Competition between Two Species of Mites. I. Experimental Results

Abstract

Two principal pests of apple and peach trees in southwestern Ontario are the European red mite, Panonychus ulmi (Koch), and the two-spotted spider mite, Tetranychus telarius (L.). Usually only P. ulmi is present on the trees in large numbers during the spring and early summer, at which time T. telarius lives predominantly on the ground cover. In August, many T. telarius move from the ground cover to the trees, and large numbers of both species may then be present. In mite control investigations in an apple orchard at the Harrow Research Station, T. telarius moved onto the trees, especially in the central plots, regardless of the acaricides previously applied or the numbers of P. ulmi that were or had been present. This phenomenon posed the question of whether the residual effects of acaricides applied to the trees were mainly responsible for the size of P. ulmi populations in the central plots, or whether competition resulting from the ingress of T. telarius was partially responsible.

Amensalism via webs causes unidirectional shifts of dominance in spider mite communities

“…Previous laboratory experiments have demonstrated that T. urticae is a superior competitor, whereas P. ulmi is an inferior competitor (Foott 1962;Morimoto et al 2006), and Weld observations have indicated that T. urticae annually invades the habitats of P. ulmi (Lienk and Chapman 1951;Rodriguez 1958;Kim and Lee 2003).…”

“…This implies that T. urticae is a superior competitor, whereas P. ulmi is an inferior competitor. Several authors have therefore speculated that T. urticae suppresses the population growth of P. ulmi as a consequence of interspeciWc competition (Foott 1962(Foott , 1963Slone and Croft 2001; but see Belczewski and Harmsen 1997). However, Weld observations have not been able to elucidate the eVects of interspeciWc competition between them (Foott 1962(Foott , 1963Slone and Croft 2001).…”

“…In contrast, P. ulmi uses threads as lifelines and egg covers but never constructs webs; its sibling species Panonychus citri (McGregor) avoids its own threads when they accumulate beyond a certain level (Saito 1979). When a large portion of a leaf is covered by webs produced by T. urticae, active forms of P. ulmi are trapped by the webs (Foott 1962). This implies that T. urticae is a superior competitor, whereas P. ulmi is an inferior competitor.…”

“…The seasonal change in the species composition of spider mites, from Panonychus ulmi (Koch) to Tetranychus urticae Koch (Acari: Tetranychidae), has been observed in apple orchards around the world (Lienk and Chapman 1951;Rodriguez 1958;Foott 1962Foott , 1963. P. ulmi is an oligophagous spider mite that uses primarily pomaceous fruit trees as its host plants.…”

The Weaving Pattern and Structure of the Guy Ropes in Citrus Red Mite, Panonychus citri (McGregor) (Acari: Tetranychidea)

“…Consequently, a canopy of silk formed on the substrate. This canopy increased as the mite family become abundant, which served as a nest to live in the colony (Foott, 1962). The amount of silk spun depends on various factors, which include humidity, temperature, substrate smoothness and species of host plant (Hazan et al, 1974;Saito, 1977).…”