Spider fauna of soybean crops in south‐east Queensland and their potential as predators of Helicoverpa spp. (Lepidoptera: Noctuidae)

Abstract

Spiders are among the most abundant predators recorded in grain crops in Australia. They are voracious predators, and combined with their high abundance, may play an important role in the reduction of pest populations. The significance of spider assemblages as biological control agents of key pests such as Helicoverpa spp. in Australian agroecosystems is largely unknown. A thorough inventory was made of the spider fauna inhabiting unsprayed soybean fields at Gatton, south-east Queensland. Onehundred-and-two morphospecies from 28 families were collected using vacuum sampling and pitfall traps across two summer seasons . No-choice feeding tests in the laboratory, using eggs and larvae of Helicoverpa armigera (Hübner) as prey, were used to ascertain the predatory potential of each spider group. The field-collected spider assemblage ate on average 2.4 ( ± 0.7 standard error) to 5.0 ( ± 0.8) eggs per 24 h per spider (10-25% of those available), depending on level of starvation. Clubionidae were the only spiders to readily consume eggs in the laboratory (mean of 18.4 ± 1.5 eggs per starved spider and 8.2 ± 3.9 per non-starved spider after 24 h). Starved spiders consumed 9.4 ( ± 0.1) first-instar larvae per 24 h per spider (90% of those available). This information was combined with field observations and literature from Australian and overseas studies to assess the potential of spider groups as predators of Helicoverpa spp. Lycosidae, Clubionidae, Oxyopidae, Salticidae and Thomisidae have the capacity to contribute to control of Helicoverpa spp.

Predatory potential of three hunting spiders inhabiting the rice ecosystems

“…The pest's status (alive, killed or eaten) was recorded after every 4-h interval for 24 h. Dead pests were examined under an enlarging scope and compared their appearance to that of dead pests from the control containers. The nymphs killed by spiders appeared shriveled, which indicated that spiders were feeding on them (Pearce et al 2004). …”

“…The dishes were examined after every 4-h interval for 24 h after the introduction of predator and the number of larvae dead or consumed was recorded. Control dishes (n = 10) containing ten larvae but no spider, were used to assess the number of larvae that died during same time (Pearce et al 2004). …”

Population dynamic of the swallowtail butterfly, Papilio polytes (Lepidoptera: Papilionidae) in dry and wet seasons

“…Natural enemies are the important component in the population dynamics of this butterfly. The natural enemies have influence on total insect number and some-times their impact is related to the density of their prey (Hirosie et al 1980;Watanabe 1981;Feeny et al 1985;Stefanescu 2000;Zalucki et al 2002;Pearce et al 2004;Nava et al 2005;Stefanescu et al 2006). .00* Note: L1 = first instar larvae; L2 = second instar larvae; L3 = third instar larvae; L4 = fourth instar larvae; L5 = fifth instar larvae; Significant values marked with an asterisk "*" are significantly different (Friedman test, P < 0.05) Table 2.…”

“…The most important predator, spider was well adapted to living on the same host plant with P. polytes larvae. On grain crop in Australia, Pearce et al (2004) reported that spiders were also among the most abundant predators. Since the spiders are voracious predators and combined with their high abundance, they played an important role in the reduction of the pest populations.…”

Impact ofCheiracanthium pelasgicum(Araneae: Miturgidae) andChrysoperla carnea(Neuroptera: Chrysopidae) intraguild predation on the potential control of cotton pestHelicoverpa armigera(Lepidoptera: Noctuidae)

“…the cursorial spiders Miturgidae or Salticidae). The activity of these cursorial spiders may be harnessed for the control of pests such as Lepidoptera, whose eggs and larvae cannot be captured in a web (Mansour, 1987;Pearce, Hebron, Raven, Zalucki, & Hassan, 2004;Pfannenstiel, 2008). Recently, Pérez-Guerrero et al (2013) reported that certain cursorial families (Miturgidae and Philodromidae) displayed greater potential predation on lepidopteran larvae than other hunting families (e.g.…”