Effects of tangerine (Citrus reticulata) foliage age onStreblote panda larval development and performance

Abstract

The effects ofCitrus reticulata Blanco (tangerine) foliage age on larval survival and performance of the lappet mothStreblote panda Hubner (Lepidoptera: Lasiocampidae), a polyphagous Mediterranean species, were studied. Larvae were reared under controlled laboratory conditions on young and mature excised leaves of tangerine. Survival, duration of development, and post-ingestive indices of larval growth were determined. Mature leaves significantly reduced survivorship of early instar larvae. Larvae which were fed on mature leaves grew more slowly and were less efficient at utilizing plant biomass and nitrogen than larvae fed on young leaves. Growth rates were 30% higher on young leaves, overall efficiency of conversion of ingested food was greater also, as consequence of an increase of 46% in the assimilation efficiencies, whereas the efficiency of conversion of digested matter into larval biomass was similar in both food treatments. The rate of consumption of biomass was higher in mature leaves, but that of nitrogen was similar, indicating that mature leaves restricted growth primarily by restricting the efficiency of utilizing this nutrient. The nitrogen utilization efficiency was reduced more than 20%, and the relative accumulation rate of nitrogen was suppressed 30% for larvae on mature leaves, which may explain the protracted development time of larvae fed on mature leaves. Survival was consistently higher when larvae were fed with young leaves although no differences were found for mature larvae or pupae. No differences were found in pupal mass (a fecundity correlate) between food treatments. Our results confirm the bibliographic records ofCitrus spp. like host plants ofS. panda in Spain, but also suggest that much variation must be expected in the temporal and spatial incidence of this insect, depending upon the cultivated species, associated plant phenology and management techniques employed in the culture.