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Switchgrass (Panicum virgatum) and a mix of native warm season grasses with forbs (NWSG-mix) have received attention as cellulosic biofuel sources. While numerous studies support greater biodiversity within those biofuel crops than corn, it is unclear how switchgrass and NWSG-mix affect beneficial insects such as pollinators (PO) and predators/parasites/parasitoids (PPP). Also, few empirical studies have explored the effects of biofuel crop harvest on insects. We investigated the responses of PO and PPP insects to those two biofuel crops and harvest frequency in Mississippi, USA, during 2011–2013. We established 16 fields on agricultural lands and randomly assigned each one of 4 treatments: switchgrass with single harvest; switchgrass with multiple harvests; NWSG-mix with single harvest; NWSG-mix with multiple harvests. We set up 3 sampling stations per field and conducted insect sampling 1–3 times monthly during summer to fall using colored pan traps. We tested treatment effects with general linear mixed models and redundancy analyses. While treatment effects varied by season and year, biofuel crop type influenced abundance and insect family diversity but harvest frequency did not. During summer, total abundance and guild-level (PO and PPP) abundance were high in switchgrass in 2011. During fall, total abundance and abundance of PPP were high in NWSG-mix in 2011 and 2012 and abundance of PO in 2011 and 2013. Family richness was also greater in NWSG-mix across seasons in 2011 and 2012 and during fall in 2013. More families tended to be associated with NWSG-mix than switchgrass. Our results suggest that 1) biofuel crop type is a more important factor influencing beneficial insects than harvest frequency and 2) compared to NWSG-mix, switchgrass may provide more resources for insects during summer or during the first year after establishment; however, NWSG-mix could enhance insect diversity and abundance of pollinators for a longer period of time.

The parasitoid communities in organic and integrated pest management (IPM) kiwifruit orchards have previously been found to differ significantly, but we do not know if this affects the quality or quantity of biocontrol services. We compared parasitism of two leafroller (Lepidoptera: Tortricidae) pest species, Ctenopseustis obliquana (Walker) and Cnephasia jactatana (Walker), in the two types of orchard. Within each orchard, we focussed on a large shelterbelt between the kiwifruit vines and an alternative land-use to also investigate whether the shelterbelts and neighbouring habitat were a source of pests or beneficial insects for these orchards. Sentinel larvae were used to determine both parasitoid identity and parasitism rate each month during the kiwifruit growing seasons in 2013/14 (16 orchards) and 2014/15 (12 orchards). The numbers of Tortricidae and parasitoids in the shelterbelt on each orchard in each month was also assessed in 2014/15. Four parasitoid species emerged from the sentinel larvae, although average parasitism rates were very low (1–3%). There were no detectable effects of orchard management, shelterbelt type or neighbouring land-use on parasitism rates. Parasitoid numbers were low in all orchards in 2014/15, although more parasitoids were collected from the IPM orchards than the organic ones. This may have been in response to the increasing numbers of Tortricidae in the shelterbelts on the IPM orchards during the season, a trend that was not observed in the organic orchards. Both shelterbelt composition and neighbouring land-use were found to affect total combined counts of Tortricidae and parasitoids, with higher counts in shelterbelts composed of Cryptomeria japonica and where adjacent land contained native bush or tree-based scrub. Each may therefore be a source of both taxa for the orchards. Modifications to the shelterbelts that increase parastoids but not Tortricidae are needed.

Soybean, the main crop of Argentina, has promoted spatial and temporal homogenization of the agricultural landscape accompanied by significant losses of biodiversity, along with increases in the use of chemical inputs. One of the possible solutions to overcome these effects is the diversification of the agroecosystem, avoiding the control of weed species that could act as attractants of beneficial insects and deterrents of herbivory, without compromising crop yield. The aims of this work were to evaluate the composition, abundance and richness of insect assemblages in different soybean-weed (Artemisia annua and Chenopodium album)-herbivory combinations and to determine the relationship between insect assemblages and volatile signals emitted by the different combinations. Two factorial experiments were conducted during two consecutive seasons under field conditions. Factors were: i) crop-weed combinations with five levels: pure soybean (PS), soybean + 2 A. annua plants m−2 (2A), soybean + 4 A. annua plants m−2 (4A), soybean + 2 C. album plants m−2 (2C) and soybean + 4 C. album plants m−2 (4C) and ii) herbivory with two levels: with (+H) and without (−H). Volatile signals were measured with an electronic nose and insects were sampled with pitfall traps located in the center of each plot. Different insect assemblages related to treatments were identified. Richness increased when soybean was accompanied by weeds. The proportion of non-herbivores was always higher than that of herbivores. In both seasons, the same sensors detecting volatile cues were the main explanatory variables of the insect data, being responsible for the separation of A. annua treatments from the others. Many non-herbivore species were attracted to A. annua and repelled by signals captured by these sensors and, on the contrary, many herbivore and non-herbivore species were attracted to those blends associated to PS and C. album. PS and C. album could represent a food source for herbivores and alternative food or host for non- herbivores. Herbivory was not a discriminant explanatory variable. This work highlights that insect assemblage varies according to different crop-weed combinations and their volatile signals. Considering the positive impact on insect diversity of some species currently considered as weeds, could be useful to design future agro-ecosystems in which the regulation of pests is accomplished by increasing the fauna of beneficial insects and, thus, reducing the use of pesticides.

Insect predators and parasitoids act as biological pest control agents in agro-ecosystems, and thus provide valuable ecosystem services. These natural enemies of pest species often need a greater diversity of resources than the crops themselves provide. In intensive farm management the numbers of these beneficial arthropod species may be constrained by a lack of additional prey, floral resources or suitable overwintering sites. While previous studies have indicated that targeted field margin management can positively influence the population dynamics of beneficial insects, the relative contribution of the various resources provided by these targeted margins remains unclear. To help optimise field margins for conservation biological control, this study assessed the relative contribution of three key resources; aphid prey, floral resources, and grass overwintering sites, in supporting natural enemies of cereal aphids within an agricultural landscape. Trial plots were managed adjacent to wheat fields within agro-ecosystems in the UK to assess the relative importance of these three resources in isolation and in combination. The abundance of aphidophagous natural enemies was monitored with respect to these resources during two periods; prior to cereal aphid infestation in the crop, and during the infestation period. In addition, the abundance of cereal aphids and natural enemies was monitored in the crop next to the trial plots during the infestation period. The results show that resource needs of natural enemies vary both over time and between natural enemy groups. Some predators benefited from higher aphid abundance, particularly in combination with the availability of floral resources. Floral resources had the greatest individual effect in increasing natural enemy abundance, both prior to and during periods of aphid infestation. Grassy overwintering habitat provided little overall benefit during the two study periods. In the UK, most non-crop habitat in agro-ecosystems is grass dominated winter habitat. Few Stewardship scheme initiatives are designed to provide suitable floral resources targeting natural enemies of crop pests, or to provide suitable additional prey. Given the importance of floral resources to the majority of natural enemies, providing suitable nectar and pollen sources represents the greatest opportunity for enhancing naturally occurring predators and parasitoids in agro-ecosystems.

Increasing evidence suggests that landscape composition is an important driver of beneficial insect populations and resulting ecosystem services. Additionally, local-scale manipulations such as planting floral strips are used at the field-level to provide resources for beneficial insects to increase their services. It has been proposed that the benefits of local manipulations will depend on the landscape context, with greater benefits in simplified landscapes and smaller benefits in landscapes with an abundance of non-crop resources. To test this, we used soybean aphid, Aphis glycines, and its coccinellid predators as a model system to elucidate the effects of habitat management and landscape on biocontrol services in soybean. We selected pairs of soybean fields in landscapes of varying composition and planted buckwheat, Fagopyrum esculentum, strips adjacent to one field in each pair. We measured coccinellid abundance and biocontrol in each field. Coccinellid abundance was higher in buckwheat than in control field margins in all landscapes, and coccinellid abundance in soybean was positively related to amount of semi-natural vegetation in the landscape. We found no evidence of an interaction between landscape and local variables, and biocontrol services were high in all contexts. For soybean aphid suppression, landscape factors are the key drivers of predator abundance.

Organic farmers cannot use most commonly available synthetic insecticides to control crop pests and reduce economic losses due to pest outbreaks. Instead, they rely heavily on the activities of naturally occurring predators and parasitoids, particularly in broad-acre crops such as cereals. It is still unclear whether organic farms which typically support greater levels of biodiversity also experience greater levels of pest control services. We assess whether organic farming systems were better able to control cereal aphids due to a greater diversity and activity of naturally occurring parasitoid species. We anticipated greater parasitism rate of aphids in organic arable fields due to closer proximity to plants that provide resources for adult parasitoids and places that are suitable for overwintering, and the presence of alternate aphid hosts when cereals are absent. Aphids were collected from organic and conventional cereal crops, and screened for parasitoid DNA using diagnostic polymerase chain reaction (PCR). Aphid abundance was low across the season, however organic cereal fields had significantly greater aphid abundance. From the 1446 aphids screened we detected 12 parasitoid taxa. There was no difference in parasitism rate between the farming systems (org. mean mortality 20.9 ± 3.3% s.e., con. 29.8 ± 4.9%). Furthermore, there was no difference between farming systems in hyperparasitoid attack and multiparasitism rates, parasitoid richness and parasitoid community diversity. The most abundant species recorded on organic and conventional farms was the generalist aphid primary parasitoid Ephedrus plagiator. It appears that the extra plant diversity and greater area of semi-natural habitats on organic farms offer no advantage for increasing cereal aphid parasitoid diversity, at least at the aphid abundances encountered during the sampling period.

Non-selective chemical control of crop pests disrupts beneficial insects and spiders. For Australian cotton crops, a beneficial disruption index (BDI) has been developed that ranks the impact of different insecticides on beneficial arthropods. To evaluate this index as a measure of natural enemy disruption, the abundance of beneficial arthropods was monitored in ten conventional and nine INGARD ® Bt cotton fields on ten commercial farms during the 2001–2002 season. Beneficial insects were more abundant in those fields subjected to a more selective insecticide regime (low BDI) than in fields that received broad-spectrum insecticide treatments (high BDI). However spider abundance did not change in relation to insecticide regime. Family composition of spider communities was affected by BDI and crop type (Bt or conventional), whereas family composition of insect communities only showed a trend to be affected by BDI and crop type. This difference may indicate that insects are more uniformly affected by the BDI than spiders. The beneficial disruption index is an effective measure of insecticide impacts on beneficial insects in Australian cotton crops.

Dipsacus fullonum ( Dipsacus sylvestris ) is a native biennial, common in the UK agricultural landscape, providing floral resources for potential crop pollinators, natural enemies of cereal pests, and other insects. In north America, the plant has become established as an invasive alien, threatening to displace native species of sensitive conservation status. Surveys of farmland in Cambridgeshire, UK, over a three year period indicated that the plant's distribution along field boundaries rendered it prone to damage by routine boundary management practices. In experiments, some stems cut before flowering regrew but produced significantly fewer flowerheads than uncut plants; stems cut during or after flowering produced no new flowerheads. Seeds borne in flowerheads of plants cut during or immediately after flowering failed to germinate. Although the local persistence of D. fullonum did not appear to be threatened by routine management in this study, resulting loss of floral resources has implications for the plant's insect fauna. Flexibility in the timing of boundary management could alleviate potential negative effects on beneficial insects in UK agroecosystems. Knowledge of the suppression of seed production by appropriately timed stem-cutting might be incorporated into control programmes in systems where the plant is an invasive alien.

The existing literature was examined to assess the extent to which wildlife (plants, soil organisms, above-ground insects/arthropods, mammals, birds) living in terrestrial habitats has been affected by use of agricultural herbicides in temperate landscapes. Although North America was of special interest for regulatory reasons, the review was extended to western Europe because the most extensive and intensive work has been done there. The half-life of herbicides in the environment ranges from less than 1 month to more than 1 year. Wildlife within fields is most likely to be exposed to herbicides, particularly when fields are planted with crops (e.g. corn, soybean, wheat, cotton) which are routinely sprayed. Wildlife is also likely to be exposed in non-crop habitats adjoining croplands, primarily from direct overspray (especially during aerial application), and drift during and/or volatilisation after application. The most conclusive scientific evidence for direct effects of herbicides on arable weeds, and associated indirect effects on insects and birds exists in the United Kingdom. Evidence for similar effects in North America is primarily circumstantial at present. Little work has been done anywhere on impacts of herbicides on plants and their associated fauna in non-crop habitats adjoining treated fields. Chemical farming (in particular, the use of herbicides) has dramatically altered the habitat pattern of temperate landscapes in North America and western Europe. Strong evidence exists for adverse effects of changes in habitat pattern on beneficial insects and arthropods in the United Kingdom, and on birds in North America and western Europe. Toxicity testing guidelines for non-target plant protection need to be developed and enforced to support pesticide registration. In addition, research is needed to include more ecologically relevant plant species in laboratory tests, to develop multi-species tests (particularly in the field), to improve methods for risk assessment, and to develop options for mitigating risks. Large scale, long-term trans-disciplinary research of different farming systems is needed, particularly in North America, to integrate and better evaluate ecological, agronomic, and socio-economic costs and benefits of agricultural herbicide use in temperate landscapes.

Parasitoids of Russian wheat aphid, Diuraphis noxia (Kurdjumov), from Morocco, and the Middle East were imported, reared, and mass produced for classical biological control use in Washington State. In total, more than 200 000 parasitoids were released over 53 sites from 1988 to 1992. Some species have established, but the long term effect of the program has yet to be documented.

Dactylopius opuntiae reduced an Opuntia stricta var. stricta population in the Central Tablelands of New South Wales, an area where Cactoblastis cactorum has little impact. Cactoblastis cactorum was bivoltine at the experimental site. The proportion of C. cactorum eggs hatching and larvae penetrating segments was much greater for the generation commencing between November and January compared with that commencing between February and June. Failure of first instar C. cactorum to establish during the latter generation appeared to prevent C. cactorum from having a significant impact on the cactus population. Dactylopius opuntiae released at the site decreased new growth of O. stricta var. stricta and caused direct damage to segments. This damage led to a decline in the cactus population in the area. The use of D. opuntiae for biological control of O. stricta var. stricta in similar areas is discussed.

In 1983, the species composition and diversity of carabids, spiders and harvestmen was investigated by pitfall traps in a grassy field margin and in an adjacent, biologically farmed wheat field at Obere Lobau, Vienna, Austria. The carabid fauna of both habitats was diverse; it showed a high degree of similarity, the abundant species in both habitats being represented by typical field species. Only Metophonus spp. predominantly lived in the margin. Numerous species of different habitat origin occurred in the margin at low abundances indicating transitional stay rather than permanent populations. In contrast, the spider fauna showed a low degree of similarity, with few agrobiotic species strongly dominating field fauna. In the field margin, a rich spider fauna containing rare elements indicates the general importance of grassy margins for nature conservation. The apparently low faunal exchange of spiders between the two habitat types is discussed. Harvestmen occurred mainly in the field margin; only two thermophilic species invaded the field. Seasonal fluctuations in the trapping numbers of Bembidion lampros, Platynus dorsalis and Brachinus explodens are interpreted as indicating migrations between field margin and field. Poecilus cupreus and certain other field species, however, apparently spend their entire life cycle in the field. The possible function of field margins for restoration of carabid losses due to impacts of intensive cultivation is discussed. It is concluded that both grassy field margins and sustainable farming methods, in particular biological farming, are necessary to maintain a diverse predatory arthropod fauna in agroecosystems.

The interactions of predatory arthropods between natural habitats and arable land were explored. Three questions were asked: (1) Does habitat quality in field margins determine the density of natural enemies overwintering in field margins? (2) Are good sites for natural enemies also habitats which support greater general arthropod diversity? (3) Does the density of predators overwintering in field margins determine their distribution and abundance in adjacent cereal fields in spring? The value of field margins to agriculture was assessed as the density of arthropods overwintering in these habitats. The arthropod groups used for the assessment were known aphid predators which moved out into cereal crops in the spring. This assessment was compared with general arthropod diversity at each site to test whether field margins supporting high densities of predators were also of value to nature conservation in supporting greater arthropod biodiversity. In spring, the spatial dynamics of predatory arthropod species were investigated in cereal crops adjacent to field-margin overwintering sites. The influence of field-margin habitats on natural enemy populations within adjacent crops was evaluated. The enhancement of natural enemies and general arthropod conservation are discussed as components of overall biological diversity at the farm scale.

Lantana camara L., a fast-growing verbenaceous shrub from Central and South America, is a toxic invasive weed in many countries. Taxonomically, L. camara is a complex of several cultivars (forms) whose diversity has frustrated attempts at biological control by insect natural enemies that show preferences for some cultivars and an inability to survive on others. Of the 16 insect herbivore species imported into South Africa for biological control of L. camara, six have become established and two were already present. Two leaf-feeding chrysomelid beetle species, Octotoma scabripennis Guerin-Meneville and Uroplata girardi Pic, usually in association with the tingid bug, Teleonemia scrupulosa Stal, are exerting some degree of control. A seed-feeding agromyzid fly, Ophiomyia lantanae (Froggatt), may be contributing to the overall stress on the plant, but its contribution to biocontrol has not been determined. A flower-feeding pyralid moth, Salbia haemorrhoidalis Guenee, is established in low numbers at isolated sites over a wide area. A noctuid moth, Hypena strigata (F.), an African species that was mistakenly ‘imported’ into South Africa, contributes little to biocontrol of L. camara in this country, although it was very successful in Hawaii. The biocontrol of L. camara in South Africa, with its problems and shortcomings, is reviewed and the future of the programme is discussed. A better understanding of the functional relationships and interactions between the various cultivars of L. camara and insect herbivores may improve the chances of succeeding with biological control.

Hypericum perforatum L. is a herbaceous perennial plant that was first noticed as an invader in the Southwestern Cape of South Africa in 1945. Following an unsuccessful chemical control programme, a leaf-feeding beetle, Chrysolina quadrigemina Suffrain, was introduced in 1960, which almost completely destroyed dense stands of the weed. In 1972, a gall-midge, Zeuxidiplosis giardi Kieffer, was released and has proved valuable in damaging seedlings in moist habitats. Attempts to establish three other insect herbivore species failed. Hypericum perforatum is now considered to be under satisfactory control in the Southwestern Cape. Although C. quadrigemina, together with Z. giardi, has been pivotal in eliminating the dense stands of H. perforatum, other factors, such as climate, unsuitable habitats and a lack of dispersal agents, have probably also contributed to containing the weed.

Sesbania punicea (Cav.) Benth., a South American leguminous shrub or small tree, has recently become a weed, principally of river banks and of wetlands, throughout South Africa. Three weevil species have been introduced for its biological control: a florivorous apionid, Trichapion lativentre (Beguin-Billecocq), that was inadvertently introduced in the 1970s, and two curculionids that were first released in 1984, a seed-feeder, Rhyssomatus marginatus Fahraeus, and a stem borer, Neodipiogrammus quadrivittatus (Olivier). The reproductive potential of S. punicea has been markedly reduced throughout South Africa by T. lativentre and, to a lesser extent, by R. marginatus. In the vicinity of release sites, many large S. punicea plants have been killed by N. quadrivittatus and the density of at least one infestation has been reduced to acceptable levels within 4 years. A critical assessment of this biocontrol programme is presented.

Two of the Australian acacias that are weeds in South Africa are also exploited commercially and the desirability of exoticAcacia spp. is disputed. This conflict has created problems for the implementation of a biological control programme. After considerable debate, the issue was satisfactorily resolved by mainly considering insects that attack reproductive plant parts, thus suppressing the invasive potential of the weeds while not affecting the vegetative parts that are utilized. Four insect species have been released in South Africa: a bud-galling wasp,Trichilogaster acaciaelongifoliae Froggatt, which has had a major impact on the reproduction of its host plant,Acacia longifolia (Andr.) Willd., and three seed-feeding weevils,Melanterius spp., which have been released on A. longifolia, Acacia melanoxylon R. Br. and the closely relatedParaserianthes lophantha (Willd.) Nielsen (=Albizia lophantha (Willd.) Benth.) with as yet unfinalized results. In this review, the biological control of Acacia spp. andP. lophantha in South Africa is described. The rationale for the types of agents that are suitable, and the issues that arisen through the conflict of interests, are presented.

Jointed cactus, Opuntia aurantiaca Lindley, has been a problem weed in South Africa for nearly a century. Its taxonomic status, history of introduction, and chemical and biological control were reviewed in 1979. The present account updates this information and deals with recent South African research on the ecology of O. aurantiaca and its biological control agents, and on the management of the weed. This review places some emphasis on the primary agent, the cochineal insect Dactylopius austrinus De Lotto (Homoptera: Dactylopiidae), with a shorter commentary on the phycitid moth Cactoblastis cactorum (Bergroth) that has also become established on jointed cactus. Research on three other introduced moths, Tucumania tapiacola Dyar (Phycitidae), Mimorista pulchellalis Dyar (Pyraustidae) and Nanaia sp. Heinrich (Phycitidae), is abstracted. Of the latter three species, only M. pulchellalis has become established, but its role in biological control is insignificant. It is concluded that: (i) the utility of insects as biological agents against jointed cactus has probably been fully exploited; (ii) the importance and threat of O. aurantiaca as a weed in South Africa may have been overestimated; (iii) future research emphases should be on the role of pathogens as biocontrol agents and on the formulation of area-specific integrated management procedures involving D. austrinus and herbicides.

The biological control of Cirsium vulgare (Savi) Tenore in South Africa has been a recent opportunistic project using insects that had already been introduced into other countries. The capitulum gall-full. Urophora stylana L. (Tephritidae), from West Germany and Western France, and the seed-feeding weevil. Rhinocyllus conicus (Froelich) (Curculionidae), from Western France, were released on infestations of C. vulgare in South Africa on several occasions from 1983 onwards. Initially, both herbivores became established, but only at one locality in Natal, and there is now doubt that the population of U. stylata has persisted. The population of R. conicus has dispersed up to 1.5 km from the original point of release, but it is premature to gauge the usefulness of the weevils for biological control of C. vulgare in South Africa.

Hakea sericea Schrader is a proteaceous shrub or small tree from southeastern Australia which has become an invasive weed of major importance in South Africa, particularly in the mountain catchments of the Southwestern and Southern Cape Province. Two biological control agents were released in 1970 to try and reduce the vast numbers of seeds produced by this weed. A weevil, Erytenna consputa Pascoe, which attacks the immature fruits, is now widely established and is contributing substantially to the reduction of the seed crop. A moth, Carposina autologa Meyrick, destroys seeds in the mature fruits and, after a prolonged period of releases, has recently established thriving colonies in the field. A second weevil, Cydmaea binotata Lea, which feeds on and develops in succulent vegetative growth, was released in 1979 principally to suppress seedling regeneration. It has established at a few sites, but with little effect. Apart from E. consputa which may be restricting the rate of spread of the plant, the programme has not yet fulfilled its promise, although recent prognoses are encouraging. The history of the programme and possible reasons for its limited successes are reviewed.

The outstanding success of a cochineal insect, Dactylopius opuntiae (Cockerell), and, to a far lesser extent, a phycitid moth, Cactoblastis cactorum (Bergroth), in biocontrol of the prickly pear, Opuntia ficus-indica (L.) Miller, in South Africa was fully reviewed in 1978. The present account updates this information. Today, the weed infests less than 100 000 ha (of the 900 000 ha originally colonized) in the cooler, higher rainfall areas where D. opuntiae is relatively ineffective. Cactoblastis cactorum is able to kill only the small prickly pear plants and suffers lossess because of ant predation, climatic extremes and, partly, to host plant incompatibility. Integrated chemical and biological control methods are described which allow O. ficus-indica to be managed as necessary and also to be exploited as a drought fodder for stock, as a fruit and vegetable source for humans, and as a host plant for the commercial production of dye stuff from the cochineal, Dactylopius coccus O. Costa. As a result of successful biological control over the past 50 years, the public has forgotten the former severity of the prickly pear weed problem in South Africa. The residual O. ficus-indica populations are now highly valued and the biological control agents themselves are regarded as pests. The consequences of these changed perceptions are discussed.

Chromolaena odorata (L.) King and Robinson, an asteraceous shrub from the neotropical region, has become a major weed of crops, plantations and pastures in many parts of the world. Since its introduction into Southern Africa, in the 1940s, C. odorata has spread extremely rapidly along the eastern coast to become the most problematic of the alien invader plants threatining nature conservation areas in Natal. An arctiid moth, Pareuchaetes pseudoinsulata Rego Barros, was released on C. odorata in Natal at the beginning of 1989, but there have been no signs of establishment, probably because of heavy egg predation by ants. Prospects for the biological control of C. odorata are nevertheless considered to be good because there are still many other insect herbivores and fungal pathogens that can be tried.

The origin, distribution, weed status and biological control of 13 species of alien invasive cacti of lesser economic importance in South Africa are reviewed. (The biological control of two major cactus weeds, Opuntia aurantiaca Lindley and Opuntia ficus-indica (L.) Miller, is fully reviewed elsewhere.) The species include two in the genus Austrocylindropuntia (A. exaltata (Berger) Backeberg and A. salmiana (Parmentier));Cereus peruvianus (L.) Miller; three in the genus Cylindropuntia (Cyl. imbricata (Haworth) Knuth, Cyl. leptocaulis (De Candolle) Knuth and Cyl. rosea (De Candolle) Backeberg); Eriocereus martinii (Labouret) Riccobono; five in the genus Opuntia (O. dellenii (Ker-Gawler) Haworth, O. lindheimeri Englemann, O. spinulifera Salm-Dyck, O. stricta (Haworth) Haworth and O. vulgaris Miller); and, lastly, Pereskia aculeata Miller. Total success has been achieved in biocontrol against Cyl. leptocaulis and O. vulgaris using the cochineal insects Dactylopius tomentosus (Lamark) and Dactylopius ceylonicus (Green), respectively. Introduced insect agents, together with sporadic chemical or mechanical control, have arrested the invasion of E. martinii (where a pseudococcid Hypogeococcus festerianus (Lizer y Trelles) was the agent used), Cyl. imbricata and Cyl. rosea (using D. tomentosus in both cases), and O. lindheimeri (using Dactylopius opuntiae (Cockerell)). Recognition of these cacti as weeds, before they became widely distributed or of much economic importance, and timely initiation of biological control, coupled with the locality of the weed species in hot dry areas that enhance the debilitating effects of cochineal insects on the plants, seem to have contributed most to the successes. Relatively isolated, refuge populations of the weeds that escape colonization by the imported insect agents, together with the inimical, but mandatory herbicidal control practices that often kill the natural enemies, seem to have been the two main reasons for reduction in the levels of biocontrol achieved.

Crofton weed, Ageratina adenophora (Sprengel) King and Robinson, an asteraceous shrub from Mexico, was probably introduced into Southern Africa during the 1940s. Although it is a problem weed of crops, plantations and pastures in many parts of the world, A. adenophora is still largely restricted to the mist-belt region in Natal. In an attempt to contain the spread of the weed, a stemgalling fly, Procecidochares utilis Stone, and a leaf spot fungus, Phaeoramularia sp., have been established recently on A. adenophora in South Africa, but with little apparent effect as yet.

The pteromalid gall wasp Trichilogaster acaciaelongifoliae (Froggatt) has been successfully used to reduce the reproductive potential and vegetative growth of the invasive shrub/tree Acacia longifolia (Andr.) Willd. (Fabaceae) in South Africa. The success of this project is shown to be the combined result of certain features of the wasp, its host plant, and the interaction of the two. Practical features which contributed to the success of this project are discussed. Of the ecologically important features, some provide new guidelines for the future selection of gall-forming agents for weed biocontrol.

Amitraz is effective against all stages in the life cycle of the cotton whitefly, Bemisia tabaci, but the egg is more tolerant than the nymphal instars and adult. An excitatory effect on the adult has been demonstrated, which may have implications in control. Ground application trials in Turkey and aerial trials in Sudan illustrate the activity of amitraz in the field. In aerial application trials, the use of a mixture with endosulfan is particularly effective. The safety of amitraz to beneficial insects is discussed.

Insect pests of windbreaks and agricultural crops, their natural enemies and other beneficial insects use windbreaks for food, protection, pupation sites and overwintering sites. Management of these insects in a windbreak should start before planting and end only when the windbreak is removed. Insect-management plans must integrate techniques developed for detecting, assessing, predicting and controlling an insect population with information on the insect's biology and impact and with agriculture and forestry practices that promote optimum plant growth and yield. This chapter describes the types and importance of insect damage to plants and describes possible methods for detecting, evaluating and reducing damage to plants in windbreaks. Recent research on the impact of windbreaks on distribution and abundance of insects associated with agricultural plants is discussed.

The coconut hispid beetle Brontispa longissima (Gestro) was accidentally introduced into Western Samoa in 1980. Consequently in 1981 several beneficial insect species, including the pupal parasite Tetratichus brontispae and a eulophid larval parasite (Asecodes sp.), were collected in other Pacific countries, mass reared and released in W. Samoa. A study of the mortality factors in 120 subpopulations of B. longissima was carried out in 1987. The larval parasite Asecodes sp. was present in 37% of the samples, thus being the dominant parasitoid in the field. Tetrastichus brontispae was only recovered from 3% of the samples and was not an important cause of mortality. An extensive damage survey comprising 37 000 coconut trees showed that B. longissima is well under control and does not at present cause any significant yield losses. (Initially production losses in outbreak areas were estimated to be as high as 50–70%.) The benefit-cost ratio of this project was 3.9:1 during the implementation period (1981–1986) and 9.9:1 for the period from 1987 to 1990. The internal rate of return (IRR) calculated for a 10-year period (1981–1990) exceeds 40%, thus highlighting a very succesful biological-control project. The average coconut grower in Western Samoa obtains an estimated WS$ 24 ha−1 year−1 with no additional costs involved.

The formulation, testing protocol, lethal effects, sub-lethal effects, ecological relationships and selectivity of microbial pesticides on non-target, beneficial arthropod natural enemies of insect and mite pests are reviewed for viruses, bacteria, fungi and protozoa. In general, it was found that: (1) effects from indirect mortality of natural enemies are probably more significant across all microbial types than are direct mortalities from microbial pesticides; (2) significant levels of direct mortality of beneficial insects can be caused by bacterial and protozoan microbial pesticides; (3) no direct mortality from viruses of pests has been documented for arthropod natural enemies; (4) the direct effect of fungi on arthropod natural enemies has not been well studied and probably has been underestimated; (5) unique standard methods need to be developed for microbial assays and for expressing more exactly the dosage administered to the host or natural enemy.

In Egypt, season-long control of pink bollworm (Pectinophora gossypiella) has been accomplished with 3–4 applications of the pheromone, Gossyplure. Gossyplure applied at the pin-square stage of the cotton plant is achieving control by mating disruption comparable to 3–5 applications of broad-spectrum chemical insecticides. This has resulted in the abolition of all chemical-insecticide treatments in some pheronome-treated cotton fields, and in a reduction of up to three pesticide applications in the areas where the spiny bollworm (Earias insulana) infestation is common or where the pink bollworm infestation is exceptionally high. In the latter areas, a single insecticide treatment at the end of the cotton-growing season (when beneficial insects are no longer abundant) is applied for suppressing bollworm populations. The area of cotton treated commercially with Pectinophora pheromone is continually rising in Egypt and in 1986 about 20 000 ha have been treated with three formulations. By the time of preparing this report on 10 September, 1986, most of the data and results of this season were either still coming in or awaiting analysis. However, some of the 1986 preliminary results are included in this report.

Varieties of crop plants showing resistance to insect pests have been in use in modern agricultural production systems for nearly 40 years. The need for their continued use is especially critical in developing countries today, since both food and food production costs have increased greatly. The expanding populations of some developing countries currently endanger the habitats of the germplasm of several major crop plants. For this reason, major efforts are now necessary to collect, preserve and maintain as much wild germplasm of major crop plants as possible. These efforts may lead to the exchange of advanced biotechnology techniques from developed countries for exotic crop plant germplasm from developing countries. Many varieties of insect-resistant crop plants rely on allelochemicals to convey antibiotic effects on pest insects. However, high levels of allelochemicals can have detrimental effects on beneficial insects, and induce insecticide tolerance in non-target insect pests. Therefore, a need for caution exists in the development of crop varieties which utilize allelochemicals in their resistance. Accurate, reproducible bioassay techniques are essential to the continued development of insect-resistant varieties. This is especially important today, since groups of scientists at different locations may be involved cooperatively in identifying and categorizing plant resistance to insects. Insect, plant and environmental variables should be standardized, since each can greatly affect the validity of bioassay results.

Beneficial insects have long been recognized as important in suppressing the depradations of insect pests and in some cases they naturally control pests to a degree sufficient to prevent the need for any other control practice. In other cases classical biological control, i.e., the introduction of exotic beneficials, has provided a level of control that eliminates the need for further control. However, many parasitoids, whether indigenous or introduced, are unable to keep the host population below economic injury levels due to a number of factors. Further, some exotics are unable to survive certain periods of environmental stress in the introduced region. Sometimes parasitoids are ineffective when a host occurs on certain crops, because these crops do not appear to orient the parasitoid. These and other problems can be overcome with the augmentation approach to biological control. I believe that the augmentation approach to biological control is at the threshold of becoming one of the most important approaches to the control of pest insects. Work over the last several decades has shown that the parasitoids are oriented to hosts by chemical and physical factors that emanate from the host's habitat, the food or organisms associated with the host, or the host itself. The identification of these factors offers the potential for the manipulation of beneficial insects. We are also at the threshold of being capable of rearing parasitoids artificially, thus eliminating the expense of rearing their host. The artificial rearing of parasitoids leads to the possibility of insect husbandry. The future holds the potential to selectively breed parasitoids for specific traits and offers the potential of inundative releases for control. Another area with immense potential is the finding that many species of braconids and ichneumonids have a symbiotic virus which they inject along with their egg into their host. Such viruses appear essential to these parasitoid's survival in the host. The existence of the virus in influencing host suitability offers the possibility of altering host specificity in the future.