Profile: Factitious foods to reduce production costs of beneficial insects

November 12, 2015

Factitious Prey for Production of Stinkbug Predators for Biological Control of Agricultural Pests – Juan A. Morales-Ramos and M. Guadalupe Rojas

Stinkbug predators (Heteroptera: Pentatomidae) are among the most efficient biological control agents against many agricultural pests including caterpillars, rootworms, and particularly the Colorado potato beetle. At least one species of stinkbug predator, Podisus maculiventris, also known as the spined soldier bug, is commercially available in the U. S. and Europe. Studies of prey preference and suitability for growth and development of P. maculiventris have determined that the cabbage looper, Trichoplisia ni, is the best prey item for this predator. However, rearing the cabbage looper in large numbers is expensive and technically complicated. The high cost of producing the prey results in high prices of commercially produced predators, making biological control an expensive alternative to other less environmentally friendly methods of pest control.

One way to reduce the costs of producing stinkbug predators is by using factitious prey species that are easier to produce or are already commercially available. Relative success has been achieved producing P. maculiventris using the greater wax moth larvae, Galleria mellonella, as prey. Other species of commercially available insects like the yellow mealworm, Tenebrio molitor, have been less successful as factitious prey items for P.maculiventris. The yellow mealworm is a highly desirable alternative because of its low cost and wide-spread availability. Many studies on the suitability of T. molitor as prey have been focused on using the larval stage of the beetle, but recent work conducted in the USDA-ARS National Biological Control Laboratory has been more successful using the pupal stage of T. molitor as prey for P. maculiventris.

Studies showed that the nutritional contents of T. molitor drastically change during metamorphosis making pupae more suitable prey items for P. maculiventris. The content of protein increases and lipid content decreases three days after pupation had occurred. Younger pupae retain the nutritional characteristics of the larvae. A colony of P. maculiventris has been maintained in culture for 3 years using exclusively T. molitor pupae as food for the predators with no significant impact on life cycle parameters or fecundity.

Other stink bug predators like Brontocoris tabidus, Podisus nigrispinus and P. distinctus have been reared successfully using T. molitor pupae and the housefly, Musca domestica, larvae in Brazil. In China, the stinkbug predator Arma chinensis is being produced using silkworm, Antheraea pernyi, pupae as prey item. Other important stinkbug predators, like Perillus bioculatus, are yet to be successfully produced in factitious prey. These predators are highly selective and it is difficult to rear them using alternative prey species. Future research will focus on discovering alternative, easy to produce, prey species to mass produce these selective predator species.

Factitious Food for Ladybird Beetles: Nutritional Route to Cost-Effective Mass Rearing for Augmentative Biological Control – Eric W. Riddick, PhD

Ladybird beetles (Coleoptera: Coccinellidae) have a distinguished record as predators of plant-feeding insects and mites throughout the world (Hodek and Evans 2012). Because of their potential to suppress insect pests, research efforts to propagate or mass rear ladybirds for augmentative biological control in greenhouses, high tunnels, and plantscapes have been ongoing. One impediment to mass rearing ladybirds in the large quantities necessary for augmentative biological control is the cost associated with rearing natural prey (e.g., aphids) as food for many ladybird species. As a strategy to reduce costs, researchers have been using several alternative food sources (i.e., factitious foods), in lieu of natural prey

(Riddick 2009). Natural prey (aphids) require rearing live host plants as food. Factitious foods can be reared on grain and other stored products.

Exemplary factitious foods, including the ladybird species tested against, are listed in Table 1. Despite several decades of research, only several foods have been found suitable, to some extent, for rearing ladybirds (Riddick 2009, Riddick and Chen 2014). For example, eggs of the Mediterranean flour moth Ephestia kuehniella (Lepidoptera: Phycitidae) is an effective food source that supports normal development and survival, but not fecundity, in some coccinellids, such as Cryptolaemus montrouzieri (Attia et al. 2011; Table 1). On the other hand, E. kuehniella does support normal fecundity in the coccinellid

Hippodamia convergens and increased fecundity, in comparison to natural prey, in the coccinellid Harmonia

axyridis (Kato et al. 1999). Nevertheless, E. kuehniella eggs are rather expensive to mass produce; an alternative, more cost-effective factitious food is necessary (Riddick et al. 2014). As a more cost-effective alternative to E. kuehniella, eggs of brine shrimp Artemia franciscana Kellogg (Anostraca: Artemiidae) have been tested in the laboratory, with somewhat promising results (Table 1). Adalia bipunctata can develop and have normal fecundity when fed A. franciscana eggs with plant pollen (Bonte et al. 2010). Coleomegilla maculata can develop normally but have reduced fecundity when fed A. franciscana eggs. Interestingly, fecundity improved two-fold when A. franciscana eggs were blended into a very fine dust-like powder (Riddick and Wu 2015). Clearly, more research on the utilisation of A. franciscana as food for C. maculata and other ladybird beetles is necessary. The potential of using feeding and/or oviposition stimulants in combination with powdered A. franciscana eggs appears promising (Riddick and Wu 2015) and ripe for follow-up investigations.