As decomposers, predators, and pollinators, insects play a vital role in ecosystem health, e.g., decomposers help aerate the soil, turning more soil than earthworms, and increasing soil rainwater retention and tillage (Pimentel, 2002). Predatory insects help keep the natural system in balance and prevent explosive pest population growth from taking over essential natural resources. There are over 6000 insect species that have been considered biological control agents and are being used to fight insect and weed pests (Pimentel, 2002). Moreover, countless other insect species act as pest population regulators but often go unnoticed. Insects also are a crucial part of food security in the United States, with 87 of the leading 115 food crops depending on insect pollinators (U.S. Fish and Wildlife Service, 2016).
Plants use a variety of characteristics, such as color, shape, and odor, to attract insects ensuring that these flower visitors will not leave without being dusted with pollen. Certain flower types are adapted for attracting particular insect groups, such as bees, butterflies, wasps, moths, beetles, and flies (Lázaro and Totland, 2014). Many plants depend on their mutualistic relationships with pollinating arthropods for survival. In turn, pollinators rely on flowering plants to acquire food including pollen and nectar (Kearns and Inouye, 1997).
Research shows that pollinators contribute to 35% of the world’s food production and 24 billion dollars in the U.S. economy (Astegiano et al., 2015). Likewise, native pollinators, such as bumble bees, sweat bees, and leafcutter bees, provide crop benefits that are valued at more than 9 billion dollars (Astegiano et al., 2015). Evidence suggests that pollinating insects of many important plants are declining worldwide (Astegiano et al., 2015; Fukase and Simons, 2016; NRC National Research Council, 2007). Land use, loss, and fragmentation of habitat, modern agricultural practices, and pesticide use pose great threats to insect pollinators and natural enemies (Nicholls and Altieri, 2013). Since 2006, it has been reported that western honeybee (Apis mellifera L.) colony loss rates have increased to an average of 30% each winter due to a variety of factors including loss of natural forage and inadequate diets, mite infestation and diseases, loss of genetic diversity, and exposure to certain pesticides (Astegiano et al., 2015). Other native pollinators, including bumble bees and monarch butterflies (Danaus plexippus L.), have experienced population declines as well (NRC National Research Council, 2007). Systemic pesticides used in production of agricultural products, including ornamental plants, as one of the factors contributing to declining pollinator health (Astegiano et al., 2015).
Providing essential floral resources to natural enemies and pollinating insects can increase biological control and pollination (Fiedler and Landis, 2007; Woltz et al., 2012). Research suggests a diverse butterfly population can be attained through the addition of annual, perennial, and woody shrub ornamental species to a landscape (Poythress and Affolter, 2015; Wilde et al., 2015). Several studies have noted that gardens provide resources through flowers as well as nesting areas that contribute to the survival and reproduction of bees (Frankie et al., 2005; Matteson et al., 2008; McIntyre and Hostetler, 2001). Likewise by attracting pollinators and beneficial insects, ecosystem services can also be attained.
By monitoring pollinator and beneficial insect occurrence within habitat management sites through the use of sweep-net sampling and visual observations, ornamental plant species can be evaluated for their arthropod attractiveness and the provision of arthropod-mediated ecosystem services including pollination and biological control in southeastern landscapes (Kremen et al., 2007). The goal of this study was to provide detailed information on the attractiveness of a wide selection of ornamental floral resources to pollinators, natural enemies, and phytophagous insects as detailed and systematic assessment of pollinators and biological predators on plant species have been limited.
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