At least in Australia, methods for the control of insect pests in agricultural situations, including grain storage facilities and animal rearing enclosures, typically comprise the use of highly toxic chemicals, including organophosphates and carbamates, which typically require the involvement of skilled technicians for their application.
However, evidence indicates that at least certain insect pests are developing resistance to these chemicals, and some of these pests, especially certain beetle larvae, adopt behavioural mechanisms, such as burrowing, when disturbed, which reduce the effectiveness of the chemical treatments.
One particularly evident case of this is the increasing problem being posed by the darkling beetle in intensive chicken farming. The darkling beetle, Alphitobius diaperinus (Panzer) (or its larva, the lesser mealworm), a member of the tenebrionid family of beetles, is now a common pest of poultry houses, in particular broiler sheds and egg barns. The larvae of this beetle are often present in the litter of chicken sheds in vast numbers, reducing yield (due to consumption of the chicken feed_, and being capable of leucosis or Marek's disease, Gumboro disease, turkey coronavirus, Newcastle disease, ionfectious bursal disease, reovirus, enterovirus, fowl pox, and avian influenza; bacteria such as Salmonella typhimurium, Campylobacter, Escherichia coli, and Staphylococcus ssp.; protozoans such as Eimeria ssp. that cause coccidiosis; fungi such as Aspergillus SPP.; HELMINTHS SUCH AS THE NEMATODE Subulura brumpti Lopes-Neira; and fowl cestodes. There are also human-related disease risks associated with exposure to this beetle. In addition, the beetle and/or their larvae are known to damage soft materials, such as Styrofoam, fiberglass, and polystyrene insulation panels in the walls of poultry houses, especially when seeking pupation sites. The resulting damage can cause increased heating bills and additional building repair costs when the infested area is replaced.
Because of its tropical origin, the lesser mealworm is well suited for warm, humid conditions, such as frequently occur in chicken sheds. After mating, a female beetle has the potential to lay over 2,000 eggs, and does so in cracks and crevices in the poultry house or ground, in manure or litter, in grain hulls, and under feed and water lines. Adults can live three to twelve months, with females continuing to produce eggs most of their life at one to five day intervals. Larvae hatch in four to seven days and complete development to the adult stage in 40 to 100 days, depending on temperature, humidity and food quality, chicken sheds providing near, if not ideal conditions (including high humidity, temperatures between 30 and 40° C., and copious nutrients including chicken feed, chicken faeces, feathers and dead chicks).
Typically, maintenance, disinfection and disinfestation of chicken sheds in Australia is carried out in approximately 50 day cycles, with an approximately seven week growing period for the chickens. Once the market-ready chickens are removed from the sheds, the sheds are cleaned out, including the waste litter. The sheds are then washed down with an alkaline wash, inspected, and then sprayed with an organophosphate or carbamate, such as fenitrothion or carbaryl, by a licensed contractor. Formaldehyde is typically also sprayed after the insecticide treatment, as an antiviral treatment (although this is highly toxic to most organisms), and the sheds need to be left vacant for 2 to 3 days after this. Once treated, fresh litter is laid on the ground of the shed, and chickens introduced (typically over a two week period in a time-stepped procedure).
Notwithstanding the use of toxic chemicals, such as fenitrothion and cyfluthrin, often followed up by formaldehyde or glutaraldehyde treatments (requiring leaving the chicken sheds empty for up to three days), darkling beetle loads in Australian chicken sheds have been increasing rapidly, and the beetle numbers observed reflect poor kill of the larvae or adult beetles during the maintenance/disinfestation cycle.
Studies have indicated that many beetles and larvae stay concealed in the floor, and or in wall structures and/or insulation, especially when disturbed, thereby avoiding contact with toxic levels of the insecticides. This results in ever increasing starting populations of the pests in subsequent rearing cycles, and reduced yields as a result of waste litter also creates problems in terms of release of large numbers of pests into the environment, along with any diseases they carry, when the litter is disposed of.
The darkling beetle is also a pest of stored flour, meal, and other grain products, especially in poorly maintained grain processing plants or storage structures.
A number of other pests of agricultural structures exist, many of them being residual levels of pesticide in the structures and/or stored grain is of increasing concern.
There is a need for improved methods for controlling the presence and/or spread of pests or pathogenic organisms in agricultural structures which involves the use of less toxic substances. There is also a need for more effective methods for controlling the numbers and/or the spread of such pests or pathogenic organisms in said structures.
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