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Wild Blueberries

Wild Blueberries

Wild blueberry (Vaccinium angustifolium Ait) is native to Northeastern North America and is one of Nova Scotia’s most important crops (Sutton, 1993). In 2017, the lowbush blueberry industry contributed over $100 million to the provincial economy (Anonymous, 2018) and was Nova Scotia’s largest agricultural export at $76.3 million (Nova Scotia Department of Agriculture, 2018). The perennial lowbush blueberry is a small deciduous shrub that reproduces through secondary seed dispersal from birds or mammals (Vander Kloet, 1978), but mainly reproduces clonally through extensive underground rhizome systems (Bell, 1950). Lowbush blueberries thrive in a wide-range of conditions but predominately occur on well-drained soils with a pH of 4-5 (Hall et al., 1964; Jensen & Yarborough, 2004).

Integrated Pest Management Strategies Using Biological Weed Control

Biological control for weeds is achieved through use of classical and augmentative biocontrol, the use of grazing animals, or through conservation of natural weeds enemies (Naranjo et al., 2015). The use of classical, augmentative, and grazing animal approaches relies on humans to introduce or apply living organisms to weed populations for weed control (Naranjo et al., 2015). In contrast, conservation biological control is the modification or protection of the surrounding environment to safeguard and enhance favorable conditions for existing natural enemies (McFadyen, 1998). The use of biological controls in agriculture incorporates natural enemies of pests and is a critical component for economic success and sustainability. For instance, in 2013, biological control by insects was estimated to provide a net-benefit of $5.5 billion in the United States alone.

Field Crickets as Natural Enemies

The field cricket, G. pennsylvanicus  is found throughout northeastern North America and is among the most well distributed crickets in the region (Carmona et al., 1999; Lundgren, 2009). G. pennsylvanicus are recognized as natural enemies in various agricultural systems (Carmona et al., 1999; Cutler et al., 2016; Lundgren & Rosentrater, 2007; O’Rourke et al., 2006; van der Laat et al., 2015) and while they are predominantly herbivorous, they also exhibit omnivorous behaviour and consume dead and living insects, broadleaf plant leaves, grasses, and seeds (Carmona et al., 1999).

Seed Characteristics

Weed seeds are an abundant, nutritious food source for granivorous insect communities (Lundgren & Rosentrater, 2007). That said, these seeds have developed structural and chemical features to help defend themselves from granivory, which in turn, influences the insect’s seed preferences. Seed preference among and within granivorous insect taxa is dependent on a number of factors including seed size (Honek et al., 2007), hardness (Lundgren & Rosentrater, 2007), nutritional quality (Kulkarni et al., 2015), density (Lundgren & Rosentrater, 2007), exposure (i.e. buried vs on soil surface) (White et al., 2007), sprouted vs unsprouted (Carmona et al., 1999), and allelochemicals (Honek et al., 2007).

Size

Within the plant kingdom, seed sizes range over ten orders of magnitude with the outermost measures belonging to some species of orchids as the smallest and the diaspore of the coconut palm as the largest (Booth et al., 2010). Seed size is amongst the most influential factors in terms of the dietary preferences of seed consumers. Theoretically, organisms should prefer large seeds with the highest nutrition in respect to smaller seed species with less nutrition per seed to optimize their net energy intake (Schoener, 1971).

Seed Coat Strength

In addition to seed size, the seed coat strength can enhance the seeds chances of germination within their environment and likewise, defend them from granivory. The testa, or seed coat is generally made up of layers of wax and fat which creates a tough, defensive, encapsulating shell that helps protect the seed from destruction. To test the strength of a seed, the force that is necessary to fracture the seed coat and allow access to the core nutrients is measured using compression computer control software (Lundgren & Rosentrater, 2007). It was found that strong seeds requiring more than 20 N to fracture them were less preferred by two ant species (Rhytidoponera metallica and Pheidole sp. 4) (Rodgerson, 1998).

Density

In addition to seed size and strength, another potential preference among granivores is their ability to assess the density of a seed. Lundgren and Rosentrater (2007) found that seed density was influential for granivorous insects Anisodactylus sanctaecrucis and Harpalus pensylvanicus with denser seeds being the only noted characteristic that positively influenced A. sanctaecrucis’ feeding choices. That said, preferences based on seed density is largely understudied, and further studies should be carried out to determine how this can affect other granivores.