Plants in the rearing of arthropod predators and parasitoids: benefits, constraints, and alternatives.

This review explores the roles of plants in rearing systems for arthropod biological control agents, addressing benefits and drawbacks. The utilization of plant materials in mass rearing processes for predators and parasitoids serves various purposes. Natural rearing systems require plants for cultivating hosts or prey. Whereas these rearing systems can be economically viable, they also have important practical limitations. Alternative rearing strategies make use of plant components as sources of moisture or nutrients, and as living or oviposition substrates. Plant-derived foods, such as honey and pollen, can be used as stand-alone foods for the rearing of several omnivorous parasitoids and predators. Certain omnivorous predators show enhanced life table parameters when suboptimal food is supplemented with plant materials. However, the integration of plants into rearing systems introduces complexities that challenge their efficiency, as plant defenses and contaminants can impact natural enemy fitness. Therefore, alternatives to plant foods or substrates in the rearing environment are discussed.

An artificial diet containing plant pollen for the mealybug predator Cryptolaemus montrouzieri.

BACKGROUND: The specialist predatory ladybird Cryptolaemus montrouzieri is an effective natural enemy of mealybugs and plays a key role in the biological control of these pests. However, its mass production is complicated by the dependence on parallel cultures of mealybugs or the need for Ephestia kuehniella eggs as an expensive factitious prey. RESULTS: Here we developed a pollen-based artificial food for the predator to lower its dependence on natural prey. We found that this artificial diet was an effective alternative food for larvae and adults of this predator. The artificial food supported the development and reproduction of the predator not only in the first generation (F0) but also in the next generation (F1). Although the developmental time and preoviposition period of C. montrouzieri on the artificial food were ca 1.5 days and 4 days longer than on the natural prey, the citrus mealybug Planococcus citri, respectively, its immature survival, fecundity and egg hatch were similar to those on mealybugs. In addition, adult C. montrouzieri maintained on natural or artificial food had a similar starvation resistance. CONCLUSIONS: Our results suggest that the pollen-based artificial diet can be used as an alternative food in the rearing of C. montrouzieri, and indicate its potential to support the mass production and wider application of this predator in biological control programmes. © 2016 Society of Chemical Industry.

Supplementation of an Artificial Medium for the Parasitoid Exorista larvarum (Diptera: Tachnidae) With Hemolymph of Hermetia illucens (Diptera: Stratiomyidae) or Antheraea pernyi (Lepidoptera: Saturniidae).

The effect of supplementing hemolymph of the black soldier fly, Hermetia illucens (L.), or the Chinese oak silkworm, Antheraea pernyi (Guérin-Méneville), to a basic insect-free artificial medium for the tachinid Exorista larvarum (L.) was investigated. The supplementation (20% w/w) was based on the assumption that insect additives may optimize the media for this parasitoid. Egg hatch, pupal and adult yields, and sex ratio did not differ among the enriched and basic media. Preimaginal development was faster on both hemolymph-enriched media than on the basic medium. Despite the shorter development on the medium supplemented with H. illucens hemolymph than on the basic medium, on the two media puparium weights were comparable. The female flies reared on the medium enriched with H. illucens hemolymph did not lay more eggs, but the latter yielded significantly more puparia compared with the control females. Conversely, the medium enriched with A. pernyi hemolymph yielded lower female puparium weights than the basic medium and produced only one ovipositing female out of the five obtained female adults. These results indicate that the in vitro development of E. larvarum improved when the basic artificial medium was enriched with H. illucens hemolymph, whereas the supplementation with A. pernyi hemolymph negatively affected the quality of the in vitro-reared females.

Supplemental food for Amblyseius swirskii in the control of thrips: feeding friend or foe?

BACKGROUND: In integrated pest management systems in greenhouse crops, the predatory mite Amblyseius swirskii is becoming increasingly important as a biological control agent of various pests, especially thrips and whiteflies. An emerging strategy to promote the predator's establishment and retention in the crop consists in providing food supplements. However, when faced with omnivorous pests, such as the western flower thrips, Frankliniella occidentalis, food supplements need to be applied with extreme care, in order not to boost population growth of the pest. This laboratory study was conducted to evaluate the impact of commercial products of Typha angustifolia pollen and decapsulated brine shrimp cysts (Artemia sp.) on populations of both pest and predator and on predator-prey interactions. RESULTS: Pollen was highly supportive for both F. occidentalis and A. swirskii, whereas Artemia cysts supported thrips populations to a lesser extent than those of the predator. Furthermore, a less pronounced reduction in thrips consumption by A. swirskii was observed in the presence of Artemia cysts as compared with T. angustifolia pollen. CONCLUSION: Artemia might be a valuable alternative to pollen for supporting populations of A. swirskii in order to improve thrips management, as they are less beneficial for the pest but do support population growth of A. swirskii.

Moisture source and diet affect development and reproduction of Orius thripoborus and Orius naivashae, two predatory anthocorids from Southern Africa.

The effect of moisture source and diet on the development and reproduction of the pirate bugs, Orius thripoborus (Hesse) and Orius naivashae (Poppius) (Hemiptera: Anthocoridae) was examined in the laboratory. Both species had been collected in and around sugarcane fields in South Africa. Supplementing eggs of the flour moth Ephestia kuehniella (Zeller) (Lepidoptera: Pyralidae) with a green bean pod as a moisture source yielded better nymphal survival and faster development, as compared with free water encapsulated in Parafilm, suggesting that the predators may extract extra nutrients from the bean pod. The impact of two factitious foods and moist honey bee pollen on developmental and reproductive parameters of both predators was also investigated. The overall performance of both Orius species on E. kuehniella eggs and cysts of brine shrimp, Artemia franciscana Kellogg (Crustacea: Artemiidae) was better than on pollen. Nonetheless, a pollen diet alone allowed 66 and 78% of the nymphs of O. thripoborus and O. naivashae, respectively, to reach adulthood. Overall, developmental and reproductive performance of O. thripoborus on the tested diets was superior to that of O. naivashae. The implications of these findings for the mass production of these predators and their potential role in biological control programs in southern Africa are discussed.

Temperature-dependent development of the two-spotted ladybeetle, Adalia bipunctata, on the green peach aphid, Myzus persicae, and a factitious food under constant temperatures.

The ability of a natural enemy to tolerate a wide temperature range is a critical factor in the evaluation of its suitability as a biological control agent. In the current study, temperature-dependent development of the two-spotted ladybeetle A. bipunctata L. (Coleoptera: Coccinellidae) was evaluated on Myzus persicae (Sulzer) (Hemiptera: Aphididae) and a factitious food consisting of moist bee pollen and Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) eggs under six constant temperatures ranging from 15 to 35° C. On both diets, the developmental rate of A. bipunctata showed a positive linear relationship with temperature in the range of 15-30° C, but the ladybird failed to develop to the adult stage at 35° C. Total immature mortality in the temperature range of 15-30° C ranged from 24.30-69.40% and 40.47-76.15% on the aphid prey and factitious food, respectively. One linear and two nonlinear models were fitted to the data. The linear model successfully predicted the lower developmental thresholds and thermal constants of the predator. The non-linear models of Lactin and Brière overestimated the upper developmental thresholds of A. bipunctata on both diets. Furthermore, in some cases, there were marked differences among models in estimates of the lower developmental threshold (tmin). Depending on the model, tmin values for total development ranged from 10.06 to 10.47° C and from 9.39 to 11.31° C on M. persicae and factitious food, respectively. Similar thermal constants of 267.9DD (on the aphid diet) and 266.3DD (on the factitious food) were calculated for the total development of A. bipunctata, indicating the nutritional value of the factitious food.

Development and reproduction of Adalia bipunctata (Coleoptera: Coccinellidae) on eggs of Ephestia kuehniella (Lepidoptera: Phycitidae) and pollen.

Due to growing criticism over the use of non-indigenous coccinellids, the two-spot ladybird, Adalia bipunctata (L.), has enjoyed increasing attention for aphid biocontrol in Europe. In the current study, eggs of the Mediterranean flour moth, Ephestia kuehniella Zeller, whether or not supplemented with bee pollen, were evaluated as a factitious food for larvae and adults of A. bipunctata. The predator showed slower larval development and lower survival when reared on live pea aphids, Acyrthosiphon pisum (Harris), than on E. kuehniella eggs. Survival on gamma-irradiated eggs of E. kuehniella was superior to that on frozen flour moth eggs, but other developmental characteristics were similar. Adults of A. bipunctata reared on Ac. pisum were only half as fecund as those offered irradiated or frozen E. kuehniella eggs, but egg hatch was markedly better on live aphids than on flour moth eggs (61 versus 20-27%, respectively). However, when a diet of flour moth eggs was supplemented with frozen moist bee pollen, egg hatch of A. bipunctata was equally as good as on live aphids. Supplementing flour moth eggs with dry pollen did not yield satisfactory results. Only 10% of larvae reached adulthood on moist bee pollen alone and resulting adults weighed less than half as much as those obtained on flour moth eggs. Our findings indicate that A. bipunctata is able to compensate for a suboptimal diet of animal prey by supplementary feeding on flower pollen. It is concluded that pollinivory may be a crucial trait for both the rearing of this natural enemy and its use in biological control programmes.

Influence of diet on life table parameters of Iphiseius degenerans (Acari: Phytoseiidae).

Abstract. Studies on the reproduction, longevity and life table parameters of Iphiseius degenerans (Berlese) were carried out under laboratory conditions of 25 +/- 1 degree C, 75 +/- 5% RH and 16L:8D h. As food sources for the predatory mite, Ricinus communis L. pollen, all stages of the spider mite Tetrranchus urticae Koch, Frankliniella occidentalis (Pergande) larvae, and Ephestia kuehniella Zeller eggs were selected. All diets were accepted as food by the adult mites. Female longevity ranged from 29.5 to 42.4 days, the highest value was recorded on a diet of Ephestia eggs. The highest percentage of females escaping the experimental arena was observed on the diet consisting of thrips larvae. The highest oviposition rate (1.9 eggs/female.day) was recorded when the predator was fed on spider mites on an artificial substrate. For other diets, oviposition rates ranged from 1.0 to 1.3 eggs/female.day. The intrinsic rate of natural increase (r(m)) of I. degenerans varied between 0.015 and 0.142 females/female x day. The diet consisting of castor bean pollen resulted in the highest population growth whereas the diet on spider mites brushed off onto a bean leaf arena resulted in the slowest population growth. This can be explained by the inability of the predator to cope with the webbing of T. urticae, and the high escape rate of the progeny when reared on spider mites. The percentage of females in the offspring ranged from 40 to 73%.