The role of spiders as predators of two lepidopteran Brassica pests

Abstract

Spiders are thought to play a significant role in limiting pest outbreaks in agroecosystems such as vineyards, orchards and cotton. The diversity and impact of spiders in vegetable crops are less well understood, although there is evidence that predators may be important for suppression of lepidopteran pests in Brassica crops, particularly early in the season before parasitoids become established. Sampling was conducted in early season plantings of Brassicas in the Lockyer Valley (South East Queensland, Australia) in order to determine the most commonly occurring spider families. The most numerous were Theridiidae, which were more strongly associated with cauliflower and poorly associated with cabbage. The Lycosidae and Clubionidae/Miturgidae (formerly in the 'catchall' family Clubionidae) also occurred commonly. Lycosidae (and to a lesser extent Salticidae) had above average abundance in Chinese cabbage and below average abundance in broccoli compared with average abundance for these spider families; Clubionidae/Miturgidae had above average abundance in cauliflower. Laboratory studies were then conducted to explore the predatory capacity of these three most commonly occurring spider families. All three were capable of feeding on larvae of the diamondback moth, Plutella xylostella (Linnaeus), and cabbage cluster caterpillar, Crocidolomia pavonana (Fabricius), under laboratory conditions. Theridiidae, which are thought to prey on small pests such as leafhoppers and aphids, were able to successfully attack larvae up to five times their body size. Predation rates varied from an average of 1.7 (SE = 0.47) (1.6 control corrected) larvae consumed over a 24 h period in the case of the Theridiidae, to 3.3 (SE = 0.60) larvae for the Clubionidae/Miturgidae.

The Spatiotemporal Dynamics of Insect Predator–Prey System Incorporating Refuge Effect

“…Moreover, the predator-prey models with ratio dependence also demonstrate that the refuge effect supports the coexistence of the predator and prey [35]. Notably, the discrete-time predator-prey system, which is more compatible in describing the dynamics of insects than the continuous system considering the generation nonoverlapping of many insects [3,[24][25][26], also confirms the stabilizing effect of refuge in predator-prey systems [35,36]. However, the spatiotemporal dynamics of discrete insect predator-prey systems with the refuge effect are still unclear.…”

“…A series of experiments have shown that predator–prey interactions among insects (e.g., moths and spiders) conform to the Holling type II functional response [ 24 , 25 , 26 ]. In most prior studies, the Holling type II predator–prey models were continuous and analyzed by phase plane and bifurcation diagrams, without integrating ecological phenomenon to analyze dynamic behaviors [ 25 , 26 , 27 ].…”

Money spider dietary choice in pre‐ and post‐harvest cereal crops using metabarcoding

“…As a community, they employ a diversity of foraging techniques (Turnbull, 1973; Riechert & Lockley, 1984) which influence food webs via a range of hunting strategies including passive sit‐and‐wait predation from webs, and active hunting (Michalko & Pekár, 2016). Acknowledgement that spiders are an effective biocontrol agent has existed for decades (Riechert & Lockley, 1984; Sunderland et al ., 1997; Sunderland, 1999) since they regularly consume pests such as aphids (Sunderland et al ., 1986; Beck & Toft, 2000; Mayntz & Toft, 2000; Bilde & Soren, 2001; Harwood et al ., 2003; Nyffeler & Sunderland, 2003), planthoppers (Wang et al ., 2016; Wang et al ., 2017), psyllids (Petráková et al ., 2016), medflies (Monzó et al ., 2010), lepidopterans (Quan et al ., 2011; Pérez‐Guerrero et al ., 2013; Senior et al ., 2016), and weevils (Vink & Kean, 2013). Whilst crop rotation disrupts biocontrol by many generalist predators, spider generation times often coincide with crop cycles, with early pest population establishment coinciding with peak spider abundances in Spring, thus facilitating early pest suppression (Riechert & Lockley, 1984; Symondson et al ., 2002; Harwood & Obrycki, 2005; Welch et al ., 2011).…”