Extreme high-temperature events are the key factor to determine population dynamics of the rice leaf folder, Cnaphalocrocis medinalis (Guenée), in summer. Although we know that adult of this insect can migrate to avoid heat stress, the behavioral response of larva to high temperature is still unclear. Therefore, impacts of high temperature on behavioral traits of C. medinalis including host choice, settling and folding leaf were observed. The results revealed that these behavioral traits were clearly influenced by high temperature. The larvae preferred maize leaves rather than rice and wheat at normal temperature of 27°C, but larvae experienced a higher temperature of 37 or 40°C for 4 h preferred rice leaves rather than maize and wheat. Capacity of young larvae to find host leaves or settle on the upper surface of leaves significantly reduced when they were treated by high temperature. High temperature of 40°C reduced the leaf-folding capacity of the third instar larvae, but no effects were observed on the fourth and fifth instar larvae. Short-term heat acclimation could not improve the capacity of the third instar larvae to make leaf fold under 40°C.

Pheromone-binding proteins (PBPs) are believed to be involved in the recognition of semiochemicals. In the present study, western blot analysis, fluorescence-binding characteristics and immunolocalization of CmedPBP4 from the rice leaffolder, Cnaphalocrocis medinalis, were investigated. Western blot analysis revealed that CmedPBP4 showed obvious antenna-specific expression patterns in female and male antenna, and made a clearly different sex-biased expression. Immunocytochemical labeling revealed that CmedPBP4 showed specific expression in the trichoid sensilla. Competitive fluorescence binding assays indicated that CmedPBP4 could selectively recognize three sex pheromone components (Z13-18:Ac, Z11-16:Al and Z13-18:OH) and eleven rice plant volatiles, including cyclohexanol, nerolidol, cedrol, dodecanal, ionone, (−)-α-cedrene, (Z)-farnesene, β-myrcene, R-(+)-limonene, (−)-limonene, and (+)-3-carene. Meanwhile the CmedPBP4 detection of sex pheromones and host odorants was pH-dependent. Our results, for the first time, provide further evidence that trichoid sensilla might be play an important role in detecting sex pheromones and host plant volatiles in the C. medinalis moth. Our systematic studies provided further detailed evidence for the function of trichoid sensilla in insect semiochemical perception.

The rice leaf roller, Cnaphalocrocis medinalis (Guenée), is a serious insect pest of rice with a strong migratory ability. Previous studies on the migration of C. medinalis were mostly carried out in tropical or subtropical regions, however, and what the pattern of seasonal movements this species exhibits in temperate regions (i.e. Northern China, where they cannot overwinter) remains unknown. Here we present data from an 11-year study of this species made by searchlight trapping on Beihuang Island (BH, 38°24′N; 120°55′E) in the centre of the Bohai Strait, which provides direct evidence that C. medinalis regularly migrates across this sea into northeastern agricultural region of China, and to take advantage of the abundant food resources there during the summer season. There was considerable seasonal variation in number of C. medinalis trapped on BH, and the migration period during 2003–2013 ranged from 72 to 122 days. Some females trapped in June and July showed a relatively higher proportion of mated and a degree of ovarian development suggesting that the migration of this species is not completely bound by the ‘oogenesis-flight syndrome’. These findings revealed a new route for C. medinalis movements to and from Northeastern China, which will help us develop more effective management strategies against this pest.

An artificial diet developed for the rice leaffolder, Cnaphalocrocis medinalis was used in a bioassay of endotoxin proteins from Bacillus thuringiensis (Bt) strains and plant-derived protease inhibitors against the leaffolder, C. medinalis, and the yellow stemborer, Scirpophaga incertnlas. Of the 14 samples of endotoxins derived from different strains of Bt (sub-species kurstaki and sphericus) tested, 5 samples — BT 29, BT 47, BT 61, BT 70 and HD-1— were effective against leaffolder larvae in preliminary tests. Subsequent tests indicated HD-1 to be the most effective against the leaffolder, followed by BT 61 and BT 70, with non-overlapping 95% fiducial limits of LC50 values (3.9,18.2 and 41.1 mg protein/kg diet, respectively). Mortality was observed after 48 h of release of neonate larvae. In contrast, the two protease inhibitors tested, namely soybean trypsin inhibitor (SBTI) and jackfruit seed trypsin inhibitor (JSTI) were less lethal to the two pests. The latter was more effective against the yellow stemborer at much lower concentrations.

Two species of rice leaffolders, Cnaphalocrocis medinalis (Guenée) and Marasmia patnalis Bradley are usually found in association on rice plants in South and Southeast Asia. Larvae of the two species are similar in morphology, as is their feeding behaviour. Spinning, the process of stitching leaf margins together to form a leaf roll before the initiation of feeding process, is an important behaviour of leaffolder larvae. The spinning behaviour of two species of rice leaffolders was compared to find out if accurate differentiation between larvae of the two species is possible. The manner of spinning, average number of stitch bands made, average time spent to complete one band, order of spinning, number of turns taken by the larvae per band made, and feeding behaviour, while spinning a leaf roll were compared. The results revealed that the two leaffolder species have similar spinning behaviour.

Nature of resistance against the rice leaffolder, Cnaphalocrocis medinalis (Guenee) was studied in 16 rke varieties selected on the basis of greenhouse feeding test. Resistant varieties as a group were less preferred for feeding by the larvae in a free choice test lasting 10 days. Cut leaf assay with limited choice brought out subtle differences among some of the test varieties In larval settling response. Larval preference was correlated positively with the leaf area damage noted In feeding test, per cent pupation and leaf width, and negatively with trichome density. However, oviposltton preference was neither distinct nor correlated with resistance or leaf morphology. An antibiosis component in the test varieties ARC 11128, Balam, Gorsa, ARC 7064 and Ptb 19 was distinctly manifested as reduced larval survival, lower pupation rate and pupal weights in comparison with the susceptible check. When neonate larvae were reared on the meridic diets containing the leaves of the varieties Darukasail, Balam or Ptb 12, antibiotic effects were much more pronounced in comparison with the larvae reared on the diet containing the leaves of the susceptible check TN 1.

This bibliography on rice leaffolders contains 886 published and unpublished references for the period 1854 to June 1987. References are arranged alphabetically by the name of author and also classified by subjects. A distribution map, tables of alternate host plants, outbreaks, resistant rice varieties, resistant wild rices, natural enemies and developmental stages, and a brief description of current status of the leaffolders are also provided.

Yield losses from insect pests were determined by the insecticide check method in 60 crops in the Philippines from 1976–1986 in three rice environments with traditional and modern cultivars in 10 sites. Plot size of 100 m2 minimized interplot interference from insecticide protection on untreated plots. Low and high crop losses were recorded across sites in drylands (2–39%, = 25%), rainfed wetlands (13–24%, = 21%), and irrigated wetlands (5–40%, = 18%). Weighted crop loss for the Philippines based on production by environment and cultivar type averaged 18.3% or 0.57 t/ha per crop. Consistently greater yield loss occurred in the vegetative (50%) than reproductive (30%) or ripening (20%) stages across environments and cultivars. No epidemics affected the trials therefore crop losses were those from chronic pests. The major chronic pests in the wetlands were stem borers, leaffolders, whorl maggot, and rice bug; and in the drylands were ants, seedling maggots, white grubs, leaffolders, stem borers and rice bug. Yield loss variability was greater between fields than crops or sites, therefore a control strategy based on corrective actions when pest numbers reach threshold levels is more efficient than prophylactic actions. Yield loss was more in early maturing cultivars stressing the importance of compensation in tolerating insect damage. Insect stresses perhaps can be compensated by total crop management to increase the plant's ability to tolerate insect damage.