Unsprayed Sites Research Articles

High pesticide exposure and risk to bees in pollinator plantings adjacent to conventionally managed blueberry fields

Wildflower plantings adjacent to agricultural fields provide diverse floral resources and nesting sites for wild bees. However, their proximity to pest control activities in the crop may result in pesticide exposure if pesticides drift into pollinator plantings. To quantify pesticide residues in pollinator plantings, we sampled flowers and soil from pollinator plantings and compared them to samples from unenhanced field margins and crop row middles. At conventionally managed farms, flowers from pollinator plantings had similar exposure profiles to those from unenhanced field margins or crop row middles, with multiple pesticides and high and similar risk quotient (RQ) values (with pollinator planting RQ: 3.9; without pollinator planting RQ: 4.0). Whereas samples from unsprayed sites had significantly lower risk (RQ: 0.005). Soil samples had overall low risk to bees. Additionally, we placed bumble bee colonies (Bombus impatiens) in field margins of crop fields with and without pollinator plantings and measured residues in bee-collected pollen. Pesticide exposure was similar in pollen from sites with or without pollinator plantings, and risk was generally high (with pollinator planting RQ: 0.5; without pollinator planting RQ: 1.1) and not significant between the two field types. Risk was lower at sites where there was no pesticide activity (RQ: 0.3), but again there was no significant difference between management types. The insecticide phosmet, which is used on blueberry farms for control of Drosophila suzukii, accounted for the majority of elevated risk. Additionally, analysis of pollen collected by bumble bees found no significant difference in floral species richness between sites with or without pollinator plantings. Our results suggest that pollinator plantings do not reduce pesticide risk and do not increase pollen diversity collected by B. impatiens, further highlighting the need to reduce exposure through enhanced IPM adoption, drift mitigation, and removal of attractive flowering weeds prior to insecticide applications.

Effect of desert locust control on non-target edible termites in eastern Uganda

Effects of widescale locust control with insecticides on non-target edible insects have been scarcely assessed. This study was carried out to investigate the effect of spraying desert locust with cypermethrin and chlorpyrifos on: (1) termite mound activity; (2) safety of edible termites from contamination with pesticide residues; and (3) nutritional composition of non-target edible termites. Incidences of inactive termitaria in the sprayed and unsprayed sites were enumerated. Edible soldiers ofMacrotermes spp. from sprayed and unsprayed colonies whose alates swarm around dusk, midnight and dawn were analysed for cypermethrin and chlorpyrifos residues, and proximate, mineral and flavonoid compositions. The pesticide sprays did not influence the incidence of inactive termitaria. No cypermethrin and chlorpyrifos residues were detected in the termites. Chlorpyrifos spraying lowered crude fibre and protein contents in soldiers of dawn and midnight swarming colonies, respectively; whereas cypermethrin spraying lowered ash and crude fat contents in soldiers from dawn and dusk swarming colonies, respectively. Cypermethrin spraying increased moisture content in soldiers from midnight swarming colonies. The level of manganese in soldiers from dawn swarming colonies was lowered by cypermethrin spraying, while contents of aluminium and cobalt from the same type of colony were lowered by chlorpyrifos spraying. However, levels of calcium, potassium, magnesium, phosphorus, zinc, aluminium, manganese and iron were enhanced in soldiers from different termite colonies sprayed with cypermethrin and/or chlorpyrifos. Similarly, soldier termite samples from both insecticide sprayed sites contained higher flavonoid levels than the samples from unsprayed sites. Freedom of the edible soldier termites from the pesticides residues renders them safe for consumption. The results provide insights into the likely effects of wide-scale pesticide sprays against locust on the nutritional profiles of edible termites.

Response of cavity nesting birds to Lymantria dispar (Lepidoptera) and aerial spraying – An experimental approach

Eruptive population dynamics of forest insect species regularly attract the interest of ecologists but also often evoke debates among stakeholders concerning impacts that outbreaks or pest control activities have on forest communities including insectivorous birds. Lymantria dispar is the most serious native defoliator in mixed oak-broadleaf forests in Central Europe. To investigate the treatment effects of L. dispar density, aerial application of the insecticide Mimic (tebufenozide) and nest box accessibility for L. dispar caterpillars on nest box success of cavity nesting birds, we deployed 352 nest boxes in a full factorial experimental design with 11 replicates. L. dispar density was predicted by egg mass counts made in the year before the study. The accessibility of nest boxes for L. dispar caterpillars was manipulated in all study sites by placing nest boxes on trunks for easy access to caterpillars and on branches for more difficult access. Successful nest boxes (binary metric that combines failed breeding attempt and empty nest box) and nest productivity (number of fledged chicks in successful boxes) were monitored in the peak year of a L. dispar outbreak, during which half of the plots were treated with Mimic, as well as in the following year when L. dispar populations had widely collapsed, and no further treatments were applied. L. dispar and non-target caterpillar biomass was sampled by canopy fogging to quantify prey abundance. Caterpillar biomass was significantly reduced by Mimic in the treatment year and remained low in the post-treatment year. Despite the reduction of caterpillars, our zero-inflation model found no effect of any tested variables on nest box success of the early brood. However, in the late broods the number of successful nest boxes was reduced in Mimic treated plots in the first year by 42%, while unaffected by initial L. dispar density. The number of successful nest boxes in the second year was lower in areas with initially high L. dispar densities and there was a marginal carry-over effect of insecticide treatment. L. dispar caterpillars entered nest boxes on the trunk in higher numbers than boxes on the branch, but nest box position had no effect on nest box success of birds.We conclude that despite its strong negative impact on caterpillar prey, aerial application of Mimic targeting L. dispar caused an increase in the number of failed boxes in late broods in sprayed plots, particularly in the year of application and to some extent in the year after. We presume this delayed effect of Mimic only on late broods to be caused by Mimic-induced caterpillar shortages during first broods leading to an increased parental effort and a subsequent reduced number of second broods. The generally limited impact of Mimic might be explained by the overall extensive availability of alternate prey in oak forests in May during first broods and the ability of tits to increase their parental effort in times of caterpillar shortage. In unsprayed sites, L. dispar densities can create legacies of impact in following years, but caterpillars do not directly affect birds nest box success despite entering cavities.

Short Persistence and Vector Susceptibility to Ficam 80WP (bendiocarb active ingredient) During Pilot Application of Indoor Residual Spraying in Burkina Faso, West Africa.

Indoor residual spraying (IRS) was applied in addition to the use of long-lasting insecticidal nets in the South West in Burkina Faso, where Anopheles gambiae s.l. the major malaria vector was resistant to pyrethroids. This study was designed to evaluate the efficacy and residual life of bendiocarb (active ingredient) used for spraying on different wall surfaces (mud and cement). Cone bioassays were done monthly with the susceptible An. gambiae 'Kisumu' strain and the local wild populations to determine the duration for which insecticide was effective in killing mosquitoes. Cone bioassay data showed low efficacy and short persistence of bendiocarb applied on mud and cement walls, lasting 2 mo with the susceptible insectary strain and less than 1 mo with An. gambiae wild populations. In addition, WHO tube assays confirmed resistance of An. gambiae wild populations to 0.1% bendiocarb with mortality rates less than 80% in both study sites (sprayed and unsprayed sites). The pilot study of IRS with bendiocarb showed that the residual efficacy of bendiocarb was very short, and resistance to bendiocarb was confirmed in wild populations of An. gambiae s.l. Therefore, Ficam 80 WP was not suitable for IRS in this area due to the short residual duration related mainly to vectors resistance to bendiocarb. While waiting for innovative malaria control tool, alternative insecticide (organophosphate or neonicotinoid classes) or combinations of insecticides have to be used for insecticide resistance management in Burkina Faso.

Malaria vector species composition and entomological indices following indoor residual spraying in regions bordering Lake Victoria, Tanzania

BackgroundVector control through long-lasting insecticidal nets (LLINs) and focal indoor residual spraying (IRS) is a major component of the Tanzania national malaria control strategy. In mainland Tanzania, IRS has been conducted annually around Lake Victoria basin since 2007. Due to pyrethroid resistance in malaria vectors, use of pyrethroids for IRS was phased out and from 2014 to 2017 pirimiphos-methyl (Actellic® 300CS) was sprayed in regions of Kagera, Geita, Mwanza, and Mara. Entomological surveillance was conducted in 10 sprayed and 4 unsprayed sites to determine the impact of IRS on entomological indices related to malaria transmission risk.MethodsWHO cone bioassays were conducted monthly on interior house walls to determine residual efficacy of pirimiphos-methyl CS. Indoor CDC light traps with or without bottle rotator were hung next to protected sleepers indoors and also set outdoors (unbaited) as a proxy measure for indoor and outdoor biting rate and time of biting. Prokopack aspirators were used indoors to capture resting malaria vectors. A sub-sample of Anopheles was tested by PCR to determine species identity and ELISA for sporozoite rate.ResultsAnnual IRS with Actellic® 300CS from 2015 to 2017 was effective on sprayed walls for a mean of 7 months in cone bioassay. PCR of 2016 and 2017 samples showed vector populations were predominantly Anopheles arabiensis (58.1%, n = 4,403 IRS sites, 58%, n = 2,441 unsprayed sites). There was a greater proportion of Anopheles funestus sensu stricto in unsprayed sites (20.4%, n = 858) than in sprayed sites (7.9%, n = 595) and fewer Anopheles parensis (2%, n = 85 unsprayed, 7.8%, n = 591 sprayed). Biting peaks of Anopheles gambiae sensu lato (s.l.) followed periods of rainfall occurring between October and April, but were generally lower in sprayed sites than unsprayed. In most sprayed sites, An. gambiae s.l. indoor densities increased between January and February, i.e., 10–12 months after IRS. The predominant species An. arabiensis had a sporozoite rate in 2017 of 2.0% (95% CI 1.4–2.9) in unsprayed sites compared to 0.8% (95% CI 0.5–1.3) in sprayed sites (p = 0.003). Sporozoite rates were also lower for An. funestus collected in sprayed sites.ConclusionThis study contributes to the understanding of malaria vector species composition, behaviour and transmission risk following IRS around Lake Victoria and can be used to guide malaria vector control strategies in Tanzania.

Effect of Bendiocarb (Ficam® 80% WP) on Entomological Indices of Malaria Transmission by Indoor Residual Spraying in Burkina Faso, West Africa

Context: The vector control is essential in malaria prevention strategies in several endemic countries in Africa including Burkina Faso. The high transmission of malaria occurs during the period of high vector abundance (August to October) in Burkina Faso. Therefore, a vector control strategy based on the use of indoor residual spraying targeting this period should provide effective protection against malaria. This study aimed to evaluate the effect of bendiocarb applied in indoor residual spraying on entomological parameters of malaria transmission in a pyrethroid resistance area in southwestern, Burkina Faso. Methods: CDC light trap and early morning collections by pyrethrum spray catches were performed monthly to determine the change in entomological parameter within malaria vector in sprayed (Diebougou) and unsprayed sites (Dano). The female’s malaria vectors collected by both methods were used to determine their blood feeding pattern, biting and sporozoites rates as well as the malaria transmission risk estimated by entomological inoculation rate. Results: A total of 26,276 mosquitoes (13,555 anopheline and 12,721 other culicines) were collected using both CDC light trap (9158 mosquitoes) and PSC collection methods (17,118 mosquitoes) from June to December 2012. An. gambiae complex was the predominant species collected. An. gambiae was the predominant species collected (P = 0.0005), comprising 88% of the total collected and the most infected species. Malaria vectors densities were significantly lower in sprayed villages (n = 4303) compared with unsprayed villages (n = 12,569) during post-spraying period (P = 0.0012). In addition, mean human biting rate of An. gambiae s.l. and An. funestus s.l. were significantly lower in sprayed areas compared to unsprayed areas (P (An. gambiae s.l. and An. An. funestus s.l.). Conclusions: The results showed that in the sprayed area (Diebougou), vector densities, human biting rates and malaria transmission risks were very lower than unsprayed areas (Dano). The findings also showed a change in vector behavior especially within An. funestus s.l. which became more zoophagic following IRS. The indoor residual spraying could be promoted as a control tool in areas where malaria transmission occurs during a given period of year.

Effects of the organophosphate fenthion for control of the red-billed quelea Quelea quelea on cholinesterase and haemoglobin concentrations in the blood of target and non-target birds

The red-billed quelea bird Quelea quelea is one of sub-Saharan Africa's most damaging pests, attacking small-grain crops throughout semi-arid zones. It is routinely controlled by spraying its breeding colonies and roosts with organophosphate pesticides, actions often associated with detrimental effects on non-target organisms. Attributions of mortality and morbidity of non-targets to the sprays are difficult to confirm unequivocally but can be achieved by assessing depressions in cholinesterase activities since these are reduced by exposure to organophosphates. Here we report on surveys of birds caught before and after sprays that were examined for their blood cholinesterase activities to assess the extent to which these became depressed. Blood samples from birds were taken before and after sprays with fenthion against red-billed quelea in colonies or roosts, and at other unsprayed sites, in Botswana and Tanzania and analysed for levels of haemoglobin (Hb) and activities of whole blood acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). Background activities of AChE, BChE and Hb concentrations varied with bird species, subspecies, mass, age and gender. Contrary to expectation, since avian erythrocytes are often reported to lack cholinesterases, acetylcholinesterase activities in pre-spray samples of adult birds were positively correlated with Hb concentrations. When these factors were taken into account there were highly significant declines (P < 0.0001) in AChE and BChE and increases in Hb after contact with fenthion in both target and non-target birds. BChE generally declined further (up to 87 % depression) from baseline levels than AChE (up to 83 % depression) but did so at a slower rate in a sample of quelea nestlings. Baseline activities of AChE and BChE and levels of Hb were higher in the East African subspecies of the red-billed quelea Q. q. aethiopica than in the southern African subspecies Q. q. lathamii, with the exception of BChE activities for adult males which were equivalent.

Investigating the Effect of Invasion Characteristics on Onion Thrips (Thysanoptera: Thripidae) Populations in Onions With a Temperature-Driven Process Model

A temperature-driven process model was developed to describe the seasonal patterns of populations of onion thrips, Thrips tabaci Lindeman, in onions. The model used daily cohorts (individuals of the same developmental stage and daily age) as the population unit. Stage transitions were modeled as a logistic function of accumulated degree-days to account for variability in development rate among individuals. Daily survival was modeled as a logistic function of daily mean temperature. Parameters for development, survival, and fecundity were estimated from published data. A single invasion event was used to initiate the population process, starting at 1-100 d after onion emergence (DAE) for 10-100 d at the daily rate of 0.001-0.9 adults/plant/d. The model was validated against five observed seasonal patterns of onion thrips populations from two unsprayed sites in the Riverina, New South Wales, Australia, during 2003-2006. Performance of the model was measured by a fit index based on the proportion of variations in observed data explained by the model (R (2)) and the differences in total thrips-days between observed and predicted populations. Satisfactory matching between simulated and observed seasonal patterns was obtained within the ranges of invasion parameters tested. Model best-fit was obtained at invasion starting dates of 6-98 DAE with a daily invasion rate of 0.002-0.2 adults/plant/d and an invasion duration of 30-100 d. Under the best-fit invasion scenarios, the model closely reproduced the observed seasonal patterns, explaining 73-95% of variability in adult and larval densities during population increase periods. The results showed that small invasions of adult thrips followed by a gradual population build-up of thrips within onion crops were sufficient to bring about the observed seasonal patterns of onion thrips populations in onion. Implications of the model on timing of chemical controls are discussed.

Change of Abundance of Arthropods in Pine Forests Caused by Aerial Insecticide Spray

As pine wilt disease (PWD) spread rapidly throughout the Republic of Korea, pine stands were subjected to insecticide spraying that was gradually increased, which raised concerns regarding the negative impact of insecticides sprayed on nontarget organisms of pine forests. This study aims to estimate the changes in the abundance of arthropods caused by long-term insecticide spraying common in PWD-infected forests. Four pine stands were selected as sprayed and unsprayed sites in two locations in the southern regions of Busan and Gyongnam-do, showing the peaks of PWD epidemics. Beatings, sweepings, and pitfall trappings were used for collecting arthropods at the crown, undergrowth, and ground for 4 years, starting in May 2001. Long-term effects caused by yearly repeated insecticide treatments were not found to be related to changes in the abundance of arthropods, but short-term impacts within a year showed different influences according to habitats and functional groups.

Species composition and population dynamics of leafmining flies and their parasitoids in Victoria

Abstract Mined leaves were sampled from unsprayed sites in Victoria to record the range of leafminers and their parasitoids. Three agromyzid leafminers, Liriomyza brassicae (Riley), Liriomyza chenopodii (Watt) and Chromatomyia syngenesiae Hardy, and one drosophilid leafminer, Scaptomyza flava (Fallén), were collected, along with 15 parasitoids, mainly Eulophidae. The most common parasitoids were Hemiptarsenus varicornis (Girault) (42.5%), Diglyphus isaea (Walker), 14.6%, Closterocerus mirabilis Edwards &amp; La Salle (10.5%), and Opius cinerariae Fisher (8.5%). Most parasitoids were collected from two or more leafminer hosts. Weekly collections from Chinese cabbage (Brassica rapa var. pekinensis) infested with L. brassicae and S. flava, and beetroot (Beta vulgaris var. crassa) infested with L. chenopodii were made over two seasons at Knoxfield, Victoria to assess the relative impact of these parasitoids on agromyzid fly populations in crops. A further two parasitoid species were identified at low densities. Hemiptarsenus varicornis and D. isaea were the most numerous parasitoids collected in both crops. A different sampling method in the second year showed that O. cinerariae made up 25% of the sample from Chinese cabbage and was probably more common than estimated in the first season. Control exerted by local parasitoids was high, with 100% control of L. chenopodii reached in beets within 1–3 weeks of mines appearing and 100% control of L. brassicae within 6 weeks.

Effects of aerial insecticide sprays on ant communities to control pine wilt disease in Korean pine forests

Pine wilt disease is one of the most serious diseases in the pine forests of Korea. Since the first report of the disease in Busan, Korea, in 1988, the disease has been gradually spreading into neighboring regions and now occurs in many regions of the southern part of the Korean Peninsula. The control of the disease is focused on the killing of the sawyer, Monochamus alternatus, an insect vector, by aerial insecticide spraying for adult control and by fumigation or burning infected trees for larval control. This study was conducted to evaluate the effects of aerial insecticide application on pine forest fauna by comparing ant communities in insecticide-sprayed and unsprayed areas. Samples were collected from five regions using three different sampling methods (pitfall trap, sweeping net, and shaking net). The results showed that community indices such as abundance, species richness and species diversity were not significantly different between insecticide-sprayed sites and unsprayed sites. According to a cluster analysis and a correspondence analysis, ant communities were generally grouped based on the location of the sampling sites with a slight variation of insecticide application, but not grouped by insecticide application, showing that ant community structures were not significantly different between the insecticide-sprayed sites and the unsprayed sites. Our results, overall, support the theory that the impact of the aerial insecticide application on pine forest fauna may be less severe than expected.

Impact of locust control on harvester termites and endemic vertebrate predators in Madagascar

Summary Between 1997 and 2000 a plague of migratory locust in Madagascar triggered large‐scale control operations. The widespread use of insecticides in a biodiversity hot‐spot raised concern about hazards to wildlife. The aim of this study was to inform locust control policy by monitoring the effects of insecticides on key non‐target organisms. The focus was on the harvester termite Coarctotermes clepsydra and its vertebrate predators. Effects on Coarctotermes clepsydra were studied in two areas. At Ankazoabo in 1998, we monitored rainy season barrier treatments with fipronil and triflumuron. At Malaimbandy in 2000, we monitored early dry season, full‐cover sprays with fipronil and deltamethrin and also studied effects on the lizards Chalarodon madagascariensis and Mabuya elegans, the lesser hedgehog tenrec Echinops telfairi and their non‐termite arthropod prey. At both sites, fipronil caused a strong reduction of the activity of Coarctotermes clepsydra colonies, culminating in high mortality. At Ankazoabo 10 months post‐spray, colony mortality was 44·9%, 7·7% and 4·7%, respectively, in fipronil, triflumuron and unsprayed sites. Mortality within spray barriers was 90·7% and 10·8% for fipronil and triflumuron, respectively. Similar results were obtained at Malaimbandy 6 months post‐spray, where fipronil caused 80·5% colony mortality, compared with 3·5% and 3·7% in unsprayed and deltamethrin plots. We observed a significant decline in the relative abundance of Chalarodon madagascariensis and Mabuya elegans in fipronil plots at Malaimbandy, with effective reductions (compared with pre‐spray levels) of 52·7% and 45·2%, respectively. Echinops telfairi was not found in fipronil plots, while being frequent in unsprayed and deltamethrin plots. Termites proved to be important dietary components of all vertebrates studied, especially during the dry season. Echinops telfairi, the large‐eared tenrec Geogale aurita and Mabuya elegans were more termite‐specialized than Chalarodon madagascariensis. The abundance of lizards and Echinops telfairi was positively correlated with the density of live Coarctotermes clepsydra colonies. This suggests that reduced abundance of these insectivorous species in fipronil plots resulted from deprivation of their principal prey. Synthesis and applications. The present study provides evidence of food chain perturbations induced by fipronil. This has important implications for the management of locusts in Madagascar and other locust‐affected countries. In recognition of the precautionary principle, we recommend that fipronil be withheld from full‐cover spraying to ensure that locust control does not lead to biodiversity loss. Its use in barrier spraying requires further investigation of the long‐term ecological effects, in particular with respect to the consequences of substantial termite mortality, before its environmental acceptability can be determined.

POTENTIAL IMPACTS OF BACILLUS THURINGIENSIS VAR. KURSTAKI ON FIVE SALAMANDER SPECIES IN WEST VIRGINIA

Abstract Indirect effects of the microbial pesticide, Bacillus thuringiensis var. kurstaki (B.t.k.), have been found in birds, mammals, and some parasitic insects as a result of reduced abundance of lepidopteran larvae. Salamanders are insectivores that often contain high percentages of lepidopteran larvae in their diets. This study tested the hypothesis that salamanders experience dietary shifts or reduced abundance on plots where B.t.k. is applied, as a function of decreased caterpillar abundance. Three plots in the Monongahela National Forest, Pocahontas County, WV were sprayed with B.t.k., three were sprayed with the gypsy moth nuclear polyhedrosis virus (Gypchek®), and three remained as unsprayed reference sites. Abundance and diet composition of five species of Plethodontidae (Desmognathus fuscus, D. monticola, D. ochrophaeus, Plethodon cinereus, P. glutinosus) were studied for two years. Neither salamander abundance nor the proportions of the major prey items in their diets differed significantly b...

Inoculative Release and Establishment of Holcothorax testaceipes (Hymenoptera: Encyrtidae), a Palaearctic Agent for the Biological Control of Phyllonorycter spp. (Lepidoptera: Gracillariidae) in Connecticut Apple Orchards

In May 1988, inoculative releases (≈6,000 adults per site) of a Japanese strain of the encyrtid Holcothorax testaceipes (Ratzeburg) were made in the center of two unsprayed and two sprayed Connecticut apple orchards infested by Phyllonorycter spp. The encyrtid became established only at unsprayed sites, killing between 1 and 35% of parasitized larvae of Phyllonorycter blancardella (F.) in generations examined between 1988 and 1991. The proportion of parasitized larvae killed by H. testaceipes was higher in the first and third generation than in the second generation, which was a pattern sometimes observed in the endoparasitic Pholetesor omigis (Weed). The relative amount of mortality caused by H. testaceipes differed between unsprayed sites. In all orchards, the braconid P. omigis or the eulophid Sympiesis marylandensis Girault tended to dominate parasitoid guilds both before and after the release. The total amount of parasitism was higher at unsprayed than at sprayed sites, and parasitism by H. testaceipes was higher in the first than in the second generation. The amount of parasitism by the encyrtid was distributed uniformly throughout orchards in four of six (66.7%)generational samples. After the first generation of 1988, the mean distance of progeny from the tree where adults initially were released was similar in each generation within an orchard. In unsprayed orchards, the density in the generation of the release was 1.0-1.7 mines per 100 leaves, and density never exceeded 6.1 mines per 100 leaves thereafter. Persistence at low mine densities, oviposition in leafminer eggs, and rapid dispersal after release are desirable attributes of H. testaceipes , but itswidespread establishment in commercial orchards will depend on modifying current chemical control programs or releasing a resistant strain.

Effects of DDT treatments applied for tsetse fly control on White-headed Black Chat (Thamnolaea arnoti) populations in Zimbabwe. Part II: cause of decline

Food supply, breeding success and DDT residue accumulation were investigated as possible causes for the decline of White-headed Black Chat populations in woodland sprayed for tsetse fly control. Gut contents from 21 birds were examined. A variety of invertebrates had been eaten, but ants, especiallyCamponotus spp. (Formicidae: Formicinae),Pheidole spp. (Myrmicinae), and termites, especiallyOdontotermes spp. (Isoptera: Termitidae), predominated in the dry season. In the early rains, more beetles (Coleoptera (predominantly Curculionidae)) and fewer termites were eaten. Ant and termite activity at sprayed sites in the study area was as great as or greater than that at unsprayed sites. Ants (Camponotus spp.) from sprayed sites held mean residue levels of 8.71 µg g(-1) dry weight (max. 218 µg g(-1) dry weight) total DDT, of which 67% was unaltered DDT. Termites and beetles had mean residue levels of 3.32 µg g(-1) dry weight (max. 14 µg g(-1) dry weight) and 0.92 µg g(-1) dry weight (max. 8 µg g(-1) dry weight) total DDT, of which 44% and 37% was unaltered DDT, respectively. Fledging success of White-headed Black Chats in adjacent sprayed and unsprayed areas was similar. Residues of DDT, DDD and DDE were found in all 23 chat carcasses examined. Birds collected in the dry season (July) from an area sprayed one month before contained up to 2206 µg DDT, 367 µg DDD and 578 µg DDE, g(-1) extractable lipid (86, 17 and 27 µg g(-1) dry weight, respectively). On average, residue levels were 50 times higher than in birds from the unsprayed area, and 4 times higher than in birds taken from another, recently sprayed area in the early rains (November). It is concluded that DDT spraying did not reduce availability of prey or fledging success. Initial population decline in sprayed areas was due to a lethal accumulation of DDT residues from prey, especiallyCamponotus spp. ants. Possible reasons for continued decline for 2-3 years after spraying, are discussed.

Results of Experimental and Natural Food Reductions for Breeding Black‐Throated Blue Warblers

We examined effects of natural and experimentally created reductions in food abundance on the reproductive ecology of Black—throated Blue Warblers (Dendroica caerulescens). The study was carried out between 1982 and 1985 on four 30—ha plots of temperate deciduous forest within and near the Hubbard Brook Experimental Forest, New Hampshire, USA. Experimental food reduction using aerially sprayed Bacillus thuringiensis created significant differences in caterpillar biomass between one sprayed and two unsprayed plots throughout the breeding season in 1983. Where caterpillar abundance was reduced, Black—throated Blue Warblers made significantly fewer nesting attempts and diets of neslings included fewer caterpillars. Clutch size, hatching success, and numer of young fledging per nest did not differ among the food reduction site and controls. Also, the reduced number of nesting attempts per pair on the food reduction site in 1983 did not significantly lower production of young per pair. No detectable differences in caterpillar biomass between sprayed and unsprayed sites were created in 1984 or 1985 because natural caterpillar abundances were already low. Natural declines in food abundance for Black—throated Blue Warblers occurred from 1982 through 1985, primarily because of a decrease in caterpillar abundances. Significant reductions in number of young fledging per nest, nestling growth rates and survival, and number of nests attempted per pair corresponded with the natural decline in food abundance. Of those measures, a reduced number of nesting attempts per pair lowered annual production the most. When effects of food limitation were calculted separately from those of nest predation, food limited annual breeding productivity to below that needed to balance annual mortality in at least one of the four years of this study. These findings indicate that neotropoical migrant bird species are probably limited periodically by food when breeding in north—temperate habitats.

The ground beetle and spider fauna of managed and unimproved upland pasture

Ground beetles and spiders were sampled in 1985 and 1986 by pitfall trapping in improved upland grassland and unimproved grass and heather moorland. The aim of the work was to gain a preliminary idea of some effects of upland management on the dominant groups of epigeal polyphagous predatory arthropods. Unimproved sites had a much more diverse fauna and a larger catch of both groups, when compared with the improved grassland. There were, however considerable differences between the faunae of the individual unimproved sites. Improved grassland sites all had a rather similar, depleted fauna of both ground beetles and spiders. Improved sites which had been sprayed with the pesticide chlorpyrifos had a very low catch of ground beetles compared with unsprayed sites, but the catch was more diverse, consisting of small numbers of individuals of a wide range of immigrant species. There were no clear differences between the spider faunae caught on chlorpyrifos-sprayed and unsprayed sites. It is suggested that pasture improvement has a more drastic effect on ground beetle and spider communities than does subsequent pesticide use.

Nuvan resistance in a field strain of Aedes aegypti (L.) in Lagos, Nigeria

Field strains of Aedes aegypti in their larval stages were obtained from six selected sites in Lagos mainland. Their responses to dichlorvos (2,2-dichlorovinyl-0,0-dimethyl phosphate) were compared with that of standard insecticide-susceptible larvae from the Federal Ministry of Health Laboratory, Lagos. The standard susceptible strain had an LC 50 value of 0·022 μg g −1. Field strains from five unsprayed sites had low resistance factors of less than × 2·1 in each case, while the field strain obtained from the Health Centre surroundings in Lagos University Campus had a high resistant factor of ×8·2. This site has been sprayed regularly with dichlorvos (Nuvan) as a larvicide for the past four years. The fact that this significantly high level of resistance observed in the mosquito strain inhabiting the sprayed site resulted from the selection pressure of dichlorvos was further illustrated by exposing two successive generations of larvae from the standard susceptible laboratory strain to sublethal concentrations of dichlorvos; by the F 2 generation the measured level of resistance of the larvae to dichlorvos had increased by a factor of 2·5.

Numbers of Scolytus multistriatus (Coleoptera: Scolytidae) Caught on Multilure-Baited Sticky Traps Increase with Methoxychlor1

Multilure-baited sticky traps were attached to various methoxychlor-sprayed and unsprayed trap sites to determine the effect of the insecticide treatments on catches of the smaller European elm bark beetle, Scolytus multistriatus (Marsham). Significantly more bark beetles were captured by baited sticky traps attached to the boles of sprayed healthy American elms, Ulmus americana L., and also by traps attached to the boles of sprayed elms infected with the Dutch elm disease fungus, than were captured by traps on comparable unsprayed elms. Bark beetle catches on traps attached to sprayed and unsprayed utility poles and tree trap sites other than elms were not significantly different. These tests suggest that other beetle attractants associated with healthy and diseased elms and the presence of methoxychlor on the trap sites significantly affected trap catches.

Relative Abundance of the Spotted Tentiform Leafminer, Phyllonorycter blancardella (F.), and the Apple Blotch Leafminer, P. crataegella (Clemens) (Lepidoptera: Gracillariidae), on Sprayed and Unsprayed Apple Trees in Connecticut

The relative abundance of Phyllonorycter blancardella (F.) and P. crataegella (Clemens) was examined on sprayed and unsprayed apple trees in Connecticut by identifying pupae collected from fallen leaves during the third leafminer generation of 1980–1982. P. crataegella dominated at eight of nine sprayed sites. By contrast, P. blancardella dominated at seven of eight unsprayed sites. The widespread occurrence of P. blancardella on apple trees and especially its dominance in one sprayed orchard contradicts published reports on its absence in Connecticut. Temporal and spatial variation in species composition at unsprayed sites is attributed partly to defoliation by the gypsy moth, Lymantria dispar (L.), and to the proximity of potential colonists in commercial orchards. Dominance of P. crataegella in most commercial orchards is probably related to its resistance to insecticides. The cause of P. blancardella dominance at most unsprayed sites is unknown.