Intensive vegetable crop rotations can have detrimental effects on soil health, draining soil of organic matter reserves and necessitating nitrogen (N) inputs. In addition, many vegetable crop rotations leave little time or space to integrate beneficial arthropod and pollinator habitat into crop rotations; the lack of habitat may cause declines in beneficial arthropods, which can lead to insufficient pollination services and increased pest pressure. Nine treatments, each containing one to seven species of cover crops, were evaluated for flowering, aboveground biomass production and N content, soil ${\rm NO}_3^-$-N contribution after biomass incorporation, and beneficial arthropod visitation. A seven-species mix composed of oat (Avena sativa L.), field pea (Pisum sativum subsp. Arvense L.) and five clover species (Trifolium spp.) added the largest amount of biomass (8747 kg ha−1). Likewise, this mix contributed the most organic N (265.6 kg N ha−1), and increased soil ${\rm NO}_3^-$-N after biomass incorporation (10.9 mg ${\rm NO}_3^-$-N kg−1 of soil). Buckwheat (Fagopyrum esculentum Moench) and phacelia (Phacelia tanacetifolia Bendth.) monoculture produced most abundant floral resources. Beneficial arthropods observed included pollinators (native, honey and bumblebees), predators (syrphid flies and green lacewings) and parasitoids. Increased floral diversity was associated with abundance of flies in the Syrphidae family. Phacelia monoculture was most attractive for bees in the Apidae and Halictidae family, both of which may provide pollination services. These results highlight floral visitation patterns as an indicator for beneficial insect community support and conservation, especially in summer months, when greater insect reproduction occurs. Summer-planted cover crops are an underexplored rotation option for organic farming systems in the Upper Midwest, and may provide a wide range of ecosystem services including increases in available soil N and beneficial arthropod populations.

The present study aimed to determine the selectivity of the pyrethroid lambdacyhalothrin on arthropod natural enemy populations in irrigated rice fields in Rio Grande do Sul, Brazil. The study was conducted at three sites: districts of Cachoeira do Sul, Eldorado do Sul and Capivari do Sul during the crop years of 2007/2008 and 2008/2009. Each site consisted of two subareas divided into four plots. One of the subareas received a spray application of 150 ml/ha of lambdacyhalothrin CS 50, while the other subarea was untreated. Arthropods were collected at 2, 15, 30 and 45 days after the application of the insecticide to assess its impact on natural enemy populations. The results indicated consistent differences in natural enemy populations between the treated and untreated areas, especially within the first 2 weeks after the application of the insecticide. Principal components analysis together with χ2 analysis revealed differences in the populations of Tetragnathidae, Anyphaenidae, Araneidae, Coccinellidae, Phytoseiidae and Coenagrionidae between the treated and untreated areas. This study indicated the existence of a great diversity of arthropod natural enemies in irrigated rice fields in a subtropical environment similar to that reported previously from rice fields in tropical environments. In addition, lambdacyhalothrin was shown to be a rapid acting insecticide, with a significant initial decrease in natural enemy populations followed by a rapid recovery beginning at 2 weeks after the application of the insecticide. Especially disconcerting is the severe impact of the insecticide on Phytoseiidae and Araneidae, which are considered key natural enemies for the management of rice pests in southern Brazil.

An annual legume cover crop was evaluated in pecan orchards to increase coccinellids that would reduce pecan aphids. Treatments were a ‘Dixie’ crimson clover and hairy vetch mixture and a grass sod. Coccinellids were abundant on the legume ground covers, but coccinellid density in the tree canopy was rarely affected by ground cover treatment. There were substantial differences between the coccinellid species collected from the legumes and from the trees. In Oklahoma, Olla v-nigrum (Mulsant) and Cycloneda munda (Say) were the main species in the trees, while Hippodamia convergens Guerin, Coccinella septempunctata L, and Coleomegilla maculata lengi Timberlake were dominant species in the legumes. In Georgia, Harmonia axyridis (Pallas) was the dominant species in the trees, and C. septempunctata in the legumes. Pecan aphids at two Oklahoma sites usually were not affected by cover crop treatment, but at the Georgia site, early-season aphids frequently were lower with a legume cover crop than with a grass sod. The accumulated effect of all aphid predators and parasitoids attracted to the legume aphids may have reduced the density of the pecan aphid.