Total Predators Research Articles

Landscape forest cover and local vegetation structure mediate multitrophic relationships but not the leaf damage in cacao trees

Cacao is the most important agricultural product in the southern region of Bahia state, Brazil, with 70 % of its production occurring under the traditional agroforestry where cacao is mostly shaded by native trees. This traditional system allows to reconcile the production with the maintenance of the portion of original biodiversity. However, increased deforestation and intensified agroforestry management aimed at boosting productivity may impact the diversity of native species and the services they provide. In this context, our aim was to disentangle the role of landscape forest cover and the local vegetation complexity on predation of caterpillars and herbivory of cacao plants located in agroforestry systems. The study was conducted across 18 cacao agroforest sites in southern Bahia located in landscapes with different amounts of forest cover. We assessed predation rate using dummy caterpillars, sampling understory birds and arthropods and collected leaves of cacao trees to analyze damage by herbivory. We also measured shading levels and the abundance of cacao trees in each agroforestry. Predation pressure on dummy caterpillars was positively influenced by the abundance of total predators and the level of landscape forest cover and negatively by the number of cacao trees. Even so, we found no evidence that landscape, local features or the actual invertebrate assemblages (predators or herbivores) influenced the cacao leaf damage. The findings highlight the multifaceted interactions between ecological factors, predation pressure, and leaf damage within cacao agroforestry systems.

Contribution of Surrounding Flowering Plants to Reduce Abundance of Aphis nerii (Hemiptera: Aphididae) on Oleanders (Nerium oleander L.)

Oleander is very frequently planted as an ornamental shrub in urban areas of the Mediterranean. Its most common pest is the aphid Aphis nerii, and heavy infestations produce aesthetic damage and disturbances to the citizens, and they are frequently sprayed with insecticides in order to reduce the population density. One alternative method is conservation biological control which is enhanced by the provisioning of alternative food, refuges, and reproduction sites. In this study, the usefulness of four flowering service plants (Lobularia maritima, Calendula officinalis, Coreopsis grandiflora, and Achillea millefolium) is evaluated for aphid infestation levels and aphid natural enemy abundances. Aphid levels were consistently lower in oleander plots surrounded by service plants. Natural enemy abundances tended to be higher in plots surrounded by service plants, but significant differences could not be found until the fourth year of the study, when more lacewings, total predators, and mummies were higher in plots surrounded by service plants. On these plots, hoverflies, ladybeetles, and lacewings were the most common predators. Paragus sp. and Hippodamia variegata were the prevalent hoverfly and ladybeetle species, respectively. The potential toxicity effect on the prevalence of natural enemy species is discussed. On service plants, significantly more hoverflies were recorded on L. maritima than on C. officinalis and C. grandiflora, and more true bugs were recorded on C. officinalis and A. millefolium than on L. maritima or C. grandiflora. Our results suggest that planting service plants (such as sweet alyssum, marigold, or yarrow) surrounding oleanders can improve conservation biological control by enhancing the abundance of aphid natural enemies and thus a reduction of the abundance of A. nerii.

Predator-Pest Dynamics of Arthropods Residing in Louisiana Soybean Agroecosystems.

Simple SummarySoybean agroecosystems in the Midsouth support an assorted insect community. Louisiana soybean is heavily managed by growers, and the subsequent effect on residing arthropod populations is not well understood. For sustainable management of soybean, evaluations need not only focus on problematic pests, but also the resident natural enemies. This study addresses the compositional and temporal abundance of prominent insects in Louisiana soybean, both pest and beneficial. Pest and natural enemy populations were monitored to delineate potential associations. We found that the pest community was dominated by those that fed on soybean through piercing-sucking mouthparts. Predator populations were comprised mainly of spiders and big-eyed bugs. Pest and predator populations were similarly more abundant later in the soybean reproductive period. A moderate positive linear relationship was observed between pest and predator communities indicating a temporal correlation. Here we present essential information about the pest and natural enemy communities residing in Louisiana.Over the past two decades, management practices within Louisiana soybean production have shifted. Successful application of an integrated pest management (IPM) strategy requires an understanding of how these changes have affected predator-pest dynamics. Surveys monitoring foliage-foraging arthropod populations in soybean took place across six locations within Louisiana over six years (2012–2014 and 2015–2018). Temporal associations of pest groups, defoliating and piercing-sucking, and predator groups relating to soybean phenology were observed. Additionally, soybean maturity groups (III, IV, and V) were also evaluated to delineate potential differences. Results indicated higher abundances of piercing-sucking pests compared to defoliating pests across both datasets (2012–2014 and 2015–2018). Pest groups were more abundant in later soybean reproductive periods, mainly attributed to Chrysodeixis includens and Piezodorus guildinii. Predator populations were mainly comprised of Araneae and Geocoridae throughout the survey periods. From 2015 to 2018, soybean growth had a significant effect on total predator abundance with more predators present at the pod-fill and soybean maturity stage. Correlations between total pest abundance and total predators exhibited a moderate positive linear relationship. Soybean maturity groups only influenced piercing-sucking pest abundance, with later maturing groups (IV and V) having higher numbers. Thus, control tools and tactics aimed at controlling late season pests should be modified to avoid reducing predator populations.

Diversity of Predators Associated with the Mealybug Complex in Cassava Growing Districts of Tamil Nadu, India

An extensive survey was carried to study the diversity of predators associated with the mealybug complex in the cassava growing districts viz., Salem, Namakkal, Erode, Tiruppur and Coimbatore of Tamil Nadu, India from January to September, 2021. The survey revealed the dominance of Phenacoccus manihoti Matile-Ferrero 1977 (Hemiptera: Pseudococcidae) than other mealybug species in all the surveyed districts. The incidence of P. manihoti ranged from 12 to 90 per cent while Paracoccus marginatus Williams and Granara de Willink 1992 (Hemiptera: Pseudococcidae) incidence was found to be between 8 and 54 per cent. The incidence of Ferrisia virgata Cockerell 1893 (Hemiptera: Pseudococcidae) was found to be very low (8-16%) compared to other mealybug species. Association of total predators with P. manihoti were found to be maximum (30.87%) followed by the total predators with P. marginatus (6.49%) whereas 0.53 per cent of total predators associated with F. virgata. The fourteen different predators viz., Cryptolaemus montrouzieri Mulsant 1853 (Coleoptera: Coccinellidae), Menocheilus sexmaculatus Fabricius 1781 (Coleoptera: Coccinellidae), Anegleis cardoni Weise 1892 (Coleoptera: Coccinellidae), Hyperaspis maindroni Sicard 1929 (Coleoptera: Coccinellidae), Brumoides suturalis Fabricius 1798 (Coleoptera: Coccinellidae), Scymnus spp. (Coleoptera: Coccinellidae), Chrysoperla spp. (Neuroptera: Chrysopidae), Mallada spp. (Neuroptera: Chrysopidae), Spalgis epeus Westwood 1851 (Lepidoptera: Lycaenidae), Geocoris spp. (Hemiptera: Geocoridae), Cardiastethus spp. (Hemiptera: Anthocoridae), Diadiplosis spp. (Diptera: Cecidomyiidae), Oxyopes spp. (Araneae: Oxyopidae) and Argiope spp. (Araneae: Araneidae) were found to associated with the mealybug species viz.,P. manihoti, P. marginatus and F. virgata. Among the predators of the mealybug complex, the most relative abundant species were H. maindroni (11.74%) associated with P. manihoti and C. montrouzieri (6.49%) associated with P. marginatus followed by S. epeus (0.67%) associated with F. virgata. The diversity of predators assessed through Simpson’s Index of Diversity, Shannon-Wiener, Pielou’s Evenness and Margalef indices revealed highest species diversity, species richness and species evenness in Namakkal district.

Does fertilization with dehydrated sewage sludge affect Terminalia argentea (Combretaceae) and associated arthropods community in a degraded area?

Nutrients from dehydrated sewage sludge play an essential role in the development of many plants such as Terminalia argentea, in the recovery of degraded areas. The aims were to assess the abundance, diversity and species richness of phytophagous, pollinators and predators arthropods, as well as the percentage of defoliation of T. argentea trees, fertilized (or not) with dehydrated sewage sludge in a degraded area. The abundance, diversity and species richness of phytophagous Coleoptera and total predators (predator insects + protocooperating ants + spiders); abundance and species richness of Diptera, pollinator insects, spiders, and predators (predator insects + spiders) were higher on trees fertilized with dehydrated sewage sludge. The abundance of phytophagous Coleoptera declined with the presence of phytophagous Hemiptera and protocooperating ants; population of phytophagous Orthoptera declined in response to phytophagous Coleoptera and total predators; the numbers of the leafminer Lyriomyza sp. directly increased with the numbers of spiders. The ecological indices of phytophagous, pollinators, and predator arthopods increased on Terminalia argentea trees fertilized with dehydrated sewage sludge; such a better ecological indices in fertilized than in unfertilized trees, show it more suitable for the recovery of degraded areas. We discuss the competition between phytophagous insects groups as well as herbivory reduction by predators.

Effects of Diamide Insecticides on Predators in Soybean.

Predatory arthropods can be important for preventing insect pests from reaching damaging levels in soybean. However, the predator community can be compromised when pest control strategies include the application of broad-spectrum insecticides. The use of selective insecticides such as diamides could conserve predators while still providing necessary pest control. We evaluated two selective diamide insecticides, chlorantraniliprole and flubendiamide, and a broad-spectrum insecticide, lambda-cyhalothrin in combination with chlorantraniliprole, for impact on predators in soybean. We applied insecticides to field plots and documented predator abundance prior to and up to 3 wk postapplication using sticky card, beat sheet, and sweep net sampling methods. In sweep net samples, total predator abundance in plots treated with the selective insecticides was not significantly different from untreated control plots. For beat sheet samples, there were no significant differences in the abundance of total predators on any day postapplication between the selective diamide insecticides or the untreated control, but abundance decreased after application of lambda-cyhalothrin + chlorantraniliprole and did not recover. For sticky cards, there were no differences in predator abundance among treatments on any day postapplication. Over all, results showed that there were no significant differences in the abundance of total predators, Anthocoridae, Araneae, or Geocoridae after application of flubendiamide or chlorantraniliprole compared with the untreated control for up to 3 wk after application. All insecticides significantly decreased populations of lepidopteran pests compared with the untreated control, but only lambda-cyhalothrin + chlorantraniliprole reduced predatory arthropod abundance.

Benthic foodweb structure in a large shallow lake studied by stable isotope analysis

Abstract: The benthic foodweb structure of Lake Vortsjarv, a large (270 km2), shallow, and turbid Estonian lake, was evaluated based on C and N stable-isotope signatures (δ13C, δ15N). Variation in δ13C between sampling sites was not related to site proximity to the littoral zone or the more vegetated southern part of the lake, but rather appeared to be influenced by in-situ site peculiarities. δ13C was stable temporally and between functional feeding groups, a result implying that the whole benthic food web of the lake relies largely on the same C source admixture, essentially particulate organic matter (POM). Thus, the foodweb composition of Lake Vortsjarv is remarkably homogeneous given the lake's large surface area. Apparent trophic-level δ15N fractionation between total collectors and total predators (mean 1.7‰) was lower than the value of 3.4‰ generally adopted in foodweb studies, but the higher value was valid for specific prey—predator links. The low δ13C signature of some chironomid samples indica...

Predator–prey relationships in a Mediterranean vertebrate system: Bonelli’s eagles, rabbits and partridges

How predators impact on prey population dynamics is still an unsolved issue for most wild predator-prey communities. When considering vertebrates, important concerns constrain a comprehensive understanding of the functioning of predator-prey relationships worldwide; e.g. studies simultaneously quantifying 'functional' and 'numerical responses' (i.e., the 'total response') are rare. The functional, the numerical, and the resulting total response (i.e., how the predator per capita intake, the population of predators and the total of prey eaten by the total predators vary with prey densities) are fundamental as they reveal the predator's ability to regulate prey population dynamics. Here, we used a multi-spatio-temporal scale approach to simultaneously explore the functional and numerical responses of a territorial predator (Bonelli's eagle Hieraaetus fasciatus) to its two main prey species (the rabbit Oryctolagus cuniculus and the red-legged partridge Alectoris rufa) during the breeding period in a Mediterranean system of south Spain. Bonelli's eagle responded functionally, but not numerically, to rabbit/partridge density changes. Type II, non-regulatory, functional responses (typical of specialist predators) offered the best fitting models for both prey. In the absence of a numerical response, Bonelli's eagle role as a regulating factor of rabbit and partridge populations seems to be weak in our study area. Simple (prey density-dependent) functional response models may well describe the short-term variation in a territorial predator's consumption rate in complex ecosystems.

Impact of area-wide malathion on predatory arthropods and secondary pests in cotton during boll weevil eradication in Texas

The boll weevil, Anthonomus grandis grandis, has been eradicated from much of the cotton producing region of the US and to-date eradication efforts continue in Texas. While providing long-term economic and environmental benefits, area-wide applications of malathion used by the eradication program have been implicated in the disruption of biological control of some cotton pests. This study evaluated the impact of the area-wide boll weevil eradication on abundance of predatory arthropods and key pests of cotton during four years in central Texas. Multiple applications of malathion ULV significantly reduced seasonal mean densities of spiders, predatory bugs ( Orius spp. Pseudatomoscelis seriatus, Nabis spp., Geocoris spp.), Chrysopidae larvae and red imported fire ant, Solenopsis invicta, collected from the cotton canopy. In contrast, densities of beet armyworm, Spodoptera exigua, heliothine and other lepidopteron larvae, cotton aphid, Aphis gossypii, and adult and larval convergent lady beetle, Hippodamia convergens, often increased in cotton fields under boll weevil eradication. The density of total predators measured during the mid-season (period of blooming and early boll development) was significantly and negatively correlated with density of beet armyworm larvae during the late-season (boll maturation period). Results suggest that the community of predatory arthropods in the cotton canopy, rather than one or several key predators, is important in suppressing outbreaks of S. exigua and other lepidopteran pests in cotton. Furthermore, the potential to use densities of generalist predators in mid-season to anticipate late-season outbreaks of beet armyworm during boll weevil eradication is discussed.

Community structure of pre-dispersal seed predatory insects on elevenShorea(Dipterocarpaceae) species

Abstract:The Dipterocarpaceae in South-East Asia are known for their strict mast fruiting. During fruiting, pre-dispersal seed predation by insects contributes to mortality of dipterocarp seeds. We documented the community structure of insect seed predators on 11Shoreaspecies in Peninsular Malaysia. Fruits were sampled sequentially throughout seed development, and 2144 and 1655 individuals of seed predator weevils and moths were collected in two mast-fruiting events. Four weevils:Nanophyes shoreae, nanophyid sp. 1,Alcidodes dipterocarpiandAlcidodes humeralis, and one mothAndrioplecta shoreaewere abundant in seeds of theShoreaspecies. The proportion ofN. shoreaeto the total predators became larger in the latter fruiting event than the former while that ofAlcidodesspp. became smaller. The predator species composition changed during seed development; nanophyid spp. emerged from immature fruits whileAlcidodesspp. emerged from mature fruits.Andrioplecta shoreaeemerged from both immature and mature fruits. The level of host specificity measured by Kullback–Leibler distance was low for most predator species in both events. Predator species composition of manyShoreawas similar to each other due to the dominance ofN. shoreaethough it might gradually differ with the phylogenetic distance between hosts. In conclusion, predator species composition ofShoreavaried during seed development within a host rather than among hosts. Intermittent synchronized fruiting by congenericShoreatrees would be advantageous to avoid pre-dispersal insect seed predators, and contribute to their reproduction.

Organic versus conventional management in an apple orchard: effects of fertilization and tree‐row management on ground‐dwelling predaceous arthropods

Abstract1 Organic and conventional management of apple orchards may have a different effect on arthropod communities.2 We conducted a 3‐year study to assess the effect of two strategies of fertilizer treatment (organic versus chemical) and three tree‐row management systems (straw mulching, tillage and herbicide) on activity‐density and biodiversity of epigeic predators. Ground beetles (Carabidae), rove beetles (Staphylinidae), ants (Formicidae) and spiders (Araneae) were sampled monthly with pitfall traps in the same apple orchard during 2003, 2004 and 2005.3 A total of 4978 individuals were collected. Carabids (56.8% of the total catches) were the most abundant taxonomic group, followed by spiders (20.7%), ants (14.8%) and rove beetles (7.7%). Tree‐row management had a greater influence on predator catches than fertilizer treatment. Total predator catches were lower under the mulch. Mulching also reduced carabid abundance, but increased staphylinid catches.4 Tree row management also had a significant effect on biodiversity parameters. Species richness did not significantly differ among treatments for ants, spiders or the total catches, but was higher on herbicide‐treated plots for carabids and on mulched plots for staphylinids. Shannon–Wiener’s diversity index was significantly greater in the mulched and herbicide treated plots for total predators and carabids. For staphylinids, this index was significantly greater on the mulched plots. Fertilizer application strategy only influenced the species richness of rove beetles, which was greater in the chemically‐treated plots.5 The results showed that a change from conventional to organic fertilizer treatment of apple trees may be performed without differential effects on predator activity‐density or biodiversity. However, a change from herbicide treatment to mulching or mechanical weed control may be significant, depending on the taxonomic group.

Role of syrphid larvae and other predators in suppressing aphid infestations in organic lettuce on California's Central Coast.

Organic lettuce, Lactuca sativa L., growers on the Central Coast of California rely on conservation biological control to manage Nasonovia ribisnigri Mosley (Hemiptera: Aphididae) and other aphid pests of lettuce. In 2006, we carried out five replicated field trials to determine the importance of syrphid larvae in the suppression of N. ribisnigri and other aphids infesting organic romaine lettuce. We used Entrust, a spinosad-based insecticide approved for use on organic farms, to suppress syrphid larvae in aphid-infested romaine. Romaine treated with Entrust was unmarketable at harvest because of aphid infestation, whereas insecticide-free romaine was marketable. Syrphid larvae composed 85% or more of total predators in most trials, and they were the only predators consistently recovered from romaine that was infested with aphids early and largely aphid-free by harvest. The species mix of nonsyrphid predators varied from site to site. Applications of Entrust suppressed nonsyrphid predators in two trials, and so was an imperfect tool for selectively suppressing syrphid larvae. The relative importance of syrphid larvae and other predators in the conservation biological control of aphids in organic romaine is discussed. We conclude that syrphid larvae are primarily responsible for the suppression of aphids in organic romaine on California's Central Coast.

Activity of Selected Neonicotinoids and Dicrotophos on Nontarget Arthropods in Cotton: Implications in Insect Management

Certain neonicotinoids are used in cotton, Gossypium hirsutum (L.), to control various piercing-sucking pests. We conducted field studies using three neonicotinoids (acetamiprid, thiamethoxam, and imidacloprid) and an organophosphate (dicrotophos) to assess the activity of these insecticides against nontarget arthropods, particularly predators, and to determine the potential economic consequences of such activity. Mortality among populations of the big-eyed bug, Geocoris punctipes (Say), and the red imported fire ant, Solenopsis invicta Buren, was highest after thiamethoxam and dicrotophos treatments. Numbers of arachnids were consistently lower after dicrotophos treatments, whereas none of the neonicotinoids caused appreciable mortality. Total predators in pooled data from five separate studies revealed that numbers, compared with untreated plots, were reduced by -75% in dicrotophos, 55-60% in thiamethoxam, and only 30% in both acetamiprid and imidacloprid plots. Acetamiprid and thiamethoxam exhibited significant mortality against field-deposited eggs of bollworm, Helicoverpa zea (Boddie). Both thiamethoxam and dicrotophos plots exhibited bollworm numbers that were approximately three times higher than treatment thresholds (three per 100 plants), whereas numbers in untreated plots were below threshold levels. In one study on Bt cotton, a significant negative correlation was observed between numbers of predators and bollworm larvae. Results demonstrated that neonicotinoids differ in activity against predaceous arthropods and bollworm eggs and that high predator mortality can result in resurgence of bollworm larvae and additional insecticide costs.

Impact of farm-scale Bt maize on abundance of predatory arthropods in Spain

Transgenic maize expressing the Cry1Ab toxin from Bacillus thuringiensis (Bt-maize) has been grown in Spain since 1998, representing about 5% of the total maize area. As part of a Spanish specific monitoring program for Bt maize, a farm-scale study was initiated in 2000 to assess the potential impacts of Bt maize on predatory arthropods. The trials were conducted at two maize growing areas (Lleida and Madrid) over 3 years. In each locality three treatments (each with 3–4 replicates of 0.4–0.7 ha) were arranged in a completely randomised block design, Bt-maize (cv. Compa CB) being compared with the isogenic cv. Dracma under conventional farm practices, with or without the insecticide (imidacloprid) seed treatment. Predator abundance was monitored from late May to mid September in Lleida and from mid June to mid September in Madrid by visual surveys and pitfall traps. Anthocoridae, Coccinellidae, and Araneae represented about 90% of the total number of predators recorded in visual samplings whereas Carabidae and Araneae were the two prevalent predator groups (85–90% of the total predators) collected in pitfall traps. Their abundance varied from year to year and between locations, but no clear tendencies related to Bt maize was recorded. Insecticide treatment reduced anthocorid numbers occasionally but no consistent effects were found for the rest of predators. Our data suggest that Bt maize is compatible with the naturally occurring predators.

INFLUENCE OF HABITAT FRAGMENTATION AND CROP SYSTEM ON COLUMBIA BASIN SHRUBSTEPPE COMMUNITIES

Crop production in much of the western United States has caused extensive fragmentation of shrubsteppe and other grasslands and has increased regional levels of disturbance through repeated tillage of crop fields and applications of agrochemicals. Although there have been numerous studies of the effects of fragmentation on arthropods in forests, old fields, and cropland, there have been very few studies of fragmentation effects on grassland arthropods. I conducted a two-year study in the Columbia Basin region of the U.S. Pacific Northwest to determine the effects of fragmentation and regional disturbance on shrubsteppe communities. I sampled plants and arthropods in 20 shrubsteppe fragments associated with annual crops, 20 fragments associated with perennial crops, and 20 large sections of shrubsteppe distant from crop fields. Fragments were corners of crop irrigation circles, and only sites that were undisturbed, with an apparent high coverage of shrubs, were included in the study. Results indicated no significant differences in coverages of shrubs, perennial grasses, total perennial forbs, total annual/biennial forbs, and species richness of grasses and shrubs between fragments and large sections of shrubsteppe. Mean percent coverage of the annual grass Bromus tectorum was 18.6% greater in small fragments than in large sections of shrubsteppe distant from crop fields, and mean coverage of bare ground was 22.9% higher and coverage of biological soil crusts was 41.5% lower in the fragments than in large shrubsteppe sections. Shrubsteppe fragments had significantly lower abundances of obligate herbivores, omnivores, total herbivores, obligate predators, total predators, plant detritivores, total detritivores, and butterflies, as well as fewer individuals of numerous other taxa within these trophic groups. Fragmentation had very little effect on species richness within trophic groups, probably because fragments were not that isolated from each other and large sections of shrubsteppe. Shrubsteppe communities that were next to highly disturbed annual crops had greater coverages of total annual/biennial forbs, and lower coverages of total perennial forbs and biological soil crusts when compared to shrubsteppe near perennial crops. Abundances of obligate herbivores, omnivores, total predators, plant detritivores, vertebrate-detritus feeders, and bees were similar in shrubsteppe near annual crops and near perennial crops. However, within these trophic groups, shrubsteppe near annual crops supported fewer obligate shrub-feeding grasshoppers, herbivorous ground beetles, harvestmen, antlions, darkling beetles, and butterflies than did shrubsteppe near perennial crops. The results suggest that a reduction in resources within fragments and regional disturbances caused by the production of annual crops were responsible for changes in arthropod trophic structure in fragments. Changes in trophic structure were probably not due to reductions in habitat heterogeneity or habitat isolation because plant community structure was similar in fragmented and unfragmented shrubsteppe, and fragments were not isolated from large sections of shrubsteppe.

Field Surveys and Evaluation of Native and Established Predators of the Hemlock Woolly Adelgid (Homoptera: Adelgidae) in the Southeastern United States

There has been little research conducted on the effects of native or established predators on populations of the hemlock woolly adelgid, Adelges tsugae Annand. This study used field surveys and cage exclusion experiments to examine the relationship between established predators and A. tsugae in the southeastern United States. Predators were collected in very low densities in both years. Harmonia axyridis Pallas (Coleoptera: Coccinellidae), lacewings (Neuroptera: Chrysopidae and Hemerobiidae), and gall gnats (Diptera: Cecidomyiidae) represented 81% of the total predators collected in 1998. Cage exclusion experiments revealed no significant predator effects in all three sites in 1997 and 1998. It is unlikely that established predators are exhibiting any significant control on adelgid populations because of the low densities of predators that were encountered at a time when adelgids were abundant. Therefore, controlled releases of non-native predators into these sites should be considered.

Catastrophic wildfire and its short-term effects on families of Order Coleoptera (beetles) in Eucalyptus regnans forest in the Central Highlands of Victoria

Summary The effects of a single high-intensity catastrophic wildfire on insect order Coleoptera (beetles) at litter level were assessed in wet sclerophyll Mountain Ash (Eucalyptus regnans F.Muell.) forest over a three year period. The study was based on 14 283 specimens representing 31 families contained in 1920 pitfall trap samples from a burnt ‘high elevation’ and ‘low elevation’ site, as well as an unburnt ‘control’ site. The effects of the wildfire were minimal, with only the predatory Carabidae (and therefore total predators) and the less common ‘minor’ families undergoing an apparent short-term decrease and increase in activity respectively within the two years following the wildfire. However, the activity of the more common ‘major’ families Staphylinidae, Nitidulidae, Leiodidae, Curculionidae and Cryptophagidae, and the decomposers/fungus feeding group remained unchanged after the fire. Coleopteran families in terms of diversity, taxon richness and community evenness were also found to be unaffected by the wildfire, as were the proportions of the total Coleoptera in the wider arthropod spectrum based on 91 929 specimens. Coleopteran families at litter level therefore appear to withstand, or recover fairly quickly from, the effects of a single catastrophic wildfire (and by inference also from a single low-intensity prescribed fire) so that the order must be considered as a fire-stable part of the E. regnans forest. However, further study is required to determine whether this apparent coleopteran stability at family level is also reflected at the genus and species level.

Predator Conservation in Cotton: Using Grain Sorghum as a Source for Insect Predators

Abstract Adjacent plots of cotton, Gossypium hirsutum L., and grain sorghum, Sorghum bicolor (L.) Moench, were established in 1997 and 1998 to study the movement of generalist predators in this system. Previous authors have suggested that sorghum acts as a source of generalist insect predators for cotton pests but several questions about the dynamics of insect movement remain unanswered. Mark–recapture methods were used to determine the timing of predator movement and to measure the net gains, if any, for cotton in terms of predators. Destructive sampling of cotton and grain sorghum plants was used to determine which environmental factors might cause predator movement in this system. Results showed that several generalist predators move between cotton and sorghum, most frequently Orius spp. and Hippodamia convergens Guerin-Meneville. Movement of predators into cotton peaked during the hard-dough and soft-dough stages of sorghum phenology in 1997 and 1998, respectively. Although cotton received a net gain in total predators, the number of insects leaving cotton once exceeded the number entering from sorghum, indicating that predator movement is not unidirectional in this system. Further, data on predator dispersal rates suggest that predators possess the necessary mobility for their use in field-scale conservation (as opposed to strip cropping). Results of destructive sampling show that predator movement was positively correlated with ambient temperatures and negatively correlated with local aphid levels. These results support the use of sorghum as a predator conservation tool in cotton and are particularly relevant as the boll weevil eradication programs increase the feasibility of pesticide reductions and conservation in cotton.

Longitudinal distribution of predatory benthic macroinvertebrates in a karstic river

The longitudinal distribution of predatory macroinvertebrates and their diversity were investigated on boulder, cobble and gravel substrates along the River Kupa, a karstic river in the NW Dinarid area (Croatia). Depending on substrate type and river section, the predator biomass constituted 6.9 % to 20.2 % of the total macro-invertebrate biomass. In the headwater streams more than 80 % of predator biomass was represented by rhyacophilid, perlid and perlodid larvae. In the upper river section Hirudinea species, rhyacophilids and the dipteran larva, Atherix ibis, constituted approximately equal percentages of total predators. In the lower river section Hirudinea species, Odonata larvae, tanipod and ceratopogonid larvae were the most dominant predators. Along the river gradient the increase of predator biomass corresponded with the increase of scraper, collector-gatherer and filterer biomass. The Shannon index of diversity showed that the diversity of predators increased from the source area to the downstream reaches. A significant and positive association was found between diversity of predators and diversity of collector-gatherers. This positive relationship between predators and collector-gatherers may be interpreted as the diversity response of predators to the diversity of prey.

Insect Pests and Arthropod Predators Associated with Tree-Turf Landscapes2

Sweep-nets and pitfall traps were used to examine the distribution and dynamics of predominant predators and pests in turfgrass foliage in parks, golf courses and suburban/rural landscapes in 1991 and 1992. Araneae, Formicidae, and Coccinellidae were the most abundant predators in the sweeps, while Araneae, Formicidae, and) Carabidae were the most abundant predators in the pitfall traps. In both years, Araneae comprised over 60% of the total predators in the sweep samples. Formicidae (>70%) and Araneae (13–19%) were the most abundant arthropod predators in the pitfall samples. Cicadellidae, Chrysomelidae, and Orthoptera accounted for over 96% of the prey in the sweep samples, while Cicadellidae, Orthoptera (grasshoppers and crickets), and Aphididae comprised over 90% of the prey in the pitfall samples. Abundance of predators and prey, and prey / predator ratios fluctuated with site, date, and distance from the trees. During the season, high prey / predator ratios usually preceded peak prey abundance in the sweep samples. Predators usually were more prevalent in sweep samples closer to tree borders, while prey populations tended to be higher at distances further from the tree borders. These results suggest that tree borders provide food, shelter, and refuge for predators during periods of environmental stress.