The soybean aphid, Aphis glycines Matsumura, has become the single most important arthropod pest of soybeans in North America. Native to Asia, this invasive species was first discovered in North America in July 2000 and has rapidly spread throughout the northcentral United States, much of southeastern Canada, and the northeastern United States. In response, important elements of the ecology of the soybean aphid in North America have been elucidated, with economic thresholds, sampling plans, and chemical control recommendations widely adopted. Aphid-resistant soybean varieties were available to growers in 2010. The preexisting community of aphid natural enemies has been highly effective in suppressing aphid populations in many situations, and classical biological control efforts have focused on the addition of parasitoids of Asian origin. The keys to sustainable management of this pest include understanding linkages between the soybean aphid and other introduced and native species in a landscape context al...

Ecology and Management of the Soybean Aphid in North America

Declining species number (richness) harms ecosystems, and conservation efforts have largely focused on conserving or restoring particular rare species. However, greater disparity in species relative abundances (evenness) might also do ecological harm, which could only be reversed by altering the densities of many species at once. A new survey of organic and conventionally managed potato fields shows that species evenness is greater under organic management. Replicating these levels of evenness in a field trial shows that the evenness of natural enemies found in organic fields promotes pest control and increases crop biomass. In organic crops many beneficial species (that eat pest insects) are equally common, which in potatoes leads to fewer pests and larger plants. A survey of organic and conventional potato fields shows that species evenness is greater under organic management. Replicating these levels of evenness in a field trial shows that the evenness of natural enemies found in organic fields promotes pest control and increases crop biomass. This is independent of the identity of the dominant enemy species, so is a result of evenness itself. Human activity can degrade ecosystem function by reducing species number (richness)1,2,3,4 and by skewing the relative abundance of species (evenness)5,6,7. Conservation efforts often focus on restoring or maintaining species number8,9, reflecting the well-known impacts of richness on many ecological processes1,2,3,4. In contrast, the ecological effects of disrupted evenness have received far less attention7, and developing strategies for restoring evenness remains a conceptual challenge7. In farmlands, agricultural pest-management practices often lead to altered food web structure and communities dominated by a few common species, which together contribute to pest outbreaks6,7,10,11. Here we show that organic farming methods mitigate this ecological damage by promoting evenness among natural enemies. In field enclosures, very even communities of predator and pathogen biological control agents, typical of organic farms, exerted the strongest pest control and yielded the largest plants. In contrast, pest densities were high and plant biomass was low when enemy evenness was disrupted, as is typical under conventional management. Our results were independent of the numerically dominant predator or pathogen species, and so resulted from evenness itself. Moreover, evenness effects among natural enemy groups were independent and complementary. Our results strengthen the argument that rejuvenation of ecosystem function requires restoration of species evenness, rather than just richness. Organic farming potentially offers a means of returning functional evenness to ecosystems.

Organic agriculture promotes evenness and natural pest control

Chlorpyrifos is a member of the organophosphorus or organophosphate class of insecticides. This class has become one of the most widely used groups of pest control chemicals. In 1989 nearly 40% of the $6.2 billion global insecticide market was comprised of organophosphates (OPs) (Phillips and McDougall 1990). Although Clermont (1854) had first synthesized tetraethylpyrophosphate (TEPP), it was not until much later that the insecticidal properties of this OP were described (Schrader 1942). This milestone led to further synthetic work with insecticidal OPs and thus provided the impetus that would lead to the launch of an entirely new class of insecticides. Early OPs found to be efficacious for insect control and thus brought into widespread use included parathion (1944) and malathion (1952) (Matsumura 1985). These successes stimulated further discovery work on the part of synthetic chemists and entomologists within a number of research organizations.

Environmental Fate of Chlorpyrifos

PERSPECTIVES AND OVERVIEWThe behavior of insects, and all animals, is governed by interactions amongneurons within their nervous systems. Insecticides have been selected andsometimes designed for their remarkable ability to kill insects. Most attackspecific sites within the insect’s nervous system (59, 63; see section on modesand sites of action). Therefore it is not surprising that insecticides at levelsthat do not lead to mortality can influence behavior. However, there havebeen few detailed studies concerning the potential behavioral effects ofsublethal doses of insecticides.Studies of the behavioral effects of neurotoxicants are important for severalreasons (89). First, detailed observations of the behavioral symptoms poisoned insects will help to elucidate the modes of action of both novel andconventional insecticides. Second, it is clear that almost all insecticidesinterfere with the normally well-orchestrated behavioral patterns of pestinsects and thus might contribute to management of their populations. Animportant related point is that beneficial insects may be adversely affected bythese compounds in a way that is overlooked by current screening procedures.Lastly, selection may favor those insects that respond to insecticides in theenvironment by minimizing their contact with the toxic material; thus thepotential for evolution of behavioral resistance to insecticides is anotherimportant consideration.Insecticides are the cornerstones upon which pest management practices arebased, and are likely to remain so as long as effective and inexpensivechemicals are available. However, many insect-pest management techniques1490066-4 170/88/0101-0149 $02.00Annual Reviews www.annualreviews.org/aronline

Sublethal Effects of Neurotoxic Insecticides on Insect Behavior

Synthetic pyrethroid insecticides are photostable analogs of the natural pyrethrins of botanical origin. Their structures range from very similar to the original (e.g., allethrin, Fig. 1) to highly dissimilar compounds (e.g., flucythrinate, Fig. 1). Directed synthesis by groups in Japan (Sumitomo Chemical Co.) and England (NRDC) resulted in very potent insecticides and a commercial success for the synthetic pyrethroids.

Comparative toxicology of the pyrethroid insecticides.

Host aphids of the parasitoid Diaeretiella rapae (M’Intosh,) are defined for Washington State, together with a listing of world findings. Specifics are given on host habitats frequented by the parasitoid, comparative population abundance, associated parasitoid species, and host switching. D. rapae is a common parasitoid of Brachycorynella asparagi (Mordvilko), Hayhurstia atriplicis (L.), Brevicoryne brassicae (L.), Diuraphis noxia (Kurdjumov), and sometimes Myzus persicae (Sulzer). In total, 19 species of aphids were positively linked with D. rapae and 6 are reported as hosts for the first time— Acyrthosiphon lactucae (Passerini), Phorodon humuli (Schrank), Dysaphis plantaginea (Passerini), Brachycaudus tragopogonis (Kaltenbach), Uroleucon ivae Robinson, and Braggia sp. D. rapae was shown to switch or alternate successfully between hosts, which suggests that certain host habitats might be used in conjunction with farmlands to enhance host opportunities for the parasitoid and improve its population stability. Two of its primary aphid hosts, B. asparagi and D. noxia, reached pest status shortly after their arrival in Washington but are less problematic today, in part at least because of host switching and acceptance by D. rapae.

Host range and habitats of the aphid parasitoid Diaeretiella rapae (Hymenoptera: Aphidiidae) in Washington State.

Aphid parasitoids (Hymenoptera: Braconidae: Aphidiinae) of Northwest USA.

In the northwestern United States, insect pests of potatoes (Solanumtuberosum L.) have typically been controlled using broad-spectrum insecticides. However, the loss or impending loss of many broad-spectrum chemicals is increasing the use of selective insecticides, and organic potato production is growing in the region. In the 2001 and 2002 growing seasons, we intensively sampled the arthropods in 31 (14 in 2001 and 17 in 2002) production potato Þelds under three pest management regimens: conventional Þelds treated with broad-spectrum insecticides (Hard), conventional Þelds treated with selective insecticides (Soft), and organic Þelds treated with insecticides certiÞed for organic production (Organic). All Þelds were within the Columbia Basin of Washington, grown under center-pivot irrigation. We sampled arthropods using three techniques: D-vac suction sampling, pitfall trapping, and visual searching. Geocoris spp. and Nabis spp. bugs (Hemiptera) and spiders (Araneae) were the most abundant predators in plant foliage, together making up 90% of the foliar predator community in both years. Total predator densities and densities of Geocoris, Nabis, and spiders not in the family Linyphiidae were highest in Organic and Soft, and lowest in Hard Þelds. Linyphiid spider densities were marginally elevated in Soft compared with Hard Þelds. On the ground, carabid (Coleoptera: Carabidae) and staphylinid (Coleoptera: Staphylinidae) beetles and a diverse group of spiders dominated the community, together making up 90% of the ground-active predator com- munity in both years. Total predator densities and densities of carabid beetles, staphylinid beetles, and linyphiid spiders were highest in Organic and Soft and lowest in Hard Þelds, whereas densities of these arthropods did not differ between Organic and Soft. Densities of nonlinyphiid spiders were highest in Organic, intermediate in Soft, and lowest in Hard Þelds. While predator densities were generally high in organic Þelds, these Þelds also had the highest densities of the two most injurious insect pests, the green peach aphid (Myzus persicae Sulzer) and the Colorado potato beetle (Leptinotarsa decem- lineata Say). Selective insecticides allowed conventional growers to achieve predator densities similar to those seen in organic Þelds while retaining low pest densities typical of Þelds treated with broad-spectrum insecticides.

https://www.fcnym.unlp.edu.ar/catedras/controlbiologico/TP%201%20Predadores%20en%20papa.pdf

Comparison of Predator and Pest Communities in Washington Potato Fields Treated with Broad-Spectrum, Selective, or Organic Insecticides

New information is provided on the small-grain aphid parasitoids of eastern Washington—species population diversity, relative abundance, hosts, and spatial and temporal distribution across differing precipitation and cropping zones. In total 13 species of primary parasitoids were discovered attacking grain aphids: Aphelinus albipodus Hayat & Fatima, A. asychis Walker, A. varipes (Foerster), Aphidius avenaphis (Fitch), A. ervi Haliday, A. matricariae Haliday, Diaeretiella rapae (M'Intosh), Ephedrus sp., Lysiphlebus testaceipes (Cresson), Monoctonus washingtonensis Pike & Star´y, Praon unicum Smith, P. occidentale Baker, and P. yakimanum Pike & Starý. The predominant parasitoids were D. rapae on Russian wheat aphid, Diuraphis noxia (Kurdjumov); L. testaceipes on bird cherry-oat aphid, Rhopalosiphum padi (L.) and corn leaf aphid, R. maidis (Fitch); and A. avenaphis, A. ervi , and D. rapae on English grain aphid, Sitobion avenae (F.). This study provides baseline information essential for assessing future changes in aphid parasitoid species dynamics for eastern Washington. A comprehensive key to the known primary and secondary parasitoids associated with grain aphids in North America also is provided.

Small-Grain Aphid Parasitoids (Hymenoptera: Aphelinidae and Aphidiidae) of Washington: Distribution, Relative Abundance, Seasonal Occurrence, and Key to Known North American Species

Pentalonia nigronervosa (sensu Hardy 1931) samples from banana and from Zingiberaceae and Araceae species exhibit fixed differences in DNA sequence in mitochondrial cytochrome oxidase subunit 1 (“DNA barcode”) and in the nuclear gene elongation factor 1α, and have morphometric differences, including non-overlapping ranges in the length of the distal rostral segment. It is thus proposed that the name P. nigronervosa Coquerel be restricted to banana-feeding ‘nigronervosa’ specimens, and that the name Pentalonia caladii van der Goot be restored to full species status for specimens typically feeding on Zingiberaceae and Araceae.

/pdf/the-identity-of-pentalonia-nigronervosa-coquerel-and-p-3xr4n0zxni.pdf

Keith S. Pike

Papers

Host range and habitats of the aphid parasitoid Diaeretiella rapae (Hymenoptera: Aphidiidae) in Washington State.

Aphid parasitoids (Hymenoptera: Braconidae: Aphidiinae) of Northwest USA.

Comparison of Predator and Pest Communities in Washington Potato Fields Treated with Broad-Spectrum, Selective, or Organic Insecticides

Small-Grain Aphid Parasitoids (Hymenoptera: Aphelinidae and Aphidiidae) of Washington: Distribution, Relative Abundance, Seasonal Occurrence, and Key to Known North American Species

The identity of Pentalonia nigronervosa Coquerel and P. caladii van der Goot (Hemiptera: Aphididae) based on molecular and morphometric analysis