Journal of Chemical Ecology

Haynes, Kenneth; Baker, Thomas

doi: 10.1007/BF01012521pmid: 24276428

FemalePectinophora gossypiella (Saunders) from most of the desert cotton-growing areas of southern California emitted significantly more pheromone in 1984 and 1985 than in preceding years (1982 and 1983). This increase amounted to almost 20% by 1985. It is unlikely that this small change would represent effective resistance to disruptant pheromones, but this increase could reflect the result of selection pressure imposed by the use of mating disruption for population control. A worldwide survey of emitted pheromone from this species found that there was much more variation in the emission rate than the blend ratio of the two pheromone components. The emitted blend ratio was remarkably consistent over time (in southern California) and throughout the worldwide range of the insect. Small differences in the blend ratio that were detected probably have no major biological significance because of the relatively broad response spectrum of males to changes in the blend of pheromonal components. Populations of males did not consist of several phenotypes, each with a different preference for specific blend ratios. Rather, the broad response spectrum to blend ratios in a population can be attributed to variation in the response of any individual. Therefore, selection for a response phenotype that is narrowly tuned to the blend emitted by females may be difficult.

Schmidt, S.

doi: 10.1007/BF01012522pmid: 24276429

Bacteria that can degrade juglone (5-hydroxy-1,4-naphthoquinone) were isolated from soil beneath black walnut trees. Autecological studies with one of these bacteria (Pseudomonas J1), demonstrated that it could grow rapidly using juglone as its sole source of carbon and energy. Using nonlinear regression analysis and the Monod equation, it was determined that this bacterium had a high affinity for juglone (K s = 0.95 μg/ml).Pseudomonas J1 can also utilize other aromatic compounds from plants as its sole source of carbon and energy. Compounds such as chlorogenic acid, ferulic acid, gallic acid, and 2-hydroxy-1,4-naphthoquinone (Lawson) were rapidly degraded byPseudomonas J1. The rapid degradation of juglone and other suspected allelochemicals by soil bacteria make it unlikely that these compounds are important mediators of plant-plant interactions under natural conditions.

Paszkowski, Wojciech; Kremer, Robert

doi: 10.1007/BF01012523pmid: 24276430

The biological activity of aqueous extracts of velvetleaf (Abutilon theophrasti Medik.) seed coats and their flavonoid components against three plant species and five soil fungi was investigated. Aqueous extracts slightly inhibited germination and significantly inhibited radicle growth of all plant species tested. Fungal growth was inhibited or not affected, depending on species, by aqueous extracts. The aqueous extracts were extracted into methanol and separated using paper chromatography for identification of compounds responsible for inhibition of seedling and fungal growth. Six flavonoid compounds were isolated and tentatively identified as delphinidin, cyanidin, quercetin, myricetin, (+)-catechin, and (−)-epicatechin. Bioassays revealed that the flavonoid compounds significantly inhibited germination and radicle growth of all test species at a concentration of 1.0 mM. Individual flavonoids had variable effects on fungi but appeared to inhibit growth and sporulation of potential seed-decomposing fungi rather than “beneficial” fungi. These results indicate that the flavonoid complement of velvetleaf seed coats may function in a dual defensive role against competing seedlings and seed-attacking fungi.

Hérard, F.; Keller, M.; Lewis, W.; Tumlinson, J.

doi: 10.1007/BF01012524pmid: 24276431

Heliothis zea (Boddie) larvae fed cowpea seedlings produced volatile semiochemicals to whichMicroplitis demolitor Wilkinson responded in a wind tunnel. However, mostM. demolitor females reared fromH. zea larvae fed an artificial diet were not responsive at emergence to the same volatile semiochemicals. A preflight contact with frass fromH. zea fed cowpea was needed to stimulate a response of sustained flight in a wind tunnel. The most consistent flight response was 7–10 days postemergence. Response resulting from both antennal and ovipositor contact with host frass during preflight stimulation was no better than from antennal contact alone. Chilling the parasitoid pupae rendered most of the emerging females unresponsive to volatile semiochemicals.

Hérard, F.; Keller, M.; Lewis, W.; Tumlinson, J.

doi: 10.1007/BF01012525pmid: 24276432

Microplitis demolitor Wilkinson were reared fromHeliothis zea larvae fed either an artificial diet or a diet of cowpea seedlings. Responses of females from these two sources to semiochemicals from the insect hostcowpea complex were compared in a flight tunnel. Very limited responses were obtained from females reared from hosts fed artificial diet unless they first had preflight contact with frass from plant-fed hosts. Female parasite is reared from plant-fed hosts were generally responsive without preflight contact. Contact with cocoons containing frass of the plant fed host at the time of emergence was an important source of stimulation. It increased their subsequent responsiveness to the volatile semiochemicals of the insect host-plant complex. The cocoons of females reared from artificial diet-fed hosts were apparently lacking plant chemicals that are vital to their subsequent responsiveness. Imprinting of the adults at time of emergence from the cocoon is strongly indicated.

Drost, Y.; Lewis, W.; Tumlinson, J.

doi: 10.1007/BF01012526pmid: 24276433

Rearing the parasitoidM. croceipes on hosts fed cowpea-seedling leaves instead of artificial diet increased the percentage of oriented flights to odors of a cowpea seedling-H. zea complex in a flight tunnel. However, the increase in response was much stronger after adult females had searched a fresh plant-host complex just prior to a test. The host plant appears to be of major importance in the parasitoid-host relationship: host-plant species, growth phase, and part of the host plant influence the parasitoid's response in the flight tunnel. The percentage of inexperienced females responding to infested leaves was higher for 4- to 5-day-old females than for 0- to 1-day-old females, while the response to uninfested flowers was equally high for both age groups. Olfactory experience with odors of an attractive plant-host complex increased the response to an unattractive plant-host complex. Possible implications of the results are discussed.

Bradow, Judith; Connick, William

doi: 10.1007/BF01012527pmid: 24276434

The effects of nine methyl ketones previously identified in the mixture of volatiles released byAmaranthus palmeri (AMAPA) residues upon onion, carrot, AMAPA, and tomato seed germination were determined. Three-day exposures to these volatiles significantly inhibited germination of all assay seeds, and the degree of inhibition was dependent upon seed species, exposure time, and concentration. Based on the degree of inhibition observed in both time- and concentration-dependent assays, the following activity series was obtained: 2-octanone, 2-nonanone > 2-undecanone > 2-heptanone > 2-hexanone, 3-methyl-2-butanone, 2-pentanone, 3-hydroxy-2-butanone > 2-butanone. The activities of these compounds appear to be additive and dependent on relative volatility and hydrophilicity.

Bradow, Judith; Connick, William

doi: 10.1007/BF01012528pmid: 24276435

Effects of 3-pentanone and eight low molecular weight aliphatic alcohols and aldehydes identifed in the mixtures of volatiles released byAmaranthus palmeri S. Wats. (AMAPA) residues were determined on germination of onion, carrot, AMAPA, and tomato seeds. Three-day exposures to these volatiles significantly inhibited germination of these assay seeds, and the inhibition was dependent upon exposure time and concentration. Based on the degree of inhibition observed in both time- and concentration-dependent assays, the following activity series was obtained: 2-heptanol > 3-methyl-1-butanol, 1-hexanol > hexanal, 1-pentanol, 3-pentanone, acetaldehyde > ethanol, 2-methyl-1-propanol. The activities of this group of compounds with that of 2-heptanone appear to be additive and related to test compound volatility and hydrophilicity. 2-Heptanol and 2-heptanone also significantly inhibited the germination of other species, including shepherdspurse, soybean, lettuce, alfalfa, common purslane, oats, and lovegrass.