The role of spiders in regulating phytophagous pest populations is very difficult to investigate in open fields. In 2001 we began to observe the activity of these predators upon grapevine moth, and we continued this study in 2006-2007 with research to quantify their impact on the key pest of vineyards in Southern Italy, i.e. Lobesia botrana (Denis & Schiffermüller) (Lepidoptera Tortricidae). The research was realized in an experimental screenhouse vineyard completely covered by one single piece of insect-proof net. The screenhouse was subdivided into two isolated equal parts by a vertical net. The experiment consisted in collecting the spiders from each vine of one half of the vineyard and transferring them into the second half, then evaluating the variation of population density both of L. botrana and spiders over the seasons. In order to evaluate the spider population density, we randomly selected three plots in each half vineyard; each plot consisting of 10 cv Italia vines. Spiders were collected weekly from each vine of the plot using an entomological umbrella. From bloom to harvest, grapevine moth infestation was assessed by collecting one inflorescence or one cluster per vine and counting the numbers of infested berries and live larvae. Grapevine moth adults were collected weekly using sex pheromone traps and then counted. The regular transfer of spiders from one half of the vineyard to the other caused a noticeable variation in their density. The total number of spiders in the enriched vineyard was about double that in the depleted vineyard in 2006, and more than four times the number in 2007. As a consequence of spider enrichment in the release plot, the grapevine moth adults diminished, reaching the lowest density in the second year of study, when the number of adults trapped was less than one half of the number trapped in the plot where spiders were removed. The usefulness of spider activity in limiting L. botrana adults was not followed by a similar effect on phytophagous larvae, mainly because predators have poor possibilities of reaching the endophytic larvae of L. botrana carpophagous generations.
The impact of spiders (Araneae) on Lobesia botrana (Denis & Schiffermüller) population density
ADDANTE, Rocco;CALCULLI C;POLLICE, Alessio
2008-01-01
Abstract
The role of spiders in regulating phytophagous pest populations is very difficult to investigate in open fields. In 2001 we began to observe the activity of these predators upon grapevine moth, and we continued this study in 2006-2007 with research to quantify their impact on the key pest of vineyards in Southern Italy, i.e. Lobesia botrana (Denis & Schiffermüller) (Lepidoptera Tortricidae). The research was realized in an experimental screenhouse vineyard completely covered by one single piece of insect-proof net. The screenhouse was subdivided into two isolated equal parts by a vertical net. The experiment consisted in collecting the spiders from each vine of one half of the vineyard and transferring them into the second half, then evaluating the variation of population density both of L. botrana and spiders over the seasons. In order to evaluate the spider population density, we randomly selected three plots in each half vineyard; each plot consisting of 10 cv Italia vines. Spiders were collected weekly from each vine of the plot using an entomological umbrella. From bloom to harvest, grapevine moth infestation was assessed by collecting one inflorescence or one cluster per vine and counting the numbers of infested berries and live larvae. Grapevine moth adults were collected weekly using sex pheromone traps and then counted. The regular transfer of spiders from one half of the vineyard to the other caused a noticeable variation in their density. The total number of spiders in the enriched vineyard was about double that in the depleted vineyard in 2006, and more than four times the number in 2007. As a consequence of spider enrichment in the release plot, the grapevine moth adults diminished, reaching the lowest density in the second year of study, when the number of adults trapped was less than one half of the number trapped in the plot where spiders were removed. The usefulness of spider activity in limiting L. botrana adults was not followed by a similar effect on phytophagous larvae, mainly because predators have poor possibilities of reaching the endophytic larvae of L. botrana carpophagous generations.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
