Light and pheromone traps were compared for their relative efficiecy and importance in monitoring the Heliothis armigera (Hubner) moths at the farm of Rajasthan Agriculture University, Udaipur, Rajasthan, India, during the years 1984/85 (4 June 1984 to 3 June 1985) and 1985/86 (4 June 1985 to 3 June 1986). Both kinds of traps showed three periods of moth activity during both the cropping years. Both types of traps showed almost a similar trend in population fluctuation during the cropping years and there were significant positive correlations between light and pheromone trap catches, (r=0.87 for 1984/85 and r=0.93 for 1985/86). However, pheromone traps had many advantages over light trap in monitoring the Heliothis armigera moths.

Investigations of the phlebotomine sandflies fauna in a visceral leishmaniasis focus of Aba Roba in Ethiopia were carried out. This resulted in finding Phlebotomus celiae for the first time in the country. Previously, this species was incriminated as a vector of visceral leishmaniasis in Kitui, Kenya where the disease is endemic. It is possible that P. celiae has a wide distribution covering areas of similar ecological niches as those of its first description.

Laboratory bioassay tests showed that Bacillus thuringiensis (B.t.) (Bactospeine) treatment of second instar larvae of Heliothis armigera (Hbn.) and Spodoptera litura F. increased their susceptibility to endosulfan, monocrotophos, fenvalerate and cypermethrin. The LC50 of these insecticides to both the species of larvae were lowered when treated with B.t. Comparison of susceptibility ratios showed that the increased susceptibility to insecticides was more in H. armigera than in S. litura larvae.

Larval establishment and feeding site selection of Eldana saccharina Walker were studied on maize (Katumani Composite B) and sorghum (Serena). These parameters were defined as the location within the plant of the larva 7 days after hatching; and feeding activity was measured by the extent of stalk tunnelling. In naturally infested maize, more larvae settled in the basal section of the plants between second and fifth node/internode, and in sorghum they settled between fourth and seventh node/internode. In the artificially infested plants of both crops, larvae settled in the middle section of the plant mainly between fourth and seventh node/internode. The neonate larvae first settled in the leaf sheath until they were third instars when they entered the stalks. However, in sorghum stalk entry was limited by stalk wall toughness and waxes on the stalks.

The extent of stalk tunnelling indicated that in maize larval feeding is highest in the internodes whereas in sorghum it is in the peduncles.

The ability of three anti-juvenile hormone agents (AJHAs) to prevent the juvenile hormone dependent phase of larval-pupal transformation has been investigated. Neck-ligated post-feeding last instar larvae of Spodoptera mauritia were treated topically with different doses of a juvenile hormone analog (JHA) or the AJHAs, tetra-hydro-4-fluoromethyl-4-hydroxy-2H-pyran-2-one (FMev), ethyl-4-[2-(tert-butyl carbonyloxy)butoxy] benzoate (ETB) and ethyl-[E]-3-methyl-2-dodecanoate (EMD). Untreated ligated larvae or those treated with acetone survived for 12 ± 1 days without showing any sign of pupal cuticle secretion. On the other hand treatments of ligated larvae with different doses of JHA induced pupation. Among the three AJHAs tested treatments of ETB promoted pupation. Treatments of ligated larvae with lower doses of EMD induced the formation of larval-pupal intermediates whereas those treated with higher dose moulted into either pupae or larval-pupal intermediates. FMev-treated larvae exhibited a complete inhibition of moulting and metamorphosis. In order to study whether AJHAs would prevent the JHA induced pupation, neck-ligated larvae were treated simultaneously with different doses of AJHAs and 1 μg JHA. Co-application of JHA with different doses of EMD induced pupation in majority of the ligated larvae and thus appears to a certain extent to counteract the effects of treatments of same doses of EMD alone. Co-application of JHA with different doses of ETB elicited pupation in all the surviving ligated larvae. To a large extent co-application of JHA with different doses of FMev failed to induce pupation. The significance of the findings is discussed in the context of the mode of action of these AJHAs.

Populations of Rhipicephtdus sanguineus, Dermacentor variabilis and Amblyomma maculatum with high and low oviposition capacities were successfully bred in the laboratory. Mating of male and female ticks which possess high oviposition capacity produced female progenies with high oviposition capacity; male and female ticks which possess low oviposition capacity produced female progenies which possess low oviposition capacity. Crossmatings of males with females of opposite oviposition capacity produced female progenies which acquired the category of oviposition capacity of the males in predominant numbers after fourth and fifth generations. It is suggested that the genetic factor for high or low oviposition capacity is either possessed by male ticks alone or is stronger and dominant in the male over that of the female. This genetic factor is also potentiated by successive crossmatings of males and females possessing opposite oviposition capacities.

The possible application of these results to tick control through the suppression of natural population by field release of laboratory-bred populations of male ticks which possess low oviposition capacity is discussed.

Effects of nitrogen on stem borer damage in a sorghum/millet m ixture were investigated in Nigeria. Millet and sorghum grain yield as well as stem borer infestation were not significantly influenced by rate and time of nitrogen application. Borer (Acigona ignefusalis) infestation on millet was very severe in 1984, resulting in total crop failure. In 1985, millet produced grains because of lower borer infestation and damage; the yield of sole millet was thrice that of millet in mixture, whereas the sole crop density was twice that in the mixture. Unlike millet, sorghum produced grains in 1984 despite severe damage by Busseola fusca. Sole sorghum yielded five times the mixture in 1984 but two and a half times in 1985. Borer damage was generally more severe in the mixture.

The influence of temperature and humidity on the biology of insecticide-resistant and susceptible strains of Tribolium castaneum (Herbst) was studied and compared.

At all temperatures (20, 25,30 and 40°C) and r.h. (30, 50,70, 90) tested, the insecticide-resistant strain matured earlier than the susceptible strain. For both strains, the lowest and highest temperature limits for embryonic development and egg hatching were 20 and 40°C, respectively. The incubation period for eggs of both strains averaged 14 days at 20°C and 4 days at 30°C.

Females of the insecticide-resistant strain matured for egg laying earlier (24 hr) than the susceptible strain (60 hr) but laid fewer eggs (36 eggs) than the latter strain (238 eggs). At 30°C and 70% r.h. the resistant strain had a shorter developmental period (15 days) than the susceptible strain (21 days).

Temperature influenced the development of larvae of both strains of T. castaneum. Larvae of the susceptible strain did not develop at 20°C and 30% r.h., 20°C and 90 % r.h. and 40°C and 30%. r.h., whereas larvae of the resistant strains did.

The pupae of both strains developed at all the temperature and relative humidity regimens tested. Temperature and humidity of stored food would therefore, act together to influence the abundance of strains of T. castaneum and the two factors could be manipulated to suppress the population growth of this beetle on stored food.

The predacious mite, Cydnodromella negevi (Swirski & Amitai) completed life cycle when fed on the tetranychid mites Eutetranychus orientalis (Klein), Tetranychus urticae Koch and pollen grains of Ricinus communis (L.) as an alternative food substance in the laboratory. The duration of the immature stages and adult stage were determined. Immature stages of C. negevi consumed in total an average of 27 E. orientalis and 34 T. urticae, whereas each day throughout her life, the adult female consumed an average of 11 of E. orientalis and T. urticae. While feeding on these prey, C. negevi laid 1.3 and 1.0 eggs per day. The number of eggs deposited per day increased (3.3 eggs/female/day) when fed on eriophyid mites. Females neither fed nor reproduced on liquid nutrients.

Influence of age, sex pheromone concentration and mating status on the response of Earias vittella and Earias insulana males to their female sex pheromone was studied using a T- shaped olfactometer. Males of both the species showed age related variation in their response to female sex pheromone and 4-day-old males were maximally responsive. Response of males of both the species to the female sex pheromone was concentration dependent and the level of response generally increased with an increase in pheromone concentration. In E. vittella, response of mated males was comparable with unmated males. In E. insulana, mating caused some reduction in the response of males.

The anatomy of damaged and undamaged young stem, peduncle and young pods were examined from transverse sections in three varieties of cowpea in order to evaluate the anatomical basis of resistance to the pod borer Maruca testulalis.

While tissue development in the stem, peduncle and pods of the three varieties of cowpea were similar, the relative thickness of the various tissues were different in the order Vita-1>ICV-2>TVu 946. The smaller diameter and the relative abundance of strengthening tissues in the stem and peduncle of TVu 946, by limiting total ingestible biomass, might be restricting the damage to these organs by the pod borer.

Pod damage, on the other hand, was concentrated on the parenchymatous tissue of the pod wall lining and inter-seed spaces and the sizes of this tissue were also different among the varieties in the order Vita-1>ICV-2>TVu 946, the same order of susceptibility to attack by M. testulalis.

The influence of drought on egg development, survival and hatchling weight was studied in the solitary phase of Locusta migratoria migratorioides (Reiche and Fairmaire). There was retarding effect of drought on the rate of egg development. The level of egg survival was lowered during prolonged drought, which also led to a decline in hatchling weight. Also the rate of egg survival was lower in eggpods experiencing longer incubation period.

Studies on the vertical distribution of phlebotomine sandflies were carried out at Marigat (Kenya) at determined heights above ground level in both wooded and open fields. Traps set up at different heights from 0–11 m (in wooded area) and 0–9 m (in open field), showed a clear vertical zonation of sandflies as large numbers were collected between 0–7 m in the first site and 0–4 m in the second ones. Among the nine sandfly species collected, Sergentomyia bedfordi Newstead and S. antennatus Newstead were the only species recorded at a height of 11 m above the ground and the commonest sandflies at all studied heights. Overall, more sandflies were collected from the wooded area than the open field. The relationships between the sandfly relative abundance and their heights of flight above the ground showed significant negative correlation coefficients.

A large number of male and female tenerals and young non-teneral female G. pallidipes were attracted to the exterior of the trap but appeared not to enter the trap readily. About 20% of tenerals of both sexes that visited the trap were captured in the retaining cage and the remaining 80% on the outside. The sex ratio of flies stuck on the outside was 1:1 whereas that of flies from the retaining cage was 1:1.5 females:males. The efficiency of the trap for non-teneral G. pallidipes was about 39%. Direct observation using binoculars from a stationary vehicle about 10–15 m from the trap showed that the catching efficiency of the biconical trap was 30% for a total of the four categories of non-teneral females and males, and teneral females and males.

Culex quinquefasciatus (Wiedemann) mosquitoes, which are refractory to Brugia pahangi (Buckley and Edeson) microfilariae, were fed simultaneously on Wuchereria bancrofti (Cobbold) and B. pahangi microfilariae. A selected stock of Aedes aegypti (L) which is susceptible to both of these filariae was used as a control. The exsheathment and migration rates of B. pahangi in C. quinquefasciatus increased significantly as compared to those of B. pahangi when given as a feed by itself. These two processes did not show any trend with time. On dissection, 12 and 14 days postinfection, 27% of C. quinquefasciatus were found to be infected with an average of two larvae per mosquito. Of the total number of larvae found 78% were W. bancrofti while 22% were B. pahangi.

Feeding C. quinquefasciatus on in vitro exsheathed B. pahangi microfilariae suspended in serum did not increase the rate of migration, whereas 71–100% of Ae. aegypti became infected with a mean of 3.5 larvae per mosquito.

Inoculation of C. quinquefasciatus mosquitoes into the thorax and abdomen with exsheathed B. pahangi did not increase their infection rate, whereas in Ae. aegypti 67–82% became infected.

Adults of various phlebotomine sandfly species were obtained from leishmaniases endemic foci in Kenya using several trapping methods. Ten species were successfully reared from egg to adult in the laboratory; and large colonies of Sergentomyia schwetzi, S. bedfordi, S. ingrami, S. antennatus, S. adleri, S. garnhami, Phlebotomus duboscqi and P. martini established. Generally, the development of Phlebotomus spp. from egg to adult took longer (54.7–57.2 days) than Sergentomyia spp. whose developmental time with the exception of S. garnhami, varied between 36.5–42.3 days.

Varietal differences with respect to yield losses due to whitefly, Bemisia tabaci Genn. attack were observed at the “sooty-mould level” and “economic threshold (ET) level” of infestation. At the peak infestation level leading to sooty-mould development, the losses varied from 21.7 to 31.8% in boll numbers, 10.3 and 23.7% in boll-weight; 25.9 and 48.9% in seed cotton yield; 12.4 and 153% in seed oil and 29.4 and 66.5% in seed germination among the group of promising new cultures viz., LK 861, LPS 141 and L 389 and other group of commonly cultivated varieties viz., JKHY 1, MCU 5 and ADB 10050, respectively. Besides, the fibre qualities like length, strength, fineness and maturity were also found to be adversely affected.

The predacious mite, Pachylaelaps aegyptiacus Hafez & Nasr completed life cycle when fed on eggs of housefly, Musca domestica (L.) at 25 ± 2°C and 70–80% r.h. in the laboratory. The durations of the immature stages and of the adult stage were determined. Immature stages of P. aegyptiacus consumed in total an average of 16 eggs of housefly, whereas each day throughout her life, the adult female consumed an average of 7.6 eggs of housefly. Daily rate of single and multiple mating was 0.93 and 1.0 eggs/female respectively. Description of immature stages of the predatory mite was given.

The effects of established phenomena of plant resistance on the levels of tolerance to malathion of an organophosphate resistant strain of Myzus persicae were investigated using topical application insecticide bioassay. Tolerance was significantly decreased when aphids were reared on the moderately aphid-resistant Brussels sprout variety Early Half Tall or on sprout plants given reduced nitrogen fertilization. Differences in insecticide tolerance were found to occur only at older plant ages. It is argued that the differences (less than 50% in LC50 terms) reported are of practical importance, and attention is drawn to much greater differences (5-fold) obtained in experiments at different times of the year.

Laboratory evaluation of food consumption, food utilization, weight gain, development, fecundity and egg-hatchability were made from the beginning of the first instar to sixth instar on castor, groundnut, Indian bean, jute, sesame and sunflower. Total food consumption was highest on castor and lowest on jute. Development was fastest on castor, and castor was most efficiently digested followed by sunflower, sesame, groundnut, Indian bean and jute. Consumption index and digestive efficiency on all host plants declined with larval age. Digested portion of jute was most efficiently converted into body matter. Variations in fecundity and egg-hatchability for different host plants were statistically significant at P = 0.01. The differences in these parameters may be due to the variations in the nutritional quality of the hosts.