scholarly journals Modular Habitat Refugia Enhance Generalist Predators and Lower Plant Damage in Soybeans

2000 ◽  
Vol 29 (2) ◽  
pp. 383-393 ◽  
Author(s):  
Juraj Halaj ◽  
Alan B. Cady ◽  
George W. Uetz
Keyword(s):  
Generalist Predators ◽  
Plant Damage ◽  
Habitat Refugia ◽  
Lower Plant

Ethephon for American Ginseng (Panax quiquefolium L.) Inflorescence Removal

HortScience ◽  
1998 ◽  
Vol 33 (3) ◽  
pp. 481b-481
Author(s):  
A.E. Fiebig ◽  
J.T.A. Proctor ◽  
D. Murr ◽  
R. Releeder
Keyword(s):  
Additive Concentration ◽  
Root Mass ◽  
Panax Quinquefolium ◽  
Fruit Removal ◽  
Plant Damage ◽  
Low Concentrations ◽  
Production Practice ◽  
Whole Plants ◽  
Mass Increase ◽  
Standard Production

Varying concentrations (500-4000 mg·L–1) of ethephon, an ethylene-releasing compound, were applied to 3-year-old ginseng (Panax quinquefolium L.) plants in fields of southern Ontario. The effects of this chemical on fruit removal, plant damage, infructescence morphology, and root mass were studied and compared to the normal practice of manual inflorescence removal. The highest concentrations had the highest rates of removal but also caused the greatest amount of damage to the whole plants when compared to the mid-range concentrations. The lowest concentrations showed less foliar damage but did not provide sufficient fruit removal to mimic hand removal. When individual inflorescences of the ethephon treatments were studied, the seed heads had fewer ripe berries and more unpollinated florets than the untreated controls. When root masses were compared, high and low concentrations showed lower masses than those of the standard production practice of hand removal. However, mid range concentrations showed similar root mass increase to manual removal. When all parameters were considered, the concentration range giving the best results was 1000-1500 mg·L–1. Multiple applications of ethephon, at weekly intervals, had an additive effect on flower removal and plant damage. Treatments having an additive concentration of over 2000 mg·L–1 had detrimental effects on all parameters. Those within the 1000–1500 mg·L–1 range showed the highest similarity to the hand removal benefits.

Indices of Plant Damage and Heritability of Tolerance to the Spotted Alfalfa Aphid in Alfalfa

Crop Science ◽  
1989 ◽  
Vol 29 (6) ◽  
pp. 1337-1340 ◽  
Author(s):  
H. O. Jimenez ◽  
J. L. Caddel ◽  
R. C. Berberet ◽  
R. W. McNew
Keyword(s):  
Plant Damage

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

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.

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

Insects ◽  
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.

scholarly journals Post-Dropping Behavior of Potato Aphids (Macrosiphum euphorbiae)

2021 ◽  
Vol 34 (4) ◽  
pp. 223-239
Author(s):  
Rosalind K. Humphreys ◽  
Graeme D. Ruxton ◽  
Alison J. Karley
Keyword(s):  
Recovery Rate ◽  
Tactile Stimulus ◽  
Plant Architecture ◽  
Tonic Immobility ◽  
Macrosiphum Euphorbiae ◽  
Chrysoperla Carnea ◽  
Antipredator Defense ◽  
Plant Parts ◽  
Potato Aphids ◽  
Lower Plant

AbstractDropping behavior is an effective antipredator defense utilized by many insects including aphids, which drop from plants to lower plant parts or underlying substrates to avoid attack from predatory invertebrates. While research commonly focusses on triggers of dropping, less attention is given to what happens to prey individuals following escape drops. In this study, the duration of tonic immobility, recovery rates, and cases of “instant recovery” (re-clinging to lower plant parts) exhibited by potato aphids (Macrosiphum euphorbiae) that dropped from potted seedlings in response to introduced ladybird (Adalia bipunctata) adults, lacewing (Chrysoperla carnea) larvae, and a standardized tactile stimulus were investigated in relation to a range of environmental factors. Air temperature had a negative correlation with the duration of post-dropping tonic immobility; as temperature increased, time spent motionless decreased. Aphids also showed a pattern of increased recovery rate at higher temperatures. Aphids may be selected to move off the substrate quicker to avoid risks of overheating/desiccation at higher temperatures; and/or higher body temperature facilitates locomotion. Stimulus type also influenced recovery rate back to the original seedling, with aphids generally recovering after the standardized stimulus quicker than after dropping triggered by a real predator. Considering cases of instant recovery onto lower-reaches of the host seedling, seedling height influenced the likelihood of re-clinging, with aphids that managed to instantly recover dropping from, on average, taller seedlings than aphids that dropped to the substrate. Plant architecture could mitigate the costs of dropping for aphids, but further studies quantifying understory foliage cover are needed.

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

Insects ◽  
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.

scholarly journals The return of the frogs: The importance of habitat refugia in maintaining diversity during a disease outbreak

2019 ◽  
Author(s):  
Donald T. Mcknight ◽  
Monal M. Lal ◽  
Deborah S. Bower ◽  
Lin Schwarzkopf ◽  
Ross A. Alford ◽  
...  
Keyword(s):  
Disease Outbreak ◽  
Habitat Refugia

scholarly journals Flea Beetle Control in Lower Rainfall Se Washington, 1995

1996 ◽  
Vol 21 (1) ◽  
pp. 205-205
Author(s):  
D. E. Bragg ◽  
D. Mayer
Keyword(s):  
Flea Beetle ◽  
Plant Introduction ◽  
Plant Damage ◽  
Total Destruction ◽  
Cotyledon Stage ◽  
Untreated Check ◽  
Plant Stand

Abstract Plots were planted 9 June at the USDA-ARS Western Plant Introduction Center at Central Ferry, WA at a rate of 6 lb/acre in rows 7 inches apart. Plots were 15 x 3 ft replicated in a RCBD 4 times, and were situated with replicates perpendicular to a crested wheat grass field. Precounts (PrCt) of plant stand per 6.6 ft row, and damage on 20 randomly selected plants on a scale of 0 to 6, with 0 = no damage and 6 = total destruction, were made 21 Jun. A treatment consisting of Furadan CR-10 granules at a rate of 2.5 lb product per acre was applied at seeding. Four other insecticide treatments were made with a CO2 backpack sprayer at 20 gpa and 20 psi on 22 Jun. An untreated check was established. Conditions at treatment were 70°F with a 2 mph wind at 11 a.m. All plants were in the cotyledon stage with meristem visible. Evaluations of stand reduction and plant damage were made on 2, 5, 7, and 10 DAT. All surviving plants were in the rosette stage (5 to 7 leaf) at 10 DAT.

Assessing the role of generalist predators in the biological control of alfalfa weevil (Coleoptera: Curculionidae)

2017 ◽  
Vol 149 (4) ◽  
pp. 525-533 ◽  
Author(s):  
Tatyana A. Rand
Keyword(s):  
United States ◽  
Biological Control ◽  
Experimental Work ◽  
United States Of America ◽  
Acyrthosiphon Pisum ◽  
The United States ◽  
Generalist Predators ◽  
Alfalfa Weevil ◽  
Exclusion Experiment ◽  
Predator Exclusion

AbstractAlfalfa weevil (Coleoptera:Curculionidae) is a major pest of alfalfa throughout the United States of America. Biological control research has disproportionately focussed on introduced parasitoids. Generalist predators may also be important, but experimental work evaluating their impacts is lacking. I combined a cross-site survey with a predator exclusion experiment to identify key predators, and test for impacts on weevil survival and plant defoliation levels in Montana and North Dakota, United States of America. Spiders (Araneae) dominated the complex, followed by Nabidae (Hemiptera) and Coccinellidae (Coleoptera). None of the dominant predators showed aggregative responses to weevil (Hypera postica (Gyllenhal); Coleoptera: Curculionidae) or pea aphid (Acyrthosiphon pisum (Harris); Hemiptera: Aphididae) densities across 10 sites surveyed. However, weevil densities were positively correlated with both coccinellid and nabid densities across transects at the experimental site. Thus, predator groups traditionally associated with aphids can show strong aggregative numerical responses to alfalfa weevil larvae at smaller scales. Predator exclusion revealed no significant predator effects on larval survival or alfalfa damage. However, final densities of pea aphids were significantly higher in exclusion treatments relative to controls. The results suggest that even under conditions where predators exert significant pressure on aphids, they may still have minimal impacts on weevils. Additional experimental work is necessary to determine the broader potential of generalist predators as alfalfa weevil control agents.

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