Effect of mulching with cereal straw and row spacing on spread of bean yellow mosaic potyvirus into narrow-leafed lupins (Lupinus angustifolius)

Two field experiments examined the effect of straw spread on the soil surface on the incidence of bean yellow mosaic potyvirus (BYMV) in plots of narrow-leafed lupin (Lupinus angustifolius) sown at narrow (17.5 cm) vs wide (35 cm) row spacing and low (25–30 kg/ha) vs medium (50–60 kg/ha) seeding rates. Virus ingress was by vector aphids flying from adjacent pastures dominated by subterranean clover. In Expt 1, in which BYMV infection was extensive, straw greatly decreased the rate and amount of virus spread regardless of row spacing or plant density, decreasing infection more than 70% by the final assessment date. This effect of straw was attributed to decreased landing rates of incoming vector alates. In the plots without added straw, narrow row spacing decreased BYMV % infection by 38% by the last assessment date. Sowing at the medium seeding rate also decreased infection. The effect of wide row spacing seemed due to delayed canopy closure between rows which is likely to have increased the landing of aphids while the effect of medium seeding rate was attributed partly to the dilution effect of greater plant numbers and partly to the effects of partial canopy development in decreasing landing rates. In Expt 2, in which the incidence of BYMV infection was low, added straw again decreased BYMV spread, but by only 25–27% at final assessment; there were no effects of row spacing or seeding rate. In both experiments, an additional “reference” treatment was included which had a high (90–100 kg/ha) seeding rate, narrow rows and no straw. The dense canopy it developed also decreased BYMV incidence but less than in the plots with added straw in Expt 1. In Expt 1, adding straw and the resulting decrease in plants killed by BYMV, were associated with an overall increase in lupin grain yield of 20%. The greater plant densities resulting from the medium seeding rate also increased grain yield but row spacing did not affect it significantly. These results indicate that retaining stubble on the soil surface at seeding will assist in management of BYMV infection in lupin crops but that wide row spacing in the absence of retained stubble is undesirable.     

Are two strategies better than one? Manipulation of seed density and soil community in an experimental prairie restoration

Restoration practitioners have a variety of practices to choose from when designing a restoration, and different strategies may address different goals. Knowledge of how to best use multiple strategies could improve restoration outcomes. Here, we examine two commonly suggested strategies in a single tallgrass prairie restoration experiment: increased forb sowing density and prairie soil inoculation. We designed a study with two different forb seeding densities. Within these densities, we transplanted seedlings into 1‐m² plots that had been grown in either a whole prairie soil inoculum or sterilized prairie soil. After 4 years, we found positive effects of both high forb sowing density and inoculation treatments on the ratio of seeded to nonseeded plant cover in these plots, and negative effects of both treatments on nonseeded plant diversity. No effects of either treatment were seen on seeded plant diversity. Each strategy also affected the plant community in different ways: high forb sowing density increased seeded forb richness and decreased native nonseeded plant cover, while inoculation decreased non‐native cover, and tended to increase average successional stage of the community. These effects on restoration outcome were typically independent of each other, with the result that plots with both manipulations had the most positive effects on restoration outcomes. We thus advocate the combined use of these restoration strategies, and further studies which focus on both seeding and soil community manipulation in restoration.     

Expanding horizons for herbaceous ecosystem restoration: the Grassy Groundcover Restoration Project

Summary The Grassy Groundcover Restoration Project (GGRP) has sown thirteen 1 ha plots of species‐rich grassland or herbaceous understorey in previously weedy agricultural paddocks in a range of rural locations across southern and western Victoria, Australia. The sown plots are intended as both experimental trials and ‘core’ areas for the restoration of herbaceous communities native to these regions. Approximately 200 species were grown in Seed Production Areas (SPAs) and successfully sown in the field. Species were most successfully established on areas that were scalped prior to seeding, and least successful on plots that were pre‐treated with 1, 2 or 3 years of traditional herbicide weed control. Weed presence was lowest in scalped plots and highest in non‐scalped plots. Long‐term monitoring will be required to understand the development trajectories and degree of persistence of the sown communities, but in the shorter term (3–6 years of post‐seeding) an average of 80% of sown species have established and remain as adult populations. Surveys indicate that in scalped plots (n = 130) vegetation composition, structure and quality has been maintained. Conversely, composition, structure and quality have declined markedly in non‐scalped plots (n = 130). Formal surveys and field observations have also revealed that all sites provide a range of habitats which have been colonized by fauna from a variety of trophic levels. The implications of building on these trials to realize complex grassy ecosystem restoration at larger scales are discussed including the securing of sufficient quantities of high‐quality seed, the use of mechanized broad‐scale direct‐seeding techniques and the effectiveness of using complex mixtures of species early in the restoration cycle.     

Effect of tillage on abundance of Japanese beetle, Popillia japonica Newman (Col., Scarabaeidae), larvae and adults in highbush blueberry fields

Abstract:  At 15 commercial highbush blueberry farms, fields where row middles were tilled had 72% lower larval density of Popillia japonica than fields with grass in row middles. Popillia japonica larval populations were similar in the perimeters of tilled and untilled fields. Soil parameters measured in these sites were not correlated with larval density of P. japonica. Samples of adult beetles on bushes showed that they were significantly less abundant in tilled fields compared with fields with grass in the row middles. The abundance of larvae inside fields during the spring was significantly correlated with early, but not late summer abundance of adult beetles on bushes. Comparisons of different tillage timings showed that grassy plots between rows of blueberry bushes that were tilled in spring and kept bare all year round had lower abundance of P. japonica larvae than those that retained perennial ryegrass. The effect of tillage timing on larval abundance was not consistent across 2 years, but most timings caused similar reduction in P. japonica larval density in the row middles. Tillage in the spring and in the autumn caused 50.5% and 68.8% reduction of larval density in each year respectively. These results indicate that tillage can reduce P. japonica larval and adult abundance in highbush blueberry fields.     

Temporal patterns of diversification in Andean Eois, a species-rich clade of moths (Lepidoptera, Geometridae)

The timing of the origin of present day Neotropical animal diversity is still a matter of debate. For a long time, a preponderance of glacial (i.e. Pleistocene) radiations has been proposed. However, recent data from molecular clock studies indicate a preglacial origin for most of the examined taxa. We performed a fossil-calibrated molecular dating analysis of the genus Eois, which is a major component of one of the world's most diverse assemblages of herbivorous insects. We found that diversification of Eois took place in the Miocene following a pattern best explained by density-dependent diversification. A strong slowdown of diversification towards the present was detected. Diversification of Eois does overlap with increased Andean uplift and diversification of the most commonly used host plant genus Piper. These findings match the patterns found for the majority of Neotropical tetrapods and for three other unrelated, ecologically different lepidopteran genera.     

Present and future prospects for entomopathogenic nematode products

Entomopathogenic nematodes in the genera Steinernema and Heterorhabditis have emerged as excellent candidates for biological control of insect pests. Attributes making the nematodes ideal biological insecticides include their broad host range, high virulence, safety for nontarget organisms and high efficacy in favourable habitats. Progress achieved in liquid fermentation, formulation stability and application strategy has allowed nematode‐based products to become competitive with chemical insecticides in medium‐ and high‐value crops on the basis of cost/benefit ratio and ease of application. Further technological advancements are needed to expand and improve the market potential of the nematode‐based products.     

Oat residue and soil compaction influences on common root rot (Aphanomyes euteiches) of peas in a fine-textured soil

Management of common root rot (Aphanomyces euteiches Drechs.) in peas (Pisum sativum L.) is sought primarily by host crop avoidance for several years. Soil compaction is known to aggravate A. euteiches disease in peas but effects on infection and subsequent symptom development are not sufficiently known to assist in cultural control. Several isolated observations have noted that oat crop residues may suppress A. euteiches infection and disease in pea roots. The individual and combined influence (a factorial combination of two factors each at two levels) of a prior oat crop and soil compaction were studied for their effects on common root rot severity in processing peas grown in an A. euteiches disease nursery on a fine-textured soil in the northern Corn Belt of the USA. A previous crop of summer oats relative to prior-year peas significantly suppressed common root rot and increased pea fresh vine weight 210% at peak bloom stage. Both fresh vine weight and green pea yield were reduced as much as 63% by soil compaction and increased as much as 48% by a prior oat crop. Greater soil bulk density at the 10 to 25-cm depth identified wheel traffic compaction patterns in each year. A 10-fold reduction of saturated hydraulic conductivity in the 10 to 25-cm compacted zone and high soil-water potentials within the upper 60 cm both confirmed an impaired water drainage, especially during infiltration events. These observations support the use of a previous full season or summer oat crop jointly with chisel plowing, plus the prevention of excessive traffic during secondary tillage and planting, to reduce common root rot in a field infested with A. euteiches. Shallow incorporation of oat shoot and root residue by chiseling could be a crucial component of the cultural control of the disease. R Rodriguez Kabana Section editor