Evaluation of Rice Cultivars for Resistance to \u3ci\u3eCnaphalocrocis medinalis\u3c/i\u3e Guenée (Lepidoptera: Pyralidae)

Greenhouse screening of 17,914 accessions of rice, Oryza sativa L., from 62 countries identified 115 accessions from 10 countries having resistant or moderately resistant reactions to Cnaphalocrocis medinalis Guenée. Of 264 wild rices (Oryza spp.) screened, 10 (3.7%) were resistant. Several breeding lines having “Ptb33” and “W1263” as donor parents were moderately resistant. All of the resistant accessions are from regions where C. medinalis is an important pest, except for one accession from Italy, which is beyond the range of C. medinalis distribution

Response of Lowland Rice Plants to Simulated Insect Defoliation in West Africa

Field experiments were conducted to investigate the impact of simulated insect-caused defoliation on irrigated rice. Defoliation levels tested were 0% (control), 25% defoliation at 21 days after transplanting (dat), 25% defoliation at 41 dat, 25% defoliation at 21 and 42 dat, 50% defoliation at 21 dat, 50% defoliation at 42 dat, 75% defoliation at 21 dat, 75% defoliation at 42 dat, 75% defoliation at 21 and 42 dat, 100% defoliation at 21 dat, and 100% defoliation at 21 and 42 dat. Tiller height, total number of tillers, percent panicle-bearing tillers, weight of 100 grains, and grain yields were recorded. The rice plant when defoliated just before tillering or in the tillering stage has the ability to compensate for defoliation damage. No yield losses occurred at 25% defoliation. Defoliation of 100% had a significant effect on the total number of tillers and on grain yield. Yield losses at 100% defoliation over the 3 years of the study averaged 40% in the 21 dat treatment and 55% in the 21 and 42 dat treatment. The implications of the development of cultural practices to manage lowland rice defoliating insects are discussed

Rice Insects: The Role of Host Plant Resistance in Integrated Management Systems

Insects are among the most important abiotic and biotic constraints to rice production. National rice research programs are in various stages in the development and implementation of integrated pest management (IPM) stratagies for rice insect control. Among the various control tactics, insect resistant cultivars are sought as the major tactic in rice IPM. Through the activities of interdisciplinary teams of scientists significant progress has been made in the development and release of insect resistant cultivars to farmers. Because of its compatibility with other control tactics insect resistance has proven to fit well into the IPM approach to rice insect control agents and minimize the need for insecticide applications. The development of biotypes which overcome the resistance in rice plants has been a significant constraint in the breeding of rice for resistance to insects. Most notable examples in Asia are the green leafhopper, Nephotettix virescens, brown planthopper, Nilaparvata lugens and the Asian rice gall midge, Orseolia oryzae. The current breeding stratege is to develop rice cultivars with durable resistance on which virulent biotypes cannot adapt. In spite of the significant progress made in the breeding of insect resistant cultivars there are still numerous important rice insect species for which host plant resistance as a control tactic has not been fully utilized. Advances in biotechnology provide promise of solving some of the problems that have limited the use of host plant resistance as a major tactic in the integrated management of rice insect pests

Variable Resistance to Homopterans in Rice Cultivars

Rice-breeding programs in Asia have successfully provided farmers with cultivars that have genetic resistance to the major insect pests, including the leafhoppers and planthoppers. The widespread planting of resistant cultivars has resulted in the selection of hopper populations that have overcome the resistance factor(s) in the plant. Procedures to measure the degree and rate of selection for virulence on resistant cultivars have been developed, and rice-breeding strategies to increase the stability of hopper-resistant cultivars have been implemented. Resistant cultivars have been widely and successfully used in Asia and Central and South America in the management of certain rice homopterans. Rice-breeding lines with resistance to additional homopteran species are in the pipeline. To most successfully utilize the diversity of insect-resistant germplasm requires novel rice-breeding techniques and the integration of the resistant cultivars into rice insect management programs so as to provide an increased level of stability

Resistance to the rice gall midge \u3ci\u3eOrseolia oryzae\u3c/i\u3e in rice

Orseolia oryzae, the rice gall midge is a major pest of rice in many areas of tropical Asia and is becoming an important pest in Africa. A chronological review of the progress made in various national programs on varietal resistance, sources of resistance and breeding for resistance is given. Many resistant varieties have been identified and have been utilized in breeding programs to develop high yielding varieties with multiple resistance to the gall midge and other insect pests and diseases. Mechanisms and inheritance of resistance in rice varieties are discussed. Rice varieties resistant in various countries and sources of resistance used in breeding programs are listed. Biotype variations in different countries and within the countries are revealed and a preliminary classification of gall midge biotypes based on varietal reactions is proposed

Resistance to the rice gall midge \u3ci\u3eOrseolia oryzae\u3c/i\u3e in rice

Orseolia oryzae, the rice gall midge is a major pest of rice in many areas of tropical Asia and is becoming an important pest in Africa. A chronological review of the progress made in various national programs on varietal resistance, sources of resistance and breeding for resistance is given. Many resistant varieties have been identified and have been utilized in breeding programs to develop high yielding varieties with multiple resistance to the gall midge and other insect pests and diseases. Mechanisms and inheritance of resistance in rice varieties are discussed. Rice varieties resistant in various countries and sources of resistance used in breeding programs are listed. Biotype variations in different countries and within the countries are revealed and a preliminary classification of gall midge biotypes based on varietal reactions is proposed

Seasonal Lipid Content of Bagworm Larvae

It is common knowledge to many who have attempted to control bagworms Thyridopteryx sp., that early instars are fairly easy to control, while later larval stages are less susceptible to insecticides. Studies of other insects (Bennett and Thomas 1963, Munson and Gottlieb 1953, Munson et al. 1954, Reier et al. 1953) have shown that as the lipid content increases, the susceptibility to insecticides (especially chlorinated hydrocarbons) decreases. To determine whether the lipid content of the bagworm larva increased with age a series of lipid extractions was conducted

Integration of Host Plant Resistance and Insecticides in the Control of \u3ci\u3eNephotettix virescens\u3c/i\u3e (Homoptera: Cicadelli-dae), a Vector of Rice Tungro Virus

Combined effects of levels of vector resistance and insecticide application in control of rice tungro virus (RTV) were determined in three field tests. Cultivar “IR28,” with high levels of resistance to the vector, Nephotettix virescens (Distant), had low RTV infection in all treatments including the untreated check. In moderately resistant “IR36,” RTV decreased with an increase in level of insecticide but did not decrease to a level equaling the untreated “IR28.” The N. virescens-susceptible cultivar “IR22” had extremely high levels of RTV infection at all insecticide levels. Economic analysis indicated that gross profit and net gain were highest in the N. virescens-resistant “IR28,” intermediate in moderately resistant “IR36,” and lowest in susceptible “IR22.

Parasites, Predators, and Other Arthropods Associated with \u3ci\u3eChoristoneura houstonana\u3c/i\u3e (Lepidoptera: Tortricidae) on \u3ci\u3eJuniperus\u3c/i\u3e Species in Kansas

One parasitic dipterous species and 27 parasitic hymenopterous species were collected. Parasites were primarily collected by mass-rearing host larvae on cut host plant foliage in the laboratory or by rearing larvae on artificial diet. The tachinid Nemorilla pyste (Walk.) and five hymenopterous species, Glypta n. sp. (Ichneumonidae), Campoplex sp. (Ichneumonidae), Agathis acrobasidis (Cushman) (Braconidae), Elasmus atratus How. (Eulophidae), and Catolaccus aeneoviridis Girault (Pteromalidae), were definite parasites, and biological notes are given. Collection data are also given for the other 22 species. One reduviid predator, Zelus socius Uhler, and six spiders were observed feeding on C. houstonana

The Biology of \u3ci\u3eChoristoneura houstonana\u3c/i\u3e (Lepidoptera: Tortricidae), a Pest of \u3ci\u3eJuniperus\u3c/i\u3e Species

Choristoneura houstonana (Grote) lays eggs singly in July. Egg development ranged from 8 to 11 days, with the majority hatching 10 days after oviposition. Larvae are solitary, and mine during early instars, but later instars feed externally on leaves in shelters made by webbing foliage together. There is one generation each year, and overwintering occurs in a hibernaculum, in mined leaves. Field-collected head-capsule width frequencies indicated nine larval instars. Rearing larvae on seedling junipers indoors indicated a range of 8–11 instars. Pupation occurs during June and July in the shelter where the larva feeds. The pupal stage lasted about 10 days at a constant temperature of 80°F