The Japanese beetle is a polyphagous insect that typically aggregates on preferred host plants in the field. We studied the response of Japanese beetles to artificial damage, fresh feeding damage, and overnight feeding damage to test the hypothesis that beetles are attracted to feeding-induced volatiles. Crabapple leaves that had been damaged overnight by Japanese beetles or fall webworms attracted significantly more Japanese beetles than did undamaged leaves. Artificially damaged leaves or leaves freshly damaged by Japanese beetles, however, were not significantly more attractive than undamaged leaves. Leaves that had been damaged overnight by Japanese beetles or fall webworms produced a complex mixture of aliphatic compounds, phenylpropanoid-derived compounds, and terpenoids. In comparison, artificially damaged leaves or leaves with fresh Japanese beetle feeding damage generated a less complex blend of volatiles, mainly consisting of green-leaf odors. Feeding-induced odors may facilitate host location and/or mate finding by the Japanese beetle.

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Antifungal potentials of volatile oxygenated alkyl compounds were determined by bioassay of Alternaria alternata germ tube growth. Compounds were naturally occurring lipoxygenase enzyme system products or related to them chemically. Results were based on headspace concentrations of test compounds.Among six-and nine-carbon aldehydes and ketones related to hexanal, nonanal, 3-hexanone, and 2-nonanone, respectively, the presence of an a,/3-unsaturated bond adjacent to the carbonyl moiety generally enhanced antifungal activity. Among six-carbon alcohols related to 1-hexanol, however, an a,d-unsaturated bond enhanced antifungal activity only slightly. Abundant, naturally occurring (E)-2-hexenal that higher plants emit as a response to wounding tested negatively for mutagenicity; a volatile compound modification of the Ames test with several strains of Salmonella typhimurium was used.

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Botrytis-inoculated fruit were treated with three levels of naturally occurring volatile compounds in capped bottles and rated for Botrytis development and evidence of phytotoxicity during 7 days of storage at 2 °C followed by 3−6 more days at 22 °C for strawberry and 7 days at 15 °C for blackberry and grape. Hexanal, 1-hexanol, (E)-2-hexen-1-ol, (Z)-6-nonenal, (E)-3-nonen-2-one, methyl salicylate, and methyl benzoate exhibited potential as postharvest fumigants for control of Botrytis on strawberry at the lowest level tested. Ten compounds were evaluated on blackberry and grape. None caused phytotoxic responses as with strawberry, while nearly all of the compounds inhibited Botrytis at all three test levels. Strawberry, blackberry, and grape metabolized (E)-2-hexenal with reduction of the aldehyde to an alcohol and saturation of the carbon−carbon double bond adjacent to the carbonyl, but strawberry yielded more esters as major products. Keywords: Fragaria × ananassa; Rubus; Vitis vinifera; metabolism; antifungal; (E)-2-hexenal

A role of some volatile compounds produced by plant tissues may be as defensive molecules against various pests, including arthropods. Volatile six-carbon compounds derived in plant tissue from polyunsaturated fatty acids via lipoxygenase/hydroperoxide lyase reduced tobacco aphid fecundity at certain concentrations when added to headspace vapor to which aphids were exposed. Both C6 aldehydes and alcohols were effective, with the alcohols having greater activity. (Z)-3-Hexenyl acetate at levels in the headspace similar to those of the alcohols and aldehydes did not reduce aphid fecundity. A 6-hr exposure period to the C6 aldehydes and alcohols was needed for maximum effect on the aphids feeding on tobacco leaves. Analysis of the direct versus indirect effects of these compounds indicates that the volatile aldehydes had both direct effects on aphid fecundity and indirect effects due to induced changes in the leaves upon which the aphids were feeding, while only indirect effects were observed for the alcohols. Tomato leaves have the capacity to produce volatile compounds at levels that impact aphid population increase, with the volatiles produced from crushed leaves having a much larger effect. The C6 aldehydes and alcohols may be components of the fecundity reduction seen with tomato volatiles; however, volatile terpenes showed no effect. These results can be of significance for the genetic alteration of plants for improved aphid resistance.

Survival of Escherichia coli O157:H7 was studied on strawberry, a fruit that is not usually washed during production, harvest, or postharvest handling. Two strains of the bacteria were tested separately on the fruit surface or injected into the fruit. Both strains of E. coli O157:H7 survived externally and internally at 23 degrees C for 24 h and at 10, 5, and -20 degrees C for 3 days. The largest reduction in bacterial population occurred at -20 degrees C and on the fruit surface during refrigeration. In all experiments, the bacteria inside the fruit either survived as well as or better than bacteria on the surface, and ATCC 43895 frequently exhibited greater survival than did ATCC 35150. Two strains of E. coli also survived at 23 degrees C on the surface and particularly inside strawberry fruit. Chemical agents in aqueous solution comprising NaOCl (100 and 200 ppm), Tween 80 (100 and 200 ppm), acetic acid (2 and 5%), Na3PO4 (2 and 5%), and H2O2 (1 and 3%) were studied for their effects on reduction of surface-inoculated (10(8) CFU/ml) E. coli O157:H7 populations on strawberry fruit. Dipping the inoculated fruit in water alone reduced the pathogen population about 0.8 log unit. None of the compounds with the exception of H2O2 exhibited more than a 2-log CFU/g reduction of the bacteria on the fruit surface. Three percent H202, the most effective chemical treatment, reduced the bacterial population on strawberries by about 2.2 log CFU/g.