Showing papers by "Peter Witzgall published in 2005"

Antennal and behavioral responses of grapevine moth Lobesia botrana females to volatiles from grapevine.

Abstract: Grapevine moth Lobesia botrana is the economically most important insect of grapevine Vitis vinifera in Europe. Flower buds, flowers, and green berries of Chardonnay grapevine are known to attract L. botrana for oviposition. The volatile compounds collected from these phenological stages were studied by gas chromatography-mass spectrometry, and the antennal response of L. botrana females to these headspace collections was recorded by gas chromatography-electroantennography. The compounds found in all phenological stages, which consistently elicited a strong antennal response, were pentadecane, nonanal, and alpha-farnesene. In a wind tunnel, gravid L. botrana females flew upwind to green grapes, as well as to headspace collections from these berries released by a piezoelectric sprayer release device. However, no females landed at the source of headspace volatiles, possibly due to inappropriate concentrations or biased ratios of compounds in the headspace extracts.

Plant volatiles affect oviposition by codling moths

Abstract: Oviposition in wild codling moth females, collected as overwintering larvae from apple, pear and walnut, was stimulated by volatiles from fruit-bearing green branches of these respective hostplants. Analysis of headspace collections showed that eight compounds present in apple, pear and walnut elicited a reliable antennal response in codling moth females: (E)-β-ocimene, 4,8-dimethyl-1,(E)3,7-nonatriene, (Z)3-hexenyl acetate, nonanal, β-caryophyllene, germacrene D, (E,E)-α-farnesene, and methyl salicylate. Any one of these compounds is found in many other non-host plants, and host recognition in codling moth is thus likely encoded by a blend of volatiles. A large variation in the blend proportion of these compounds released from apple, pear and walnut suggests a considerable plasticity in the female response to host plant odours. Wild females, collected as overwintering larvae in the field, laid significantly fewer eggs in the absence of host plant volatiles. The offspring of these females, however, reared on a semi-artificial diet in the laboratory, laid as many eggs with or without plant volatile stimulus. Tests with individual females showed that this rapid change in oviposition behaviour may be explained by selection for females which oviposit in the absence of odour stimuli, rather than by preimaginal conditioning of insects when rearing them on semi-artificial diet. Oviposition bioassays using laboratory-reared females are therefore not suitable to identify the volatile compounds which stimulate egglaying in wild females.

Pheromone-mediated communication disruption in Guatemalan potato moth, Tecia solanivora

Abstract: The Guatemalan potato moth, Tecia (Scrobipalpopsis) solanivora, is a serious potato pest in Central America and adjacent South American countries. Recently, it has been introduced to the Canary Islands, Spain. Insecticide treatments are not sufficiently effective against eggs and larvae of Guatemalan potato moth, which are protected from sprays in soil crevices and in galleries inside potato tubers, respectively. Deregulation of insecticides and restrictions in the use of the few available insecticides, parallel to a public demand for reduction of pesticide use in potato production, have increased the interest in biological control techniques. Behaviour-modifying chemicals, including sex pheromones, which target the adult life stage, are a particularly promising alternative to insecticides for control of Guatemalan potato moth. The aim of this study was to study T. solanivora sex pheromone and to investigate the feasibility of pheromone-mediated mating disruption as environmentally safe control technique. Chemical analysis of female pheromone gland extracts confirmed two previously identified compounds (E)-3-dodecenyl acetate (E3-12Ac) and (Z)-3-dodecenyl acetate (Z3-12Ac), plus an additional, saturated compound, dodecyl acetate (12Ac). These three compounds elicited significant male antennal responses by GC-EAD. Field trapping studies showed that a 100:1:20-blend of these compounds formulated at 1000 μg on rubber septa, captured more males than the main compound alone. This trap lure can accordingly be used in field traps for detection and population monitoring. During two years, potato fields were treated with a 100:56:100-blend of the three pheromone compounds formulated in polyethylene tube dispensers. Male attraction to E3-12Ac and Z3-12Ac is optimal at a 100:1 blend ratio, and only few males were attracted to traps baited with a 100:50-blend. Mating disruption pheromone dispensers, containing these two compounds in a 100:56 ratio, did not attract males in the wind tunnel or in the field. The application rate of the 100:56:100-blend of the three pheromone compounds was 28 g/ha in the first, and 86 g/ha in the second year. In both years, T. solanivora male attraction to synthetic pheromone traps were almost completely suppressed, indicating that sexual communication was disrupted. During the second year, additional tests confirmed that the pheromone treatment prevented mate-finding and mating. Attraction to traps baited with live calling females was reduced by 89% in the pheromone treatment, during two months. In addition, matings in small field cages were significantly reduced. Visual observations showed that few males were observed in the pheromone-treated, as compared to the control field. At harvest, potato infestation was significantly lower in the treated field, as compared to control. Future studies will aim at the optimization of dispenser formulation, and area-wide implementation of the mating disruption technique for control of Guatemalan potato moth.

New Pheromone Components of the Grapevine Moth Lobesia botrana

Abstract: Analysis of extracts of sex pheromone glands of grapevine moth females Lobesia botrana showed three previously unidentified compounds, (E)-7-dodecenyl acetate and the (E,E)- and (Z,E)-isomers of 7,9,11-dodecatrienyl acetate. This is the first account of a triply unsaturated pheromone component in a tortricid moth. The monoenic acetate (E)-7-dodecenyl acetate and the trienic acetate (7Z,9E,11)-dodecatrienyl acetate significantly enhanced responses of males to the main pheromone compound, (7E,9Z)-7,9-dodecadienyl acetate, in the wind tunnel. The identification of sex pheromone synergists in L. botrana may be of practical importance for the development of integrated pest management systems.

Pheromone pre-exposure and mating modulate codling moth (Lepidoptera: Tortricidae) response to host plant volatiles

Abstract: Two codling moth Cydia pomonella kairomonal attractants, ethyl (E,Z)-2,4- decadienoate (pear ester) and (E)-b-farnesene, were tested in an insecticide- sprayed apple orchard and an orchard treated for mating disruption with synthetic pheromone (E,E)-8,10-dodecadienol (codlemone). Male captures with pear ester were higher in the pheromone-treated than in the insecticide- treated orchard, whereas captures with (E)-b-farnesene were not different. Subsequent wind tunnel experiments confirmed that pre-exposure to sex phero- mone codlemone increased the behavioural response of codling moth males to pear ester. This supports the idea that male attraction to the plant volatile pear ester and sex pheromone codlemone is mediated through the same sensory channels. 2 Pear ester is a bisexual codling moth attractant and even captures of female moths were significantly increased in the pheromone-treated orchard. In the laboratory wind tunnel, pheromone pre-exposure had no effect on female response to pear ester, but significantly more mated than unmated codling moth females flew upwind towards a pear ester source. Differences in mating status in insecticide-treated vs. pheromone-treated orchards may thus account for the differences in female trap captures with pear ester. 3 These findings are important with respect to monitoring of codling moth with pear ester in mating disruption orchards. They also emphasize the importance of host plant volatiles in pheromone-mediated mating disruption, which has been neglected to date.

Attractiveness of year‐old polyethylene Isonet sex pheromone dispensers for Lobesia botrana

Abstract: In this study, we have compared the release of sex pheromone from mating disruption dispensers exposed in the field for 12 months and from calling females. The main pheromone component of the grapevine moth, Lobesia botrana (D. and S.) (Lepidoptera: Tortricidae), is (E)-7,(Z)-9-dodecadienyl acetate, and a minor component is (Z)-9-dodecenyl acetate. Aged dispensers from two different years emitted a much higher amount of both pheromone components than calling females. However, the summer temperature during field exposure influenced the release from mating disruption dispensers the following year. In the wind tunnel, male L. botrana were equally attracted to 12-month, field-exposed dispensers, a standard monitoring pheromone lure, and to synthetic (E)-7,(Z)-9-dodecadienyl acetate sprayed at the rate of 0.6 ‐ 60 ng h − 1 . Field trapping tests confirmed that aged dispensers from both years were at least as attractive to L. botrana males as a standard monitoring pheromone lure . The possible contribution of previously applied dispensers to the mating disruption efficacy during following applications is discussed.

Evaluacion de la tecnica de la interrupcion de la copula de Tecia solanivora Povolny (Lepidoptera: Gelechiidae)

Abstract: One of the promising applications of pheromones is their use to control insects through mating disruption, in which multiple pheromone sources are created at high concentrations to produce male confusion, masking female pheromone detection and disrupting mating. In order to evaluate this technique for Tecia solanivora control, dispensers formulated with a pheromone blend were deployed in the field and in potato storage conditions. When adult male populations were monitored under field conditions, 39 males were caught in the area treated with pheromone dispensers, compared to 1593 males in the untreated area. Under storage conditions 39% of damage incidence and 100% of severity in tubers were observed in untreated storage rooms, compared to 9% of incidence and lower severity in rooms treated with pheromone dispensers.

When does the apple fruit moth (Argyresthia conjugella) fly and oviposit

Abstract: Apple fruit moth, Argyresthia conjugella Zeller (Lepidoptera: Argyresthiidae), is a serious pest of apple in Fennoscandia (Ahlberg, 1927). Its primary host is the rowan, Sorbus aucuparia L. (Schøyen, 1913; Ahlberg, 1927; Edland, 1969). However, the fruit setting of rowan is highly variable in Fennoscandia (Kobro et al., 2003). In years of poor fruit setting on rowan in forests, the apple fruit moth females invade nearby apple orchards for oviposition, where the entire crop can be destroyed. The most widely used and most efficient insecticide against apple fruit moth, azinphos-methyl, will be deregulated in Norway after 2005 (Mattilsynet, 2004). In order to develop alternative, environmentally safe control methods, it is critical to investigate the reproductive behaviour of the apple fruit moth. Its sex pheromone has already been reported (Jaastad et al., 2002). The goal of this study was to examine the diel periodicity of male attraction to sex pheromone, and female oviposition behaviour under varying meteorological conditions.