Invertebrate biodiversity affects predator fitness and hence potential to control pests in crops

Natural enemies that control pests usually allow farmers to avoid, or reduce, the use of pesticides. However, modern farming practices, that maximize yields, are resulting in loss of biodiversity, particularly prey diversity. Does this matter? Pests continue to thrive, and without alternative prey the predators should, perforce, concentrate their attentions upon the pests.We showed that a diverse diet significantly enhances predator fecundity and survival. Experiments were conducted using common generalist predators found in arable fields in Europe, the carabid beetle Pterostichus melanarius (Coleoptera: Carabidae) and the linyphiid spider Erigone atra (Araneae: Linyphiidae). We tested the hypothesis that mixed species diets were optimal, compared with restricted diets, with respect to parameters such as predator weights, egg weights, numbers of eggs laid, egg development times, egg hatching rates and predator survival. In carabids, an exclusive earthworm diet was as good as mixed diets containing earthworms for egg production and hatching, but less good than such mixed diets for increase in beetle mass and sustained egg laying. For spiders, aphids alone (Sitobion avenae) or with the Collembola Folsomia candida, drastically reduced survival. Aphids plus the Collembola Isotoma anglicana improved survival but only aphids with a mixed Collembola diet maximized numbers of hatching eggs.Predators offered only pests (slugs or aphids) had lowest growth rates and fecundity. We therefore demonstrated that conservation of a diversity of prey species within farmland, allowing predators to exploit a diverse diet, is essential if predators are to continue to thrive in crops and regulate agricultural pests.     

Development and reproduction of Adalia bipunctata on factitious and artificial foods

The native coccinellid Adalia bipunctata (L.) (Coleoptera: Coccinellidae) may be an alternative to exotic species like Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) for the biological control of aphid pests in Europe. The availability of adequate factitious or artificial foods may help optimize its mass production. This study examines the nutritional value of Ephestia kuehniella Zeller (Lepidoptera: Phycitidae) eggs plus bee pollen, pea aphids Acyrthosiphum pisum (Harris) (Hemiptera: Aphididae) and mixtures of bee pollen and cysts of Artemia franciscana Kellogg (Branchiopoda: Artemiidae) and/or a lyophilized artificial diet based on bovine meat and liver. Reproducing adults of A. bipunctata were obtained on all diets tested, but immature survival, adult weights, development times and reproductive rates differed among diets. Over 84% of first instars fed on E. kuehniella eggs plus pollen or aphids survived to adulthood. Feeding predator larvae on pollen combined only with A. franciscana cysts or artificial diet yielded 40–55% immature survival, but survival increased to 74% when all of these components were mixed. Adult weights of A. bipunctata on the mixtures of pollen, A. franciscana cysts and/or artificial diet were 55–75% of those on aphids or on E. kuehniella eggs plus pollen. Lifetime fecundity was superior on E. kuehniella eggs plus pollen (1,864 eggs) to that on the other diets (264–889 eggs). The use of mixtures of plant and animal foods for A. bipunctata and other predators may contribute to increasing the cost-effectiveness of commercial mass production by reducing inputs of natural prey like aphids, or of nutritious but expensive factitious foods like lepidopteran eggs.     

Essential versus alternative foods of insect predators: benefits of a mixed diet

Although many predatory insects appear to be opportunistic generalists in their selection of prey, only a subset of prey species may in fact serve as “essential foods” capable of supporting immature growth and adult reproduction. It has been suggested that other, “alternative foods” serve only to maintain the predator when essential foods are not available, but little research has evaluated the significance of a mixed diet of essential and alternative foods for predator growth or reproduction. Here we test the general hypothesis that although alternative prey may be inadequate to support reproduction when consumed alone by adult predators, consumption of such prey may enhance the predator's reproductive output when the predator also has access to essential prey. We compared egg production by two aphidophagous lady beetles, Coccinella septempunctata and C. transversoguttata, provided with diets of aphids (essential prey) and weevils (alternative prey). As predicted, female predators produced greater numbers of eggs when a diet of pea aphids in limited number was supplemented by alfalfa weevil larvae. The predators laid no eggs when provided only with weevils or only with sugar. But once aphids were added to the diet, females of C. transversoguttata (but not C. septempunctata) laid eggs in greater numbers when they had fed previously on weevils than on sugar. Females of both species also produced eggs in modest numbers when provided with both weevils in excess and sugar, but this diet supported a lower rate of egg production than did a diet of weevils in excess plus a limited number of aphids. Although C. septempunctata has a longer history of association with the alfalfa weevil than does C. transversoguttata, the former species was not more effective in exploiting this alternative prey in support of reproduction. The tendency of generalist predators such as adult lady beetles to consume alternative as well as essential prey probably enhances considerably their ability to capitalize on short-lived and scattered opportunities as they seek out suitable sites in which to reproduce. Received: 11 May 1998 / Accepted: 1 May 1999     

Diet-dependent fecundity of the spiders Atypena formosana and Pardosa pseudoannulata, predators in irrigated rice

1 The fecundity of the spiders Atypena formosana and Pardosa pseudoannulata was assessed on diets of brown planthopper Nilaparvata lugens (BPH), green leafhopper Nephotettix virescens (GLH), Collembola (Entomobryidae), Droso phila melanogaster and three prey mixtures; BPH–GLH, BPH–GLH–Collembola and a full mixed diet of BPH–GLH–Collembola–D. melanogaster. 2 Egg production and hatching success was high in A. formosana except on the BPH, the GLH and the BPH–GLH diets. In P. pseudoannulata egg production and hatching success was lowest on diets of GLH and BPH–GLH, whereas this spider used BPH better. 3 Differences between offspring sizes were small. 4 Survival of A. formosana females was lowest on the GLH and BPH–GLH diets. In P. pseudoannulata survival did not differ significantly. 5 Food conversion efficiency was highest on the Collembola and the D. melanogaster diets for both spiders. 6 Overall, diets of Collembola and D. melanogaster had the highest quality for both spiders, the BPH–GLH–Collembola and the full mixed diets were intermediate in quality, the quality of the BPH diet was intermediate to low and quality of the GLH and BPH–GLH diets was low. 7 There need not be a contradiction between low dietary value of hoppers and successful natural biological control provided that the nutritional needs of the spiders are met by sufficient alternative prey. 8 The hopper‐spider relationship is comparable to that of aphids and spiders in temperate cereals, suggesting that low dietary quality of Homopterans to spiders may be widespread.     

Two Meridic Diets for Perillus bioculatus (Heteroptera: Pentatomidae), a Predator of Leptinotarsa decemlineata (Coleoptera: Chrysomelidae)

Two artificial diets, devoid of insect components, were developed for the predator Perillus bioculatus (Fabricius). The diets based on chicken liver and tuna fish were designed to approach the nutritional characteristics of the primary insect prey, Leptinotarsa decemlineata (Say) eggs. P. bioculatus was reared on diet 2 for 11 consecutive generations without cumulative detrimental effects on its biology. Developmental time and preovipositional period were significantly longer, and egg viability, survival from egg to adult, and fecundity were significantly lower in P. bioculatus individuals reared on artificial diets than in those reared on L. decemlineata eggs. A significant reduction in developmental time, increase in survival from egg to adult, and reduction in length of the preovipositional period were observed after 11 generations of in vitro reared P. bioculatus on diet 2. These changes may indicate that the predators experience some degree of adaptation to the diet after several consecutive generations of in vitro rearing. No changes in egg viability were observed after 11 generations of in vitro rearing. Adult female weight was unaffected when reared on artificial diet, but a significant increase was observed after 11 generations of in vitro rearing. Females under all treatments weighed an average of 11.6 mg more than the males.     

Potential of the predatory mite Phytoseius finitimus (Acari: Phytoseiidae) to feed and reproduce on greenhouse pests

Phytoseiid mites of the genus Phytoseius are natural enemies of tetranychid and eriophyid herbivorous mites mostly found on hairy plants where they feed on prey, as well as on pollen. Nevertheless, the nutritional ecology and the role of these predators in biological pest control are only rarely addressed. In the present study, we evaluated the potential of Phytoseius finitimus to feed and reproduce on three major greenhouse pests, the two-spotted spider mite, the greenhouse whitefly and the western flower thrips. Additionally, we estimated the effect of cattail pollen when provided to the predator alone or in mixed diets with prey. Contrary to thrips larvae, both spider mite larvae and whitefly crawlers sustained the development of P. finitimus. In addition, females consumed more spider mite eggs and larvae, as well as whitefly crawlers than thrips larvae, but laid eggs when feeding on all prey. When provided alone, cattail pollen sustained the development and reproduction of the predator. The addition of pollen in mixed diets with prey reduced prey consumption, though it increased the predator’s egg production. We discuss the implications of our findings for biological pest control.     

Effects of maternal diet quality on offspring performance in the rove beetle Tachyporus hypnorum

Abstract.  1. The reproductive output of an individual is known to be influenced by diet quality, but the quality of the parent's diet can also influence the performance of the offspring. Dietary maternal effects may interact with the effects of the offspring's diet to produce a variety of response patterns.
2. Maternal effects were investigated in a polyphagous predator, the rove beetle Tachyporus hypnorum , using three single-species diets: two low-quality diets consisting of the aphids Sitobion avenae and Rhopalosiphum padi , and the high-quality control Drosophila melanogaster diet. Offspring of females fed these diets were raised on the same monotypic diets and allowed to reproduce. Several fitness parameters were measured to indicate possible maternal effects in both F1 and F2 generations.
3. Maternal diet effects in F1 were found in egg size, hatching success, time to hatching, larval development time, larval survival, and sex ratio. Both aphid diets resulted in smaller eggs. A diet of R. padi resulted in reduced hatching success, longer time spent in the egg stage, and a female-biased sex ratio. A maternal diet of R. padi also prolonged larval development on S. avenae diet, while a maternal diet of S. avenae decreased survival on the R. padi diet. These effects were independent of egg size.
4. A maternal diet of R. padi enhanced the survival of F1 larvae raised on the same diet. Developmental selection operating through a high egg mortality may be the explanation for this seemingly positive effect.
5.  Sitobion avenae alone caused a significant reduction in the hatching success of F2 eggs, thus revealing grandmaternal effects.
6. The prediction that polyphagous predators are less likely to evolve adaptive maternal effects is supported by the fact that none of the documented maternal effects could be interpreted as adaptive.     

Food quality of Ephestia eggs,the aphid Rhopalosiphum padi and mixed diet for Orius majusculus

We studied the food quality of the aphid Rhopalosiphum padi to the pirate bug Orius majusculus using Ephestia eggs as high-quality comparison prey. Several performance parameters were tested on individuals that had been reared and maintained on each of the two single-prey diets or on a mixed diet. All fitness parameters were lower in individuals fed aphids only, indicating poor food quality of this prey. Compared with the pure Ephestia egg diet, the mixed diet enhanced teneral mass, while adult survival and female starvation tolerance were negatively affected and all other traits were unaffected. Body protein proportions were constant across diets, whereas lipid proportion was low in the aphid treatment. Preference for aphids was lower following a monotypic aphid diet than when reared on Ephestia eggs or a mixed diet. The results confirm that R. padi is low-quality food for O. majusculus as it is for other generalist predators, even though O. majusculus may contribute significantly to population suppression of the aphid.     

Diet-Dependent Survival, Development and Fecundity of the Spider Atypena formosana (Oi) (Araneae: Linyphiidae)Implications for Biological Control in Rice

The development time of Atypena formosana was assessed on four different diets: (1) brown planthopper (BPH), Nilaparvata lugens ; (2) green leafhopper (GLH), Nephotettix virescens ; (3) Collembola (Entomobryidae); and (4) a mixed diet of Collembola, hoppers and Drosophila melanogaster . A starvation treatment served as a control. We tested the hypothesis that because of differences in food quality, the diets would affect survival and development differently. Survival differed significantly among the diets. No spiders survived until adult on the diet of GLH, only a single individual survived on the diet of BPH, whereas 70% survived until adult on the Collembola diet and all survived on the mixed diet. Development times were significantly different among the diets tested. Spiders developed fastest on the mixed diet and the Collembola diet. The biomass of prey consumed within 48 h and the total biomass of prey consumed to complete an instar were highest on the mixed diet. Finally the mixed diet resulted in higher fecundity than the Collembola diet. It is concluded that alternative prey are an absolute necessity, as BPH and GLH diets alone would not be able to increase the number of predators, regardless of the number of hoppers present.     

Impacts on the predatory carabid beetle Ctenognathus novaezelandiae of pure and mixed diets of natural field-collected prey and Spodoptera litura fed control or transgenic avidin tobacco

The potential compatibility with biological control of transgenic insecticidal plants expressing the biotin-binding protein avidin was investigated in tri-trophic experiments with the predatory carabid beetle, Ctenognathus novaezelandiae. Beetles were provided with pure and mixed diets of 33%, 67% or 100% of Spodoptera litura larvae, fed either avidin-expressing or isogenic control tobacco, and invertebrates field-collected from the forest floor. Beetles given only tobacco-fed S. litura, whether avidin was present or not, had lower fecundity, egg fertility, body mass and male survival than beetles that received some field food. Fewer of the avidin tobacco-fed prey were consumed than the control tobacco-fed, whatever mixture or proportion offered, probably as a result of the reduced quality of biotin-deprived prey. Beetles consuming 100% avidin tobacco-fed prey had lower fecundity than those given 100% control tobacco-fed prey, although predation on eggs as well as reduced prey quality could have contributed to this result. Despite the nutritionally limiting nature of an exclusive diet of tobacco-fed prey, there was no effect of avidin on fecundity in beetles consuming 67% or 33% avidin prey, or any effect on female or male mass, survival or egg fertility, even in the 100% avidin prey treatment. Fecundity in beetles fed 33% field food with 67% tobacco-fed prey was lower than in those fed 67% or 100% field food. However, there was no added impact of avidin on fecundity, mass or survival, or egg fertility of the 33% field food diet, suggesting that under field conditions, where a mixture of prey is available, negative impacts of avidin-fed prey are unlikely.     

Quality of two aphid species (Rhopalosiphum padi and Sitobion avenae) as food for the generalist predator Tachyporus hypnorum (Col., Staphylinidae)

Abstract:  The quality of two aphid species ( Rhopalosiphum padi and Sitobion avenae ) as food for the staphylinid generalist predator Tachyporus hypnorum was investigated. Fruit flies ( Drosophila melanogaster ) were used as prey for comparison. T. hypnorum has been reported to prey on aphids, to consume large quantities and to show a high preference for aphids. This study showed that compared with fruit flies aphids are not high-quality prey for neither adult females nor larvae of T. hypnorum . Larvae were less able to utilize aphids than adult females. Reproduction was affected by both aphid species; a diet of S. avenae reduced fecundity, and a diet of R. padi reduced egg hatching success and prolonged the time spent in the egg stage compared with a fruit fly diet. For the T. hypnorum larvae pure diets of both S. avenae and R. padi resulted in high larval mortality. Overall ranking of the three prey types based on several fitness parameters differed between larvae and adults. The adult fitness parameters gave rather conflicting rankings of all three prey types though the two aphid species were of approximately the same overall value, whereas the larval fitness parameters gave identical rankings: D. melanogaster  >  S. avenae  >  R. padi . In the larval stage survival was greatly reduced by both aphid diets, while this was not the case for the adult females.     

The value of three cereal aphid species as food for a generalist predator

The value of the cereal aphid species Metopolophium dirhodum (Wlk.), Sitobion avenae (F.) and Rhopalosiphum padi (L.) as prey for the linyphiid spider Erigone atra (Bl.) was assessed. Fecundity of females was determined for spiders fed on eight experimental diets: three single‐species aphid diets, a mixed diet of all three aphid species, three mixed diets with each aphid species in combination with fruit flies Drosophila melanogaster (Meig.), and pure D. melanogaster as a high quality comparison diet. The development and survival of first‐instar juveniles fed on three diets of single aphid species, and on a diet of Collembola were compared with those subjected to starvation. Prey value for adult females was assessed by egg production, hatching success and offspring size. In pure diets all three aphid species were of low value to the spiders, causing a rapid decline in egg production and supporting no growth of significance of first‐instar juveniles. No difference in value of aphid species of single‐species aphid diets was found in the fecundity experiment, while a ranking of aphid species of M. dirhodum > R. padi > S. avenae was revealed in the survivorship experiment. A mixed‐aphid diet was not found to be advantageous compared with single‐species aphid diets, and no advantage of including aphids in mixed diets with fruit flies was found. Metopolophium dirhodum and R. padi were neutral in mixed diets, while a diet of S. avenae and fruit flies caused reduced egg production compared with the pure diet of fruit flies, revealing a toxic effect of S. avenae on the spider. The value‐ranking of aphid species in mixed diets was similar to that of single‐species diets. A similar ranking of aphid species was found for different fitness parameters (fecundity of adult females and development of juveniles). A ranking of aphids by offspring size of mothers on aphid‐only diets was S. avenae > M. dirhodum > R. padi. All aphid‐fruit fly diets resulted in larger offspring than a diet of only D. melanogaster, with the overall largest offspring being produced on the diet of M. dirhodum and fruit flies.     

Diet, fecundity and egg size in some polyphagous predatory carabid beetles

Egg size was measured at different rates of egg laying in three polyphagous carabid species, known to be useful predators of cereal aphids; the small Bembidion lampros Herbst and the medium-sized Pterostichus cupreus L. and P. melanarius Illiger. Variations in fecundity, as well as the ability of the medium-sized species to also build up fat reserves, were obtained when beetles were subjected to different dietary regimes consisting of aphids, or foods with a lower or higher protein content. Egg size was found to be dependent on the rate of egg laying within a species. A diet of cereal aphids appeared to be adequate for egg production in these polyphagous carabids, but female P. cupreus were unable to build up fat reserves when they ingested aphids contaminated with the aphicide pirimicarb. Beetles were able to devote resources to more and larger eggs (B. lampros), or to larger eggs and/or fat reserves (P. melanarius/P. cupreus) when given access to a carbohydrate-rich food with low protein content. The highest rate of egg laying was obtained when female P. cupreus and P. melanarius were given a more varied diet at frequent intervals; including regular shifts between unsprayed aphids, carbohydrate-rich food and protein-rich maggots. Within the varied diet treatment a negative relationship was obtained between egg size and egg number among similar-sized individuals of P. cupreus and P. melanarius; females producing the largest number also laid the smallest eggs. Egg size affected larval survival, since first instars hatching from large eggs were found to survive longer than those hatching from small eggs. The influence of differences in food intake on reproduction, maintenance metabolism, and survival of fieldinhabiting carabids is discussed.     

Life history characteristics of Orius insidiosus (Say) fed diets of soybean aphid, Aphis glycines Matsumura and soybean thrips, Neohydatothrips variabilis (Beach)

Field studies in soybeans have demonstrated that the endemic predator, Orius insidiosus (Say), is an important natural enemy of the soybean aphid, Aphis glycines Matsumura. Soybean thrips, Neohydatothrips variabilis (Beach), serve as an important prey resource for O. insidiosus in soybeans and may be important in sustaining O. insidiosus populations before the arrival of soybean aphid. Because soybean aphid is new to the US soybean system, the effects of a mixed diet of soybean aphid and soybean thrips on O. insidiosus life history is not known. We measured the survival, development, and reproduction of O. insidiosus when fed soybean thrips, and a mixed prey diet of soybean aphids and soybean thrips, and compared these results to a previous study of O. insidiosus life history fed soybean aphid alone. Nymphal development to adulthood (15.9 days) and fecundity (68.8 eggs per female) was improved for O. insidiosus fed ad libitum soybean thrips daily compared to O. insidiosus fed ad libitum soybean aphids daily. The contribution of alternative prey to O. insidiosus life history characteristics can be complex depending on the amount and quality of a particular prey item. At low levels of prey, the addition of prey appears to enhance O. insidiosus survival, development, and fecundity. However, as predators are fed more often, the predator’s response depends on the type of prey that predominates in the mixed prey diet. We discuss soybean thrips impact on O. insidiosus population ecology and soybean aphid dynamics.     

Phenotypic integration in a series of trophic traits: tracing the evolution of myrmecophagy in spiders (Araneae)

Several hypotheses have been put forward to explain the evolution of prey specificity (stenophagy). Yet little light has so far been shed on the process of evolution of stenophagy in carnivorous predators. We performed a detailed analysis of a variety of trophic adaptations in one species. Our aim was to determine whether a specific form of stenophagy, myrmecophagy, has evolved from euryphagy via parallel changes in several traits from pre-existing characters. For that purpose, we studied the trophic niche and morphological, behavioural, venomic and physiological adaptations in a euryphagous spider, Selamia reticulata. It is a species that is branching off earlier in phylogeny than stenophagous ant-eating spiders of the genus Zodarion (both Zodariidae). The natural diet was wide and included ants. Laboratory feeding trials revealed versatile prey capture strategies that are effective on ants and other prey types. The performance of spiders on two different diets – ants only and mixed insects – failed to reveal differences in most fitness components (survival and developmental rate). However, the weight increase was significantly higher in spiders on the mixed diet. As a result, females on a mixed diet had higher fecundity and oviposited earlier. No differences were found in incubation period, hatching success or spiderling size. S. reticulata possesses a more diverse venom composition than Zodarion. Its venom is more effective for the immobilisation of beetle larvae than of ants. Comparative analysis of morphological traits related to myrmecophagy in the family Zodariidae revealed that their apomorphic states appeared gradually along the phylogeny to derived prey-specialised genera. Our results suggest that myrmecophagy has evolved gradually from the ancestral euryphagous strategy by integrating a series of trophic traits.     

Why eat extrafloral nectar? Understanding food selection by Coleomegilla maculata (Coleoptera: Coccinellidae)

Methods of increasing predator abundance within a habitat include the incorporation of non-prey food items, yet the influence of this on predation intensity toward herbivores remains unknown. In order to gain an understanding of nectar feeding in the predaceous beetle, Coleomegilla maculata (DeGeer), laboratory studies were conducted evaluating prey consumption in the presence of extrafloral nectaries. The physiology of beetles with access to prey only and a mixed diet were compared. To elucidate results of beetle physiology, Y-tube olfactometer studies were conducted and preferences between food types evaluated. Coleomegilla maculata females consumed 9 % fewer aphids when nectar was available. Lipid and glycogen content, as well as oocyte volume were not increased upon consumption of a mixed diet. Evaluation of predator behavior when offered both food resources together and separately demonstrated that extrafloral nectaries are attractive.     

Damselfly eggs alter their development rate in the presence of an invasive alien cue but not a native predator cue

Biological invasions are a serious problem in natural ecosystems. Local species that are potential prey of invasive alien predators can be threatened by their inability to recognize invasive predator cues. Such an inability of prey to recognize the presence of the predator supports the naïve prey hypothesis. We exposed eggs of a damselfly, Ischnura elegans, to four treatments: water with no predator cue (control), water with a native predator cue (perch), water with an invasive alien predator cue (spinycheek crayfish) that is present in the damselfly sampling site, and water with an invasive alien predator cue (signal crayfish) that is absent in the damselfly sampling site but is expected to invade it. We measured egg development time, mortality between ovipositing and hatching, and hatching synchrony. Eggs took longer to develop in the signal crayfish group (however, in this group, we also observed high green algae growth), and there was a trend of shorter egg development time in the spinycheek crayfish group than in the control group. There was no difference in egg development time between the perch and the control group. Neither egg mortality nor hatching synchrony differed between groups. We suggest that egg response to signal crayfish could be a general stress reaction to an unfamiliar cue or an artifact due to algae development in this group. The egg response to the spinycheek crayfish cue could be caused by the predation of crayfish on damselfly eggs in nature. The lack of egg response to the perch cue could be caused by perch predation on damselfly larvae rather than on eggs. Such differences in egg responses to alternative predator cues can have important implications for understanding how this group of insects responds to biological invasions, starting from the egg stage.     

Increased control of thrips and aphids in greenhouses with two species of generalist predatory bugs involved in intraguild predation

The combined release of species of generalist predators can enhance multiple pest control when the predators feed on different prey, but, in theory, predators may be excluded through predation on each other. This study evaluated the co-occurrence of the generalist predators Macrolophus pygmaeus Rambur and Orius laevigatus (Fieber) and their control of two pests in a sweet pepper crop. Both predators consume pollen and nectar in sweet pepper flowers, prey on thrips and aphids, and O. laevigatus is an intraguild predator of M. pygmaeus. Observations in a commercial sweet pepper crop in a greenhouse with low densities of pests showed that the two predator species coexisted for 8 months. Moreover, their distributions in flowers suggested that they were neither attracted to each other, nor avoided or excluded each other. A greenhouse experiment showed that the predators together clearly controlled thrips and aphids better than each of them separately. Thrips control was significantly better in the presence of O. laevigatus and aphid control was significantly better in the presence of M. pygmaeus. Hence, combined inoculative releases of M. pygmaeus and O. laevigatus seem to be a good solution for controlling both thrips and aphids in greenhouse-grown sweet pepper. The predators are able to persist in one crop for a sufficiently long period and they complement each other in the control of both pests. This study also provides further evidence that intraguild predation does not necessarily have negative effects on biological control.     

Survival and diapause egg production of the copepod Centropages hamatus raised on dinoflagellate diets

Copepods are often said to require a mixed diet to maximize their survival and reproduction potential. Copepods may be forced to feed nonselectively in food limited environments, but this does not mean they require a diverse diet. In this study, we show that the right single food item, at the right stage, can be as good or better than a mixed diet for development, survival, diapause egg production and viability. Centropages hamatus was reared on unialgal or mixed diets of five dinoflagellates: Amphidinium carterae, Prorocentrum micans, Scrippsiella trochoidea, Lingulodinium polyedra, and Gymnodinium sanguineum, ranging in size from 11×16 μm to 44×57 μm. Four experiments of 12-30 days were conducted, each testing five diets against a mixed Control diet of the four larger dinoflagellates. Algal volumes were adjusted so diets would have the same initial carbon content or cell volume at a level known to be in excess of the amount required for growth. Eggs were collected on the final 2 days of the experiments, the survivors were counted and female prosome length was measured. Diapause egg viability was measured after the eggs completed a refractory period. Nauplii had high survival on unialgal P. micans and S. trochoidea diets, but the adult females did not produce eggs. Naupliar survival was low on a unialgal diet of G. sanguineum, but the adult females had the highest rate of egg production. An optimal diet fosters growth and survival at all stages and maximizes viable egg production, to ensure high recruitment to the next generation. This can be achieved with single food items appropriate for the developmental stage. Copepods fed just two dinoflagellates, P. micans to foster juvenile growth and G. sanguineum to support final maturation and fecundity, had higher total egg production than copepods reared on the mixed diet of four dinoflagellates.     

The effects of diet on herbivory by a predaceous lady beetle

We hypothesize that herbivory by predators is affected by the complexity of their diet. Coleomegilla maculata larvae fed prey – Acyrthosiphon pisum or Ostrinia nubilalis eggs – consumed two to three times more plant tissue (pinto beans) than those fed a mixed diet (containing pollen substitute and prey-based components). Simple, prey-only diets appear to lack plant-based nutrients important to this predator.