Flight periodicity and infestation size of Sitona lineatus

Sitona lineatus displays two distinct flight periods; a post-teneral flight in the late summer and a post-diapausal flight in the spring. The late summer flight begins as soon as adults start to emerge from pupal cells during late July and continues until mid-October. Maximum aerial density is observed in late August. Less than 10% of newly emerged adults leave the crop by flight, the rest remain in the soil or move to overwintering sites by walking. Spring flight begins in late March if temperatures are above the 12.5°C flight threshold and reaches a peak in mid-April. Most migratory flight is downwind. Little trivial flight occurs and once individuals have located a crop, redistribution is by walking. Laboratory studies indicate that adults fly most often during the day, particularly at noon. The size of infestations appeared to be independent of the area of legumes grown in a locality with large differences occurring even between neighbouring fields. Examination of the yields of field experiments at Rothamsted demonstrate an unexpected trend for higher yields in later sown spring bean crops. This may be because late sowing avoids infestation by spring migrants.     

ROGUING POTATO CROPS FOR VIRUS DISEASES

Removing virus-infected plants from plots of Majestic potatoes at Rothamsted on 2 July 1947 did not reduce the spread of leaf roll but reduced rugose mosaic (potato virus Y) to about one-fifth of that in plots rogued on 21 July or left unrogued. Roguing Arran Pilot potatoes on 16 June or 2 July reduced leaf roll to five-sixths of that in unrogued plots; roguing on 16 June reduced rugose mosaic to about half that in plots rogued on 2 July, and about a quarter of that in unrogued plots. Lifting Arran Pilot potatoes in mid-August reduced virus diseases to about two-thirds.
Roguing flattened the gradient (decrease in percentage plants diseased with increasing distance from the source of infection) with rugose mosaic, but had little effect with leaf roll. Evidently any plants prevented by roguing from contracting virus Y were near the initially infected plants.
In 1948, Majestic and King Edward potatoes at three places were rogued during 22–24 June and tubers were dug during 28–30 July and again at the end of the season. Leaf roll spread more in Majestic than in King Edward, and rugose mosaic spread more in King Edward. Roguing reduced the spread of both by about one-fifth at Rothamsted, but had no effect at Sutton Bonington. At Bretton, in the Derbyshire hills, roguing had no effect on leaf roll, but prevented the spread of rugose mosaic.
The small benefit occasionally achieved by roguing in the ware-growing districts of England does not make the practice economically worth while.     

THE EFFECTS OF SPRAY TREATMENTS ON INFESTATION OF THE OAT CROP BY THE FRIT FLY (OSCINELLA FRIT L.)

Criteria are given for the timing and assessment of the effect of sprays on experimental plots, based on biological observations at Silwood Park from 1950 to 1955 and on previous work.
A preliminary experiment on small plots in 1952 indicated that 'blanket spraying' with DDT and parathion throughout the life of the crop gave protection against both tiller and grain attack. A more detailed replicated plot trial in 1953 showed that for oats planted on 22 April two carefully timed tiller sprays with parathion reduced tiller infestation from 31 to 3%. Six panicle sprays at weekly intervals reduced a heavy grain attack of 60% to 13%. Dieldrin was also effective but significantly less so than parathion. Much of the damage to the crop was caused by weed growth following initial loss of the primary oat shoots.
In 1954 and 1955 two and three parathion sprays were applied to 2-acre fields in order to study recolonization. Despite almost complete control of the tiller generation, a normal evenly distributed infestation of the panicles was found.
It is concluded that good control of the tiller generation may best be achieved by a spray programme based on knowledge of the phenology of the fly combined with that of the crop. The first general emergence in early May is likely to be critical.
Reinvasion of a sprayed crop may take place within 4–5 days and panicle infestation may not be causally related to tiller infestation in the same field.     

Distribution of damson-hop aphid (Phorodon humuli) migrants on hops in relation to hop variety and wind shelter

The distribution of migrant Phorodon humuli was studied in two hopgardens during June 1972. Migrants accumulating upon the young tissues near the bines' apices were counted. Plant size affected distribution, 100 % more migrants were found on 2-bine than on single bine strings and there was a positive linear relation between bine height and log₁₀ aphid numbers. Plants surrounding wire-trellis support poles were more heavily infested than plants not at poles, and migrants were more abundant on leeward orientated than windward strings. It is argued that the distribution of alatae reflected local patterns of wind shelter. Differences between plants declined in successive weeks. The influence of hop variety on migrant settling was studied in one of the hop-gardens. Fewer migrants settled on the variety Tolhurst than on Northern Brewer, and Fuggle was intermediate. Part, but not all, of the difference between varieties was explained by the larger average size of Northern Brewer plants. The observed aphid deposition rates in the two hop gardens were compared with hypothetical deposition rates calculated from numbers of P. humuli caught in a nearby 12-2 m Rothamsted Insect Survey suction-trap, and used to estimate flight durations. The estimates indicated that most infestation probably resulted from aphids within 1 h flying time of their primary host source.     

STUDIES ON THE RELATIONSHIPS BETWEEN EARTHWORMS AND SOIL FERTILITY: I. BIOLOGICAL STUDIES IN THE FIELD

Changes in the seasonal activity of several species of earthworms have been followed in a permanent pasture field for 18 months, 1945–6. The two soil conditions which chiefly determine activity are temperature and moisture. Other factors are the occurrence of an obligatory diapause in the two species Allolobophora nocturna and A. longa , and changes in population in A. chlorotica and Lumbricus terrestris.
Soil temperature and soil moisture also determined the weight of soil thrown up in the form of wormcasts during autumn, winter and spring. It is suggested that only two species, A. nocturna and A. longa , are responsible for wormcasts and that the other four common species present play little or no part in this activity.
At Rothamsted it was found that the previous agricultural history of the field is an important factor in determining the fauna. Old permanent pasture is characterized by a high percentage of A. nocturna and a rather lower percentage of A. caliginosa. Ploughing old permanent pasture and reseeding to grass after 1 or 2 years arable reduces the proportions of A. nocturna and A. caliginosa and increases that of Eisenia rosea. Arable fields have A. chlorotica as the dominant species and pasture fields 2–7 years grass after many years of arable fanning still show a high percentage of A. chlorotica and a low proportion of A. nocturna.
A survey of the Carse of Stirling, Scotland, showed that soil type is also an important factor in determining the earthworm fauna. A. caliginosa was the dominant species on the three soil types studied, but the subdominant species varied. On clay soil, A. longa was subdominant; on loam, A. longa and L. rubellus ; on sandy soil, A. longa, L. rubellus and A. chlorotica. The dominant species of pasture land at Rothamsted, A. nocturna , was not found at Stirling.     

Patterns of Orthoptera abundance and lesser kestrel conservation in arable landscapes

The lesser kestrel Falco naumanni experienced a marked decline during the second half of the 20th century due to changes in land use that influenced breeding success by reducing the abundance and quality of prey. However, the factors governing spatial and temporal variation of prey abundance around lesser kestrel colonies has not yet been investigated. We sampled Orthoptera abundance in the main crop types and edge habitats surrounding six lesser kestrel colonies in southern Spain. Samplings focused on Orthoptera because they constitute the main prey during the nestling period. Only those Orthoptera species that are known to be preyed by lesser kestrels were considered in this study. We found differences in prey density among localities, and crop types. Semi-natural habitats such as grasslands, fallow land, and field margins held the highest densities. However, prey abundance showed a complex pattern that was not possible to explain solely on the basis of crop composition around colonies. Factors determining productivity in individual fields like soil type and productivity or biocide input, and mean size of agricultural fields contributed to explain this complex pattern of prey abundance. Our results highlight the key role of semi-natural and edge habitats in farmed landscapes as prey reservoirs and corridors. Higher conservation priorities for these habitats are suggested to benefit foraging lesser kestrels, but many other farmland species that also experienced steep population declines due to decreasing food supply resulting from modern agriculture.     

Increasing the effectiveness of spring trap crops for Leptinotarsa decemlineata

Insecticide resistance problems have increased interest in trap crops as a cultural control strategy for overwintered Colorado potato beetle adults, Leptinotarsa decemlineata Say (Coleoptera: Chrysomelidae). Growers in the north central United States have noticed and treated concentrations of adults at the edge of some of their potato fields each spring. Based on sampling in commercial potato fields over a 2-year period, early planted fields that are adjacent to the previous year's potato crop are most likely to have concentrations of adults at the field edge. Frequency of fields with significantly more adults at the edges than in the center sections as well as adult population density in the center sections of fields declined with both distance from the previous potato field and later planting date. The effects of both physical and chemical barriers to movement into potato fields from the field edges were studied in small plot trials and at the edges of commercial potato fields. In small plot trials, physical barriers had a greater impact than chemical barriers on adult beetle movement from a potato trap crop to the protected potatoes beyond the barrier. Barrier treatments reduced beetle numbers in and just beyond the barrier in commercial fields, but the effects were localized and no significant reduction of beetles was observed further into the field. Beetle flight was hypothesized to be responsible for the localized effects of barrier treatments and the lack of edge concentrations in later planted and more distantly rotated fields. In field studies, larger potato plants attracted more colonizing potato beetles than smaller plants. Attracting Colorado potato beetles to trap crops containing potato plants that were larger than those in the remainder of the field, however, provided no significant reduction of beetles in the remainder of the field. We found little opportunity to reduce beetle populations with trap crops at the edges of potato fields without controlling the adults in the trap crop itself. Growers can exploit naturally occurring concentrations of adults at the edges of early and adjacent potato plantings if they are prepared to monitor and regularly treat the field edges.     

An experimental design and procedures for testing putative controls against naturally-occurring take-all in the field

In experiments during 1983–86 take-all was more severe and eyespot and sharp eyespot less frequent in 2nd-4th crops of winter wheat at Woburn (Beds.) than at Rothamsted (Herts.). Third crops had most take-all and yielded least grain. Against this background, small plots, 37 cm × 31 cm, in which all plants were sampled, were tried as a means of increasing experimental precision. They were arranged in fours in incomplete blocks and blocks with complementary treatments (putative controls of take-all) were paired. Thirty of these block-pairs were distributed throughout each experimental site in each year to provide one replicate of the design for each of three sampling times: April, June and August. Unattributed variation in disease and plant growth for plots within blocks was compared to that in other strata (block-pairs and blocks within block-pairs) of the experiment. The variability amongst block-pairs scattered throughout the site was nearly always greater than that for blocks within block-pairs (98% of take-all assessments, 71% of soil infectivity estimates, 94% of eyespot and sharp eyespot assessments and 86% of all plant measurements). The variability of blocks within block-pairs exceeded that of plots much less frequently (56% and 69% of take-all assessments, 33% and 25% of soil infectivity measurements, 63% and 56% of eyespot and sharp eyespot assessments and 50% and 63% of plant measurements; Rothamsted and Woburn, respectively). Small plots were judged mostly on this last comparison, where a variance ratio in excess of 1 indicated that the small plots had decreased variability and increased precision. Variance ratios for different assessments of take-all indicates that small plots: i) most consistently decreased disease variability during the years of maximum disease, ii) were slightly less effective at Rothamsted than at Woburn, and iii) were usually less effective in fourth crops than in previous crops. Soil infectivity was most uniform after crops with most disease and blocks were rarely more variable than plots. hxcept when disease was severe, soil infectivity in August tended to be positively associated with the yield of the crop just harvested. These findings reveal changes in the scale of disease patterns, both during the crop sequence and within individual crops, and suggest more than one scale of pattern in take-all-infested fields. This is discussed in relation to field experimentation and take-all decline.     

Observations on the biology and ecology of Apion vorax (Coleoptera: Apionidae), a vector of broad bean stain and broad bean true mosaic viruses

In spring 1974 and 1975 many adult Apion vorax were found at Rothamsted in woods bordering fields that had been cropped with field beans (Vicia faba) the previous season. The weevils were most common on bramble (Rubus spp.), dog's mercury (Mercurialis perennis) and nettle (Urtica dioica). A decrease in the woodland population in May coincided with the appearance of the weevil on field bean crops in neighbouring areas. In laboratory feeding tests, adult weevils fed more on field bean leaves than on leaves of plants on which they were common in woodlands, and they fed more on field beans in May than at other times of the year. No difference was observed in the feeding of male and female weevils. Many A. vorax were caught on sticky traps in woodlands at Rothamsted in 1975, particularly in April and May, but very few were caught on sticky traps in bean crops. The numbers of A. vorax recorded on the upper foliage of bean crops at Rothamsted in June each year from 1970 to 1980 ranged from 0 to 10 per 10-m row. Eggs, larvae and pupae of A. vorax were found in field bean flowers collected from field crops. The larvae were feeding on the tips of the pistils and stamens. Adult weevils that emerged in mid-June from the flowers of autumn-sown beans mated and produced a second generation when caged on glasshouse-grown plants. Some Apion larvae, possibly A. vorax, were found inside flowers of common vetch (Vicia sativa). The name ‘bean flower weevil’ is considered a suitable common name for A. vorax.     

Spawn site selection and colony size of the frog (Rana temporaria) and the toad (Bufo bufo)

Information has been collected from various sources on spawn site selection and colony size of the frog ( Rana temporaria ) and the toad ( Bufo bufo ). Details are tabulated for 764 frog breeding sites in Britain and in the Republic of Ireland and for 139 toad sites in Britain (the toad does not occur in Ireland). Both species tend to breed in whatever types of site are most available. In Britain the garden pond has steadily increased in importance for both species since 1950. Frogs usually spawned in shallow water, 266 reports out of a total of 588 (45%) referring to water up to six inches (15 cm) deep. Toads tended to spawn in deeper water, 48 reports out of 82 (59%) mentioning water 7–18 inches (18–46 cm) in depth. Median depths were: frog, seven inches (18 cm); toad 13 inches (33 cm). Information on colony size was assimilated for 574 frog colonies and 86 toad colonies. Colonies in gardens were smaller than those in other types of site. Relatively fewer large frog colonies (≡100 animals) were found to occur in London than elsewhere in Britain, and British colonies were generally larger than those in Ireland. Colonies of 100 or more individuals were recorded relatively more frequently for toads than for frogs. By combining information on choice of site and colony size, rough estimates can be derived of the percentage of frogs and toads breeding in gardens and other types of site. For instance, in the London area in the 1960s perhaps 20–25% of the frogs bred in gardens and private grounds. The ecological significance of these observations is discussed.     

Autumn sowing increases severity of pasmo (Mycosphaerella linicola) on linseed in the UK

Surveys and field experiments showed pasmo to be the most serious disease affecting UK winter linseed in the 1997–98, 1998–99 and 1999–2000 growing seasons. Survey data indicated that pasmo was widespread in England and Scotland, causing extensive loss of leaves and stem and capsule symptoms, on both winter and spring linseed crops. In winter linseed experiments at ADAS Boxworth and Rothamsted, when severe epidemics occurred (1997–98 and 1999–2000), control of pasmo with one or two MBC fungicide sprays increased yield. In experiments when severe pasmo epidemics did not occur (1998–99), fungicide applications did not increase yield. In all three growing seasons, large numbers of air-borne Mycosphaerella linicola ascospores were collected in the summer months. At the time when the winter linseed crop was emerging and becoming established in October/November, there were more air-borne M. linicola ascospores in 1999 than in 1998. April/May rainfall was much greater in 1998 (135 mm) and 2000 (223 mm), when severe pasmo epidemics developed by July, than in 1999 (68 mm) when disease severity in July was less. Regression analyses suggested that yield decreased as percentage area affected by pasmo on leaves or stems in July increased. The formulae relating yield loss to pasmo severity, derived from these experiments, were combined with disease survey data to estimate, retrospectively, the UK national losses from pasmo. Estimated national losses from pasmo on winter linseed, although >50% of crops were sprayed with fungicide, were approximately £2.9M in 1998, £1.6M in 1999 and £0.37M in 2000 (when the area of winter linseed had decreased greatly). Estimated combined losses on winter and spring linseed were approximately £14.8M in 1998, £34.9M in 1999 and £11.0M in 2000.     

Small wild bee abundance declines with distance into strawberry crops regardless of field margin habitat

The preservation of pollinator habitat on croplands in the form of hedgerows, wildflower strips, and natural and semi-natural areas can help maintain and enhance wild bee populations in agricultural landscapes. However, there have been few comparisons of the effectiveness of different types of field-margin pollinator habitat in maintaining bee diversity and pollination of the focal crops. We compared wild bee abundance, species richness and community composition between strawberry crops bordered by hedgerows, and those bordered by larger expanses of natural land (forests). Strawberry is an ideal crop in which to investigate pollinator export from field margins as the rows are covered with straw, which reduces habitat for ground-nesting bees within the crop; thus, most wild pollinators need to enter the crop from the margins. We sampled bees in six strawberry fields with hedgerow margins and six strawberry fields with forested margins of at least 200 m in length, using a paired design. We examined strawberry pollen deposition at regular intervals into the fields, and the magnitude of pollinator export from the field margins towards the centre of the crops. We found that bees as a group were no more species-rich or abundant in crops bordered by forests than in crops bordered by hedgerows, although large-bodied bees were more abundant in the former than the latter. Regardless of field-margin type, we found that small wild bee abundance declined significantly from the edge to the centre of the crop, but honey bee (Apis mellifera L.) and large-bodied bee abundance did not. Strawberry pollen deposition also did not decline with distance into the crop. Although previous work indicates that small wild bees are more effective (yield-increasing) pollinators of strawberry on a per-visit basis, their limited foraging ranges suggest they may only pollinate areas near the crop margins, given typical field sizes in our area.     

The consequences of clustering by Aphis fabae foundresses on spring migrant production

Aphis fabae (Homoptera: Aphididae) foundresses were shown to have a clustered distribution on leaves of their primary host, Euonymus europaeus. Two field experiments were carried out to determine the costs or benefits of this clustering behaviour to aphid clones. The first experiment, in spring 1996, excluded predators from colonies formed by single fundatrices or clusters of three. No density-dependent effects on colony growth were observed early in the season, but the total production of migrants per foundress was significantly lower for clustered foundresses. This demonstrated that there was no synergistic effect of group feeding on clonal performance. All colonies were initiated on randomly selected leaves and all grew successfully, therefore clustering was not due to a shortage of feeding sites. The second experiment, in spring 1997, tested whether natural enemies cause selection for selfish herding by the foundress generation. Colonies were initiated by one or three foundresses, but half were left unbagged. If natural enemy attack is a selective force inducing clustering behaviour in foundresses, the costs of clustering should have been reduced or negated in unbagged colonies. Colonies grown from clusters produced significantly fewer migrants per foundress, irrespective of bagging treatment. Other potential factors causing clustering behaviour are discussed. Received: 19 August 1998 / Accepted: 16 November 1998     

Patterns of migration and residency in coastal cutthroat trout Oncorhynchus clarkii clarkii from two tributaries of the lower Columbia River

Coastal cutthroat trout Onchorhynchus clarkii clarkii life-history variants, migration and freshwater residency were monitored using stationary passive integrated transponder (PIT) tag arrays in two tributaries of the Columbia River from 2001 to 2005 (Abernathy Creek, river kilometre, rkm 76) and from 2002 to 2005 (Chinook River, rkm 6). In 2001–2003 and 2002–2003 (Abernathy and Chinook, respectively), 300–500 coastal O. c. clarkii were captured in each tributary by electrofishing and implanted with 23 mm PIT tags. PIT arrays monitored movements from the initiation of tagging through the spring of 2005. Rotary screw traps were also operated on both tributaries. In Abernathy Creek, 28% of tagged individuals were observed through either active capture or passive interrogation. Of these, 32% were identified as migrants and 68% were identified as residents. In the Chinook River, 48% of tagged fish were observed subsequent to tagging; 92% of these fish were migrants and only 8% were resident. In both tributaries, a greater proportion of resident fish were in the upper reaches. The majority of migrants (78–93%) moved the spring following tagging. Migrants leaving at age 2+ years tended to grow faster than those that migrated at age 3+ years or residents. Patterns of growth or growth opportunities may influence both patterns of life-history expression and the timing of migration.     

Field estimation of variation in host plant use between local populations of pea aphids from two crops

Abstract. 1. In a reciprocal transplant experiment on pea aphids (Acyrthosiphon pisum (Harris)), the relative performance of clones collected from nearby alfalfa and red clover fields was tested by allowing clonal replicates to develop on both crops under field conditions.
2. Populations from alfalfa and red clover differed in relative survivorship and probabilities of reproduction on the two crops. Clones had significantly higher performance on the crop from which they were collected (the 'home' crop) than they did on the other crop.
3. Evidence is presented that previous experience on these host plants cannot account for the increased probability of reproduction observed on the 'home' crop. Thus, the differences between these two populations in their relative performance on alfalfa and clover are likely to be genetically based.
4. These results illustrate that local adaptation to different host plants can occur within small geographical areas, despite the high probability that migrants are exchanged between nearby fields of the two crops.
5. Experimental designs of the type described here permit estimation of patterns of genetic variation within and between insect populations. When applied to pest species, such designs will facilitate the study of evolution in agricultural systems.     

An assessment of the breeding range,colony sizes and population of the Westland petrel (Procellaria westlandica)

Abstract

The Westland petrel (Procellaria westlandica) is an endemic New Zealand species and one of the very few burrowing seabird species still breeding on mainland New Zealand. It nests only on a series of coastal ridgelines near to Punakaiki on the West Coast of the South Island. Between 2002 and 2005, surveys were undertaken at 28 of the 29 known colonies. The area occupied by the colonies was 73 ha; most colonies had fewer than 50 burrows, but six colonies had 201–500 burrows and four colonies had more than 1000 burrows. We find that the current breeding range of Westland petrel and the location of individual colonies are similar to those reported in both the 1950s and 1970s. Based on total burrow counts at 28 colonies and burrow occupancy rates determined by annual monitoring, the annual breeding population is estimated to be between 2954 and 5137 breeding pairs.     

The disproportionate effect of global warming on the arrival dates of short-distance migratory birds in North America

Recent studies have shown that, in response to global climate change, diverse avian taxa are now nesting measurably earlier (< 10 days) in both the United States and Britain. Similarly, several studies on European birds have now demonstrated that a variety of species (although not all) are arriving increasingly early. However, surprisingly, widespread changes in North American migrant phenology have not been demonstrated. It is hypothesized that short-distance migrants (birds that winter in the southern United States) may be quicker to adapt to climate change than long-distance migrants (birds that winter south of the United States), as short-distance migrants can respond to meteorological cues indicating weather conditions to the north whereas long-distance migrants must rely on photoperiod. This study examined the first arrival dates of 103 migrant birds in New York and Massachusetts and found that, on average, all migrants arrived significantly earlier during the period 1951–1993 than the period 1903–1950. From 1951–1993 birds wintering in the southern United States arrived on average 13 days earlier while birds wintering in South America arrived 4 days earlier. Although a change in observer effort cannot be quantified and may be a source of bias, a comparison of the numbers of reporting observers during the 1930s and the 1980s revealed no significant difference. These results are consistent with those expected under a scenario of global warming.     

Genetic structure of fragmented November moth (Lepidoptera: Geometridae) populations in farmland

Habitats are now becoming increasingly fragmented throughout the world due to intense cultivation. As a consequence, populations of some animals with low mobility have become isolated, thus increasing the risk of inbreeding and local extinction. In Britain, weakly flying geometric moths of the genus Epirrita are a good model species with which to test the genetic effects of habitat fragmentation on insect populations. Genetic variation within and between populations of two Epirrita species captured using a network of light traps at two spatial scales (local and national) was assessed using allozyme electrophoresis, with particular reference to the local scale (the 330-ha arable farm estate at Rothamsted, Hertfordshire, in southern Britain). Populations sampled widely in England and Wales displayed low (but statistically significant) levels of genetic differentiation for both species ( F _st  = 0.0051–0.0114 and 0.0226 for E. dilutata and E. christyi , respectively). However, analysis of large samples of E. dilutata from four small woods at Rothamsted revealed low ( F _st  = 0.0046) but significant differentiation, indicating that gene flow was restricted, even at this very small scale. It was concluded that small intervening patches of farmland (often a few fields width) were enough to prevent genetic homogeneity. The close similarity between more distant Epirrita populations was considered to be a result of historical, rather than recurrent gene flow, as genetic equilibrium between drift and gene flow is unlikely over such scales.  © 2003 The Linnean Society of London . Biological Journal of the Linnean Society , 2003, 78 , 467–477.     

The effects of agricultural management on the reproductive activity of female rodents in Argentina

The aim of this study was to test if female rodents in border habitats of organic farms have higher reproductive activity than those of conventional farms in south-east Córdoba province, Argentina. The study was conducted in field borders of organic and conventional farms in 2012 and 2013 during the summer months, the time of the year when reproductive activity is more likely. We sampled field borders through a CMR trapping session and recorded vegetation cover, plant litter, vegetation volume, bare ground cover and land use of the field on both sides of the border (crop/crop or crop/pasture). We recorded the number of reproductive females and the rate of postpartum estrus. Green vegetation cover was higher in organic borders whereas plant litter was higher in borders of conventional farms. We used Generalized Linear Mixed Models (GLMM) to determine the factors that influence the number of reproductive females in borders of organic and conventional farms. The number of reproductive females was mainly determined by agriculture management and field type. There were more reproductive females in organic than in conventional borders, and borders associated with crop fields at both sides supported the highest number of reproductive females. The rate of postpartum estrus was higher in organic than in conventional borders. Our results showed that in border habitats of farms under organic management reproductive activity of female rodents was higher than in borders of conventional farms. Organic farm borders may provide high quality habitats that provide resources for reproduction and persistence of rodent populations.     

Effects of routine late-season field operations on numbers of boll weevils (Coleoptera: Curculionidae) captured in large-capacity pheromone traps

Flat and cylindrical adhesive boll weevil, Anthonomus grandis grandis Boheman (Coleoptera: Curculionidae), pheromone traps captured significantly more (P < or = 0.05) boll weevils than the Hercon (Hercon Environmental, Emigsville, PA) trap during the late cotton-growing season, and larger adhesive areas were associated with higher captures; a flat plywood board collected the most boll weevils because it had the largest surface area. The flat board trap, chosen for measuring large late-season adult boll weevil populations common to the Lower Rio Grande Valley of Texas in 2000 and 2001, collected more (P < or = 0.05) weevils when deployed in proximity to natural and cultivated perennial vegetation, and mean numbers of captured boll weevils were higher (P < or = 0.0001) on the leeward sides of the board traps than on the windward sides. The board trap had an estimated potential capacity of approximately 27,800 boll weevils, and the large capacity of the board trap allowed for more accurate measurements of large adult boll weevil populations than the more limited Hercon trap. Measurement of adult boll weevil numbers after the routine field operations of defoliation, harvest, shredding, and stalk-pulling, demonstrated that large populations of boll weevils persist in cotton fields even after the cotton crop has been destroyed. Increases (P < or = 0.05) in the percentage variation of trapped boll weevils relative to the numbers collected just before each field operation were observed after defoliation, harvest, shredding, and stalk-pulling, but the percentage variations followed a quadratic pattern with significant correlation (P < 0.0001; 0.59 < adjusted r2 < 0.73). Numbers of adult boll weevils caught on board traps deployed at 15.24-m intervals on windward and leeward edges of cotton fields suggested that boll weevil populations in flight after field disturbances might be affected by large-capacity trapping.