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<p>This study evaluated the efficacy and survival dynamics of two predatory ladybird species, <i>Cryptolaemus montrouzieri</i> Mulsant and <i>Hyperaspis trifurcata</i> Schaeffer, released under greenhouse conditions to control the cactus cochineal, <i>Dactylopius opuntiae</i> (Cockerell) (Hemiptera: Dactylopiidae). Adult ladybirds (<i>n</i> = 2,100 per greenhouse) were released at a density of 30 individuals/m<sup>2</sup>, with one species per treatment greenhouse and a third greenhouse as an untreated control. Although initial releases resulted in visible predator presence and a reduction in cochineal infestations, ladybird populations sharply declined three weeks post-release. Systematic monitoring revealed frequent intraguild predation (IGP) by native generalist spiders, notably <i>Araneus diadematus</i> Clerck, <i>Hasarius adansoni</i> Audouin, <i>Menemerus semilimbatus</i> (Hahn), and <i>Hogna radiata</i> (Latreille). In laboratory feeding trials <i>A. diadematus</i> maintained relatively high predation levels, consumed up to 13.0 ± 1.7 <i>C. montrouzieri</i> and 11.9 ± 1.3 <i>H. trifurcata</i> adults within 72 h in the absence of <i>D. opuntiae</i> (alternative prey). When <i>D. opuntiae</i> was provided, predation remained high, with 10.9 ± 1.3 [95% CI: 7.47–13.53] <i>C. montrouzieri</i> and 10.0 ± 1.3 [95% CI: 7.47–13.53] <i>H. trifurcata</i> adults consumed within 72 h. Additionally, parasitism by the mite <i>Coccipolipus chilocori</i> Husband was detected on adult and larval ladybirds, raising concerns about reproductive impairment. These results suggest that IGP by spiders and parasitism by <i>C. chilocori</i> constrain ladybird establishment and efficacy under greenhouse conditions, highlighting the need to assess natural enemy interactions before implementing biological control programs under greenhouse conditions. We caution, however, that replication at the greenhouse level was not available.</p>

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Intraguild predation by generalist spiders and mite parasitism may limit biological control of Dactylopius opuntiae (Hemiptera: Dactylopiidae) by predatory coccinellids

  • 期刊论文

  • 发表日期：

    2025年11月19日

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  • Mohamed El Aalaoui,
  • Mohamed Sbaghi

摘要

This study evaluated the efficacy and survival dynamics of two predatory ladybird species, Cryptolaemus montrouzieri Mulsant and Hyperaspis trifurcata Schaeffer, released under greenhouse conditions to control the cactus cochineal, Dactylopius opuntiae (Cockerell) (Hemiptera: Dactylopiidae). Adult ladybirds (n = 2,100 per greenhouse) were released at a density of 30 individuals/m2, with one species per treatment greenhouse and a third greenhouse as an untreated control. Although initial releases resulted in visible predator presence and a reduction in cochineal infestations, ladybird populations sharply declined three weeks post-release. Systematic monitoring revealed frequent intraguild predation (IGP) by native generalist spiders, notably Araneus diadematus Clerck, Hasarius adansoni Audouin, Menemerus semilimbatus (Hahn), and Hogna radiata (Latreille). In laboratory feeding trials A. diadematus maintained relatively high predation levels, consumed up to 13.0 ± 1.7 C. montrouzieri and 11.9 ± 1.3 H. trifurcata adults within 72 h in the absence of D. opuntiae (alternative prey). When D. opuntiae was provided, predation remained high, with 10.9 ± 1.3 [95% CI: 7.47–13.53] C. montrouzieri and 10.0 ± 1.3 [95% CI: 7.47–13.53] H. trifurcata adults consumed within 72 h. Additionally, parasitism by the mite Coccipolipus chilocori Husband was detected on adult and larval ladybirds, raising concerns about reproductive impairment. These results suggest that IGP by spiders and parasitism by C. chilocori constrain ladybird establishment and efficacy under greenhouse conditions, highlighting the need to assess natural enemy interactions before implementing biological control programs under greenhouse conditions. We caution, however, that replication at the greenhouse level was not available.