Several Vigna species were used to determine the role of pod trichomes and pod toughness in the resistance of cowpea to feeding damage by the coreid bug Clavigralla tomentosicollis Stal. The scanning electron microscopy study revealed the presence of glandular and non-glandular trichomes on the pod wall of all test genotypes. The cultivated genotypes TVu 1890, TVu 3354 and IT84S-2246 of the V. unguiculata ssp. unguiculata showed significantly lower (P<0.05) densities of glandular trichomes than accessions of the wild Vigna species (TVnu 72, TVnu 151, and TVnu 707). All pods were similar with respect to the density and length of non-glandular trichomes. The two wild accessions TVnu 151 and TVnu 707 of the V. unguiculata ssp. dekindtiana had low pod, strength similar to that of the susceptible genotype IT84S-2246, and also showed high seed damage levels comparable to that of this susceptible genotype. These accessions of the subspecies dekindtiana contrasted with the wild and resistant accession TVnu 72 of the V. vexillata species which suffered minor seed damage in spite of its low pod strength. The association between high pod strength and low seed damage was found only in the two cultivated genotypes TVu 1890 and TVu 3354. Our results suggest that tough pod wall and high density of glandular trichomes can be combined to achieve enhanced resistance to C. tomentosicollis in cultivated Vigna genotypes.

Thirty-five grain sorghum genotypes representing 6 variable groups (A/B-lines, R-lines, commercial varieties, germplasms, mutants and locals) were evaluated for the orientation, colonisation and oviposition responses of the rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae), governing the antixenosis component of resistance. In free-choice tests, the orientation and colonisation responses of the weevil were identical among all the genotypes at 24 h, varied at 48 h, and differed widely by 72 h after adult release. High degrees of antixenosis for colonisation by the adult weevils were observed among all the genotypes except 2077A and 2219B, which suggests a predominant reaction to gustatory rather than visual or olfactory stimuli. One to five egg plugs per seed were oviposited, frequently near the endosperm close to the seed base. Greater levels of antixenosis for oviposition were noticed in 2077B, DJ 6514 and IS 11758 in free-choice tests, and 2219B, M 148–138, P 721 and Nizamabad (M) in no-choice tests. To the contrary, M 35–1, Swati and Lakadi showed greater susceptibility for oviposition. Significantly less damage to seed was observed on 2219A/B, 116B, IS 9487, IS 11758, CSV 8R(M) and Local Yellow. Although the differences in seed weight loss were not significant, this parameter was relatively lower in AKMS 14B and 2219B than in the other genotypes. This indicates the need to increase the levels of resistance among the parental A/B-lines in the development of hybrids, in order to ensure better protection from rice weevil infestation in stored sorghum.

Studies were conducted to determine the effect of temperature and diet on the development of Chilo partellus (Swinhoe) and Chilo orichalcociliellus (Strand) (Lepidoptera: Crambidae). Developmental times of C. partellus and C. orichalcociliellus for the egg, larval and egg-adult life stages were inversely related to temperature. The larval developmental period of C. orichalcociliellus reared on artificial diet was longer than the developmental period on natural diet. Chilo partellus had a higher intrinsic rate of natural increase than C. orichalcociliellus at all diet/temperature combinations except natural diet at 31°C.

Surveys for population densities of the maize borer Sesamia eretica Led. (Lepidoptera: Noctuidae) were conducted for three consecutive years (1997–1999) in several localities of the Nile delta in Egypt, in order to get a better insight into the population dynamics of the pest and to propose rational basis for its biocontrol using a recently isolated granulovirus. High population densities (more than one borer per plant) were observed only in the first plantings after winter (first fortnight of April). After this peak, populations almost vanished until the end of the crop season (September-October) when a slight increase was observed (0.1 borer per plant). The drastic decrease in population densities in plantings from the end of April occurs because most final instars of the borer leave the plant to pupate in the soil. This behaviour, uncommon in maize borers, results in a very high mortality rate due mainly to pupal parasitism. Only the few larvae pupating in the stem, which are much less parasitised, give rise to adults. Spatial distribution was studied using Taylor's power laws which enabled the elaboration of enumerative sampling plans for eggs, small larvae (1st and 2nd instars) and older ones. Fixed optimal sample size and sequential sampling plans for different precision levels were developed. The precision of the estimated sample size was checked using resampling of some of the data that were not used to build the models. The validation study showed that the plans were suitable for the entire Nile delta region.

Field experiments were conducted for two seasons to assess the efficacy of the entomopathogenic fungus Metarhizium anisopliae in the control of termites in maize. Application of the fungus at planting was found to significantly reduce maize lodging and increase grain yield in both seasons. However, data from treatment application at tasselling were not consistent. Our results suggest that a granular formulation of M. anisopliae might be a useful option for the management of termites in the maize agroecosystem.

The population dynamics of the coconut mite, Aceria guerreronis Keifer (Acari: Eriophyidae) infesting the coconut fruits was studied during September 1999-May 2000 in Tamil Nadu, India where the mite is a new pest. The densities of active mites and eggs were not significantly correlated with weather factors. Mites were more abundant on the post-fertilisation bunch 3 drupes (fruits) (6.0 mites/7 mm2) than on the other drupes. They were most crowded on the fourth (outer to inner) tepal (bract) of the bunch 3 perianth (2.6 mites/7 mm2). No significant difference was evident between populations of A. guerreronis from the drupe and tepal surfaces. However, eggs were more numerous on the tepal surface (4.9 eggs /tepal) than on the drupe surface (2.5 eggs /drupe). Egg density was highest on bunch 5 drupes (8.6 eggs/tepal) than on the drupes of other bunches. The inner tepals (4–6) carried more eggs (4.6–5.6/tepal) than the outer (1–3) ones (1.2–3.8/tepal). Mite population declined by 62.6 % when the tepal area decreased by 24.3 % due to mealybug (Pseudococcus cocotis Mask.) infestation which caused the tepals to deform. The predatory mites Amblyseius sp. and mealybugs were most abundant on tepals 5 and 6 (2.5–2.6 predatory mites; 4.6–4.7 mealybugs/ tepal). Eggs of A. guerreronis could be stored in the freezer at 3.9 ± 0.3 °C for one month although hatchability decreased from 98 % one day after storage to 54.7 % one month after storage. Loss of the eriophyid mites from sample drupes after five days was minimal (54.7 %) when the drupes were stored in a thermocool box containing ice at 23.7 ± 0.4 CC. Most mites (75.8 %) died when the drupes were stored in the open at room temperature (35.3 ± 0.9 °C).

The influence of temperature on the age-specific fecundity of an aphidophagous ladybeetle, Micraspis discolor (Fabricius) (Coleoptera: Coccinellidae) feeding on the cowpea aphid, Aphis craccivora Koch (Homoptera: Aphididae) at four different temperatures, viz. 20, 25, 27 and 30 °C, was investigated. The age-specific fecundity function was triangular and oviposition rate (no. of eggs/ day) increased with increase in reproductive age of the ladybeetle, attaining a peak then gradually decreasing before finally ceasing. Young adults were more efficient at converting aphid biomass into eggs than older ones. The oviposition peak tended to shift towards younger females and the oviposition rate increased with increase in temperature from 20 to 27 °C. The maximum fecundity and percent egg viability was 750 eggs and 95 % at 27 °C and minimum 385 eggs and 65 % at 20 °C, respectively.

Scanning electron microscopic examination of the egg shell and associated structures of Eocanthecona furcellata (Wolff.) (Hemiptera: Pentatomidae) reveals a distinct pattern of structural elements, viz. microsculpture of the chorion, pseudoperculum, egg burster and aeromicropylar processes. The egg shell has a highly decorated chorion with a structural difference at both the anterior and posterior ends. A reticulate type of microsculpture with varying sizes of spine-like projections measures 4.02 ± 0.06 to 8.12 ± 0.05 μm and forms an asteroid-like shape at the anterior pole, while the surface at the posterior end has elongated striations over the chorion measuring 72.00 ± 0.074 μm. The pseudoperculum of the egg shell is a circular lid measuring 518 ± 11.43 μm in diameter. During hatching the line of rupture follows the micropylar ring, and this sometimes extends beyond the ring of micropylar processes. An inverted T-shaped black egg burster measures 202 ± 4.63 μm in length, is well developed and can be seen prior to hatching within a thin and transparent egg shell. It is a median sclerotised part of embryonic cuticle. The aeromicropylar processes are situated at the anterior pole of the barrel-shaped eggs. There are 26–28 aeromicropylar processes arranged in a circle at almost equidistance and each micropylar process is slightly curved opposite to the pseudoperculum lid with a bulbous end at the apex. The aeromicropylar processes are 25.40 ± 0.083 μm in length and 3.02 ± 0.07 μm in width. Each micropylar process has a central canal for the passage of sperm whereas the rest of its body is porous, and allows respiratory interchange.

The predation of the booklouse, Liposcelis entomophila (Enderlein) (Psocoptera; Liposcelidae) by the mite Blattisocius dentriticus (Berlese) (Acari; Ascidae) was studied in a series of laboratory experiments. Known numbers of mites and booklice were placed together in small tubes and counted after various durations. Fewer booklice were found in mite-infested tubes and it was possible to rear the mite on booklice, which supports the view that the mite is a natural predator of L. entomophila. Comparative susceptibility of the mite and booklouse to deltamethrin and fenitrothion was assessed by exposing both arthropod species to deposits of the two insecticides. The mite was found to be very susceptible to both deltamethrin and fenitrothion whereas the booklouse was only susceptible to the latter. The increased prevalence of L. entomophila in tobacco storage and grading buildings in recent years may therefore be attributed, at least in part, to the use of deltamethrin which suppresses its natural enemies.

Busseola fusca Fuller is one of the major lepidopteran stemborers of maize and sorghum in Africa. Cotesia sesamiae (Cameron) (Hymenoptera: Braconidae) is an indigenous, gregarious larval endoparasitoid that attacks mid- to late-instar stemborer larvae, which is reported to be one of the most important larval parasitoids of B. fusca in many countries in sub-Saharan Africa. Previous work has shown that two biotypes of C. sesamiae occur in Kenya which express differential abilities to develop in B. fusca. A biotype from western Kenya successfully develops in B. fusca, while a biotype from the eastern coastal area does not. We treated fourth-instars of B. fusca with calyx fluid from C. sesamiae from western Kenya (Kitale) before offering them to C. sesamiae from the Coast (Mombasa) for oviposition, and found that the eggs were not encapsulated. This suggests that factors in the calyx fluid of C. sesamiae from the western Kenya biotype were responsible for suppressing the immune system of B. fusca. We speculate that polydnaviruses in the calyx fluid were involved in disarming the host immune system, and that the polydnaviruses in the two biotypes are genetically different.