Influence of Water and Soil Temperature on the Concentration and Efficacy of Phenamiphos for Control of Root-Knot Nematodes

Field plots of Tifton loamy sand were treated with phenamiphos for control of root-knot nematodes in a multiple-crop system of turnips, field corn, and southern peas. Preplant applications of phenamiphos protected roots of turnips and corn from damage by root-knot nematodes. Concentrations of phenamiphos at application in the 0-15-cm soil layer were near 6 μg/g on turnips and near 4 μg/g on corn and southern peas. After 30 d, concentrations were approximately 1 μg phenamiphos/g of soil for all crops. Concentrations of 2.0-3.8 μg phenamiphos/g of soil for 9-d duration appeared to be adequate for control of root-knot nematodes on field corn and southern peas in this multiple-crop system. Stepwise regression analyses indicated that 31%, 62%, and 22% of the variations in concentration of phenamiphos in the soil planted to turnips, corn, and southern peas, respectively, were attributable to the amount of water that the plots received. Soil temperature had no effect on concentrations of phenamiphos.     

Spatial and temporal patterns of onion maggot adult activity and oviposition within onion fields that vary in bordering habitat

In New York, onion [ Allium cepa L. (Alliaceae)] fields often border woods or other vegetable fields. Because onion maggot adults, Delia antiqua (Meigen) (Diptera: Anthomyiidae), spend a significant portion of their time outside of onion fields, surrounding habitat may affect patterns of fly activity and oviposition within onion fields. To better understand these patterns throughout the onion-growing season, first-, second-, and third-flights maggot adult (male and female) activity was monitored using yellow sticky cards. Half of the monitored fields bordered woods, whereas the other half bordered other onion or vegetable fields. Within all fields, yellow sticky cards were placed at five distances along a transect beginning at the onion field edge extending into the field center. First-flight male and female adult activity was greatest along onion field edges and was especially high along edges bordering woods. This pattern diminished during the second flight and was absent during the third. To determine if spatial patterns of onion maggot oviposition by first-flight onion maggots were similar to first-flight adult activity patterns, potted onion plants were placed in onion fields that bordered or did not border woods in late May and early June 2003. The number of eggs laid in the soil at the base of each plant was recorded. Unlike spatial patterns of first-flight adult activity, oviposition patterns were not affected by bordering habitat or distance from the field edge. Based on the activity of onion maggot adults in onion fields, future and existing control strategies should consider targeting first-flight adults along field edges rather than across entire fields, especially in fields that border woods. In contrast, based on spatial patterns of oviposition within onion fields, controls targeting onion maggot larvae should be applied on a fieldwide basis.     

Receptive field mechanisms of cat X and Y retinal ganglion cells

We investigated receptive field properties of cat retinal ganglion cells with visual stimuli which were sinusoidal spatial gratings amplitude modulated in time by a sum of sinusoids. Neural responses were analyzed into the Fourier components at the input frequencies and the components at sum and difference frequencies. The first-order frequency response of X cells had a marked spatial phase and spatial frequency dependence which could be explained in terms of linear interactions between center and surround mechanisms in the receptive field. The second-order frequency response of X cells was much smaller than the first-order frequency response at all spatial frequencies. The spatial phase and spatial frequency dependence of the first-order frequency response in Y cells in some ways resembled that of X cells. However, the Y first-order response declined to zero at a much lower spatial frequency than in X cells. Furthermore, the second-order frequency response was larger in Y cells; the second-order frequency components became the dominant part of the response for patterns of high spatial frequency. This implies that the receptive field center and surround mechanisms are physiologically quite different in Y cells from those in X cells, and that the Y cells also receive excitatory drive from an additional nonlinear receptive field mechanism.     

Onion maggot (Diptera: Anthomyiidae) resistance to chlorpyrifos in New York onion fields

A larval immersion bioassay was developed to identify susceptibility of onion maggot, Delia antiqua (Meigen) (Diptera: Anthomyiidae), to chlorpyrifos and to determine whether this assay could be used to predict control in onion fields. Laboratory colonies were established from larvae collected in New York onion fields during 2003 and 2004, providing us with test insects to use in bioassays. The larval assay effectively determined susceptibility of D. antiqua to chlorpyrifos, and results were congruent with an adult bioassay. However, use of similar-aged larvae (4 d old) in the assays was critical because larvae became more tolerant to chlorpyrifos as they aged. In a field survey, six of the 13 populations had LC50 values above the recommended field rate of 3,600 ppm (range 4,031-6,869). Over two successive seasons in the same field, susceptibility of D. antiqua to chlorpyrifos decreased in two of three fields (by 45 and 42%) and remained the same in another field, indicating that resistance is not predictable from year to year. Based on the relationship between damage in the field and LC50 values from 11 of the populations mentioned above, all five populations that had LC50 values above the field rate caused unacceptable levels of damage, whereas five of six populations that had LC50 values below the field rate did not cause serious damage.     

The role of pre- and post- alighting detection mechanisms in the responses to patch size by specialist herbivores

Experimental data on the relationship between plant patch size and population density of herbivores within fields often deviates from predictions of the theory of island biogeography and the resource concentration hypothesis. Here we argue that basic features of foraging behaviour can explain different responses of specialist herbivores to habitat heterogeneity. In a combination of field and simulation studies, we applied basic knowledge on the foraging strategies of three specialist herbivores: the cabbage aphid (Brevicoryne brassicae), the cabbage butterfly (Pieris rapae L.) and the diamondback moth (Plutella xylostella L.), to explain differences in their responses to small scale fragmentation of their habitat. In our field study, populations of the three species responded to different sizes of host plant patches (9 plants and 100 plants) in different ways. Densities of winged cabbage aphids were independent of patch size. Egg‐densities of the cabbage butterfly were higher in small than in large patches. Densities of diamondback moth adults were higher in large patches than in small patches. When patches in a background of barley were compared with those in grass, densities of the cabbage aphid and the diamondback moth were reduced, but not cabbage butterfly densities. To explore the role of foraging behaviour of herbivores on their response to patch size, a spatially explicit individual‐based simulation framework was used. The sensory abilities of the insects to detect and respond to contact, olfactory or visual cues were varied. Species with a post‐alighting host recognition behaviour (cabbage aphid) could only use contact cues from host plants encountered after landing. In contrast, species capable with a pre‐alighting recognition behaviour, based on visual (cabbage butterfly) or olfactory (diamondback moth) cues, were able to recognise a preferred host plant whilst in flight. These three searching modalities were studied by varying the in flight detection abilities, the displacement speed and the arrestment response to host plants by individuals. Simulated patch size – density relationships were similar to those observed in the field. The importance of pre‐ and post‐ alighting detection in the responses of herbivores to spatial heterogeneity of the habitat is discussed.     

Effects of fall and spring seeding date and other agronomic factors on infestations of root maggots, Delia spp. (Diptera: Anthomyiidae), in canola

Several agronomic benefits can result from fall seeding of canola (Brassica spp.), but extensive research data are lacking on the potential impact of this practice on infestations of root maggots (Delia spp.) (Diptera: Anthomyiidae), which are major pests of the crop in western Canada. Field experiments making up 13 location by year combinations were conducted in central Alberta, Canada, from 1998 to 2001 to determine the effect of fall versus spring seeding of canola on root maggot damage. Depending on the experiment, interactions with seeding rate, seed treatment, timing of weed removal, and canola species (cultivar) also were investigated. Root maggot damage declined with an increase in seeding rate for plots seeded in May but not in fall or April. Susceptibility to infestation was greater for plants of Brassica rapa L. than Brassica napus L., but seed treatment had no effect on damage by these pests. Combined analysis using data from all experiment by location by year combinations indicated that seeding date had no significant effect on root maggot damage. The extended emergence of Delia spp. adults, which spans the appearance of crop stages vulnerable to oviposition regardless of seeding date, prevented reduced root maggot attack. Covariance analysis demonstrated the importance of increasing seeding rate for reducing root maggot infestations, a practice that can be especially beneficial for May-seeded canola when growing conditions limit the ability of plants to compensate for root maggot damage. Results determined with the small plot studies described here should be validated in larger plots or on a commercial field scale, but both the combined and covariance analyses indicate that seeding canola in fall does not predispose plants to greater damage by larval root maggots than seeding in spring.     

Size of orchard trees as a factor affecting behavioural control of apple maggot flies (Dipt., Tephritidae) by traps

Over a 3-year period (1997–1999), we examined the influence of tree size on effectiveness of traps for behaviourally controlling apple maggot flies, Rhagoletis pomonella (Walsh), in small blocks of trees in Massachusetts commercial apple orchards. Traps were red spheres coated with Tangletrap and baited with an attractive synthetic host fruit odour (butyl hexanoate). Traps were placed 6 m apart on perimeter apple trees of each block and were designed to intercept apple maggot flies immigrating into blocks from unmanaged host trees. Based on captures of adults by unbaited red spheres placed near the centre of each block to monitor degree of adult penetration into the interior and on percentages of fruit injured by apple maggot, traps surrounding blocks of small trees (1.5 m canopy diameter) planted at high density were more effective in controlling apple maggot flies (relative to control obtained by insecticide sprays used in comparison blocks) than were traps surrounding blocks of large trees (3.7 m canopy diameter) planted at low density, with traps surrounding blocks of medium-size trees (2.5 m canopy diameter) planted at medium density generally providing an intermediate level of control.     

Nonwoven fiber barriers for control of cabbage maggot and onion maggot (Diptera: Anthomyiidae).

We investigated the use of nonwoven fiber barriers for control of cabbage maggot, Delia radicum (L.), and onion maggot, D. antiqua (Meigen). The barriers consist of arrangements of minute fibers loosely intertwined in "web" form. Results from a greenhouse experiment showed that manually applied graphite fibers placed at the base of broccoli plants reduced the number of D. radicum eggs by 64-98%, and that efficacy increased with greater fiber density. Using a melt extrusion process, we devised a method for on-site creation of nonwoven fibers of ethylene vinyl acetate (EVA). In field trials with broccoli and onion plants, EVA fibers significantly reduced the number of cabbage and onion maggots infesting plants. Fiber barriers provided comparable control to standard insecticide applications. The addition of blue, yellow, red, or black pigments, as well as optical brighteners that absorb UV light did not enhance fiber efficacy. Incorporation of capsaicin olfactory repellent to EVA also did not enhance fiber efficacy. Nonwoven fiber barriers may offer an alternative to insecticides for control of cabbage maggot and onion maggot and possibly other insect pests. Additional research is needed to improve the application process and to identify economically feasible and biodegradable compounds for fibers.     

Delaying onion planting to control onion maggot (Diptera: Anthomyiidae): efficacy and underlying mechanisms

Onion maggot, Delia antiqua (Meigen) (Diptera: Anthomyiidae), is an important pest of onion, Allium cepa L., in northern temperate areas, especially in the Great Lakes region of North America Management of D. antiqua relies on insecticide use at planting, but insecticide resistance can cause control failures that threaten the long-term viability of this strategy. Delaying the time onions are planted was investigated as an alternative management approach for D. antiqua and the ecological and behavioral mechanisms underlying host age and insect relationships were examined in laboratory and field experiments. Delaying onion planting by two to four weeks reduced damage to onions by 35 and 90%, respectively. Onions planted later emerged later and this reduced the period overwintered flies had to oviposit on the plants. Moreover, flies tended to lay few to no eggs on these young, late-planted onions. As anticipated, D. antiqua laid 4-8 times more eggs on older onions than on young onions, and older onions were more resilient to injury caused by D. antiqua neonates compared with younger onions. However, the resiliency to maggot attack lessened as the density of D. antiqua increased from 2 to 10 eggs per plant, which probably explains why greater levels of maggot damage are typically observed in early onion plantings compared with later plantings. Delaying onion planting until mid-May reduced D. antiqua damage without jeopardizing the period required to produce marketable yield, but this cultural tactic must be combined with other management strategies to prevent economic loss.     

沈阳市郊秋菜田的景观生态研究I．秋菜田斑块特征

对沈阳市郊区农业景观中的秋菜田斑块的大小,形状及与其它斑块或廓道的邻接情况等基本特征进行了典型调查,分析和讨论了菜田斑块在景观中的镶嵌特征,在距城区约5km以内的近区,许多秋菜田斑块相互邻近,并与各类公路相邻接,距城区5－10km的中郊区,许多秋菜田斑块与玉米田斑块相邻接,并与乡村道路相邻接,在距城区10km以上的远郊区,多数秋菜田斑块被玉米田斑块所包围,并与乡村道路相邻接。     

Field Application of Entomopathogenic Nematodes for Control of Delia radicum in Collards

Control of Delia radicum (cabbage maggot) in field collards (Brassica oleracea) was compared after one or two applications of entomopathogenic nematodes, Steinernema carpocapsae (All strain) and Heterorhabditis bacterophora (HP88 strain), a single application of granular chlorpyrifos, and a water-only treatment. Nematodes were applied with a sprayer during the egg stage of first-generation D. radicum, and chlorpyrifos was hand placed around collard stems during the same period. A second nematode application was made 10 days later. Chlorpyrifos treatment resulted in fewer puparia per plant, less root damage and higher yield than all other treatments, including the control. Collard yield from nematode-treated beds did not differ from controls. These data indicate that, under these field conditions, the species or strains of entomopathogenic nematodes tested did not reduce the number of active cabbage maggots, nor did they prevent collard root damage.     

Foundations of spatial ecology: the reification of patches through quantitative description of patterns and pattern repetition

Insect populations tend to be patchy, and the nature of the patches is a critical component of ecology. Predator-prey interactions, coexistence of competing species, survival of rare species as habitat is destroyed, and damage to crops are just a few examples of spatially-dependent ecological processes. For want of tractable quantitative approaches, understanding of spatial ecology has lagged far behind recognition of its importance. We assert that a quantitative foundation of a spatial ecology involves the reification of patches as objects of study. We introduce two new measures of patch dynamics: total covariance for comparing degrees of patchiness between populations, and quantile variance for quantifying the constancy of dispersion patterns through time. These new measures, in combination with the long-established spatial covariance from geostatistics, comprise a rudimentary toolbox for reification of patches and empirical field studies in spatial ecology.     

Combined effects of patch size and plant nutritional quality on local densities of insect herbivores

Plant–insect interactions occur in spatially heterogeneous habitats. Understanding how such interactions shape density distributions of herbivores requires knowledge on how variation in plant traits (e.g. nutritional quality) affects herbivore abundance through, for example, affecting movement rates and aggregation behaviour. We studied the effects of plant patch size and herbivore-induced differences in plant nutritional quality on local densities of insect herbivores for two Brassica oleracea cultivars, i.e. white cabbage and Brussels sprouts. Early season herbivory as a treatment resulted in measurable differences in glucosinolate concentrations in both cultivars throughout the season. Herbivore induction and patch size both influenced community composition of herbivores in both cultivars, but the effects differed between species. Flea beetles (Phyllotreta spp.) were more abundant in large than in small patches, and this patch response was more pronounced on white cabbage than on Brussels sprouts. Herbivore-induction increased densities in all patches. Thrips tabaci was also more abundant in large patches and densities of this species were higher on Brussels sprouts than on white cabbage. Thrips densities were lower on induced than on control plants of both cultivars and this negative effect of induction tended to be more pronounced in large than in small patches. Densities of the cabbage moth (Mamestra brassicae) were lower on Brussels sprouts than on white cabbage and lower on herbivore-induced than on uninduced plants, with no effect of patch size. No clear effects of patch size and induction were found for aphids. This study shows that constitutive and herbivore-induced differences in plant traits interact with patch responses of insect herbivores.     

Biodiversity and stability of herbivore populations: influences of the spatial sparseness of food plants

Returning to the classical diversity–stability problem about population densities, we propose a hypothesis that the spatial sparseness of food plants of herbivores, which is frequently observed in diversified communities such as those in the tropics, may be a potential source of the low variability in herbivore densities. The hypothesis consists of the following components: (1) sparseness of food plants of several herbivores increases with increasing number of plant species in a given amount of area, (2) spatial sparseness of food plants reduces the dispersal rate of herbivores between food plants, (3) such a decrease in dispersal rate causes a larger spatial variance in the consumption rate of food plants, (4) such a large spatial variance in the consumption rate of food plants reduces the temporal variance in the amount of food plants, and (5) the reduced temporal variance in the amount of food plants yields a smaller variance in the temporal dynamics of herbivores. A simple mathematical model was constructed to show a theoretical basis of the fourth component of the hypothesis. To exemplify the second, third, and fourth components of the hypothesis in fields, we conducted field experiments on the interaction between butterfly larvae and cabbages, in which cabbage seedlings were planted by two levels of sparseness: 1 m apart and 0.2 m apart. The spatial variance in the amount of leaf dry weight that escaped from larval feeding was larger in sparsely planted fields, which was in accordance with the third component of the hypothesis. The variability in the mean amount of leaf dry weight was smaller in sparsely planted fields, which was in accordance with the fourth component of the hypothesis. Received: June 14, 2001 / Accepted: February 14, 2002     

Effects of Spray Application of Lanthanum and Cerium on Yield and Quality of Chinese Cabbage (Brassica chinensis L) Based on Different Seasons

The use of single light rare earth elements in agriculture was studied using the application of single rare earth elements (La and Ce) to Chinese cabbage (Brassica chinensis L.) in field plot experiments where the soil conditions remained the same but the season (spring or autumn) in which application occurred was altered. The results showed that the Chinese cabbage’s nutrition quality between the two seasons had obvious differences. When planted in the autumn, the soluble sugar and vitamin C content was higher, the titratable acid and nitrate content was lower, and the ratio of sugar to acid was higher, while when planted in spring, the situation was opposite. La or Ce treatments in spring and autumn promoted the growth of the Chinese cabbage, the fresh and dry weight of the stems and leaves increased, the ratio of dry to fresh weight increased, and the observed effects were greater in the Ce treatments than the La treatments. Moreover, the soluble sugar content increased and the titratable acid content decreased, which meant that the ratio of sugar to acid increased. There was an increase in the vitamin C and nitrate content in the spring Chinese cabbage, while there was a decrease in the vitamin C and nitrate content in the autumn. The levels of the heavy metals Cu, Zn, Cd, Pb, and Ni decreased. The La treatment had greater effects on the spring Chinese cabbage, while the Ce affected the autumn Chinese cabbage more.     

Strongwellsea castrans (Phycomycetes: Entomophthoraceae), a fungal parasite of the adult cabbage maggot,Hylemya brassicae (Diptera: Anthomyiidae)

Strongwellsea castrans is a parasite of the adult cabbage maggot, Hylemya brassicae, in Canada. Laboratory cultures of H. brassicae became infected when exposed to infected, field-collected flies. Infected flies lived a maximum of 5–7 days after the appearance of the characteristic abdominal hole through which the conidia are discharged. Attempts to culture the fungus on artificial media were not successful. Under field conditions, infection rate varied considerably within a season and between years; a high rate of infection was associated with a high relative humidity and possibly a comparatively low temperature.     

The ecology and economics of damage to Brassicae by wood-pigeons Columba palumbus

Damage caused by wood-pigeons, Columba palumbus, to spring cabbage and Brussels sprouts was measured during three winters in two areas in the Vale of Evesham, Worcestershire. In one area (experimental) special attempts were made to reduce pigeon damage in addition to the normal efforts of the growers. In the other (control) area no such additional measures were taken. There was slightly more damage in 1969-70, but low market prices made it less important than in 1968-9 or 1970-1. There was no significant difference in any season between the damage in the control and experimental areas. No damage was caused to Brussels-sprout buttons as the birds ate only the tops of the plants; they preferred Brussels sprouts to cabbages and it is likely that the presence of the former helped to reduce the amount of damage to nearby cabbage fields. The amount of damage was not correlated with the amount spent on crop protection; actual damage was not correlated with the grower's estimates in the control area. In the second season a very intensive shooting campaign in the experimental area did not result in less damage, but the movements of local inhabitants and farm workers near a village did afford protection. The significance of the damage in the Vale and elsewhere is assessed in relation to the economics of crop production, the cropping pattern for cabbages and the behaviour and ecology of the wood-pigeon.     

Impact of a glossy collard trap crop on diamondback moth adult movement, oviposition, and larval survival

One component of developing a systematic approach for deployment of trap crops is to understand how the trap crop modifies pest behavior. Glossy‐leafed collards, Brassica oleracea L. var. acephala (Brassicaceae), were evaluated as a potential trap crop for diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), because they are attractive to P. xylostella adults and are a poor host for P. xylostella larvae compared to cabbage, Brassica oleracea L. var. capitata. We used large field plots to measure the changes in adult, egg, and larval P. xylostella densities in cabbage when the trap crop was planted in the field. Furthermore, we planted the trap crop in dispersed and concentrated spatial arrangements to determine the impact of trap crop arrangement on the behavior of P. xylostella. In 2002, results showed that the presence of collards within a cabbage field reduced larval density on cabbage. In 2003, neither trap crop arrangement had a significant impact on P. xylostella larval density on cabbage. Adult moths aggregated in proximity to collards in 2002, but not in 2003. Egg and larval data in both years in all treatments showed that total oviposition was highest near a central release point, indicating that females lay many eggs before dispersing very far when suitable host plants are available. The mean direction of P. xylostella movement and oviposition from a central release point was not consistent or correlated to wind direction. Plant size of the trap crop in relation to the main crop and environmental factors may have been responsible for the inconsistent effectiveness of the trap crop.     

Overwintering sparrow use of field borders planted as beneficial insect habitat

Field borders are an effective conservation strategy for providing habitat to overwintering sparrows, and may be a venue through which beneficial insect populations are promoted. However, traditional fallow field borders lack sufficient pollen and nectar sources required to sustain beneficial insect populations; therefore, borders planted to a mix of native prairie flowers and grasses may be needed if increases in beneficial insect populations are desired. Although the value of fallow borders to birds has been established, little is known about bird use of beneficial insect habitats. Using single-observer transect surveys, we compared overwintering sparrow densities among 4 field border treatments (planted native warm season grasses and prairie flowers, planted prairie flowers only, fallow, and mowed) replicated around 9 organic crop fields from November to March 2009–2010 and 2010–2011. Sparrow densities were 5–10 times lower in mowed borders than in other border treatments in 2009–2010 and 2010–2011, but did not differ among planted and fallow borders in either year. Planted field borders may be a useful conservation practice for providing habitat for both overwintering sparrows and beneficial insects. © 2012 The Wildlife Society.     

Western corn rootworm adult movement and possible egg laying in fields bordering maize

Abstract:  Western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte, larval damage in maize following soybean was observed in Croatia in 2003 along the edges and within soybean fields which bordered continuous maize fields in previous year. The explanation was that WCR adults moved from the continuous maize to the neighbouring soybean fields to lay eggs. This study was designed to measure how far WCR adults will enter into neighbouring fields to lay eggs. The WCR adult population was monitored in continuous maize fields in 2003 and 2005 by using Pherocon^® AM non-baited yellow sticky traps in the middle and on the borders of the maize field and at different distances and directions into neighbouring fields planted by wheat and soybean. Larval presence and root damage ratings (Iowa State University 1–6 ) were recorded at different locations within the maize field in following years. Approximately, the same concentration of WCR adults was recorded along the edges of the maize fields as recorded in the centres of those fields. A significant number of WCR adults was recorded up to a distance of 50 m into neighbouring fields. Regression analysis showed medium negative correlation between distance from previous maize field and root damage in the following year. Findings indicate that WCR egg lying can reach approximately 20 m into fields neighbouring maize fields and that significant root damage caused by WCR larvae in first-year maize following soybean and wheat can happen up to a distance of 20 m into those fields. Most farmers's fields in Croatia are up to approximately 50 m wide. As an edge effect for WCR egg laying can reach approximately 20 m into fields neighbouring maize fields, our research results indicate that it is possible to see WCR larval damage in rotated fields without those WCR's being the variant form.