Phytophagous insects utilize visual, olfactory and gustatory cues to find food. The brown marmorated stink bug, Halyomorpha halys (Stål), quickly approaches fresh peanut seeds newly introduced into the rearing cage in the laboratory but shows less interest in stale peanut seed previously infested by conspecifics. This observation suggests that H. halys can perceive the quality of food by detecting the volatile(s) from fresh peanut seeds. A bioassay revealed that H. halys adults could more quickly find fresh peanut seeds than three-day-infested peanut seeds, which is consistent with laboratory observations. Hexanal was found to be the major volatile component of fresh peanut seeds but not of previously infested ones. In the two-choice assays, the adult bugs that did respond were significantly attracted to fresh peanut volatiles and hexanal. Hexanal also induced proboscis-protruding behavior in adult H. halys, which suggested that this compound is a key stimulant of foraging behavior of laboratory-reared H. halys adults.
The ethyl acetate extract of the culture filtrate of Phlebia tremellosa promoted elongation of the lateral roots of lettuce seedlings at 250 µg/mL. We purified two compounds that promote root elongation by using activity-guided chromatographic fractionation. On the basis of spectroscopic analyses, these compounds were identified to be isolactarane sesquiterpenes derived from the dehydrogenation of merulactone, which was previously isolated from the same species. We named the purified compounds phlelactones A and B. Phlelactones A and B promoted primary root elongation at 100–300 and 10–30 µg/mL and the elongation and formation of lateral roots at 300–1000 and 30–100 µg/mL, respectively.
The relationships between plant growth stage and pesticide-uptake ability were investigated via cultivation of Brassica rapa L. var. perviridis in soil to which was added four pesticides of relatively high log KOW: fenobucarb, procymidone, flutolanil, and tolclofos-methyl. The root concentrations of pesticides were low in very young seedlings with undeveloped root systems, highest in seedlings with developed root systems, and tended to decrease until the usual harvesting stage. Additionally, the shoot concentrations of tested pesticides showed the same trends as the roots. The pesticide-uptake abilities of roots were lowest in very young seedlings and then constant for seedlings until the harvesting stage. In contrast, the pesticide-translocation abilities from root to shoot were constant regardless of growth stage. The results indicated that changes in shoot concentrations with growth stage were affected by the development of the root system and pesticide-uptake ability of roots.