Incidence of okra stemfly, Melanagromyza hibisci Spencer in India was high (40–60%) in winter months, i.e. during October, November, December and January sowings. Mean maximum and minimum temperature that prevailed 30 days after sowing had significant negative correlation with percentage main stem damage. Carbofuran, phorate, quinalphos and aldicarb, applied at 1 kg per ha reduced damage to main stem at the seedling stage but could not control subsequent damage to petioles. Eurytoma sp., a parasitoid on M. hibisci, had a high density-dependent relationship with its host, and played a significant role in keeping it under control.

Sixty selected rice varieties were tested for resistance to damage by the African striped borer, Chilo zacconius. Artificial infestation with first instar larvae in screenhouse showed that Lac 23 (white), IR 2035-120-3, 1R 4625-132-1-2, Colombia 1 and N 21-1 had significantly low “dead hearts” and larval survival. Damage was also low when these varieties were exposed to adults in the screenhouse and in the field. Both local and exotic varieties possessed resistance. Antibiosis conferred resistance to the borer in the varieties screened.

Plants express evolutionary adaptations in response to overall environmental stresses (selection pressures), of which insect infestation usually represents only a minor component. The majority of insect-host plant relationships involves adaptations of insect species to existing plants. Over time, plants have evolved a variety of physical and chemical defence mechanisms against environmental stresses. Only some of these are active against insects, and then not against all species. Plants rarely seem to evolve defences specifically against insects. Parameters of plant resistance to parasites are classified as constitutive or inducible. Soybean resistance to agromyzid stem-miners involves both constitutive and inducible components. Expression of such resistance parameters involves controls ranging from single genes (e.g. for trichome traits) to various combinations of genes (e.g. for the metabolic pathway for phenyl-propanoids). Environmental stresses (e.g. high illumination) especially affect the expression of resistance parameters which involve dynamic metabolic pathways. Soybean (Glycine soja) resistance to beanflies is an example of ‘horizontal’ resistance. Thus, the expected stability is long-term. Such stability is attributable to its major parameters being fundamental components of the soybean's primary and secondary growth and differentiation. These kinds of parameters are major products of the soybean's successful evolutionary experience at survival.

In an experiment to test the efficiency of carbofuran, as furadan 5G, as an oil palm nursery insecticide, its rate of application is recommended at 1.5 g furadan 5G per plant, which had no adverse physiological effects on seedlings. The number of mealybugs/plant was reduced by between 58 and 95% with increasing application of carbofuran, and the percentage of transplantable seedlings increased by about 6%. The percentage of stunted seedlings decreased with decreasing numbers of mealybugs. Major nursery pests identified were Temnoschoita quadrimaculata and mealybugs (Pseudococous sp.). Minor pests identified were Arantia rectifolia, Eulioptera reticulata, Homeogryllus reticulatus and Pyrgomorpha sp.

A tick assembly pheromone present in the excretory waste product of the soft tick, Ornithodoros porcinus porcinus (Walton), has been separated by high performance liquid chromatography (HPLC). It has been identified as guanine on the basis of absorption and mass spectral data, and bioassays using nymphs of Argas persicus (Oken). Guanine was active at a low concentration of 8 × 10 −12 M/cm2 of filter paper. Guanine was shown to induce assembly in Amblyomma cohaerens Donitz larvae and Rhipicephalus appendiculatus Neumann adults.

Various purines and ammonium salts tested in the assembly bioassay, and with exception of adenine, were shown to be active for A. persicus.

A new 6a-hydroxylated pterocarpan, named hildecarpin, has been isolated from the healthy roots of Tephrosia hildebrandtii. It has been assigned the structure (−)-3, 6a-dihydroxy-2-methoxy-8, 9-methylenedioxypterocarpan on the basis of its spectroscopie data, optical rotation and chemical transformations. Hildecarpin has exhibited insect antifeedant activity against the legume pod-borer Maruca testulalis, an important pest of the cowpea (Vigna unguiculata), and antifungal activity against Cladosporium cucumerinum. This finding suggests that the pterocarpan phytoalexins formed as a result of microbial infection of the cowpea plant may constitute a basis for induced resistance in the plant against M. testulalis.

There are five caterpillar instars in the life cycle of Spodoptera exempta (Walk.) when they feed upon star grass, Cynodon dactylon (L.) Pers., maize, Zea mais L. and Kikuyu grass, Pennisetum clandestinum Chiov. at 25–30°C. When the temperature is 18°C, however, there was an additional instar in the cycle. Similarly extra instars are formed on Guinea grass, Panicum maximum Jacq., Setaria plicatilis (Hochst.) Hack, and a sedge, Cyperus maranguensis K. Schm. even when the temperature appears to be sufficiently high for normal development. Occasionally the additional sixth instar is also too small to pupate, in which case a seventh instar is formed. It appears that caterpillars on nutritionally inadequate host plants or those at low temperatures are being partially starved and must continue moulting until the appropriate size is attained or exceeded. Measurements of the head capsule widths or distances between the frontal clypeal setae suggest that only individuals reaching or exceeding a species specific threshold size pupate. Extra moults appear to be an adaptation to environmental fluctuations obtaining within the range of occurrence of S. exempta.

A survey of phlebotomine sandflies was carried out in northern Nigeria to determine the distribution of Phlebotomus (Phlebotomus) duboscqi which is suspected to be the vector of cutaneous leishmaniasis in West Africa. P.(P.) duboscqi was found to be confined to the very dry areas of the Sudan savanna vegetation zone, where it utilizes termite hills as the main breeding habitats in association with rodents and lizards. Rock hyrax were located in some adjacent rocky areas. The restricted distribution range includes locations where cutaneous leishmaniasis has been recorded in Nigeria.

Some factors affecting oviposition by Plodia interpunctella (Hubner) were studied under various controlled conditions in the laboratory. The effect of temperature, relative humidity, light and mating on oviposition were investigated.

Temperatures of 25 and 30°C were optimal for oviposition. The best condition was 30°C and 80% r.h. at which an average of 315.3 eggs were laid per female during its lifetime. The least favourable temperatures investigated were 15 and 35°C. Relative humidity did not have significant effect on the number of eggs laid at 15 and 25°C but at higher temperatures of 30 and 35°C, high r.h. increased the number of eggs laid by individual moths.

Light regimes of 12 hr light and 12hr darkness (LD) and 24 hr darkness (DD) were more favourable than 24 hr light (LL) for oviposition.

Virgin females laid fewer eggs than mated females while prolonged virginity reduced the number of eggs laid and caused resorption of immature oocytes and retention of ripe eggs in the ovaries.

Studies on the effect of various diets on development, longevity and fecundity of Oxycarenus gossypinus were conducted in the laboratory at temperatures of 25–33°C. The mean periods of nymphal development when reared on seeds of okra, kenaf, roselle and cotton were 15.5, 15.7, 15.8 and 18.1 days, respectively.

Mated males lived longer and in decreasing order on okra (59.2 days), roselle (57.5 days) and kenaf (57.3 days) than on cotton (43.5 days). Mated females also lived longer on okra (41.4 days), kenaf (40.1 days) and roselle (39.3 days) than on cotton (32.5 days).

Mated females reared on okra seeds laid significantly the highest mean number of eggs per female per day (15.05 ± 0.87 eggs). But the mean number of eggs oviposited when fed on seeds of kenaf (12.9 ± 1.01 eggs) and roselle (10.9 ± 1.18 eggs) was not significant.

The biology of the aphid, Cerataphis variabilis H.R.L., on Raphia hookeri Mann & Wendl., was studied in the laboratory and the field using a ‘clip-on’ cage and a sleeve cage. The first instar lasted 5.1 days. The second and third instars each lasted 2.45 days, while the fourth instar lasted 2.4 days. The total developmental period of the nymphs was 11.3 days at 26.4 ± 1.43°C and r.h. 83 ± 1.46%; 11.6 days at 26.4 ± 1.63°C and r.h. 85 ± 1.19%; 12.9 days at 27.9 ± 1.04°C and r.h. 75.5 ± 1.64%; 12.95 days at 27.8 ± 0.33°C and r.h. 69 ± 1.23%; 15 days at 21.4 ± 0.58°C and r.h. 45 ± 1.77%. These periods were significantly different at 5% level (LSD = 0.59 days). The higher the temperature and relative humidity the shorter the developmental period (with temperature: r = −0.69, 20.8–28.9°C; r.h.: r = −0.97, 43.2–86.2%). The number of progeny per adult ranged from 54 to 60 in a period of 28–31 days. The longevity ranged from 31 to 34 days.

In Acanthoscelides obtectus (Say) (Coleoptera, Bruchidae) several first instar larvae can use a hole made in the seed coat by a conspecific to enter the seed. The present study tests whether there exists different seed-coat piercing abilities related to the hatching rank. The hatching rhythm was found to be well synchronized with the periodic conditions. The hatching rank had no influence on the piercing behaviour. On the basis of these observations the hypothesis of a behavioural dimorphism as has been suggested in the literature may be rejected.

The treatment of different developmental stages and adults of Z. paravittiger with precoceneI failed to produce any precocious metamorphosis, but it definitely proved to be toxic at very low doses to eggs, first instar and second instar and showed an antigonadotrophic effect when adults were topically treated. The ID50 concentrations for emergence were 0.076, 0.005, 1.00, 1000 and 90 ppm for egg, first instar, second instar, third instar and pupae, respectively. The adult longevity and fecundity was reduced even when adults were treated with 0.1 ppm concentration of precoceneI in 1 μl of acetone.

Resistant rice varieties have proved to be highly effective against the brown planthopper Nilaparvata lugens (Stål), but their long-term stability is threatened because of the evolution of prolific biotypes. At present, identification of biotypes is based principally on the differential reactions of host rice varieties to pest in greenhouse screenings and in field plantings of test nurseries at many locations. So far, three N. lugens biotypes that attack different rice varieties have been identified in the Philippines. Biotype 1 can survive on and damage only those varieties that do not carry any genes for resistance. Biotype 2 can thrive on varieties carrying Bph 1 resistance gene and on those susceptible to biotype 1. Biotype 3 can infest and destroy varieties having bph 2 resistance gene and those susceptible to biotype 1. However, none of these biotypes is capable of damaging varieties with Bph 3 and bph 4 genes for resistance, and the variety Ptb 33 carrying two unidentified genes is resistant to almost all known biotypes. Recently, a population of N. lugens was found thriving on the common weed grass Leersia hexandra Swartz on the IRRI farm and in some locations in Luzon, Philippines. This biotype does not survive on rice.

Several varieties which are resistant in the Philippines are susceptible in India and Sri Lanka because the South Asian biotypes of N. lugens are more virulent than the Southeast Asian biotypes. To monitor the pest biotypes in different geographical regions and to identify new sources of resistance, an International Rice Brown Planthopper Nursery (IRBPHN) has been established in many cooperating Asian countries.

Biotypes can also be differentiated by studying their behavioural and physiological responses to plants of known genotypes. Distinctive differences can be observed in insect feeding, growth, longevity, fecundity, oviposition and population increase on differential varieties and relative susceptibility or tolerance for hosts' allelochemics. Recent investigations of the existence of subtle morphological, cytological, and electrophoretic differences among N. lugens biotypes and results of hybridization experiments strongly complement other methods of biotype identification.

The evolution of biotypes is a complex process that is governed by the interactions of the genetic and other biological characteristics of the pest populations and the genetic makeup of cultivated varieties. While the strategy of sequential release of varieties with major resistance genes has been fairly successful, the monogenic nature of those varieties makes them vulnerable to the development of virulent pest biotypes. Therefore, present breeding endeavors envisage use of both major and minor resistance genes for effective pest suppression.

Field studies revealed the nettle caterpillar, Latoia ( = Parasa) viridissima, to be multivoltine with four discrete generations a year. The maximum egg (1800/100 fronds) and larval (1500/100 fronds) densities were attained in April/May 1980. The pupal population was generally low; the highest recorded density of 54/100 fronds was attained in March 1980 during the first generation.

Samples of larvae and pupae from the field were attacked by parasitoids in the families Bombyliidae, Braconidae, Chalcididae, Chrysididae, Eulophidae, Ichneumonidae and Tachinidae. These contributed to mortalities ranging from 6 to 30%, but their combined action with microorganisms (bacteria and fungi) accounted for 28–65% mortality of the insect.

In the Chitwan valley, Nepal, Chilo partellus preferred maize and sorghum over rice, teosinte, finger millet and sugar-cane. Infestation on young maize plants produced “dead hearts” and on older plants reduced growth and sometimes prevented cob formation. The yield reduction in some maize cultivars reached 60% and stem infestation levels reached 98%. Borers produced “dead hearts” in young and “whiteheads” in older rice plants.

The egg, larval and pupal periods from April through September lasted 4–5, 16–41 and 4–8 days, respectively. A complete generation took 28–48 days under summer field conditions and 192–233 days from October to May. Of the one egg, four larval and two pupal parasitoids, all hymenopterans, which were reared from C. partellus, the two most important were Trichogramma chilonis (70% egg parasitism) and Apanteles flavipes (30% larval parasitism).

The use of surfactants and their blends to improve the penetration of two insect growth regulators (IGRs; hydroprene and R-20458) into wheat kernels was investigated. It was found that formulation of IGRs with a surfactant, Tween-85 (polyoxyethylene trioleate), increased mortality and/or effectiveness of the IGRs. Formulation of hydroprene with a blend of Span-80 (sorbitan monooleate) with Tween-80 (polyoxyethylene monooleate) produced results comparable to those by hydroprene with Tween-85. However, formulations of IGRs with surfactants with high or low hydrophile-lipophile balance (HLB), failed to provide suitable control of the weevil, probably due to the type of emulsions formed. The same results were obtained with hydroprene formulations with blends of Spans and Tweens, even though their HLBs were close to that of Tween-85. Residual half-life for hydroprene was about three months; formulations with Tween-85 or a blend of Span-80 did not enhance the residual activity for hydroprene in wheat.

Larval instars of Chilo partellus Swinhoe reared on sorghum plants were determined. The larvae were separable into five non-overlapping instars by analysis of variance and Duncan's multiple range test, frequency distribution and scatter diagram of the head capsule widths. Head capsule increment from one instar to the next conformed to Dyar's rule, while at the same time agreeing with Richards' hypothesis. The stadial periods for the five instars were 6, 4, 5, 3 and 7 days, respectively.

The marked differences in the suitability of different Eucalyptus spp. for growth of the larvae of Uraba lugens was further investigated. It is suggested that non-iarval food-plants and poor larval food-plants regularly selected as ‘egg hosts’ may provide a substrate for the development of resistant strains or biotypes assuming the occurrence of matings between individuals that survive and genetic basis for survival in such difficult food-plants.

The eggplant budworm inflicts severe damage to eggplant in the Gezira area of the Sudan, the larvae feeding inside the buds on the developing stamens and ovaries. Cv. “Black Beauty” was very susceptible with often more than 80% damaged buds, cv. “Long Purple” supported lower populations. Solanum dubium a common weed, was the only alternative host among several solanaceous species examined. Insecticidal screening trials indicated the effectiveness of several synthetic pyrethroids, whereas many other chemicals were ineffective. A possibility of breeding for resistance to this pest is discussed.