Abstract
Simple SummaryFlowering plants are used to enhance pest control by predators and parasitoids, but insect herbivores can also use floral resources. We documented the species of adult rootworm beetles on key plants, and found that northern corn rootworm (NCR) adults were commonly associated with sunflower inflorescences while western corn rootworm adults were most abundant in corn and on squash blossoms. Consumption of sunflower and corn pollen by NCR adults did not impact predation of their eggs by an omnivorous mite, but a predatory soil-dwelling mite ate pest eggs less frequently and took longer to feed on eggs when NCR adults had fed on sunflower pollen. While increasing plant diversity can benefit natural enemies and pest control within agroecosystems, it is important to consider how floral resources alter dietary preferences of biocontrol agents.Landscape diversification with flowering plants can benefit pollinators and natural enemies, although insect pests can also use floral resources for nutrition and chemoprotection. Corn rootworms (Coleoptera: Chrysomelidae, Diabrotica spp.) are major pests of corn (Zea mays L.), and while subterranean larvae primarily feed on corn roots, adult rootworms commonly consume floral resources from other plant species. We quantified the species, density, and sex of adult corn Diabroticite rootworm beetles on wild and cultivated sunflower, corn, and squash, quantified pollen within the bodies of adult northern corn rootworms [NCR, D. barberi (Smith & Lawrence)], and investigated how consumption of sunflower and corn pollen by NCR adults impacted predation of their eggs by two soil-dwelling mites with different feeding specialization. NCR were the most common Diabroticite species on sunflower inflorescences and western corn rootworm (WCR, D. v. virgifera LeConte) were more abundant in corn and squash blossoms. Pollen feeding by NCR adults did not impact egg predation by omnivorous Tyrophagus putrescentiae (Schrank) (Acari: Sarcoptiformes, Acaridae), but predatory Stratiolaelaps scimitus (Womersley) (Acari: Mesostigmata, Laelapidae) ate eggs less frequently and took longer to feed on eggs from NCR females that had fed on sunflower pollen. This research suggests pollen feeding by adult NCR can impact predation of their eggs. While increasing plant diversity can benefit natural enemies and pest control within agroecosystems, it is important to consider how floral resources alter dietary preferences of biocontrol agents.
Highlights
Landscape diversification can enhance agricultural production [1] and adding flowering plants within or around agricultural fields benefits pollinators and natural enemies [2,3,4,5].insect pests are found on non-crop plants and consume floral resources that can positively impact their development, longevity, and reproduction [6,7,8,9,10]
Three Diabroticite beetle species were collected from corn, squash, and wild or cultivated sunflower: NCR, northern corn rootworm; Diabrotica barberi; WCR, western corn rootworm, D. v. virgifera; SCR, southern corn rootworm, D. undecimpunctata howardi, which is called the spotted cucumber beetle
NCR was the dominant species (Figure 2a; H = 116.06, df = 2, p < 0.0001) and more NCR females were collected per inflorescence than males (t = −16.85, df = 55.5, p < 0.0001)
Summary
Landscape diversification can enhance agricultural production [1] and adding flowering plants within or around agricultural fields benefits pollinators and natural enemies [2,3,4,5].insect pests are found on non-crop plants and consume floral resources that can positively impact their development, longevity, and reproduction [6,7,8,9,10]. Landscape diversification can enhance agricultural production [1] and adding flowering plants within or around agricultural fields benefits pollinators and natural enemies [2,3,4,5]. Pollen in particular is rich in protein, lipids, and vitamins [11,12] and contains numerous secondary compounds (e.g., alkaloids, terpenoids, phenolics, and tannins) that play a role in interspecific communication with pollinators and defense against pollinivores and microbes [11,13,14,15,16,17], only a few pollens appear to be toxic to insects, a property that has been best studied in bees [12]. Adult and immature leaf beetles (Chrysomelidae) are well-known for chemoprotection and can biosynthesize defensive chemicals or sequester them or their precursors from food plants [19,20,21,22]. Both sexes contribute to chemoprotection, with females sequestering chemicals within eggs or associated secretions (e.g., mucilage) and males passing compounds to females during mating [23,24,25,26]
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