Exclusion Cages Research Articles

Urban scavenging: vertebrates display greater sensitivity to land-cover and garden vegetation cover than invertebrates

Scavenging removes carrion or littered food waste from the environment, promoting nutrient cycling, and reducing waste management costs. These ecosystem services are important in urban environments, where high human population densities result in increased littered food waste. It is unclear how the magnitude of scavenging across urban-rural gradients is influenced by agent, land-cover type, and patch size. We investigated scavenging provision by vertebrates and invertebrates across a gradient of urbanisation, based on impervious surface cover, in woodlands and gardens in Liverpool, UK. The percentage dry weight loss of bait after 48 h, deployed within vertebrate exclusion cages or exposed to vertebrates and invertebrates, was used to quantify scavenging provision. General linear mixed effects models were used to assess the relative contributions of vertebrates and invertebrates across an urban-rural gradient, variation in scavenging between woodlands and gardens, and the effects of semi-natural vegetation cover on scavenging in gardens. We consider patch size as a preliminary assessment of how fragmentation influences scavenging. Vertebrates contributed substantially more to scavenging than invertebrates across the urbanisation gradient. Vertebrate scavenging was greater in woodlands than gardens, while invertebrate scavenging remained consistent. Scavenging increased with patch size in gardens, but not woodlands. Vertebrate scavenging increased with patch size and garden semi-natural vegetation cover. Urban woodlands and gardens make important contributions to scavenging-mediated ecosystem services. There is a need to increase the cover of semi-natural vegetation in gardens to increase their contributions, and protect and expand woodlands, especially in areas with a high demand for scavenging-mediated ecosystem services.

Cereal leaf beetle (Oulema spp.) damage reduces yield and is more severe when natural enemy action is prevented

Insect pests pose a global threat to crop yield. Biological control by natural enemies aims to reduce pest damage in a sustainable way. Cereal leaf beetles (CLB; Oulema spp.) are major pests in small-grain cereals. We studied the effect of natural enemies on CLB damage and its consequences on yield within its native distribution area in Europe. In exclusion cage experiments and by documenting a naturally occurring CLB damage gradient, we found that CLB damage reduced yield, but natural enemy action reduced the damage by CLB. Comparing exclusion and open treatments on artificially CLB-infested plants, plants accessible to natural enemies had 30% less leaf damage. CLB damage significantly affected yield parameters. Thousand grain weight was 22–29% less in maximum leaf damage scenarios. In the damage gradient field, maximal infestation reduced grain yield by 52%. However, maximal damage occurred only on a few plants and over small areas. In natural infestation cases, the number of CLB larvae per plant had a median of zero; nevertheless, there were more than 35 larvae on 10% of the plants. Patchiness explained 40% of CLB damage variance. Damage was unevenly distributed; as a result, thousand grain weight decreased only by 1.6% for 75% of the plants but by 18% for 10% of the plants. In the natural damage gradient, the estimated yield loss for the entire field was 16% due to CLB. Skewed CLB distribution may lead to perceptible yield losses locally, but natural enemies may limit overall damage to the crop.

Combined effect of timing, position and management on Halyomorpha halys feeding injury assessment on apple cultivars

AbstractHalyomorpha halys is an invasive stink bug, native to east Asia, responsible for extensive economic loss in numerous crops. Since several factors can influence the severity of the recorded injury level, we performed field and semi‐field experiments in commercial apple orchards to monitor their interaction. To establish how position (both in the orchard and on the canopy), management and cultivar interact in determining pre‐harvest injury levels, more than 100,000 apples, distributed over 106 orchard blocks, were examined in the field. Apples located higher in the canopy, on edge rows and in orchards with organic management had a higher number of external injuries and such factors were more relevant when occurring in combination, and on mid and late‐season cultivars. Exclusion cages were used to assess if the injury severity changed with the apple growth stage and with the life stage of H. halys, exposing Red delicious apples to adults and nymphs for 48 hours, from May to July. Early‐season injuries did not evolve in distinct depressions nor in wide areas with necrotic tissue. Later in season, the injury severity was higher and similar for adults and older nymphs (fourth and fifth instars), with the development of depressions externally and necrotic tissue internally. Thus, even a low number of individuals could cause severe damage, over a short exposure period, when it happened near full maturation. The combined results offer new insights to support the development of informed and sustainable control strategies.

Ecological status of a retired mine lake in a protected dune ecosystem

ABSTRACT Ottawa Sands Lake is a retired mine lake located in a protected dune ecosystem adjacent to Lake Michigan in western Michigan, USA. Development activities are planned for the lake and surrounding land, potentially threatening the lake’s ecological health. We conducted a baseline study of water quality and macroinvertebrates, combined with exclusion cage experiments, to examine the role of predation. Our results indicated the lake’s littoral zone had good water quality with low phosphorus (mean soluble reactive phosphorus [SRP] < 5 µg/L; mean total phosphorus [TP] < 10 µg/L) and nitrogen (mean nitrate [NO3-N] = 38–190 µg/L; mean ammonia [NH3-N] = 8–19 µg/L, excluding deep hole) concentrations, high dissolved oxygen (>9.5 mg/L, excluding deep hole), and low chlorophyll a (<12 µg/L, except for 1 sampling date) concentrations. The macroinvertebrate community was dominated by 9 families, with Chironomidae the most abundant. Three environmental factors—specific conductivity, total dissolved solids, and ammonia—were significantly related, albeit weakly, to macroinvertebrate community structure. The exclusion cages did not result in a statistically significant difference in macroinvertebrate community structure, although high variance may have masked differences. Overall, Ottawa Sands Lake is a high-quality system, but development plans, including the installation of a paved trail around the lake and the implementation of a nonmotorized boating program, may result in changes. The baseline conditions outlined in this work will allow lake managers to assess the impact of development activity and add to the limited database regarding the limnology of retired mine lakes around the globe.

Aphid parasitism in winter wheat fields in a heterogeneous agricultural landscape.

The number, timing, and fitness of colonizing parasitoids in fields of ephemeral crops often depend on factors external to the fields. We investigated cereal aphid parasitism in 23 winter wheat fields using sentinel plants infested with bird cherry-oat aphids, Rhopalosiphum padi (L.) (Hemiptera: Aphididae), and we investigated the effect of parasitoids on cereal aphid population growth using exclusion and parasitoid-accessible cages infested with bird cherry-oat aphids. Lysiphlebus testaceipes (Cresson) (Hymenoptera: Braconidae), Aphelinus nigritus (Howard) (Hymenoptera: Aphelinidae),and Diaeretiella rapae (McIntosh) (Hymenoptera: Braconidae), in decreasing order of abundance, parasitized R. padi on sentinel plants. The mean percent parasitism in parasitoid-accessible cages was 5.2% in autumn and 35.0% in spring. Aphid population intensity was greater in complete exclusion than in parasitoid-accessible cages. Measures of landscape composition and configuration were quantified, and aphid parasitism in autumn by L. testaceipes and A. nigritus was positively associated with % landcover by summer crops and patch density. Parasitism by both species was negatively associated with contagion and % woodlands. Parasitism during spring was positively associated with % grassland and fractal dimension and negatively associated with % canola. The number of braconid mummies per sentinel plant was positively correlated to the number of braconid mummies on wheat stems from parasitoid-accessible cages. Results indicate that cereal aphid mortality caused by parasitoids and their ability to exert effective biological control is related to landscape structure. Comparing this study to an earlier study in the same agroecosystem demonstrated temporal stability of the landscape influence on aphid parasitism by L. testaceipes in winter wheat.

Predation risk of the sea urchin Paracentrotus lividus juveniles in an overfished area reveal system stability mechanisms and restocking challenges.

Where sea urchin harvest has been so intense that populations have drastically regressed, concerns have arisen about the effectiveness of harvesting management. According to the theory of phase transition in shallow rocky reefs between vegetated and barren habitats, sea urchin recruitment, a key population structuring process, seems hampered by some stabilizing feedback despite an end to local human harvest of sea urchins. To shed a light on predation effects on sea urchin recruits, a 27-day field experiment was conducted using mega-predator exclusion cages (40x40x40 cm, 1 cm in mesh size) in barren and turf substrates. To facilitate this, 672 recruits (1.1 ± 0.02 cm in size) reared under control conditions were positioned in groups of 42 in each experimental unit (n = 4). Exclusion of mega-predators had a significant effect regardless the substrate, since a higher number of recruits was found under cages both in turf and barren. However, the results showed that in uncaged treatments the size of recruits that survived was larger in turf than in barren, as in the former substrate predation had reduced the abundance of the smallest recruits, highlighting that mega-predator presence affects differently the size of the recruits that had survived depending on the substrate. Overall, these results provide valuable information to address restocking actions of sea urchin populations in overharvested areas, where algal turfs are widespread, and assist studies on habitat stability mechanisms.

162 Nutritive value and dry matter yield of stockpiled tall fescue across plant hardiness zones 7 and 8

Abstract Pastures in Tennessee comprise mainly tall fescue [Schedonorus arundinaceus (Schreb.) Dumort.], a cool-season perennial grass. Given that producers in Tennessee feed hay for an average of 143 d per year, there is interest in utilizing the practice of stockpiling to extend the grazing season. Although this practice has been proven to reduce hay needs (Freeman et al., 2019), it is vital to maintain up-to-date recommendations using data from across the southeastern US to inform grazing decisions. The objective of this study was to determine the nutritive value and dry matter yield of stockpiled tall fescue across plant hardiness zones 7 and 8. Fourteen farms across Tennessee and Alabama were identified as sampling sites. In September 2021, three exclusion cages (1.3 m × 1.3 m) were constructed at each site, forage was clipped to a 5-cm height, and plots were fertilized at a rate of 67 kg N/ha. During years 2021-2022 and 2022-2023, samples were clipped at a 5-cm height from a 0.1-m2 quadrat monthly from October through February. Samples were collected from a different location within the plot each month to ensure there was no overlap. Samples were dried and weighed to determine dry matter yield and then ground for NIRS analysis to determine nutritive value. Data were analyzed using PROC GLIMMIX for a completely randomized design. Independent variables were stockpile period length and plant hardiness zone. Results indicate that plant hardiness zone did not have a significant effect on forage yield (P = 0.2098). Dry matter yield increased over the length of the stockpiling period (P &amp;lt; 0.0001) from 2,637 to 4,922 kg DM/ha. Crude protein (CP) and total digestible nutrients (TDN) concentrations decreased (P &amp;lt; 0.0001 and P = 0.0358, respectively) throughout the stockpiling period; however, ranges were still within those needed to support the nutritional needs of a lactating cow with CP ranging from 15 to 17% and TDN ranging from 68 to 70%. As expected, neutral detergent fiber (NDF) and acid detergent fiber (ADF) concentrations increased over the stockpiling period (P = 0.0029 and P = 0.0145, respectively) as plants matures. There were no significant changes in ash and fat concentrations due to stockpiling length. Results from this study conclude that stockpiled tall fescue in plant hardiness zones 7 and 8 can support the nutritional requirements of mature cows at all stages of production through the winter months. Results will be used to inform Extension recommendations to assist producers in making management decisions that increase grazing days and reduce supplemental feed input costs.

Trophic impacts of a rolled‐rye cover crop on the lettuce aphid (Nasonovia ribisnigri) and associated insect fauna in cultivated Histosols

AbstractCultivated peatland (Histosol) in Southern Québec (Canada) is a rapidly declining non‐renewable resource used to grow most Canadian lettuce (Lactuca sativa L., Asteraceae). Rolled‐rye (Secale cereale L., Poaceae) cover crop is one of the conservation practices proposed to reach a more sustainable lettuce production, but the overall impact on the agroecosystem remains poorly studied in Histosols. We assessed multiple effects of rolled‐rye cover crop on the trophic chain associated with the lettuce aphid, Nasonovia ribisnigri (Mosley) (Hemiptera: Aphididae), a major pest of lettuce. During one growing season and through two consecutive lettuce crops, we monitored in situ the impacts of rolled‐rye cover crop on insect fauna and lettuce quality. We used visual scouting and yellow pan traps to assess plant colonization by N. ribisnigri, its natural enemies, and alternative prey. Exclusion cage experiments were also conducted to measure aphid fitness and population growth. Under greenhouse conditions, following cover crop removal, we examined potential lingering effects of rye within the soil on lettuce plants and N. ribisnigri. In situ experiments showed that rolled‐rye cover crop has the potential to inhibit N. ribisnigri field colonization and recruit natural enemies and alternative prey in the first lettuce crop. Rye also reduced aphid fitness as well as lettuce foliar amino acid concentration and weight. For the second lettuce crop, an almost 50% reduction in N. ribisnigri abundance was observed with the use of rolled‐rye cover crop. In greenhouse experiments, no persistent effect of rye was observed on the quality of lettuce grown with soil collected under a cover crop, nor on the fitness of aphids inoculated on these lettuces. This study highlights the diversity of trophic effects rolled‐rye cover crop may have on lettuce production in Histosols and the potential of rolled‐rye cover crop as a cultural practice to reduce aphid populations. Mechanisms at play while underlining agronomic challenges regarding proper rye termination must be further explored to maintain high‐performing lettuce yields.

Neither sulfoxaflor, Crithidia bombi, nor their combination impact bumble bee colony development or field bean pollination

Many pollinators, including bumble bees, are in decline. Such declines are known to be driven by a number of interacting factors. Decreases in bee populations may also negatively impact the key ecosystem service, pollination, that they provide. Pesticides and parasites are often cited as two of the drivers of bee declines, particularly as they have previously been found to interact with one another to the detriment of bee health. Here we test the effects of an insecticide, sulfoxaflor, and a highly prevalent bumble bee parasite, Crithidia bombi, on the bumble bee Bombus terrestris. After exposing colonies to realistic doses of either sulfoxaflor and/or Crithidia bombi in a fully crossed experiment, colonies were allowed to forage on field beans in outdoor exclusion cages. Foraging performance was monitored, and the impacts on fruit set were recorded. We found no effect of either stressor, or their interaction, on the pollination services they provide to field beans, either at an individual level or a whole colony level. Further, there was no impact of any treatment, in any metric, on colony development. Our results contrast with prior findings that similar insecticides (neonicotinoids) impact pollination services, and that sulfoxaflor impacts colony development, potentially suggesting that sulfoxaflor is a less harmful compound to bee health than neonicotinoids insecticides.

Landscape structure influences natural pest suppression in a rice agroecosystem

Agricultural landscapes are constantly changing as farmers adopt new production practices and respond to changing environmental conditions. Some of these changes alter landscape structure with impacts on natural pest control, pesticide use, and conservation of biodiversity. In rice agroecosystems the effect of landscape structure on natural enemies and pest suppression is often poorly understood. Here we investigate the effect of landscape composition and configuration on a key pest of rice, the brown planthopper (Nilaparvata lugens). Using N. lugens as sentinel prey coupled with predator exclusions, we investigated landscape effects on herbivore suppression and rice grain yield at multiple spatial scales in two regions of Bangladesh. Ladybird beetles and spiders were the most abundant natural enemies of N. lugens with landscape effects observed at all scales on ladybird beetles. Specifically, ladybird beetles were positively influenced by road edges, and fallow land, while spiders were strongly influenced only by rice phenology. Predator exclusion cages showed that N. lugens abundance significantly increased in caged plots, reducing rice gain yield. We also used an estimated biocontrol service index that showed a significant positive relationship with landscape diversity and a significant negative impact on pest density and yield loss. These results suggest that promoting fallow lands and fragmented patches between rice fields could lead to more sustainable insect pest management in rice agroecosystems, potentially reducing the practice of prophylactic insecticide use.

Use of predator exclusion cages to enhance Orbicella faveolata micro-fragment survivorship and growth during restoration

As coral reefs face increasing threats from a variety of stressors, coral restoration has become an important tool to aid coral populations. A novel strategy for restoring boulder corals is microfragmentation, which may enhance coral growth by at least five times, depending on species and conditions. However, mortality rates are still significant during the early weeks after transplanting microfragments to impacted areas. We examined the effects of predation after transplanting fragments by caging Orbicella faveolata microfragments and testing if field survival rates would increase after an acclimation period. We tracked the health and growth of ten genotypes across different acclimation periods from a control group of no acclimation (0 months) to full acclimation (4 months). After four months, we presented a mix of acclimated and unacclimated corals to reef predators. Coral survivorship was highest in acclimation cages (near 100%) compared to the field (p &amp;lt; 0.001), with significant growth differences across genotypes (p &amp;lt; 0.001). Microfragments also grew more in acclimation cages (p &amp;lt; 0.001), with rates slowing down in the first two months after being planted into the substrate. Microfragments that had been acclimated for longer than one month also showed comparatively higher survival rates, further supporting the importance of acclimation during restoration. These results suggest caging fragments boost coral survival during initial stages of restoration by &amp;gt; 50% and increase the persistence of transplanted fragments. Results also highlight the importance of identifying and prioritizing genotypes with high survival and growth rates. Beyond coral restoration, results demonstrate the possible negative ecological effects of corallivores, particularly parrotfishes, on recent transplants of fragments.

Predator exclusion cages as visual attractants to coyotes

Predator exclusion cages as visual attractants to coyotes

Nonconsumptive Effects of Crustaceans and an Echinoderm on Spat of the Eastern Oyster Crassostrea virginica (Gmelin, 1791)

Predation by crustaceans and echinoderms is a significant driver of mortality for sessile invertebrates in near-shore marine ecosystems. As a response, shellfish growers use predator exclusion cages to grow their product. Oysters grown in these cages and clams in and under nets have been observed to exhibit thinner, brittle shells, which is not optimal for market, nor for those being grown for restoration purposes. Here, the nonconsumptive predator effects of several native and nonnative predators on shell morphology of Crassostrea virginica oyster spat. Juvenile (1–3 mm) seed oysters were exposed separately to chemical cues of five different predators and one nonpredator crab were investigated and compared with control (no exposure) spat. Significant effects of predator presence on the total wet weight (g) of the spat was demonstrated, with the highest increase for spat exposed to black-fingered mud crabs (Panopeus, 1.70 mg d–1) and the biggest decreases for spat exposed to the European green crabs (Carcinus maenas—1.34 mg d–1) and the sea stars (Asterias rubens—1.47 mg d–1). Changes to oyster length (mm) and shell density (crushing resistance) were not significant. Implications for aquaculturists and wild bivalve populations are that growth could be negatively affected by the lack of predators on these important organisms.

Carbon cycle of native pasture-based beef cattle production systems in the Pantanal area of the Paraguayan Chaco

The objective of the present study was evaluate the carbon cycle in Paraguayan Pantanal area native grassland ecosystems by measuring pasture growth and simulating animal grazing. For this purpose, soil analyzes, annual productivity and forage quality were carried out in 4 agro ecological sites of a 20,000 ha located in Alto Paraguay Department (21º 1' 29.85”S and 58º 17' 38.55” W), from Dec 21, 2019 to Feb 12, 2020. In the selected location was installed an 8 m x 8 m exclusion cage with three treatments (4 m2 subplots), corresponding to cutting intervals (35, 70 and 105 CI days, respectively). The seasonal dry matter (DM) production and the pasture growth rate, adjusted stocking rate at three production levels (50, 70 and 75% breeding rate, respectively), carbon contained in organic matter (OM), root system and aerial biomass accumulated in ground were evaluated. The data were compared using Tukey test with a 5% probability. The emission of greenhouse gases (GG) per head and per ha was simulated and adjusted to breeding livestock to a total area of 6,600 ha and 5,000 grassland ha. The 35 days CI presented 32% higher productivity than 105 days CI in carbon sequestration. The best capture/emission balance per ha was observed in 35 days CI with the 50% breeding rate, producing 1,481 kg of CO2-e ha-1, intensifying and increasing the breeding rate to 75%, the balance decreases to 1,294 kg of CO2-e ha-1. In all cases, livestock in grassland has presented a positive balance when accounting for GG per unit area.

Colonisation after disturbance on artificial structures: The influence of timing and grazing

Artificial structures are poor surrogates of natural rocky shores, meaning they generally support depauperate assemblages. These differences may result from a combination of recruitment processes, biotic interactions, and structuring by environmental factors. In this study, plots were cleared on two seawalls and two natural shores at two separate timepoints – in August 2020 (summer) and February 2021 (winter) - and monitored over one year to determine the influence of timing of disturbance on recruitment and succession. Additional plots were cleared at one of the seawalls at a single timepoint in August 2020, and exclusion cages were installed to determine the influence of grazing pressure on colonisation; these were monitored for 18 months. Disturbance during winter resulted in higher concentrations of all biofilm components up to 3 months, but did not impact benthic community composition beyond this point. Grazer exclusion on artificial structures increased biofilm concentrations and influenced community composition in comparison to plots on artificial structures without exclusion, while communities on natural surfaces differed in terms of species composition to those on artificial plots at 12 months. We conclude that the timing of routine maintenance works on artificial structures may impact initial biofilm abundances. Furthermore, while grazing pressure does influence community structure on artificial structures, this alone is not sufficient to explain biological differences between artificial structures and natural shores.

Genotype and environment effects on sunflower nectar and their relationships to crop pollination

Whether caused by genotype (G) or environment (E), floral trait variation has consequences for plants and their pollinators. Cultivated sunflower is a model system to explore floral trait variation; though sunflowers are bred to self-pollinate, benefits of pollination by bees remain substantial. To better understand sunflower-pollinator interactions, experiments were conducted to: (i) examine genotype and environment effects on nectar quantity and quality under controlled conditions, and (ii) assess effects of bags used for pollinator exclusion on nectar quantity, quality and bee foraging in a field environment. Contrasting temperature treatments (28°C, 21°C, 28°C / 16°C) reveal environment effects or G × E interactions for nectar volume (µl / floret), concentration (°Brix), and sugar composition (% sucrose). Bags used to exclude sunflower pollinators resulted in nectar volumes greater than plants with unrestricted access for bees (= open-pollination), and in ≈ 5-fold increased visitation by wild bees after bags were removed. Differences in bee visits to plants that were previously bagged versus plants never bagged decreased over the 2 h following bag removal. Though genetic variation in sunflower nectar is affected by the environment and G × E interactions, improving pollination via plant breeding still appears feasible. Future research on intraspecific variation in pollen rewards could be helpful, especially because pollen has received little research compared to nectar. For research with nectar or pollen, it seems desirable to measure floral rewards with methods that don’t rely on pollinator exclusion (bags or cages), which should provide more realistic data on what pollinators experience while foraging.

Grasshopper abundance and offtake increase after prescribed fire in semi-arid grassland

Background Fire modulates herbivore dynamics in open ecosystems. While extensive work demonstrates the interaction between fire and vertebrate grazers, less research describes how grasshopper herbivory dynamics respond to fire. Aim We examined how fire increased grass crude protein content and increased the density of and offtake by grasshoppers relative to unburned mixed-grass prairie. Methods We deployed grasshopper exclusion cages to determine grasshopper offtake of aboveground plant biomass, counted grasshopper abundance throughout the study period, and measured crude protein content of aboveground grass biomass. Key results Offtake and density were higher in burned versus unburned plots. Burned plot grasshopper density increased over time, with greater rates of increase in recently burned plots, while density remained constant in unburned locations. Conclusions We present a potential mechanism by which fire interacts with grasshoppers in open ecosystems. It is likely that greater grasshopper offtake and density in recently-burned plots is at least partially attributable to higher crude protein content, as grass in these plots has a much higher proportion of recent growth after fire removed senesced material. Implications Grasshopper herbivory likely acts as a multiplier of livestock herbivory in burned rangeland. Restoring fire regimes can balance direct negative effects of heating against nutritional benefits.

Licorice strips enhance predator-mediated biological control in China's cotton crop.

Habitat management such as field- or farm-level diversification can conserve arthropod natural enemies, enhance biological pest control and lower (or suspend) insecticide use in agricultural crops. These approaches however have been underexploited to manage the aphid Aphis gossypii in cotton cropping systems of Xinjiang, China. In this study, we investigated whether the presence of licorice (Glycyrrhiza uralensis) at the field edge benefits generalist predator abundance and aphid biological control in local cotton crops. Field trials during 2020 and 2021 showed that licorice strips enhanced the in-field abundance of generalist predators (primarily ladybeetles) 2.2-4.3 fold during early season, i.e. initial growth before A. gossypii peak infestation pressure. During peak outbreak conditions in July, treatment fields with licorice strips experienced a respective 17.5-61.2% lowered aphid density and 12.3-14.6-fold higher predator-to-aphid abundance ratio (PAR) than control fields. In late season (aphid decline phase) of either year, cotton fields with licorice strips also attained a respective 4.7-9.9 fold higher PAR. Exclusion cage assays quantitatively assessed predator-mediated A. gossypii biological control and the relative contribution of licorice strips. The biocontrol services index (BSI) was 2.8 times (2020) and 1.4 times (2021) higher at 5m distances from the licorice strip as compared to control fields. Licorice strips in the immediate vicinity of cotton fields benefit generalist arthropod predators and improve aphid biological control throughout the cotton cropping season. These findings help to integrate habitat management within integrated pest management (IPM) frameworks in the biggest cotton production region of China. © 2022 Society of Chemical Industry.

Suppression of the Sugarcane Aphid, Melanaphis sacchari (Hemiptera: Aphididae), by Resident Natural Enemies on Susceptible and Resistant Sorghum Hybrids.

The sugarcane aphid, Melanaphis sacchari (Zehntner) (Hemiptera: Aphididae), is an invasive sorghum pest that has threatened over 90% of North American sorghum production. Resident parasitoids, coccinellids, syrphids, and lacewings prey on this aphid. Our objective was to compare and estimate parasitoid and predator suppression of sugarcane aphids placed on resistant and susceptible hybrids in a field setting using natural enemy exclusion cages. During 2018 and 2019 along the Texas Gulf Coast and Central Oklahoma, three natural enemy exclusion treatments-no exclusion (full access for parasitoids and predators), partial exclusion (access limited to parasitoids), and complete exclusion (excludes parasitoids and predators)-were used. The parasitoid Aphelinus nigritus Howard (Hymenoptera: Aphelinidae) accounted for 90% of recovered natural enemies. In 2018, aphid suppression attributable to A. nigritus was ca. 95% on the resistant hybrids and 80% on the susceptible hybrids when comparing aphid counts from complete and partial exclusion treatments, while few predators were observed. In 2019, aphid suppression was attributed to a combination of predation and parasitism. Relatively more predators were recorded at both sites, accounting for 14% to 33% of specimens recovered in the no exclusion treatment. Aphid suppression attributed to predators and parasitoids ranged from 85% on aphid-resistant hybrids and 27% on susceptible hybrids in south Texas and >95% on both hybrids in Oklahoma when comparing aphid abundance in the complete and no exclusion treatments. Parasitism and predation contributed to aphid regulation on both hybrids, which may accrue multiple benefits leading to a more resilient sugarcane aphid management system.

Providing Alternative Hosts and Nectar to Aphid Parasitoids in a Plum Orchard to Determine Resource Complementarity and Distance Range Effect on Biological Control

There are many different practices that contribute to conservation biological control, but little is known about their complementarity. We tested the effects of providing food and alternative hosts to parasitoids by intercropping a plum orchard with companion plants. Oats and vetch were intercropped into the orchard either as single-species (oats or vetch) or two-species (oats and vetch combined) intercrops within an inter-row. The trophic resources provided by these intercrops were assessed, along with the incidences of aphids and their parasitoids in plum trees. We found up to ten alternative host species provided by oats and vetch, and extrafloral nectar was available from the vetch and mixed strips. An effect of intercrop type and distance to plum trees was observed on aphid incidence during one sampling period. Parasitism rates in exclusion cages were affected by intercrop type, reaching almost 60% close to the mixed intercrop. However, no general tendency was observed upon whether oats, vetch or their mixture was associated with a lower incidence of aphids. We found no evidence that providing effective sources of food and alternative hosts for parasitoids increased aphid mortality in this study. The context-dependent efficiency of intercropping is discussed.