Response of Mythimna unipuncta Males to Components of the Sesamia nonagrioides Pheromone

Abstract

Several sympatric lepidopteran species feed on maize plants, and the different components of their species-specific female sex pheromones may play a role in attracting conspecifics and/or deter heterospecific males. In this study, we analyzed the content of Mythimna unipuncta pheromone glands and tested the response of males to components of their own pheromone blend and that of Sesamia nonagrioides in the wind tunnel. Whole pheromone glands, and lures where (Z)-9-hexadecenyl acetate, Z)-11-hexadecen-1-ol or (Z)-9-hexadecenyl acetate + (Z)-11-hexadecen-1-ol were added to the major component, (Z)-11-hexadecenyl acetate, elicited significantly higher responses by M. unipuncta males than lures with main component alone, although the levels varied with concentration. In the field a rather different outcome was observed, as the addition of other compounds found in the female pheromone gland did not improve trap catch over lures with only (Z)-11-hexadecenyl acetate. The addition of (Z)-11-hexadecenal, a compound of the S. nonagrioides pheromone, to (Z)-11-hexadecenyl acetate significantly reduced attraction of M. unipuncta males both in the wind tunnel and in the field, as well as the number of sympatric clover cutworm, Discestra trifolii, under field conditions. The addition of (Z)-9-hexadecenyl acetate, a minor component of the M. unipuncta pheromone blend, reduced the number of S. nonagrioides captured in field traps that were baited with the S. nonagrioides lure. The significance of such inhibition in the reproductive isolation of sympatric species that attack maize is discussed.

Response to conspecific and heterospecific semiochemicals by Sesamia nonagrioides (L.) (Lepidoptera: Noctuidae) gravid females

“…The pheromone detection of the sympatric species O. nubilalis probably helps S. nonagrioides gravid females to detect and avoid maize fields or plants on which O. nubilalis females are present in order to prevent interspecific competition of the larvae for food and space. On the other hand, the minor component of M. unipuncta pheromone, Z9-16:Ac, did not elicit any change in behaviour of the gravid females of S. nonagrioides in the wind tunnel or the olfactometer, although the high response of the males to this component in the EAG corresponds to the inhibitory effect obtained by Eizaguirre et al (2009) in wind tunnel and field-trapping experiments. M. unipuncta has different feeding or egg laying habits to O. nubilalis: the distribution of the egg masses may be either in the leaves of the corn plant or in wild grasses; larvae feed on the leaves and the different generations during the year do not completely Fig.…”

Managing maize under pest species competition: Is Bt (Bacillus thuringiensis) maize the solution?

“…, Eizaguirre et al. ). We studied the case in which MCB has a strong negative effect on TAW ( b 21 = 0.9), while the reciprocal effect is relatively small ( b 12 = 0.1).…”

“…While under normal conditions the MCB tends to outcompete the TAW (Eizaguirre et al. (), it has been suggested that the increase of transgenic maize could affect the population dynamics of these secondary Lepidopteran pests due to the high efficiency of Bt maize against its target pests (López et al. , , Eizaguirre et al.…”

“…In this region, two other Lepidoptera, the TAW, and the corn earworm, Helicoverpa armigera (Hübner), are considered to be important secondary pests causing occasional but severe damage to maize (Eizaguirre et al 2010, Pérez-Hedo et al 2012. While under normal conditions the MCB tends to outcompete the TAW (Eizaguirre et al (2009), it has been suggested that the increase of transgenic maize could affect the population dynamics of these secondary Lepidopteran pests due to the high efficiency of Bt maize against its target pests (López et al 2000, Eizaguirre et al 2010). This would arise if TAW takes advantage of the absence of the major corn borers (Eizaguirre et al 2010).…”

“…Considering a maximum carrying capacity of five larvae per plant and a maximum damage of 30% (as indicated above), we assume that each MCB and TAW larvae is able to reduce yields by 6% per plant. It has been suggested that the due behavioral characteristics, MCB may influence negatively the TAW, however until now this effect has not been quantified (López et al 2003, Eizaguirre et al 2009). We studied the case in which MCB has a strong negative effect on TAW (b 21 = 0.9), while the reciprocal effect is relatively small (b 12 = 0.1).…”