggs over the study becoming more abundant as the crop aged. The closeness of the two parasitism rates suggests that to increase parasitoid efficacy, particularly early in the crop, the best strategy would be augmentation and to increase longevity of wasps by providing carbohydrate sources to extend their searching time. Unparasitized egg masses tended to be smaller showing they were more likely to be overlooked. The ratio between the two parasitoids was 56:44 in favour of the former. Trichogramma evanescens had be...

The rice white stemborer (WSB) Scirpophaga innotata (Walker) supplanted the closely related rice yellow stemborer (YSB) S. incertulas (Walker) in irrigated, double-rice culture in both Koronadal, South Cotabato, Philippines and Java, Indonesia. In Java, WSB became a serious pest but not in Koronadal where damage levels remained unchanged. The species shift and subsequent outbreaks are seen as independent events. The former occurred just after the El Nino droughts in 1982 – 1983 which suggests that climatic factors triggered the demise of YSB which does not aestivate. A contributing factor may have also been the crop failures from pest outbreaks that occurred during the same period creating long fallows which would have allowed WSB larvae selectively to survive. WSB larvae have been known to diapause for up to 10 – 12 months and consequently is able to survive climatically driven long fallows. Diapause is terminated by rainfall >10 mm after larvae have rested for a minimum of 4 months. Supportive ...

Although the rice white stemborer (WSB) Scirpophaga innotata (Walker) has been an epidemic pest in other locations in the Philippines and Indonesia, its population has remained at chronic pest levels in Koronadal, southern Mindanao, Philippines. Field studies were undertaken to determine the role of egg parasitoids and general predators in suppressing WSB numbers. The results revealed greater mortality levels on WSB than in any other location where beneficials have been assessed. Four hymenopteran parasitoids (Tetrasticus schoenobii Ferriere [Eulophidae], Telenomus rowani (Gahan) [Scelionidae], Telenomus dignus (Gahan), and Trichogramma japonicum Ashmead [Trichogrammatidae]) combined to parasitise 65% of eggs in the second 1990 – 1991 rice crop. Multiple parasitism occurred in 61% of parasitised egg masses. Egg predation averaged 44% principally by the tettigoniids Conocephalus longipennis (de Haan) and C. maculatus (Leth.). Generalist predators steadily built up over the rice crop. A contributin...

Rice seedling maggot Atherigona oryzae Malloch is a minor pest of upland rice Oryza sativa L. and maize Zea mays L. in the Philippines. Two cultural control methods, early planting and overseeding, were evaluated separately on upland rice in an eroded, high rainfall area in Northern Mindanao. Farmers plant maize ahead of upland rice in separate fields with the onset of the rainy season. Regression analysis from data over six seasons showed on average the first 50% of farmers who planted ahead of their neighbours suffered damage significantly below the 5% deadheart action threshold. When early rice planting relative to one's neighbours was combined with earliness with regard to sowing maize, damage was further reduced. Useful methods for forecasting deadheart incidence 1-2 months ahead of rice planting were developed. The deadheart incidence rate was highly correlated with the amount of rain that fell in February and March as well as with the number of adults collected from bait traps in March or April. Si...

Soil sampling over a two-year period in Claveria, Northern Mindanao, Philippines, revealed the presence of five white grub species (Coleoptera: Scarabaeidae) in the deforested, infertile, and highly eroded grassland environment being converted to small farms. Population dynamics data point to Leucopholis irrorata (Chevrolat), Holotrichia mindanaoana Brenske, and H. flachi Brenske being biennial with Adoretus luridus Blanchard and Anomala humeralis Burmeister being annual species. The three biennial species are synchronized to even-numbered years. Small subpopulations of the biennial species show evidence of annual or allochronic cycles. L. irrorata has an annual cycle in other areas of the Philippines on sugarcane but takes two years to develop in Claveria probably due to infertile soils and a longer feeding period. Other subpopulations of young larvae and emerged adults occurring in the late rainy season were 'attempts' at multiple generations or delayed development, but were considered suicidal due to t...