Response of specialist and generalist predators to nonprogressive annual fluctuations in herbivorous insect populations

Abstract The corn leafhopper Dalbulus maidis (Hemiptera: Cicadellidae) is a specialist herbivore that attacks maize in the tropical and subtropical regions of the Americas. It is vector of three relevant plant pathogens being responsible for severe yield losses. Modern agriculture is dependent on the addition of fertilizers, especially nitrogen, which may influence the nutritional quality of the plants possibly with a subsequent increment of herbivorous insect populations. Through a field experiment, using a randomized design with four treatments with different levels of fertilization, we evaluated the effects of nitrogen fertilization in corn on the population levels of the vector D. maidis, on the incidence of the diseases transmitted by it, and on the levels of parasitism of the vectors’ eggs. The amount of nitrogen fertilizer used significantly influenced the density of the corn leafhopper and the parasitism by egg parasitoids, but not the incidence of the diseases transmitted by it. Two weeks after fertilization, the vector density was significantly higher in the highly fertilized treatment. The disease incidence was not directly linked with the level of fertilization, however, the symptoms of the diseases were much less evident in plants that received higher fertilization. Parasitism levels by egg parasitoids increased accordingly to the level of D. maidis populations.

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Arboreal arthropod assemblages in chili pepper with different mulches and pest managements in freshwater swamps of South Sumatra, Indonesia

Biodiversitas Journal of Biological Diversity ◽

10.13057/biodiv/d220608 ◽

2021 ◽

Vol 22 (6) ◽

Author(s):

Siti Herlinda ◽

Titi Tricahyati ◽

Chandra Irsan ◽

Tili Karenina ◽

Hasbi HASBI ◽

...

Keyword(s):

Pest Management ◽

Leaf Litter ◽

Chili Pepper ◽

Species Number ◽

Herbivorous Insect ◽

Plastic Mulch ◽

Synthetic Insecticide ◽

Insect Populations ◽

Arboreal Arthropods ◽

Predatory Arthropods

Abstract. Herlinda S, Tricahyati T, Irsan C, Karenina T, Hasbi, Suparman, Lakitan B, Anggraini E, Arsi. 2021. Arboreal arthropod assemblages in chili pepper with different mulches and pest managements in freshwater swamps of South Sumatra, Indonesia. Biodiversitas 22: 3057-3066. In the center of freshwater swamps in South Sumatra, three different chili cultivation practices are generally found, namely differences in mulch and pest management that can affect arthropod assemblages. The effect of mulches and pest management on arboreal arthropod assemblages specific to chili production centers in the freshwater swamps of South Sumatra has never been investigated. This study aimed to observe arboreal arthropod assemblages in chili with different mulches and pest management. Arboreal arthropods were sampled using sweep nets in three locations with plots treated with leaf litter mulch and bioinsecticide, plastic mulch and synthetic insecticide, and weedy plot without mulch with synthetic insecticide. The species number of arboreal arthropods found was 28 species of Arachnids and 23 species of Insects, and consisting of 6 families of the Arachnids and 25 families of Insects. The abundance of arboreal arthropods was 65.60 individuals/5 nets per observation. In the chili field without mulch but with the insecticide, the species biodiversity and abundance of arboreal predatory arthropods were the highest. In contrast, in the chili field, that applied with synthetic insecticides and plastic mulch, the abundance of arboreal predatory arthropods was the lowest. The herbivorous insect populations in chili with plastic mulch and synthetic insecticides and the chili with the leaf litter mulch were higher than those in the chili without mulch. In the chili with the leaf litter mulch and bioinsecticide, the species number and abundance of the spiders were the highest compared to the other chili fields. The weedy chili field without mulch and chili with the leaf litter mulch has proved ideal habitats for the arboreal predatory arthropods.

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Demographic attritions, elevational refugia, and the resilience of insect populations to projected global warming

The American Naturalist ◽

10.1086/714525 ◽

2021 ◽

Author(s):

Carlos Garcia-Robledo ◽

Christina S Baer

Keyword(s):

Global Warming ◽

Insect Populations

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Prey removal in cotton crops next to woodland reveals periodic diurnal and nocturnal invertebrate predation gradients from the crop edge by birds and bats

Scientific Reports ◽

10.1038/s41598-021-84633-8 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Heidi L. Kolkert ◽

Rhiannon Smith ◽

Romina Rader ◽

Nick Reid

Keyword(s):

Pest Control ◽

Open Space ◽

Optimal Foraging Theory ◽

Time Of Day ◽

Camera Traps ◽

Generalist Predators ◽

Crop Cover ◽

Foraging Preferences ◽

Experimental Feeding ◽

Natural Pest Control

AbstractFactors influencing the efficacy of insectivorous vertebrates in providing natural pest control services inside crops at increasing distances from the crop edge are poorly understood. We investigated the identity of vertebrate predators (birds and bats) and removal of sentinel prey (mealworms and beetles) from experimental feeding trays in cotton crops using prey removal trials, camera traps and observations. More prey was removed during the day than at night, but prey removal was variable at the crop edge and dependent on the month (reflecting crop growth and cover) and time of day. Overall, the predation of mealworms and beetles was 1-times and 13-times greater during the day than night, respectively, with predation on mealworms 3–5 times greater during the day than night at the crop edge compared to 95 m inside the crop. Camera traps identified many insectivorous birds and bats over crops near the feeding trays, but there was no evidence of bats or small passerines removing experimental prey. A predation gradient from the crop edge was evident, but only in some months. This corresponded to the foraging preferences of open-space generalist predators (magpies) in low crop cover versus the shrubby habitat preferred by small passerines, likely facilitating foraging away from the crop edge later in the season. Our results are in line with Optimal Foraging Theory and suggest that predators trade-off foraging behaviour with predation risk at different distances from the crop edge and levels of crop cover. Understanding the optimal farm configuration to support insectivorous bird and bat populations can assist farmers to make informed decisions regarding in-crop natural pest control and maximise the predation services provided by farm biodiversity.

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Biological Control of Pest Non-Marine Molluscs: A Pacific Perspective on Risks to Non-Target Organisms

Insects ◽

10.3390/insects12070583 ◽

2021 ◽

Vol 12 (7) ◽

pp. 583

Author(s):

Carl C. Christensen ◽

Robert H. Cowie ◽

Norine W. Yeung ◽

Kenneth A. Hayes

Keyword(s):

Biological Control ◽

Environmental Impacts ◽

Pacific Islands ◽

Generalist Predators ◽

Snail Species ◽

Marine Mollusk ◽

The Pacific ◽

History Of ◽

Ecosystem Level ◽

Scientific Framework

Classic biological control of pest non-marine mollusks has a long history of disastrous outcomes, and despite claims to the contrary, few advances have been made to ensure that contemporary biocontrol efforts targeting mollusks are safe and effective. For more than half a century, malacologists have warned of the dangers in applying practices developed in the field of insect biological control, where biocontrol agents are often highly host-specific, to the use of generalist predators and parasites against non-marine mollusk pests. Unfortunately, many of the lessons that should have been learned from these failed biocontrol programs have not been rigorously applied to contemporary efforts. Here, we briefly review the failures of past non-marine mollusk biocontrol efforts in the Pacific islands and their adverse environmental impacts that continue to reverberate across ecosystems. We highlight the fact that none of these past programs has ever been demonstrated to be effective against targeted species, and at least two (the snails Euglandina spp. and the flatworm Platydemus manokwari) are implicated in the extinction of hundreds of snail species endemic to Pacific islands. We also highlight other recent efforts, including the proposed use of sarcophagid flies and nematodes in the genus Phasmarhabditis, that clearly illustrate the false claims that past bad practices are not being repeated. We are not making the claim that biocontrol programs can never be safe and effective. Instead, we hope that in highlighting the need for robust controls, clear and measurable definitions of success, and a broader understanding of ecosystem level interactions within a rigorous scientific framework are all necessary before claims of success can be made by biocontrol advocates. Without such amendments to contemporary biocontrol programs, it will be impossible to avoid repeating the failures of non-marine mollusk biocontrol programs to date.

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Floral Plantings in Large-Scale Commercial Agroecosystems Support Both Pollinators and Arthropod Predators

Insects ◽

10.3390/insects12020091 ◽

2021 ◽

Vol 12 (2) ◽

pp. 91

Author(s):

Eric G. Middleton ◽

Ian V. MacRae ◽

Christopher R. Philips

Keyword(s):

Large Scale ◽

Agricultural Land ◽

Field Margins ◽

Crop Fields ◽

Pollinator Abundance ◽

Arthropod Predators ◽

Commercial Potato ◽

Insect Populations ◽

Beneficial Insect ◽

Potato Crops

Beneficial insect populations and the services that they provide are in decline, largely due to agricultural land use and practices. Establishing perennial floral plantings in the unused margins of crop fields can help conserve beneficial pollinators and predators in commercial agroecosystems. We assessed the impacts of floral plantings on both pollinators and arthropod predators when established adjacent to conventionally managed commercial potato fields. Floral plantings significantly increased the abundance of pollinators within floral margins compared with unmanaged margins. Increased floral cover within margins led to significantly greater pollinator abundance as well. The overall abundance of arthropod predators was also significantly increased in floral plantings, although it was unrelated to the amount of floral cover. Within adjacent potato crops, the presence of floral plantings in field margins had no effect on the abundance of pollinators or predators, although higher floral cover in margins did marginally increase in-crop pollinator abundance. Establishing floral plantings of this kind on a large scale in commercial agroecosystems can help conserve both pollinators and predators, but may not increase ecosystem services in nearby crops.

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Global change in marine coastal habitats impacts insect populations and communities

Current Opinion in Insect Science ◽

10.1016/j.cois.2021.02.010 ◽

2021 ◽

Vol 47 ◽

pp. 1-6

Author(s):

Tyler M Rippel ◽

Jewel Tomasula ◽

Shannon M Murphy ◽

Gina M Wimp

Keyword(s):

Global Change ◽

Coastal Habitats ◽

Insect Populations

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Root-associated entomopathogenic fungi manipulate host plants to attract herbivorous insects

Scientific Reports ◽

10.1038/s41598-020-80123-5 ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Belén Cotes ◽

Gunda Thöming ◽

Carol V. Amaya-Gómez ◽

Ondřej Novák ◽

Christian Nansen

Keyword(s):

Host Plant ◽

Entomopathogenic Fungi ◽

Host Plants ◽

Near Infrared ◽

Delia Radicum ◽

Host Plant Selection ◽

Herbivorous Insects ◽

Herbivorous Insect ◽

Insect Performance ◽

Leaf Reflectance

AbstractRoot-associated entomopathogenic fungi (R-AEF) indirectly influence herbivorous insect performance. However, host plant-R-AEF interactions and R-AEF as biological control agents have been studied independently and without much attention to the potential synergy between these functional traits. In this study, we evaluated behavioral responses of cabbage root flies [Delia radicum L. (Diptera: Anthomyiidae)] to a host plant (white cabbage cabbage Brassica oleracea var. capitata f. alba cv. Castello L.) with and without the R-AEF Metarhizium brunneum (Petch). We performed experiments on leaf reflectance, phytohormonal composition and host plant location behavior (behavioral processes that contribute to locating and selecting an adequate host plant in the environment). Compared to control host plants, R-AEF inoculation caused, on one hand, a decrease in reflectance of host plant leaves in the near-infrared portion of the radiometric spectrum and, on the other, an increase in the production of jasmonic, (+)-7-iso-jasmonoyl-l-isoleucine and salicylic acid in certain parts of the host plant. Under both greenhouse and field settings, landing and oviposition by cabbage root fly females were positively affected by R-AEF inoculation of host plants. The fungal-induced change in leaf reflectance may have altered visual cues used by the cabbage root flies in their host plant selection. This is the first study providing evidence for the hypothesis that R-AEF manipulate the suitability of their host plant to attract herbivorous insects.

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Evaluating the Impact of Two Generalist Predators on the Leafhopper Erasmoneura vulnerata Population Density

Insects ◽

10.3390/insects12040321 ◽

2021 ◽

Vol 12 (4) ◽

pp. 321

Author(s):

Stefan Cristian Prazaru ◽

Giulia Zanettin ◽

Alberto Pozzebon ◽

Paola Tirello ◽

Francesco Toffoletto ◽

...

Keyword(s):

Field Experiments ◽

Field Studies ◽

Generalist Predators ◽

Predator Species ◽

Potted Plants ◽

Naturally Occurring ◽

Orius Majusculus ◽

Limited Effectiveness ◽

Pest Outbreaks ◽

The Impact

Outbreaks of the Nearctic leafhopper Erasmoneura vulnerata represent a threat to vinegrowers in Southern Europe, in particular in North-eastern Italy. The pest outbreaks are frequent in organic vineyards because insecticides labeled for organic viticulture show limited effectiveness towards leafhoppers. On the other hand, the naturally occurring predators and parasitoids of E. vulnerata in vineyards are often not able to keep leafhopper densities at acceptable levels for vine-growers. In this study, we evaluated the potential of two generalist, commercially available predators, Chrysoperla carnea and Orius majusculus, in suppressing E. vulnerata. Laboratory and semi-field experiments were carried out to evaluate both species’ predation capacity on E. vulnerata nymphs. The experiments were conducted on grapevine leaves inside Petri dishes (laboratory) and on potted and caged grapevines (semi-field); in both experiments, the leaves or potted plants were infested with E. vulnerata nymphs prior to predator releases. Both predator species exhibited a remarkable voracity and significantly reduced leafhopper densities in laboratory and semi-field experiments. Therefore, field studies were carried out over two growing seasons in two vineyards. We released 4 O. majusculus adults and 30 C. carnea larvae per m2 of canopy. Predator releases in vineyards reduced leafhopper densities by about 30% compared to the control plots. Results obtained in this study showed that the two predators have a potential to suppress the pest density, but more research is required to define appropriate predator–prey release ratios and release timing. Studies on intraguild interactions and competition with naturally occurring predators are also suggested.

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