For commercial vineyards, and commercial agricultural farms in general, pest management employs the use of chemical pesticides.¬† These chemicals act to disrupt the communication between male and female insects that use sex pheromones to attract one another for mating.¬† However, there are many insects such as leafhoppers and plant-hoppers that do not use long range chemical pheromones, but instead utilizes vibrational signals to attract their mates.¬† Therefore, for these types of insects, there may be other pest management solutions that are less invasive and detrimental to the environment as the use of chemical pesticides.
Insects can be the vector for many different plant diseases, including the leafhopper Scaphoideus titanus Ball, which is a vector for the grapevine disease Flavescence dor√©e.¬† This disease is lethal to the grapevine, and in Europe (among other places) it is a quarantine disease, which often employs the use of large-scale chemical insecticides for treatment.¬† In regards to communication, S. titanusmales use vibrational signals to attach mating females.¬† It was the goal of the study presented today, to take this knowledge of the breeding patterns of S. titanus and test mating disruption based on substrate vibrations, in order to potentially find an alternative to the more toxic pesticide pest management methods.
S. titanus eggs were collects from organic farms in Villazzano in Trento, Italy.¬† The adults reared from these eggs were used in both semi-field and field experiments.¬† All leafhoppers used in the experiments were sexually mature adults that were at least 8 or exactly 10 days old.
A S. titanus male calling song was recorded using a laser vibrometer in a laboratory setting with the male singing 0.5cm from the ‚Äúmicrophone‚ÄĚ.
For the semi-field experiment, measurements occurred outdoors at Pisa University in Italy during July of 2010.¬† Five potted grapevines were pruned to be similar morphologically to a height of 70-75cm, two main branches, and 8 fully developed leaves.¬† A metal wire was used to fix the plants in an upright position, similar to how wires are situated in the vineyards.¬† Plants were placed in a row and about 190cm between each plant.¬†
An electromagnetic shaker was placed on the end of the row, resulting in varying distances between it and each plant (180cm, 370cm, 560cm, 750cm, and 940cm).¬† The shaker was activated using a laptop computer with Adobe Audition software with the amplitude of naturally occurring disturbance noise amplified 20 times.¬† The male calling song was applied to the leaf via the lamina of the upper leave by a comical rod attached to a mini shaker.¬† The amplitude was adjusted to the level of naturally occurring male calling songs.
To measure signal transmission through the plant, pieces of small square reflective tape were placed along the leaves and the stems, in order to focus a laser beam.¬† The vibrational signals were recorded using a laser vibrometer and digitized with a 48kHz sample rate and 16-bit resolution.¬† Intensity was measured as the maximum substrate velocity (mm/s).
Both male calling songs and disturbance noise were played back three times for each measuring point on each plant.¬† Velocity was measured for the three pulses with the highest amplitude to obtain an average velocity for 9 pulses per plant.¬† Average velocity was calculated across the three plants for all points from not only the leaf that incurred direct vibration, but also all other leaves.
Mating experiments were performed in July and August of 2010.¬† In addition to the vibrational plants, two plants that did not receive vibrational treatments were used as controls.¬† Each experimental plant was isolated in a transparent polyester cage that had closable openings in order to release and collect insects.
Field experiments were conducted at a vineyard at Fondazione Edmund Mach in Italy during July and August of 2011.¬† Mature plants at a height of 1.5m were grown in rows with each plant 70cm from one another.¬† An MP3-drive electromagnetic shaker was used to create both male calling songs and disturbance noise.¬† The shaker was attached to the wire on the vines, and was located 100, 310, 520, 730, and 940cm from experimental plants.
The shoot from the middle part of each plant was isolated in nylon netting, with closable openings in order to release and collect insects.
All experiments were conducted between 5pm and 10am the next day, since S. titanus making rituals occur during twilight or overnight.¬† Insectswere recollected at 10am the next day.
For each overnight trial used one virgin male and female, that were both placed on separate leaves of each plant.¬† After recollecting the insects the next morning, females were isolated and dissected 10 days after isolation.¬† Differences between mated and unmated females were determined.¬† All females with 0-6 eggs were labeled as ‚Äúvirgin‚ÄĚ, and all females with greater than 10 eggs were labeled as ‚Äúmated‚ÄĚ.¬† Any female with 7 to 9 eggs were too uncertain to remain in the study and thus data were removed.
- ¬† ¬† ¬† The highest intensities of male calling signal were measured on the leaf that was vibrated on with the recorded songs.
- ¬† ¬† ¬†¬†¬†Disruptive vibrational signals masked male calling signals at all measured points.
- ¬† ¬† ¬† There was a significant difference in the number of virgin females between vibrated on and control plants.
o¬†¬† There were no differences between vibrated plants at different distances from the recorded calling source.
The results of this short study, according to the authors, provide evidence that mating call disruption is an effective and environmentally friendly approach toward pest management in vineyards.¬† The disruptive noise covered over the male calling signal enough that there were significantly more virgin females in those plants exposed to the noise than those control plants that were not exposed.
Of course, insects were not completed eradicated from the system; however, it is possible that with the vibrational disruptive technique, populations could be kept at a more manageable level that is below the threshold for economic damage/loss.¬† This type of pest management may not only be successful in keeping populations of S. titanus in check, but may also be an important pest management method for other insects that also use similar vibrational mating rituals.¬† Of course, each individual species of insect would need to be studied, in order to determine the precise disruptive noise pattern that would be most successful in preventing mating events.
In summary, though this research is still in its infancy and much more work needs to be done, this method of vibrational disruptive noise applied to grapevine leaves may serve as an efficient and environmentally friendly approach to pest management in vineyards.
I‚Äôd love to hear what you all think about this topic!¬† Please feel free to comment below (please no HTML tags.¬† Any unapproved HTML tags posted will be deleted).
Source:¬† Eriksson, A., Anfora, G., Lucchi, A., Lanzo, F., Virant-Doberlet, M., and Mazzoni, V. 2012. Exploitation of Insect Vibrational Signals Reveals a New Method of Pest Management. PLoS ONE 7(3): e32954.
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