Predators and Parasitoids-in-First: From Inundative Releases to Preventative Biological Control in Greenhouse Crops

Repeated mass introductions of natural enemies have been widely used as a biological control strategy in greenhouse systems when the resident population of natural enemies is insufficient to suppress the pests. As an alternative strategy, supporting the establishment and population development of beneficials can be more effective and economical. The preventative establishment of predators and parasitoids, before the arrival of pests, has become a key element to the success of biological control programs. This “Predators and parasitoids-in-first” strategy is used both in Inoculative Biological Control (IBC), and in Conservation Biological Control (CBC). Here, we provide an overview of tools used to boost resident populations of biocontrol agents.

The potential use of drones to help natural pest control - an example using carabids

Small automated flying vehicles (drones, by common name) are undergoing very fast development, and the range of their potential use is also fast expanding. One possible application in agriculture is to disperse biological control agents in areas that are otherwise inaccessible, or the distribution of natural enemies is uneconomic for various reasons. We develop the use of multirotor type drones (DJI S-900) as a possible vehicle to field-disperse carabid beetle adults as an inoculative biological control release against oilseed rape pests. We selected Pterostichus cupreus as a representative of common, larger species, and Anchomenus dorsalis as a similar representative of smaller species. To test the robustness of these species to being dispersed by drones, we subjected the two carabid species to simulated "drop tests", using a specially modified 1 L-sized dispenser that can be fitted to the drone. We mixed 15-20 adults with two media, buckwheat bran and vermiculite and allowed the machine "dispersing" them under laboratory conditions. Subsequently, we checked the "distributed" beetles for mortality, bodily damage, and feeding capacity. Our first tests show that A.dorsalis is suitable for drone-based distribution while the larger species likely requires further modification of the dispensing system, due to the larger size and motility of this species. The dropping caused no mortality or physical damage to A.dorsalis but some of the P.cupreus lost tarsal segments. Feeding was not impaired in either species, though. In summary, drone technology opens promising possibilities for the widening of biological control possibilities in various situations in agriculture.

Implementation of biological control

The number of species of insect pests, estimated to be maximally 10,000 worldwide, forms only a small part of the millions of species of plant-eating insects. Chemical pest control is becoming increasingly difficult and objectionable in terms of environmental contamination so that other methods of pest control need to be developed. One of the best alternatives is biological control. Natural and inoculative biological control has already proven successful against a variety of pests over large areas. One is inclined to forget, however, how successful a biological control program has been as soon as the pest problem has been solved. Other types of biological control involving the regular introduction or augmentation of natural enemies are better known, although these have been applied on a much smaller scale; a survey of the present-day application of these latter types of biological control is presented here. Phases in the implementation of biological control are illustrated and needed future developments in research are discussed. The main limitation on the development of biological control is not the research, since natural enemies are easier found and with a much lower investment than new chemical pesticides, but rather the attitudes held by growers and disinterest on the part of industry, policy-makers, and politicians. The first priority for those concerned with the development and application of safer pest control should, therefore, be to change the perceptions that these other groups have of biological control.