- Animals: bees
- Farm Business Management: farm-to-institution
- Pest Management: biological control, disease vectors, economic threshold, integrated pest management, physical control, traps
- Production Systems: organic agriculture
A comparison of Metarhizium anisopliae 5680 to Metarhizium anisopliae 3020 in field trials determined that the Metarhizium anisopliae 5680 appeared to be a sustainable and cost effective option for beekeepers. Although a higher dose of Metarhizium anisopliae 3020 was used, M. anisopliae 5680 provided better control of small hive beetle populations while maintaining hive health in the 73- day study. DNA fingerprinting of unknown pathogens retrieved from cadavers collected during the field trials indicated saprophytic fungi and potential microbial control agents.
The purpose of this project is to evaluate the fungal pathogen (Metarhizium anisopliae) against the small hive beetle Aethina tumida for the development of a sustainable approach to controlling this invasive pest species in hives in Florida. The European honey bee, Apis mellifera is the most economically important insect of agricultural crops worldwide, not only for honey production, but also for crop pollination (Sweetser, 2009). In the U.S., bee pollination of agricultural crops accounts for about one-third of the U.S. diet (Sanford, 1999). The monetary value of honey bees as pollinators in the United States is estimated at about $14.6 billion annually (Morse and Calderone, 2000). This estimate includes the benefit of production attributable to honey bees in terms of the yield increase and achieved quality from honey bee pollination, including the indirect benefits of bee pollination required for seed production of some crops. Many agricultural crops are almost totally dependent on honey bee pollination, including almonds, apples, avocados, blueberries, cranberries, cherries, kiwi fruit, macadamia nuts, asparagus, legume seeds, pumpkins, squash, and sunflowers. Honey bees also contribute to biodiversity by pollinating other wild types of plants, and honey products and bee venom are important in health food and alternative medicine. However, honey bee colonies in the U.S. have declined drastically over the past few years (Ellis et al., 2004). A new and invasive pest species, Aethina tumida (small hive beetle) is responsible for substantial loss of honey bee colonies over the last four years. Adults are long lived; surviving up to 181 days and females may lay up to 2000 eggs in their life time (Lundie, 1940). Research has found that this pest can produce up to five generations per year (Lundie, 1940). The rapid spread and high reproductive potential of the SHB both within colonies as well as in stored products coupled with the ability to hibernate in honey bee clusters make it a serious threat of apiculture (Hood, 2000). Studies also show that SHB are potential biological vectors for honey bee viruses which also make them a threat to apiculture (Eyer, 2008) Substantial damage to the honey bee colonies is caused mainly by the feeding of larvae of SHB on honey, pollen and live brood. They also tunnel and pierce wax combs; defecate in and ferment stored honey causing it to weep and froth away from the cells (vanEngelsdorp et al., 2004). It only takes two or three beetles to cause severe damage to a pile of supers (Lundie, 1940). As a result, there is a drastic reduction of all feral and managed honey bee populations and this situation threatens honey production, as well as the crops that rely on honey bees for pollination. Currently, there is no effective control measure for SHB even with the emergency use permit for in-hive application of Coumaphos (Elzen et al., 1999). In addition, the efficacy of soil drench under infested colonies with permethrin (GardStar 40% EC) is dependent on the timing of the applications (Neumann, 2004).
Although insecticides have shown a substantial efficacy in managing pest, they have also raised concern for environmental protection. Over use of insecticides can cause resistance or lead to a resurgence of a pest (Hood, 2010). Current research now focuses on methods of biological control. Biological control involves effective use of parasitoids, predators, pathogens, antagonists, or competitor populations to suppress a pest population making it less abundant and thus less damaging (Driesche and Bellows, 1996). Traditionally, it is the manipulated reduction of an insect population by natural enemies, parasites, and pathogens. Further development of biological control agents will lead to the reduction of chemical applications in honey production, the increase in the health of honey bee colonies, and the enhancement of crop pollinations. The evaluation of entomopathogenic fungi against SHB offers relevant biological control option for a successful pest management program. Some entomopathogenic fungi have shown virulence and specificity against a range of insect hosts. Entomopathogenic fungi can be found in various places and can be isolated from insects, soil, and other substrates. Metarhizium anisopliae and Beauveria bassiana, have been used to effectively control other species of Coleoptera, thus these fungi could provide new avenues for an environmentally sound management of the small hive beetle populations. Both M. anisopliae and B. bassiana were found to be harmless to honey bees (Kanga et al., 2003) Scientists have demonstrated that honey bees could be used to vector fungal control agents for control of certain coleopteran (Shipp et al., 2008) Successful control could be achieved by exposing pest populations to the most efficient fungi at the optimal concentration. Previous laboratory studies have shown that Metarhizium anisopliae and Beauveria bassiana could be used as biological control agents against the small hive beetle in soil treatments (Somorin, 2009). That same study indicated that the small hive beetle was more susceptible to M. anisopliae (Somorin, 2009).This project will consist of applied research that will investigate the feasibility of the use of M. anisopliae in effective concentrations and the optimal dispersal of entomopathogenic propagules in the field.
To determine if mortality was due to fungal infection, dead SHB (larvae or adults) were collected from the treatments and the controls. The cadavers were collected from the hive or lab rearing jars then surface-sterilized, by immersing in a sterilant disinfectant, Expor (Expor, Alcide, Redmond, WA) for 3 minutes and rinsed once with 95% ethanol for 2 minutes. The cadavers were then transferred with soft wide-tip forceps to a sterile paper to dry the ethanol, and later the specimens were plated on PDA (Potato Dextrose Agar) in a sterile hood then incubated at 27± 1 ºC for 4-10 days. Cadavers retrieved from beetle traps were plated directly on to PDA media and incubated. The Petri dishes were sealed with parafilm strips and labeled with date and description prior to incubation. Dead SHB were observed daily for the presence of external fungal hyphae. Only SHB that showed fungal growth were considered to have died of infection and used in the data analysis.
Chemical control measures are currently being used against the small hive beetle but they are inefficient and unsustainable. Therefore, the main objective if this study was to investigate biological control of the small hive beetle. The specific objective of this study was:
i. To determine the impact of M. anisopliae on small hive beetle survival and development in soil treated bioassays in the field.