Feeding site selection of first‐instar larvae of Cnaphalocrocis medinalis on susceptible and resistant rice plants

Abstract

More first‐instar larvae of the rice leaffolder, Cnaphalocrocis medinalis (Guenée), were recovered from susceptible IR36 and Roxoro rice varieties than resistant TKM6 and Oryza perennis, 24 h after infestation. Within a rice plant, a higher proportion of larvae was recovered from young whorl leaf, followed by mature leaves and leafsheaths on all the four rice varieties tested. However, differences were observed between susceptible and resistant varieties in the distribution of larvae on these three plant parts. In laboratory choice tests, first‐instar larvae preferred to settle on the young leaves of IR36 and TKM6 when presented with their respective mature leaves. No such preference was observed in tests with Rexoro and O. perennis. Larval survival was similar on young and mature leaves of Rexoro. Young leaves of IR36 and TKM6 were more suitable for survival in comparison with their respective mature leaves while the reverse was true for O. perennis. Larval movement was slower on the mature leaves and larvae took longer to reach the whorl leaf of TKM6 than on IR36. The density of trichomes of the abaxial surface of TKM6 was higher than that of the other varieties tested. Adaptive significance of feeding in the leafwhorl to young larvae is discussed.

Assessing resistance of sugarcane varieties to sugarcane borer Diatraea saccharalis Fab. (Lepidoptera: Crambidae)

“…Resistance to the southwestern corn borer Diatraea grandiosella (Dyar) and European corn borer Ostrinia nubilalis (Hubner) (Lepidoptera: Pyralidae) in resistant corn hybrids is greater in the vegetative than the reproductive stages (Klun & Robinson, 1969; Videla et al , 1992). Conversely, resistance to the rice leaffolder Cnaphalocrocis medinalis (Guené) (Lepidoptera: Pyralidae) is more pronounced in older foliage of resistant varieties than in young foliage (Ramanchandran & Khan, 1991). Therefore, the study of parameters, such as plant age and number of insects, is necessary in the study of plant resistance to insects.…”

Characterization of resistance to rice leaf folder, Cnaphalocrocis medinalis, in mutant Samba Mahsuri rice lines

“…Fewer neonate larvae preferred to settle on moderately resistant MSM lines (MSM 139 and MSM 127) than on the susceptible lines (MSM 37 and MSM 26). Earlier studies also reported a strong non-preference for larval settling and feeding on resistant wild rice species than on susceptible varieties (Medina & Tryon, 1986;Khan et al, 1989;Ramachandran & Khan, 1991). Leaf folder larvae took more time for leaf selection, making a primary fold along with more head swings in moderately resistant MSM 139 than in the susceptible MSM 37.…”

“…Tolerance is the ability of the host plant to grow and yield despite the pest attack. In the case of the rice leaf folder, both antixenosis and antibiosis mechanisms of resistance were reported (Khan et al, 1989;Ramachandran & Khan, 1991;Dakshayani et al, 1993;Xu et al, 2010;Punithavalli et al, 2014). Varying effects on leaf folding behavior by the larvae was observed in different genotypes by Punithavalli et al (2013).…”