This paper reviews and analyses literature on the effect of plant species diversity on crop pests. It is observed that populations of several crop insect pest species are depressed under conditions of plant species diversity. The factors responsible for this depression are: parasites, predators, masking, camouflage, repellency, less colonization, resource concentration, unfavourable microclimate, physical obstraction and trap cropping. Natural enemies account for more than half of the cases where the pest population was claimed to be regulated in the weed-diversity systems. However, under conditions of crop–crop diversity, natural enemy action accounted for less than a third of the cases reviewed. It is further observed that most of the reviewed crop–crop diversity systems were of annual crops. It is therefore concluded that under conditions of annual cropping natural enemies are probably of lesser importance than other regulating factors.

Most dissected Nezara viridula (91.6%) from night catches had their stomach filled (half-full-full) with food, and females had a higher feeding activity than males. Females outweighed males at the ratio 1.3: 1, and an individual was heavier in October than in May. Ovarian development corresponded closely with decreasing fat body of females, and immature individuals had maximum fat in the abdomen. The spent individuals with empty stomach and fat thinly spread over the venter were relatively abundant in April and May, implicating the possibility of large-scale oviposition during these seasons.

Field studies were done to elucidate the effectiveness of buffalo urine as a tsetse attractant under a variety of test conditions. When traps were baited with the test sample of urine placed in large-necked dispensers allowing evaporation of 2 to 2.9 ml/hr, they performed better than traps baited with similar samples placed in narrow-necked dispensers with evaporation rate of 0.2 to 0.4 ml/hr. Buffalo urine was compared with samples of cow urine: the catch size increased 1.8 times in traps with cow urine when compared to that of the control trap, whereas buffalo urine was 9.6 times more attractive than control. Acetone added to the test sample, even in very small quantity, boosted the effectiveness, increasing the catch size 2.8 times more. Urine samples that had stayed on the laboratory shelves for some weeks or months were more effective than freshly obtained ones.

This selected bibliography on the whitebacked planthopper, Sogatella furcifera (Horváth), contains 506 published and unpublished references for the period 1899 to February 1984. References are arranged alphabetically by the name of the author and also classified by subjects. A distribution map, two tables of the varietal resistance to the pest and its natural enemies, and a brief description of the current status of the pest are also provided.

Intrinsic toxicity of seven insecticides including bromophos, bromophos-ethyl and deltamethrin to the Indian hive bee Apis cerano indica is reported. Bromophos was safer than endosulfan, while deltamethrin was the most toxic.

Female Eldana saccharina Walker was found to lay 327 ± 17.1 eggs within a period of 4 days and required three surfaces to lay eggs which were mainly deposited on the inner side of leaf sheaths fitting tightly on to the sugar-cane stalk. The mated females laid more eggs per female (327.0 ± 17.1) than virgin females (212.3 ± 5.5). The incubation period of the eggs of E. saccharina was found to be 5.64 ± 0.01 (5–7) days in the laboratory and 5.82 ± 0.03 (5–7) days in the field. The mean larval duration was 31 days and pre-pupal period lasted 2.05 ± 0.05 days. Larvae were found to exude a brownish liquid from their mouth in the direction of the invading predators. The newly hatched larvae spread out in 1–3 days of hatching. The mean growth ratio of the larval instars was 1.54 ± 0.05. Pupae frequently occurred very close to the exit hole (less than 5 cm) and the pupal period varied from 7 to 13 (9.76 ± 0.05) days. The life cycle of E. saccharina was completed in 49 (36–62) days. The pre-oviposition period was 2 days and the female reproductive life lasted 4 days. It takes about 53 days for a succeeding generation to be produced. Adults of E. saccharina survived from 6 to 13 days. Adults reared from field collected larvae snowed a sex ratio of 42:51 which was significantly different from 1:1 in the laboratory bred stock, at the 5% level of probability. A comparison of the life cycle of E. saccharina populations in Ghana and Uganda suggests the existence of two biotypes of the pest.

Considering the theme of the study workshop, I would like to emphasize that both integrated control or pest management and host plant resistance date back to the earliest days of agriculture. By its very nature, agriculture is one of the most integrated activities of man. A successful farmer has many skills, which he or she (let us not forget that many farmers are women!) uses in an optimal combination to obtain food and income for the family. Integrated agriculture, control or management are therefore not a recent novelty of agricultural scientists, but rather a necessary response to scientific specialization and subsequent isolation, which has led to some degree of disintegration in modern agriculture. This disintegration is characterized by a tendency for simplification of the agricultural enterprise to the extreme of but one or a few crops, one or a few uniform cultivars and standard fertilizer and pesticide applications. It has been recognized that this development might result in an increased vulnerability and instability of this basic sector of human productivity, especially in parts of the world with a weak infrastructure, where local farmers are not able to respond in time to sudden adversities and are left with unexpected yield losses. Stable and ecologically balanced agricultural production systems are therefore especially essential to small farmers in the so-called Third World. They will benefit more from yield optimization rather than from yield maximization, because the latter is often attended by many disruptive forces.

The anterior aorta is rich in axons and axonal endings originating from the nervus corporis cardiacum (NCC) and the corpus cardiacum (CC). Neurosecretory granules in the NCC axons are small compared to large granules synthesized in the CC. Vesiculation of the secretory granules into clusters of small vesicles occur both in NCC axonal endings and axon-like processes from the CC, suggesting that both types of secretions are released into the haemolymph.

Synapses occur between the NCC axons and cardiac muscle cells, as well as with cell processes from the CC, suggesting that some of the neurohormes from the NCC axons may function as neurotransmitters. The CC consists of large neuron-like cells, that synthesize an intrinsic secretion; it also contains a neuropil of NCC axons and CC cell processes. There is no evidence of a separate storage and release lobe in the CC. No synapses occur between the axons and cell processes or with the cell bodies. The CC cell processes have their endings in the aortic wall where they make synapses with NCC axonal endings and where they most likely release their material. It is suggested that in Glossina: (a) the aortic wall has taken over the neurohaemal role of the CC whose function otherwise remains that of synthesizing an intrinsic hormone; and that (b) the activity of the CC to synthesize and/or release its intrinsic secretion is most likely controlled in the aortic wall via a neurotransmitter substance.

Sounds produced in relation to the sexual behaviour of the tsetse, Glossina m. morsitans, were investigated. During mating, a receptive virgin female adopted a relatively passive role while the male produced sound and drummed her with the tarsi of the meso- and metathoracic legs upto about 4–5 min immediately after mounting. During the long cppulatory phase, the male only produced sound when the female became restless or the pair was disturbed. No sounds were produced during the ejaculatory phase after which the flies separated.

Immediately after separation, the females were often receptive for further short copulations, but were completely unreceptive 24 hr later and showed vigorous repellent behaviour. The post-copulatory behaviour patterns and the rejection behaviour of the female were also accompanied by sound production. Although males readily mated with freshly killed females with the usual mating behaviour, sound production was less intense than when the females were live.

Mating sounds were composed of frequencies up to 50 kHz with the exception of the sounds produced by males, while mating with freshly killed females which not only lacked any ultrasonic components, but were also of low intensity. The most dominant frequency was centered between 1.5 and 2.5 kHz. Peaks were also observed between 0.5 and 0.8 kHz, around 5 and 9 kHz. On the basis of intensity, it is suggested that the frequency components below 10 kHz carry the most important part of the acoustic signal.

The use of indigenous plant materials for the construction of biconical traps to control tsetse is described. Preliminary results from field trials indicated that traps made entirely from local materials performed almost as well as a standard design. It is intended to promote the construction and use of these traps on a community self-help basis in sleeping sickness areas of Uganda.

Feeding of the adult parasite of Trichogramma evanescens Westwood on a honey solution containing 500 μg of Bacillus thuringiensis var. galleriae HD-129 for 4–5 days had no effect on their longevity, productivity or their capability to parasitize the host eggs of Spodoptera littoralis (Boisdüvalle) or Anagasta kuehniella Zeller. After spraying the freshly laid host eggs with B. thuringiensis at the same concentration, a significant decrease was observed in the percentage of parasitism. No deleterious effects were observed in the development of the immature stages of the parasite and the percentage of its emergence, as affected by B. thuringiensis, when applied to the host eggs before or after parasitism.

Damage caused by the black bean aphid, Aphis fabae Scopoli, on the common bean, Phaseolus vulgaris L., was severest when the aphids were transferred onto bean plants during the preflowering stage. There were significant reductions in the average length of the central shoot, production of flowers, pods and seeds per plant. Seed weight per plant was also significantly reduced when aphid infestation occurred during the preflowering stage. Smaller, but significant reductions to the length of the central shoot, quantity of pods and weight of seeds produced per plant caused by A. fabae were also recorded when the aphids were transferred onto plants at anthesis. When aphid infestation occurred during the grain filling stage the damage caused was minimal and insignificant. The results obtained indicated that the preflowering stage was the vulnerable stage of bean development during which aphid attack is most harmful and, if unchecked, could lead to drastic yield losses.

A keen appreciation of the types and mechanisms of resistance must be attained in order to fully understand and utilize resistant cultivars as effective tools in today's pest management schemes. A historical account of plant resistance terminology is presented. Resistance can be classified as to intensities: immunity; high, moderate and low resistance; or types of resistance: vertical or horizontal resistance. The mechanisms of resistance include: non-preference, antibiosis and tolerance. Examples of the effects of both non-preference and antibiosis resistance on insect numbers are given.

The histopathological changes caused by Bacillus thuringiensis var. entomocidus HD-635 in the cotton bollworm, Heliothis armigera, have been investigated using electron microscopy. Death of the larvae due to infection was a gradual process involving a sequence of symptoms. Most of the histopathological changes that occurred on the fourth day after treatment with B. thuringiensis were mainly localized in the midgut, where the epithelium was greatly affected losing its integrity; the peritrophic membrane and microvilli were degenerated; and the musculosa was also affected. Other associated effects were observed in the integument, nerve ganglion, fat body cells, tracheoles and Malpighian tubules. In the integument, the exo- and endocuticles were clumped with an obvious separation from each other. An obvious degeneration of the nerve cells surrounding the second abdominal nerve ganglion as well as the neurilemma of the nerve fibres occurred. Vacuolization of the fat body cells, degeneration of their nuclei and destruction of the membraneous sheath surrounding these cells occurred. Tracheoles showed excessive cellular hypertrophy with disintegration of its mitochondria. The Malpighian tubules showed a reduction in their lumen, with nuclei degeneration and nuclear chromatin clumping. Uric acid crystals were released in the lumen of the tubules and a rupture was observed in some parts of the microvilli. A rapid phagocytosis occurred in the haemocytes. The plasmatocytes and granular haemocytes phagocytosed the bacteria. The counts of haemocytes were at a minimum and bacterial numbers at a maximum on the fourth day after feeding the larvae on B. thuringiensis-contaminated diet.

Stripe (st+) is a dominant trait on chromosome 3R in region 33B on the cytological chromosome map of Anopheles albimanus. It is expressed as a white longitudinal stripe in fourth stage larvae and pupae, and marks a Y-autosome translocation stock T(Y; 3R)3. Pseudolinkage analysis of the available markers to the translocation breakpoint showed complete absence of recombinant progeny between T(Y;3R)3 and st+. The two loci most likely either overlap or are very closely linked. This translocation strain can be genetically sexed by selection of the stripe marker.

The soybean plant introduction (PI)227687 is highly resistant to 16 different insect pests of soybean in Australia, Brazil, Taiwan and the United States. In most of the pest Lepidoptera, resistance is expressed as greatly increased mortality in the later larval instars. The soybean looper, Pseudoplusia includens (Walker) is most severely affected in the final larval instar. Antibiotic effects include reduced weight gain, growth rate and increased mortality. These effects are enhanced by mechanically wounding foliage 24 hr prior to larval consumption. Antibiosis appears to be due to the combined effects of a feeding deterrent and a growth inhibitor. Resistance is location-specific on (PI)227687 plants and occurs abruptly on the third fully-expanded leaf from the plant apex. Larval growth on leaves of the susceptible variety ‘Davis’ is similar to or greater than that of the upper, susceptible leaves of (PI)227687. Resistance appears to be chemically based, since larvae fed artificial diets containing leaf extracts exhibit antibiotic symptoms similar to those fed fresh (PI)227687 leaves.