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The oligochaete Dichogaster nr. curgensis Michaelsen, has become a pest of irrigated rice in the Philippine terraced highlands. Heavy erosion of the deforested Abra River watershed deposited unnaturally high numbers (13,659 m−2) of this epigeic earthworm along the riverbank, which subsequently became concentrated in irrigated rice fields (17,294 m−2) in over 20,000 ha. The earthworms' burrowing activity caused leaks in rice levees and body setae mechanically injured roots resulting in plant stunting and seedling death. Infested fields exhibited reduced plant stand and uneven growth. Rice was more sensitive to damage occurring during the vegetative than reproductive stage. The crop could tolerate earthworm densities of 140 m−2 but suffered significant yield loss when populations were ten times higher, and complete loss at 700 m−2. Field observations and greenhouse tests showed prolonged flooding reduces earthworm densities. Seedbeds should be located away from the rice fields and taller seedlings (45–55 days old) should be transplanted to tolerate >14 cm depth ponding until the late reproductive stage. A preventative method of creating holding ponds is suggested to trap earthworms before irrigation water passes to the fields. During the off-season, infested fields may be kept flooded for 2–3 months to lower resident densities. Leaves of Gliricidia sepium (Jacq.) Steud, a popular pesticidal plant suggested by farmers, increased rather than decreased earthworm numbers when incorporated into the soil. Carbofuran granules at 0.5 kg a.i. ha−1 soil incorporated before transplanting caused over 90% mortality in a greenhouse trial.

The population dynamics of plant- and leafhoppers and associated predators and parasitoids at five rice sites in the Philippines, are compared. Twelve species of Auchenorrhyncha, nine Cicadellidae and three Delphacidae, were found in the samples. The order of abundance was Nephotettix virescens > Sogatella fucifera > Nephotettix nigropictus > Nilaparvata lugens. The dominant predators were mostly Heteroptera [Microvelia douglasi atrolineata (Veliidae) and Cyrtorhinus lividipennis (Miridae)] followed by spiders [Pardosa pseudoannulata (Lycosidae) and Callitrichia formosana (Linyphiidae)]. The delphacid and cicadellid populations were characterized by high initial densities, which reached a peak and were followed by a decline with low growth rates. Populations of heteropteran predators were similar, except that the peaks were at a later state and growth rates were higher. Predator diversity and evenness were significantly lower in Los Banos and Cabanatuan. The results are discussed in relation to implications to plant- and leafhopper management.

Rice Oryza sativa L. habitats were evaluated for their propensity to sustain rice tungro virus during the fallow period. Leafhopper vectors and associated natural enemies were sampled by a D-Vac suction machine from rice crops, nurseries, and fallow fields in Malaysia between December 1983 and May 1984. Leersia hexandra Sw. vegetation in wet, fallow rice fields harbored significantly higher densities of Recilia dorsalis (Motschulsky). Nephotettix virescens (Distant) was relatively abundant in second-stage rice nurseries. Nephotettix nigropictus (Stal) and N. malayanus Ishihara et Kawase were only moderately abundant or absent in the habitats sampled. Nephotettix parvus Ishihara et Kawase, a reported vector, was not caught. Spiders, in particular hunting spiders and orbweb weavers, numerically comprised the major natural enemy guilds in all habitats except in direct-seeded rice and single-stage nurseries, where predatory insects were more abundant. Egg parasitoids were the only parasitoid guild in all habitats except in L. hexandra vegetation where low numbers of nymphal-adult parasitoids were recovered as well. Oryza sativa, Fimbristylis miliacea (L.) Vahl and L. hexandra were the most commonly encountered tungro hosts. All habitats with rice potentially perpetuate tungro, particularly ratoon and volunteer rice which carry tungro and vectors to the next season crop and nurseries which are more susceptible to vectors and tungro infection. Fimbristylis miliacea may act as a tungro reservoir when rice is absent but cannot support vectors. Leersia hexandra harbors high densities of vectors but its role as a tungro host is more limited. Elimination of fallows with rice or tungro hosts is recommended as a preventive practice. However, weedy habitats without tungro hosts are beneficial as they harbor a variety of natural enemies of tungro vectors. Such vegetation should be tolerated where possible. Resistant varieties or selective insecticides should be used to prevent tungro infection in the nursery stage without destroying the diverse natural enemy complex.

By 1975, insect sex pheromones had been identified from 60 species (1) of moths (Lepidoptera), and nearly all of the 40 compounds involved had been found to be mono- or di-unsaturated C10 to C18 straight-chain aldehydes, alcohols, or acetates, and the sites of olefinic unsaturation were, with one exception (2), at odd-numbered positions in the carbon chain. Since that time, many more lepidopteran pheromone components have been identified, and mono-unsaturated compounds with unsaturation at even-numbered positions in the carbon chain remain extremely rare (3–6). However, in females of Ostrinia furnacalis (Guenee), called the Asian corn borer, we have discovered another mono-olefinic lepidopteran sex pheromone that has the site of unsaturation at ab even carbon position. Females of this corn-pest species produce a ca . 1:1 geometric mixture of ( Z )- and ( E )- 12-tetradecen-1-o1 acetate to attract and sexually stimulate males. On the other hand, the nearest taxonomic relative (7) of the Asian corn borer, the European corn borer, Ostrinia nubilalis (Hubner), uses a mixture of ( Z )- and ( E )-11-tetradecen-1-o1 acetate as its sex pheromone (8). Biochemical explanation of the paucity of monounsaturated moth sex pheromones with olefinic sites at even numbered carbon positions remains to be elucidated.