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.     

Parasitism of the Wheat Stem Sawfly (Hymenoptera: Cephidae) in Montana

The wheat stem sawfly,Cephus cinctusNorton (Hymenoptera: Cephidae) was first found in wild grasses and soon became an economically important pest of wheat after cultivation began in the northern Great Plains. Of the species of parasitoids that attackC. cinctusin wild grasses, onlyBracon cephi(Gahan) andB. lissogasterMuesebeck (Hymenoptera: Braconidae) have been found in wheat. Levels of parasitism vary between wheat-producing regions in Montana. Parasitism levels were increased by releasing individuals from a region with high levels of parasitism into a region where parasitism levels were low. This suggests that there has been unequal rates of parasitoid adaptation from wild grasses to wheat in different regions of Montana.     

Impact of cocoon predation and parasitism on endemic populations of the common pine sawfly, Diprion pini (L.) (Hymenoptera, Diprionidae) in different forest types

1 Predation and parasitism on litter‐buried cocoons of the common pine sawfly Diprion pini (L.) were compared in different forest types with endemic sawfly populations by field exposure of laboratory‐reared cocoons during three consecutive years (1993–1995). 2 The impact of cocoon predation was dependent on season and forest type. The highest predation (up to 95%) was found during autumn in forest stands with a dense understory vegetation. 3 Cocoon parasitism varied between year, season and forest type. The highest parasitoid attack was observed in pure pine forests with more or less barren soils, but did not exceed 24% of exposed cocoons. 4 Cocoons were exposed in small patches. Predators tended to exploit all cocoons of a patch, whereas parasitoids only attacked a few cocoons of a patch. Predation was similar on cocoons placed in the litter and those buried more deeply in the soil, whereas parasitism of soil‐buried cocoons was rare. 5 These results indicate that predators can have a remarkable potential for limiting endemic sawfly densities, if habitat conditions in a forest maintain their population and support their foraging behaviour. A notable effect of parasitoids on sawfly cocoons deposited in the litter is obviously restricted to typical pure and barren pine forests, but may play there a similar role as predation.     

Incorporating sheep into dryland grain production systems: I. Impact on over-wintering larva populations of wheat stem sawfly,Cephus cinctus Norton (Hymenoptera: Cephidae)

Wheat stem sawfly (WSS), Cephus cinctus Norton (Hymenoptera: Cephidae) is the most damaging insect pest to Montana's $ 1 billion dollar per year grain industry. Current WSS control methods are either expensive, reduce wheat yields, or are not effective. Our objective was to compare burning, grazing, tilling, trampling and clipping wheat stubble fields on over-wintering WSS larval populations. Treatments were evaluated in three experiments using a randomized complete block design and four replications at each site. Eight, six, and two sites were used for Experiments 1, 2, and 3, respectively. Contrast statements were used to make pre-planned comparisons among treatments. For Experiment 1, treatments were fall tilled, fall grazed, spring grazed, fall and spring combined (Fall/Spr) grazed, and an untreated control. Five mature ewes were confined with electric fence to 111 m² plot for 24 h in the fall and spring grazed treatments resulting in a stocking rate of 452 sheep d/ha. For Fall/Spr, the stocking rate was 904 sheep d/ha. For Experiment 2, treatments were fall grazed, fall burned, fall tilled, and an untreated control. In Experiment 3, treatments were fall trampled, spring trampled, Fall/Spr trampled, hand clipped to a stubble height of 4.5 cm, and an untreated control. Trampled treatments were done at the same stocking rates as grazing treatments but sheep were muzzled to prevent intake. Wheat stem sawfly larval numbers were collected in the fall and spring, pre- and post-treatment, respectively, by collecting all plant material from three, 0.46 m lengths of row and counting the number of live larvae present. In Experiment 1, WSS mortality was greater (P < 0.01) for the mean of all grazed treatments (68.4%) than either control (43%) or tilled (47%) plots. Mortality did not differ (P = 0.75) between fall (67%) and spring (64%) grazed plots but was greater (P = 0.02) for Fall/Spr (74%). In Experiment 2, larva mortality was greater (P < 0.01) for fall grazed (63%) than burned plots (52%). In Experiment 3, WSS mortality was greater (P < 0.01) for the mean of all trampling treatments (57%) than either control (33%) or clipped (32%) plots. Mortality did not differ (P > 0.25) between fall (54%) and spring trampling (47%) but was greater (P = 0.01) for Fall/Spr (70.6%). No differences (P > 0.25) were detected for WSS mortality when grazing was compared to trampling. These results indicate the potential for using grazing sheep to control wheat stem sawfly infestations in cereal grain production systems.     

Effects of burial and soil condition on postharvest mortality of boll Weevils (Coleoptera: Curculionidae) in fallen cotton fruit

Effects of soil condition and burial on boll weevil, Anthonomus grandis grandis Boheman, mortality in fallen cotton, Gossypium hirsutum L., fruit were assessed in this study. During hot weather immediately after summer harvest operations in the Lower Rio Grande Valley of Texas, burial of infested fruit in conventionally tilled field plots permitted significantly greater survival of weevils than in no-tillage plots. Burial of infested squares protected developing weevils from heat and desiccation that cause high mortality on the soil surface during and after harvest in midsummer and late summer. A laboratory assay showed that burial of infested squares resulted in significantly greater weevil mortality in wet than in dry sandy or clay soils. Significantly fewer weevils rose to the soil surface after burial of infested bolls during winter compared with bolls set on the soil surface, a likely result of wetting by winter rainfall. A combination of leaving infested fruit exposed to heat before the onset of cooler winter temperatures and burial by tillage when temperatures begin to cool might be an important tactic for reducing populations of boll weevils that overwinter in cotton fields.     

Location before emergence of the female bee, Centris pallida, by its male (Hymenoptera: Anthophoridae)

Large numbers of males of the bee Centris pallida Fox have been observed patrolling areas in which females are emerging. Males locate specific sites at which a buried bee is about to emerge and dig down to meet the other individual, male or female. If it is a female, mating is initiated when she scrambles into the excavation pit created by the male. Males fight intensely with one another for possession of digging sites and for unburied virgin females. Experiments indicate that males locate conspecifics beneath the surface on the basis of extremely non-specific olfactory cues; they are capable of locating buried honey bees and other insects. The evolution of digging behaviour is traced to selection favouring males that are first to reach a virgin female which will mate just once in her lifetime. A number of examples are given of other insects that have evolved similar abilities, apparently in response to similar selection pressures.     

Species and functional responses of ants to inter-row tillage and vegetation in organic Mediterranean vineyards

Ants are arthropods providing crucial ecosystem services such as soil structuring, nutrient cycling, seed dispersal and pest predation. Thus, their abundance and diversity need to be considered in approaches to improve sustainability of land use such as Mediterranean viticulture. In our study, we tested whether (1) inter-row vegetation and the absence of tillage increase the species richness and/or functional diversity of ants in vineyards and (2) ground cover vegetation drives ant species composition. We included 23 Mediterranean organic vineyards in our analyses and distinguished three types of inter-row management: all inter-rows tilled, half of the inter-rows tilled, and all inter-rows are untilled and covered by vegetation. The occurrence of ant species was analysed in six pitfall traps per vineyard. Around each trap, the floristic composition of inter-row vegetation was analysed in 2 × 2 m² plots. We found that inter-row tillage significantly affected ant species richness, being higher in partially than in fully tilled vineyards whereas untilled vineyards were not different from the other tillage types. Grass cover and the perennial/annual rate were positively correlated with ant species richness. Ant functional diversity and the frequency of most predatory ants were not correlated neither with plant functional groups nor with tillage type. In conclusion, ant communities benefit from inter-row vegetation and/or absence of soil disturbance but partial inter-row tillage of vineyards may be tolerated and even benefit several species. In particular, grasses and perennial plant species favour ants in our system and need to be considered in inter-row sowing.     

Factors affecting nest-site choice and reproductive success of Curlews Numenius arquata on farmland

Nest-site choice and reproductive success of Curlews Numenius arquata in different habitats were studied at a mixed farmland site (grasslands and flooded tilled fields relatively common) and at an arable farmland site (dry tilled fields more dominant than at the mixed site) in central Sweden. At both sites Curlews preferred to nest on grassland and fallow fields, where hatching success was higher than on tillage fields. Nests were also situated further away from forest edges than random sites, but hatching success did not vary with distance to the forest edge. Only 35.6% of the pairs were estimated to hatch young. The main cause of nest loss was predation and the second most important factor was destruction by farming practices, which was an important factor in tillage early in season. Surprisingly, nest survival was higher at the arable than at the mixed farmland site, probably being an effect of the increased proportion of fallowing during recent years. Mortality of chicks was 79.7% before fledgling age (both sites combined) and, surprisingly, chick survival was lower on meadows than on arable fields and leys. The mean production of young was only 0.25 fledglings per pair, which is lower than in areas less affected by farming practice. The low production of young is probably an important factor in the decline of Curlew populations on Swedish farmland. On bogs 1.4 fledglings per pair were produced, indicating that reproductive success of Curlews is higher in more natural habitats.     

Parasitism of Brown Planthopper and Whitebacked Planthopper by Agamermis unka in Korea

Adults of the brown planthopper (BPH) and the whitebacked planthopper (WBPH) that migrated into Korea from China were not parasitized by the mermithid, Agamermis unka. BPH and WBPH collected from Korean rice fields were parasitized. Parasitism of BPH in the lst-3rd, 4th, and 5th instars, and adults was 31.5%, 61.5%, 66.4%, and 45.5%, respectively, whereas parasitism of the same stages of WBPH was 50%, 50%, 100% and 90.7%, respectively. Parasitism of BPH by A. unka significantly reduced the number of eggs. Only 4.2% of the parasitized females contained eggs, whereas 85.6% of unparasitized females had eggs. Tilling of rice fields significantly increased mermithid parasitism of BPH. Mermithids parasitized 39.3% of caged adults in the untilled field and 77.8% in the tilled field.     

Larval parasitism by native insects on the introduced stem-galling moth Epiblema strenuana Walker (Lepidoptera: Tortricidae) and its implications for biological control of Parthenium hysterophorus (Asteraceae)

Abstract  The significance of natural enemies in the failure or reduced effectiveness of weed biological control agents remains largely unknown. Larval and pupal parasitism by native insects in the stem-galling moth Epiblema strenuana was studied in north Queensland, 4 (1986–87) and 16 (1998–99) years after its introduction as a biological-control agent for Parthenium hysterophorus . Specific questions answered in this study are: (i) Has parasitism increased over the years?; (ii) Are the levels of parasitism influenced by the host plant phenology?; and (iii) What are the potential implications of current parasitism levels for the effectiveness of E. strenuana ? There was no increase in the parasitoid species assemblage over the years. In 1986–87, Antrocephalus sp. and Bracon sp. were the most predominant species. The combined larval and pupal parasitism was low (2.6%) and there was no seasonal difference in the parasitism levels. In 1998–99 Bracon sp. was the most prevalent species. Parasitism by Bracon sp. in 1998–99 was several times higher (22.9%) than the combined larval and pupal parasitism in 1986–87. However, parasitism by Bracon sp. remained low (6.5–8.2%) at the beginning of the parthenium-growing season, and reached peak levels (49–53%) only at the end of the season. Parasitism by Bracon sp. was also significantly lower in rosettes (7.2%) than in flowering plants (22.8%). Galling can have a negative impact on the weed only when initiated at the rosette stage. In 1998–99 lower levels of parasitism early in the season when most plants are in the rosette stage suggest that the impact of parasitism on the effectiveness of the gall insect may not be significant.     

Parasitism and the demography of wheat stem sawfly larvae, <Emphasis Type="Italic">Cephus cinctus</Emphasis>

Previous research has suggested that insect herbivores in protected environments have higher mortalities from biotic factors such as parasitism compared to herbivores in less protected situations, although overall mortalities in protected environments are often lower. However, this has not been examined using life table approaches. In this study, we used demographic methods to characterize the mortality dynamics of parasitism for pre-diapause wheat stem sawfly larvae, Cephus cintus Norton (Hymenoptera: Cephidae), a stem-mining wheat pest. Larvae were intensively sampled from commercial wheat fields at two locations in Montana, USA from 2005 through 2008. The feeding larvae present in the summer succumbed to only two mortality categories: parasitism and unknown factors. In Conrad, a location with relatively high densities of the parasitoids, mortality by parasitism was largely irreplaceable. In contrast, in Amsterdam, where parasitism did not occur to any appreciable degree, overall mortality remained relatively low.     

夏休闲期复种油菜对旱地土壤水分和小麦产量的影响

以冬小麦收获后高留茬休闲地为对照,连续4年在陇东黄土旱塬设6个油菜播种期,研究了休闲期作物覆盖对土壤水分及后作冬小麦产量与水分利用效率的影响.结果表明：不同播种期夏休闲期土壤贮水量差异显著(P＜0.05),其中8月5日播种油菜的土壤蓄水效率为58.5%,产量和水分利用效率较对照提高7.5%和5.9%.平均而言,夏休闲期复种油菜后作小麦干旱年份增产16.1%,平水年份增产6.8%.夏休闲期复种油菜是西北旱地小麦抗旱增产的有益途径.     

Detecting soil and plant community changes in restored wetlands using a chronosequence approach

Wetland restoration aims to recreate or enhance valuable ecosystem services lost during wetland destruction. Regaining wetland ecosystem services depends on restarting basic wetland functions, like carbon (C) storage, which are unmeasured in many Wetlands Reserve Program (WRP) restoration sites. We collected soil and plant data from 17 WRP sites in western New York that were used for tillage or non-tillage agriculture and then actively restored as isolated depressional wetlands by excavating basins and disabling drainage systems. Sites had been restored for 0–15 years when sampled in August-October 2010. We analyzed data as chronosequences and tested whether soil and vegetation parameters in restored wetlands, over time, (1) departed from pre-restoration baselines, estimated using active agricultural fields paired to each WRP site, and (2) converged towards “natural” benchmarks, estimated from four naturally-occurring wetlands. Restored WRP soils remained similar to agricultural soils in organic matter, density, moisture, and belowground plant biomass across chronosequences, indicating negligible C storage and belowground development for 15 years following restoration. Soil changes were limited in sites restored after both tillage and non-tillage agriculture and throughout the upland meadow, emergent shoreline, and open-water habitat zones that characterize these sites. Many plant metrics like aboveground biomass matched natural wetlands within 15 years, but recovered inconsistently among tilled and untilled sites and across all habitat zones, suggesting land-use history impacts and/or zonation effects. Disparities in recovery times exists between vegetation, which can respond quickly to wetland restoration, and underlying soils, which show limited signs of recovery 15 years after being restored.     

Short-range dispersal and overwintering habitats of boll weevils (Coleoptera: Curculionidae) during and after harvest in the subtropics

Field experiments in the subtropical Lower Rio Grande Valley of Texas were conducted to determine the extent of adult boll weevil, Anthonomus grandis grandis Boheman (Coleoptera: Curculionidae), dispersal from cotton, Gossypium hirsutum L., fields during harvest operations and the noncotton-growing ("overwinter") period between 1 September and 1 February. Using unbaited large capacity boll weevil traps placed at intervals extending outward from commercial field edges, boll weevils did not move in substantial numbers during harvest much beyond 30 m, primarily in the direction of prevailing winds. From traps placed in fallow cotton; citrus; lake edge; pasture; treeline; sorghum, Sorghum bicolor (L.) Moench, and sugarcane, Saccharum spp., habitats during the overwinter period, the most boll weevils were collected in the fallow cotton fields and adjacent treelines during the fall. However, the greatest abundances of boll weevils were found in citrus orchards in the spring, before newly planted cotton fields began to square. One of the three lake edges also harbored substantial populations in the spring. Egg development in females was not detected between November and April, but in cotton fields most females were gravid between May and August when cotton fruiting bodies were available. Mated females, as determined by discoloration of the spermatheca, made up 80-100% of the female population during November and December but declined to approximately 50% in February. The lower incidence of mating indicates a reduction in physical activity, regardless of overwinter habitat, until percentages increased in March and April after cotton fields had been planted and squares were forming.     

The effect of soil tillage and fertilizer use on pearl millet yields in Niger

Farmers in Niger generally do not plow their fields and are therefore unable to incorporate phosphate. Experiments were conducted in Niger to assess the effect of soil tillage, P source, and fertilizer placement on yields of pearl millet (Pennisetum glaucum [L.] R. Br.). Treatments included single superphosphate (SSP) or ground Tahoua phosphate rock (PRT) incorporated into the soil during tillage or SSP surface applied after tillage. In plots which were not tilled, P sources (SSP, PRT, and PAPR-partially acidulated rock) were broadcast on the soil surface with no incorporation. In order to improve P efficiency under zero tillage, P was point placed in the soil near the plant with either broadcast or point-placed urea. Treatments in which tillage was used showed a slight though nonsignificant yield increase over untilled plots. The yield increase did not appear to be due to phosphate incorporation but rather to direct tillage effects on early plant growth. In a comparison of SSP with PRT or PAPR broadcast on soils not receiving tillage, PRT performed poorly relative to the other P sources. SSP outyielded PAPR and PRT in 1986, but in subsequent years, no significant difference was found between PAPR and SSP. Point placement of P or N near the plant did not significantly increase yields over broadcast treatments even though the millet was planted with wide 1×1 m spacing.     

A new species of Bracon (Hymenoptera: Braconidae) parasitic on alien sweetpotato weevils in the south-west islands of Japan

A new species of braconid, Bracon yasudai Maeto et Uesato sp. nov., is described here from the south‐west islands of Japan. It is a solitary idiobiont ectoparasitoid of the larvae of the West Indian sweetpotato weevil, Euscepes postfasciatus (Curculionidae), and the sweetpotato weevil, Cylas formicarius (Brentidae), both feeding on Ipomoea batatas (L.) (Convolvulaceae). The percentage parasitism of the braconid on E. postfasciatus in the vines of I. batatas was 19.9–40.7% in the field. Bracon cylasovorus (Rohwer) reared from C. formicarius in the Philippines is also described.     

Establishment of Citrostichus phyllocnistoides (Hymenoptera: Eulophidae) as a biological control agent for the citrus leafminer Phyllocnistis citrella (Lepidoptera: Gracillariidae) in Spain

A program of introduction of exotic parasitoids for the biological control of the citrus leafminer Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae) was carried out in València (Spain) between 1996 and 1999. Eleven species of parasitoids were imported through a total of 37 shipments coming from nine countries. Six species were released in the field, the encyrtid Ageniaspis citricola (Logvinosvskaya), and the eulophids Quadrastichus sp., Semielacher petiolatus (Girault), Galeopsomyia fausta LaSalle, Cirrospilus ingenuus (Gahan), and Citrostichus phyllocnistoides (Narayanan). A. citricola was recovered in summer in many release points, reaching nearly 50% of parasitism and dispersing more than 300 m, but it was not able to overwinter. Quadrastichus sp. and S. petiolatus established temporarily in some sites, but produced little differences in parasitism or density of host population. In 1999, a substantial expansion of C. phyllocnistoides of more than 30 km in all directions was observed from one release point. In 2000 and 2001 this parasitoid expanded to all citrus grown in continental Spain and the Balear Islands, becoming the most abundant parasitoid in all the orchards, and displacing native and other introduced parasitoids. As a consequence, parasitism on second instars increased from less than 16% to 65% and on third instars from 35–38% to 59%. Overall, the mean percentage of parasitism increased from 20–25% to near 60%. Apparently, C. phyllocnistoides reduced by 34% the number of eggs and early instars of the host, and by 72% the number of adults. Damage to citrus foliage decreased by 56%.     

化学防治对不同类型棉田害虫和捕食性天敌群落多样性的影响

分析比较了化学防治对8种不同类型棉田害虫、捕食性天敌群落多样性的影响。研究结果表明,化学防治对棉田害虫、捕食性天敌群落的多样性指数、均匀性指数、丰富度及个体数的变化有较大的影响,尤其对捕食性天敌群落的影响显著。但这种作用依不同类型棉田或棉花不同生育阶段而异：化学防治对套作棉田害虫、捕食性天敌群落的影响较小,而对单作棉田和豆间棉棉田害虫、捕食性天敌群落的影响较大;晚播棉田害虫与捕食性天敌群落较早播棉田受化学防治的影响更大;化学防治对免耕棉田害虫、天敌群落的影响更大,非免耕棉田害虫、捕食性天敌群落受其干扰较小;春套棉边害虫、捕食性天敌群落与其它棉田类型相比,受化学防治的影响较少;棉花害虫在棉花生育前期对化学防治较棉花生育后期敏感,而捕食性天敌在棉花整个生育期均对化学防治敏感。     

Potential for suppressingDiprion similis (Hymenoptera: Diprionidae) with pheromone trapping: A population model

The virgin female introduced pine sawfly, Diprion similis (Hartig ), produces a powerful sex pheromone capable of attracting males. Pending chemical identification of the substance, a pilot study in male annihilation is under consideration. A mathematical model was developed to assess the feasibility of population suppression using pheromone-baited traps. Departure from preexisting population models resulted chiefly from the arrhenotokous nature of the sawfly. The model predicts alternating sawfly generations which undergo first a large shift in the sex ratio but no population reduction, followed by a large decrease in population size with a moderating sex ratio. Four generations of intensive trapping would theoretically be sufficient to eliminate the sawfly from an isolated area.     

残茬覆盖与耕作方式对夏玉米叶片衰老代谢和籽粒产量的影响

对小麦机械收获后残茬覆盖与不覆盖两种条件下免耕、翻耕和播种行深松3种土壤耕作方式的夏玉米开花后叶片衰老生理特性和籽粒产量进行了研究。结果表明,残茬覆盖和深松耕作的玉米叶片SOD和POD活性提高、MAD含量降低、叶绿素和可溶性蛋白质含量高、降解速度慢,维持了叶片后期较高的生理功能。最终开花后干物质生产量和玉米籽粒产量表现为：覆盖显著高于不覆盖,深松显著高于翻耕和免耕,残茬覆盖与深松结合效果最好。