Mark W. Brown

Role of aphid predator guild in controlling spirea aphid populations on apple in West Virginia, USA

Abstract Spirea aphid populations and their predators were studied on apple to identify predators of importance in controlling aphid populations. Methods included random and non-random sampling from apple orchards in West Virginia, USA, sentinel aphid colonies, laboratory feeding studies, and predator exclusion studies. Aphidoletes aphidimyza (Diptera: Cecidomyiidae), chrysopids (Neuroptera: Chrysopidae), Harmonia axyridis (Coleoptera: Coccinellidae), and Orius insidiosus (Hemiptera: Anthocoridae) were the most abundant predators associated with spirea aphid colonies on apple. Parasitoids were all but absent in the study. Abundance of all predators was density dependent with greater responses to aphid populations at the orchard scale than to tree or individual colony scales. A. aphidimyza, O. insidiosus, chrysopids, and syrphids (Diptera) had the greatest degree of density dependence on aphid populations, and spiders showed inverse density dependence. Exclusion of predators with both cages and insecticides produced significantly higher aphid populations. Because of high abundance, good synchrony with aphid populations, and high impact per individual, H. axyridis adults were the most important spirea aphid predator on apple.

Effect of floral and extrafloral resources on predation of Aphis spiraecola by Harmonia axyridis on Apple

Flowering companion plants and plants producing extrafloral nectar are being proposed to enhance biological control in apple (Malus domestica Borkh.) orchards. This experiment evaluated the impact of floral and extrafloral resources on predation of spirea aphid (Aphis spiraecola Patch) on apple by adult Harmonia axyridis (Pallas) under greenhouse conditions. Predation of spirea aphids was not affected by the presence of flowering buckwheat (Fagopyrum esculentum) as compared with either buckwheat with flowers removed or an uninfested apple shoot. However, there was a significant reduction in predation of spirea aphids on an apple shoot in the presence of a peach shoot with extrafloral nectar glands compared with either a peach shoot of the same cultivar without nectar glands or an uninfested apple shoot. These findings demonstrate that alternative food resources potentially could interfere with rates of biological control and, therefore, need to be carefully evaluated before incorporating in an orchard design. More studies are needed to adequately gauge the net effects of adding floral or extrafloral resources in orchards for conservation biological control.

A comparison of conventional and alternative understory management practices for apple production: multi-trophic effects

Modification of the soil for agricultural production is commonly studied as it relates to plant health and productivity, but the implications at other trophic levels are often over-looked. This study addressed the effects of orchard understory management at several trophic levels to understand potential impacts on the whole system. The soil in a newly planted Golden Delicious apple (Malus domestica Bork.) orchard was modified with four treatments: (1) mulch layer of composted poultry manure, (2) mulch layer of synthetic fiber, (3) conventional herbicide, and (4) hand-weeded control. These treatments were evaluated for their impact on edaphic and arboreal arthropods, substrate microclimate and weed growth, and apple tree vigor during the first year of growth (1998). Understory treatment affected edaphic arthropods at three trophic levels: detritivore, herbivore, and predator. Compost mulch significantly increased both edaphic detritivores and predators. Edaphic herbivores were less abundant in plots treated with synthetic mulch. No effect was found for arboreal herbivores, but aphidophagous Aphidoletes aphidimyza (Cecidomyiidae) larvae were more abundant on trees in compost-treated plots. Host-plant growth and leaf quality (% N) were also affected by soil management, with a higher average trunk diameter and lower average leaf nitrogen (%) in compost-treated plots, despite equivalent N-input in all four treatments. Both mulches (compost and synthetic) resulted in lower soil temperatures and higher soil moistures and suppressed weed growth 10-fold better than either conventional herbicide or hand weeding. The results indicate that soil modification affects organisms at several trophic levels, and therefore, could hold important implications for the orchard ecosystem as a whole. Overall, mulching with composted manure benefited the whole orchard system the most and was superior to conventional herbicide as an understory management practice.

Leaf Extrafloral Nectaries Enhance Biological Control of a Key Economic Pest, Grapholita molesta (Lepidoptera: Tortricidae), in Peach (Rosales: Rosaceae)

Abstract Extrafloral nectaries (EFNs) in many plant species produce sugary secretions that commonly attract ants. This research determined the impact of peach (Prunus persica L. Batsch) EFNs on the biological control of the oriental fruit moth, Grapholita molesta (Busck) (Lepidoptera: Tortricidae), a key economic pest in peach orchards, and studied interactions of EFNs and ants. Studies (2002–2005) in peach orchards of the mid-Atlantic United States showed that ‘Lovell’ peach trees with EFNs supported more parasitic Hymenoptera in the spring and increased the parasitism of G. molesta larvae later in the season than those trees without EFNs. Ant exclusion experiments revealed that trees with EFNs harbored fewer G. molesta larvae when ants were permitted access to the tree canopies. Furthermore, the trees with EFNs had ≈90% less fruit injury by G. molesta, indicating that EFNs have a protective role for the fruit as well. The results show that the combined actions of ants and parasitic Hymenoptera confer an EFN-mediated protective effect spanning the whole fruit growing season. When EFNs are present, naturally occurring biological control agents can reduce damage by G. molesta in peach orchards without insecticide inputs. The EFNs are an important host-plant characteristic that should be retained in future peach cultivar selections as a means of enhancing biological control.

Interactions between Extrafloral Nectaries, Ants (Hymenoptera: Formicidae), and Other Natural Enemies Affect Biological Control of Grapholita molesta (Lepidoptera: Tortricidae) on Peach (Rosales: Rosaceae)

ABSTRACT Extrafloral nectaries (EFNs) are reported to benefit some plants when ants (Hymenoptera: Formicidae) use their secretions and fend off herbivores, but in some cases resulting competitive interactions may reduce biological control of specific herbivores. This research examined the interactions between ants and other natural enemies associated with the EFNs of peach [Prunus persica (L.) Batcsh] and the implications for biological control of a key pest, the oriental fruit moth [Grapholita molesta (Busck)]. Studies using sentinel G. molesta placed on peach trees (‘Lovell’ cultivar) with EFNs present and absent revealed that several natural enemy groups associated with the EFNs contribute to reductions in G. molesta eggs, larvae, and pupae in peach orchards. Ants on trees with EFNs antagonized the G. molesta egg parasitoid Trichogramma minutum (Riley), but the ants were crucial in reducing G. molesta in both the larval and pupal stages. Overall, individual trees with EFNs experienced higher ant and other (nonant) natural enemy densities and subsequent pest reductions, as compared with trees without EFNs. However, the implications of EFN-natural enemypest interactions to orchard-level biological control will likely depend on local G. molesta population dynamics.

Extrafloral nectar in an apple ecosystem to enhance biological control.

ABSTRACT A common goal of conservation biological control is to enhance biodiversity and increase abundance and effectiveness of predators and parasitoids. Although many studies report an increase in abundance of natural enemies, it has been difficult to document increases in rates of biological control. To enhance parasitism of the tufted apple bud moth, Platynota idaeusalis (Walker) (Lepidoptera: Tortricidae), alternate food was provided by interplanting peaches bearing extrafloral nectaries into apple (Malus spp.) orchards. Laboratory studies showed that the presence of nectar increased longevity and parasitism rates by Goniozus floridanus (Bethylidae), the dominant parasitoid of tufted apple bud moth in West Virginia. In orchard studies, we found the total number of hymenopteran parasitoids was higher on peach (Prunus spp.) trees than on adjacent apple trees. Abundance of parasitic Hymenoptera also was significantly higher on the side of traps facing away from rather than toward peach trees, indicating attraction to peach trees. However, total parasitism rates of tufted apple bud moth were not affected by the presence of peach extrafloral nectar in any field studies. Insect injury to fruit at harvest showed that fruit from orchards with interplanted peach trees had less injury from San Jose scale, Quadraspidiotus perniciosus (Comstock) and stink bugs (Pentatomidae) than fruit from an apple monoculture. Although interplanting with peach trees did not produce the hypothesized result of increased biological control, the experiment did have beneficial results for pest management. These results demonstrate the importance of collecting data on variables beyond the targeted species when evaluating habitat manipulation experiments to fully assess the impact on the ecosystem.

Role of biodiversity in integrated fruit production in eastern North American orchards

1 Diversifying agricultural ecosystems to enhance biological control is a promising way of promoting sustainable pest management. 2 In the present study, monoculture apple and peach with standard insecticide treatments were compared with three biodiverse treatments (polyculure, monoculture with companion plants and polyculture with companion plants) with reduced standard insecticide use. 3 Abundance of insect predators was increased by both the presence of companion plants and extrafloral nectar but parasitism of the leafroller Platynota idaeusalis was not affected. 4 There were no consistent effects of biodiversity treatment on either tree growth or fruit yield. Insect injury to Empire apple and peach fruit was not consistently affected by the biodiversity treatments. Granny Smith apples were harvested later than Empire and had more fruit injury in the biodiverse treatments than the standard insecticide control. 5 A reduction in pesticides with added biodiversity proved to be a viable alternative to standard chemical insecticide management for temperate tree fruit. Increases in the natural control of pests resulting from increased plant diversity has promise for reducing the reliance on chemical insecticides for pest suppression.

Biology of Oedophrys hilleri (Faust) (Coleoptera:Curculionidae): A Potential New Pest of Peach in the Eastern United States

ABSTRACT: Oedophrys hilleri (Faust), native to East Asia, has become established in the north-eastern United States. This study examined the feeding preferences of adults, larval food and phenology of adults in an unsprayed peach orchard. Adults fed on the foliage of plants in the Rosaceae family preferring peach (Prunus persicae) and pear (Pyrus communis). There was one generation per year, adults were most abundant in late June to early July but were present whenever trees were actively growing. Eggs were laid on the soil surface. Larvae fed on the fine roots and the cambium and xylem tissues of small woody roots of peach trees; roots of other species were not tested. In field observations, adult feeding removed up to 15% of the foliage on individual branches. An estimated high of 337 adults/m2 emerged from the soil under peach trees based on enclosed emergence traps. Although heavily infested trees showed no apparent loss of vigor compared with trees in the same orchard with low levels of defoliation, this exotic insect could be of concern to growers when combined with other orchard stresses.