Interactions between panicle size, insect density, and environment for genotypic resistance in sorghum to head bug, Calocoris angustatus

Abstract

Studies were undertaken on interactions between panicle size, insect density, host plant, and the environment for sorghum head bug, Calocoris angustatus Lethiery on five sorghum genotypes in terms of bug population increase, grain damage and loss in grain mass across four panicle sizes (5, 10 or 20 branches/panicle and whole panicle), and three infestation levels (5, 10 and 15 pairs of bugs/panicle). Head bug numbers increased and grain damage decreased with an increase in panicle size in the head bug susceptible cultivars, CSH 1 and CSH 5. However, the increase in bug numbers or decrease in grain damage was not significant in head bug resistant genotypes, IS 17610 and IS 17645. Head bug numbers increased with an increase in infestation level in CSH 1 and CSH 5, however, such an increase was not substantial in IS 17610 and IS 17645. Grain damage was significantly lower in IS 17610 and IS 17645 compared with CSH 1 and CSH 5 across infestation levels. Head bug population increased at a greater rate during the rainy season compared with the dry season. Panicle size and infestation levels accounted for greater variation in grain damage and percentage loss in grain mass during the rainy season than in the dry season. To identify reliable sources of resistance to insects, it is important to study insect host plant‐interactions across panicle sizes (levels of food availability), infestation levels and season

Climate Change Effects on Insects: Implications for Crop Protection and Food Security

“…Minimum temperature (<18 • C) and maximum relative humidity (<60%) had a negative effect on midge damage in the midge-resistant cultivars ICSV 197 and AF 28 but not in the susceptible cultivar CSH 5 (Figure 6). The increase in head bug, C. angustatus, population and grain damage across panicle sizes or infestation levels were greater during the rainy season compared with the dry season (Sharma and Lopez 1994).…”

“…Maximum moth catches in light traps were recorded during the 31st standard week in 1980 and the 40th standard week during 1976. Adults of M. separata are generally caught in light traps 15-20 days after the initiation of the monsoon rains in the first week of June, and they reach a peak in September, nearly 1 month after the peak in larval density (Sharma and Lopez 1994). The population and incidence of cotton bollworm/legume pod borer, H. armigera, in southern India is influenced by the amount of rainfall during the rainy and the postrainy seasons (high incidence = +A+B, moderate incidence = −A+B, and low incidence = −A-B, where A = June-September rainfall and B = October-November rainfall) (Das et al 2001).…”