Habitat manipulation of the apple orchard floor to increase ground-dwelling predators and predation of Cydia pomonella (L.) (Lepidoptera: Tortricidae)

Abstract

Augmenting generalist predator populations in new apple (Malus domestica Bork) plantings could potentially aid in the establishment of balanced orchard ecosystems that are less susceptible to pest outbreaks. Habitat can be an important factor in retaining predators in a system and can affect predator efficiency. We investigated the potential of increasing a complex of generalist ground-dwelling predators and enhancing biological control in a young ÔGolden DeliciousÕ apple orchard through ground habitat manipulation. We modified the orchard floor with four comparative habitat treatments: (1) detritus-rich compost mulch layer, (2) detritus-free synthetic mulch layer, (3) herbicide-treated vegetation thatch, and (4) bare soil with vegetation hand-removed. Relative abundances of predators and alternative prey in the habitats were measured with pitfall trapping throughout the growing season. Predation was measured using sentinel Cydia pomonella larvae and directly observed in night experiments. Throughout the season, the compost mulch treatment consistently supported significantly greater densities of alternative prey resources for predators, and generalist predators were more abundant in the compost mulch than the other habitats. Predator complex abundance was positively correlated with increasing alternative prey availability in the compost mulch habitat. However, predation of C. pomonella was significantly lower in the compost mulch than in the herbicide-treated thatch habitat. Our study revealed that a prey-rich organic mulch can enhance ground-foraging generalist predators on the orchard floor, but habitat structure may be more important than alternative prey for predation of C. pomonella.

Local, landscape, and diversity drivers of predation services provided by ants in a coffee landscape in Chiapas, Mexico

“…We assessed ant predatory impact by examining removal rates of two sentinel prey items, frozen (and presumed dead) West Indian fruit flies (Anastrepha obliqua Macquart) and coffee berry borers that were added to forest and coffee sites. In many studies with sentinel prey, prey items are restricted from moving by being glued (Armbrecht and Perfecto, 2003) or tethered (Jedlicka et al, 2011;Mathews et al, 2004) to observation locations. Other studies restrict prey movement by using frozen (and thus dead) prey items (e.g., Gardiner et al, 2014;Jones et al, 2001;O'Neal et al, 2005;Prasifka et al, 2006).…”

Plastic mulch effects on ground beetle communities (Coleóptera: Carabidae) in an organic blueberry field

“…The number of captures recorded with synthetic cover (T2) may be due to this inert material providing less availability of alternative food (such as saprophytes) for generalist predators such as the carabids (Ceccanti et al, 2007). In agreement with this interpretation, Mathews et al, (2004) demonstrated that plastic cover significantly reduced the availability of alternative food for the complex of soil predators present in an apple orchard, while a cover of compost, high in organic matter, favored the presence of both alternative prey and predators. Similarly, working with spiders, Birkhofer et al (2008) showed that the presence of organic matter triggered an increment in the availability of alternative prey (mainly dipteran larvae) and that this produced an increase in spider abundance and their control over aphids in wheat.…”

“…According to Mathews et al (2004), complex structures composed of plant remains are capable of providing adequate safe sites from other predators, which also protect the carabids from direct exposure to sunlight, resulting in increase in prey capture compared to those recorded using more simple structures. In this case the synthetic cover (T2) is a simple structure, while the cover with pine needles is more complex, thus the microclimatic conditions generated in these structures may explain the differences observed.…”

“…Also, the optical properties of the materials utilized modify the radiation balance in the soil surface, producing changes in temperature both under the cover and on the surface. These factors may affect positively or negatively the crop and other organisms present in agro systems, such as some populations of arthropods important in agriculture, including both pests and their natural enemies (Miñarro & Dapena, 2003;Mathews et al, 2004;Szendrei & Weber, 2009). The manipulation of the habitat of predatory arthropods, in this case by installing a cover, may alter not only the abundance but also the diversity of species present in the system, which could impact the efficiency of biological control by these organisms (Cardinale et al, 2006).…”

Alternatives to Chemical Control of Insect Pests

“…Candidate plants include small trees, shrubs, bushy perennials, and tall ornamental grasses with dense canopies or complex architecture. Similarly, organic mulches and ground cover plants can support large numbers of ground-dwelling predators like spiders and ground beetles (Bell et al, 2002;Mathews et al, 2004;Rieux et al, 1999;Snodgrass & Stadelbacher, 1989), which may enhance biological control of key pests (Brust, 1994). Finally, resource plants can enhance reproduction of natural enemies and provide refuge from their own enemies (Landis et al, 2000;Rabb et al, 1976).…”