The distribution of introduced parasitoids of Phthorimaea operculella (Zeller) in Victoria is described. Apanteles subandinus Blanchard and Orgilus lepidus Muesebeck were most abundant, but Copidosoma koehleri Blanchard was also recorded from several sites. Detailed analysis of data obtained through regular monitoring revealed that, in an area free from insecticides, parasitoids were a major factor in controlling P. operculella. This result differs from previously published opinions on the effect of parasitoids, and is attributed to the analysis of data, in this study, on a generational basis. The effect of insectide applications on P. operculella and its parasitoids is discussed.

Hodotermes mossambicus (Hagen) is a harvester termite which competes with livestock for natural grazing. Control by baiting is recommended. Field trials in the north-western Orange Free State and south-western Transvaal, Republic of South Africa, showed that the two most commonly used commercial baits, with carbaryl or sodium fluosilicate as the active ingredient, are ineffective in controlling this species. A simple mathematical model was developed to rate the acceptability of grasses as food for the termite colonies. This enabled the attractiveness of the bait carriers as food for termites to be compared with that of the grasses. All five grass species tested had a similar food acceptability value, while both bait carriers were unacceptable as food. Failure of the baits was due to the fact that they were not consumed by the termites. The active ingredients was found to be effective when natural grass was used as the bait carrier. The mathematical model was extended to elucidate the effect of different baits on colony survival. This approach could be further used to rate new baits and their carriers objectively.

A wild-type black-eyed strain (PALA DR) and a mutant white-eyed strain (S104) of Anopheles gambiae Giles were used to determine whether nulliparous mosquitoes of this species are polyandrous. White-eyed females were given the opportunity to mate with black-eyed and white-eyed males. As the white-eye gene is recessive and is located on the X chromosome the presence of both white- and black-eyed females in a female's egg batch denotes that she mated with males of both types. Three out of 52 egg batches gave rise to both white-and black-eyed females. Only a proportion of multiple matings can be detected in this way; those involving males of only one type go undetected. It is estimated that, under the conditions prevailing during the experiment, 12% of nulliparous A. gambiae are polyandrous.

Individual cereal aphids of the species Sitobion avenae (Fabricius) and S. fragariae (Walker) were differentiated by their peptidase electrophoretic banding patterns; S. avenae has three diagnostic isoenzyme bands (PEP-3 to -5), whereas S. fragariae has one (PEP-1). Over 90% of 5389 individuals of these two species, collected from the grass Dactylis glomerata within 50 km of Rothamsted over the course of several years, were S. fragariae. The importance of D. glomerata and other non-cereal Gramineae species as alternative summer and overwintering hosts for S. avenae is discussed in relation to this finding.

A method for intensive screening of cowpea for resistance to Maruca testulalis (Geyer) is described. It is capable of ensuring uniform infestation and thus eliminating problems due to escapes. Four cowpea varieties earlier identified from field screening trials as resistant (TVU 946, TVU 1896 AG, H 51–1 and 2 AK) and three susceptible varieties (Ife Brown, H 144–1 and 58–185) were screened using this method. The results confirmed the status of the resistant varieties. Some effects on M. testulalis included, non preference for oviposition and larval feeding, and antibiosis manifested by reduced final larval instar weight, elongated pupal period and smaller sized emerging adult females.

The juvenile hormone mimic, pyriproxyfen, applied topically to female tsetse flies, Glossina morsitans morsitans Westwood and G. pallidipes Austen, effectively sterilizes them by arresting development of their offspring in the pupal stage. Between July and November 1989, 41 odour baited traps treated with pyriproxyfen were deployed near Rekomitjie Research Station, Zambezi Valley, Zimbabwe, in a 12.3 km2 block of woodland habitat of G. m. morsitans and G. pallidipes. Tsetse entering the traps brushed against material dosed with 2 mg/cm2 pyriproxyfen and were then allowed to escape. Emergence rates from pupae of the two species collected in the block fell to 30% and 2.7%, respectively, of control levels after three months. Of more than 750 pupae of each species dissected 78% and 94%, respectively, showed incomplete development. The average ovarian age category of female G. pallidipes sampled in the block doubled during the trial. This was due to immigration of older flies and the declining birth rate which, if sustained over a large area for a year, was estimated as sufficient to cause a population reduction to 10−6 of its original level.

The aphids, Cinara cupressi (Buckton), Eulachnus rileyi Williams and Pineus pini (Macquart), have invaded conifer plantations in southern and eastern Africa between 1968 and 1986. Conifer plantations, and particularly pine plantations, are a new habitat in this region, having been established in the 1960s and 1970s. These aphids are the first non-native pests to colonize these forest plantations. As exotic pests, the aphids are suitable targets for classical biological control through the importation of natural enemies from Europe, the region of origin of the three aphids. The opportunities for biological control are explored and the prospects are encouraging. Details of the natural enemy complexes of the target pests in Europe are provided and discussed in relation to previous successful biological control programmes against conifer pests in other continents.

The CLIMEX model for matching climates in ecology is used to forecast the favourableness of the Australian environment for Diuraphis noxia (Mordvilko). Parameters used in CLIMEX for D. noxia were derived from the literature and tuned by iterative matching with the known distribution of the aphid in North America. These fitted values were then validated using the known distribution of D. noxia in southern Africa, and with the country-by-country occurrence of the aphid around the world. The results suggest that the drier inland parts of the Australian wheat belt would be very favourable for D. noxia growth and survival. A computer model of the interactions between climate, wheat growth and the biology of D. noxia was then used to simulate the likely infestation rates and potential yield reductions at selected sites in both the summer and winter rainfall regions of the Australian wheat belt. The results indicate that D. noxia has potential to cause severe losses to the wheat crop should it arrive in Australia.

Previous investigations showed that (1) predatory mites use odours volatilizing from spider-mite infested plants for remote prey selection and (2) the response to the volatiles is correlated to the predator's ability to control populations of the prey species. Based on this correlation, it is hypothesized that preselecting predatory mites with the aid of olfactometer experiments will increase the probability of finding an efficient natural enemy. Y-tube olfactometer experiments with 11 species of phytoseiids showed that only four species were attracted by the odour of cassava leaves infested with cassava green mite Mononychellus tanajoa (Bondar). If the hypothesis mentioned above is valid, the probability of finding an efficient natural enemy within this group of four will be higher than finding one by randomly taking a species from the initial group of 11 species. Since testing of phytoseiids with an olfactometer can be done in a few hours, it is suggested that these tests precede more laborious evaluation methods.

Factors involved in the origin of plagues of Schistocerca cancellata (Serville) in Argentina were examined using a simple model for locust development. Plagues were present in 48 of the 58 years between 1897–1954 with plague sequences occurring before 1900, 1903–11, 1913–28, 1931–38 and 1944–54. Plagues originated when winter rain fell in the outbreak areas in La Rioja and Catamarca resulting in three generations in a season. Plagues continued for 8–15 years. Their decline was usually gradual resulting from a combination of several seasons when it was dry in the outbreak areas, and only one generation per year was possible. Before 1954, locust swarms were common in 15 of Argentina's 22 provinces but it was not obvious where the plagues originated. Since then most swarms have been reported from two provinces in the northwest: La Rioja and Catamarca. Within these provinces, bands and swarms have been most common in the semi-arid outbreak area. Populations have been highest when the outbreak area received winter/spring/summer rain which allowed three generations in a season. However, infestations have never approached plague proportions in recent years because regular control of bands and swarms in the outbreak area has kept populations in check.

Studies were carried out at Nguruman, south-west Kenya to develop an effective trap/odour bait system that could be used for sampling and possibly controlling the tsetse Glossina longipennis Corti. Neither acetone nor cow urine increased trap catches significantly when used alone, but together they increased catches by about four to five times. Used with a target and electric screens, acetone with p-cresol, 3-n-propyl phenol and 1-octen-3-ol gave a significantly higher index of increase than did acetone and cow urine. The use of odour baits did not affect the age composition of the catch. The standard F3 trap was about three and a half times more effective for females than was the biconical trap and about eight times more effective when used without its blue floor. The NG2B was the best of the NGU series of designs, and caught about four times more females than did the biconical trap. Neither the F3 nor the NG2B caught significantly more males than the biconical trap. The NG2B caught a significantly higher proportion of parous female flies than the biconical. Either the F3 or the cheaper NG2B, baited with acetone and cow urine or phenols, is recommended as a sampling tool for G. longipennis. Electric screen experiments showed that the NG2B caught less than 10% of the flies that approached it. Despite this, it might still be effective for control of G. longipennis given the high mobility of this species and the consequent likelihood of encountering traps.

Psyllaephagus yaseenisp.n. is described from Mexico, Central America and the Caribbean as a parsitoid of the nymphs of Heteropsylla cubana Crawford. The psyllid is a serious pest of Leucaena leucocephala, a shade tree and animal fodder in the tropics.

The influence of the lepidopteran stem borer Scirpophaga incertulas (Walker), the most important pest of deepwater rice (Oryza sativa) in south-east Asia, on plant and grain yield was investigated in Bangladesh during 1982–85. Four mechanisms of crop loss were identified: (i) deadhearts at the vegetative stage, (ii) loss of damaged but apparently healthy stems in flood water, (iii) white-heads at the reproductive stage and (iv) the effect of late season stem damage on panicles. A great proportion of damaged stems was not visible and damage symptoms were found to be an unreliable indicator for the assessment of borer activities in the field, and did not represent the actual yield loss. Stem damage had a negative influence on the stem density, with reduced panicle density and grain yield. Stem borer damage also seemed to reduce the elongation ability of the rice stem causing them to rot. Late season stem damage reduced the number of filled grains, mean grain weight and panicle weight and increased grain sterility. These effects were related to severity and position of damage. The average estimated yield loss due to S. incertulas was about 17% which took place during the last 11 weeks (from flood peak to crop maturity) of the deepwater rice season (32 weeks).

Video was used to provide objective measurements of the behaviour of tsetse around an electric net. Data were collected on: (1) the number and behaviour of flies which actively avoided the net; (2) the number and fate of flies which hit the net; (3) the distribution on the ground around the net of electrocuted flies. This allowed estimates to be made of net efficiency (=No. of flies sampled/No. sampled + No. escaped%). The three components of an electric net system (netting/grids, inverter-transformer (‘spark box’) and battery) were varied to determine the effect of each on efficiency: neither the condition (age) of the netting/grids nor the design or condition of the ‘spark boxes’ had a significant effect on efficiency, but efficiency was lower with partly-charged batteries than with fully-charged ones. When account was not taken of flies which behaviourally avoided the net, the best system had an efficiency of 55% (range 49–61%), (cf. a previous estimate of 94%); when the behavioural avoiders were included in the estimate the efficiency was only 46% (range 43–49%). The efficiency of the system is discussed in terms of the way the high voltage across the electric grid is generated, and also how it might affect interpretation of sample data.

Areas in Argentina, Bolivia, Brazil and Paraguay were searched for the cassava mealybug, Phenacoccus manihoti Matile-Ferrero. The mealybug was located in the Paraguay River basin in the Santa Cruz de la Sierra area of eastern Bolivia, the Mato Grosso do Sul state in South-Western Brazil and in Paraguay east of the Paraguay River. Mealybug populations were extremely low in all areas but there was a period of increase from August to December. Eighteen species of natural enemies were found attacking P. manihoti: the most abundant and also most important were a solitary, internal parasitoid, Epidinocarsis lopezi (DeSantis) (Hymenoptera: Encyrtidae), Hyperaspis notata Mulsant and Diomus spp. (Coleoptera: Coccinellidae), and Ocyptamus spp. (Diptera: Syrphidae). Collections of a closely related mealybug, Phenacoccus herreni Cox & Williams yielded two additional encyrtid parasitoids, Epidinocarsis diversicornis (Howard) and Aenasius sp. nr vexans Kerrich, but they did not survive on P. manihoti. Four parasitoids (E. lopezi, E. diversicornis, Parapyrus manihoti Noyes and Allotropa sp.) and four predators (H. notata, Diomus sp., Sympherobius maculipennis Kimmins, and Exochomus sp.) were sent for quarantine. With the exception of Parapyrus manihoti, all mentioned natural enemy species were forwarded to the International Institute of Tropical Agriculture at Ibadan, Nigeria for mass rearing and subsequent release.

Afroryzophilus djibai is a new genus and species of weevil, which attacks rice in Senegal. Its biology, pest potential and relationships with other Erirhininae are discussed.

A heterogeneous population (Pel) of Culex quinquefasciatus Say was selected, by single family rearing, to give a strain, Pel SS, which had low levels of hydrolysis of the esterase substrates α and β-naphthyl acetate. The level of temephos resistance was three-fold lower in this strain than the original parental population, and the levels of resistance to malathion, fenitrothion, pirimiphos-methyl, chlorpyrifos and permethrin were also reduced. In contrast, temephos selection increased the temephos-resistance in the Pel-RR strain ten-fold compared to the original parental population and 29-fold compared to Pel SS. The level of temephos-resistance in Pel RR compared to Pel SS at the LC50 level was 37-fold. Larval cross-resistance, at different levels, was observed to the organophosphorus insecticides, malathion, fenitrothion, parathion, pirimiphos-methyl, chlorpyrifos, fenthion and phoxim, and to the carbamates, propoxur and bendiocarb, but the level of fenthion, propoxur and bendiocarb resistance was less than three-fold. Adults showed cross-resistance to malathion and fenitrothion, but not to propoxur. There was negative cross-resistance to permethrin in both the larvae and adults of Pel RR compared to the Pel and Pel SS strains.

Bucculatrix parthenica Bradley sp. n., a moth native to Mexico, is described. It has been released and established in Queensland, Australia, as a biological control agent for its host plant, Parthenium hysterophorus. The moth oviposits on leaves of its host. First and second instar larvae are leaf miners, and later instars feed externally on the leaves. The life cycle occupies about 25 days under field conditions. B. parthenica was narrowly oligophagous in host-specificity tests. In Mexico the insect is scarce but in Queensland it has become abundant enough to cause extensive defoliation of its host plant at some sites. Its rapid increase in Queensland is attributed to the absence of parasitism.

Simulium metallicum Bellardi larvae were collected from a variety of sites in the three onchocerciasis foci in Mexico. Their head patterns and body coloration were scored before the larvae were cytologically analysed. Cytotypes A, B, H and I were collected and in the majority of cases they could be distinguished from each other by larval morphology. An undescribed cytotype (termed cytotype X) was found in Oaxaca which, on the basis of larval morphology, was indistinguishable from cytotype B.

Non-chemical control of termites in agriculture and forestry is attracting renewed interest following increasing restrictions on the use of persistent organochlorine (cyclodiene) insecticides. Non-chemical control involves methods which attempt, without using commercial pesticides, to (i) prevent termite access to the plants, (ii) reduce termite numbers in the vicinity of the plants or (iii) reduce susceptibility/increase resistance of the plants themselves. There have been few adequate trials of any of these methods. Numerous cultural procedures have been suggested, including measures to enhance plant vigour, to manipulate termite numbers and behaviour, and others whose mode of action is unclear. Many are simply part of good agricultural/silvicultural practice and to be recommended. Biological control by predators or pathogens is unlikely to be successful due to the termites' social structure and behavioural responses to infected individuals and to loss of individuals to predators. The use of ‘natural’ insecticides from locally available plant products may be effective in some cases but, as they are not subject to the same rigorous safety and environmental evaluation as commercial pesticides, their use cannot be sanctioned unconditionally. Other locally available products, e.g. wood ash, have not been adequately evaluated. Removal of reproductives from the nest and construction of physical barriers may have limited applications, but resistant species and varieties, combined with appropriate cultural methods and, perhaps, minimal use of modern pesticides in an integrated approach, offer the greatest potential for a long term solution. The lack of critical scientific evaluation of non-chemical control makes it a field wide open for research.