Grain yield loss assessment trials were conducted between 1997 and 1999 in Samaru, Nigeria, to assess losses in millet grain caused by the stemboring crambid moth, Coniesta ignefusalis Hampson in four millet-based cropping systems. Deadhearts were scored at 35 and 45 days after planting (DAP) and bored and unbored stems at 95 DAP (harvest). Grain yield loss 35 DAP in 1997 was 265.56 kg/ha of monocropped millet and this was significantly different from the 146.29 kg/ha if millet was intercropped with cowpea. At 45 DAP in 1998, the loss of monocropped millet was 50.48 kg/ha and it was significantly higher than the 13.44 and 10.00 kg/ha of millet intercropped with groundnut or cowpea, respectively. Losses were non-significant under all cropping systems at 45 DAP in 1997 and 35 DAP in 1998. Assessing for yield losses at harvest (95 DAP) in the 3 years was difficult because in some cases, bored stems out-yielded unbored ones. However, the mean grain yields of stems bored by the stemborer under millet monocrop in 1997 (3881.37 kg/ha) and 1998 (4308.15 kg/ha) were significantly higher than those under millet intercrops in both years. Similarly, mean grain yields of unbored stems under millet monocrop were 4327.11 and 5128.78 kg/ha in 1998 and 1999, respectively, and these were also significantly different from those of unbored stems under all millet intercrops in both years. The mean grain yields of all unbored plants were non-significant in 1997. Using linear regression analysis, a significant and positive correlation was established between yield loss and larval population under millet monocrop in 1997 (r = 0.871). A similar relationship was observed between yield loss and percentage plant infestation (deadhearts) under all cropping systems in 1997 and under millet monocrop (r = 0.994) and millet–cowpea (r = 0.8487) intercrops in 1998. Percentage plant infestation rather than larval numbers was found to be the better indicator of yield loss in millet.

A rearing procedure for the pre-imaginal stages of the flea beetle Podagrica sjostedti (Jac.) was developed in the laboratory at room temperature (24–28 °C) relative humidity of 79–92% and a 12 h photoperiod. Adults were reared in a designed oviposition cage that was developed from a transparent plastic vial, which allowed the eggs to be seen. Eggs were kept in an incubation dish for eclosion, which happened within 7–11 days. One-day-old larvae were used to infest two okra seedlings (4 weeks old each) planted in 200 g sterilized soil and moistened every other day with 16.6 ml of water to half-filled capacity. Larvae were retrieved by washing off infested soil through 3 and 1 mm mesh and then a muslin cloth. Pupae were reared in a jar containing moistened sterilized soil. This procedure and the specially designed medium permitted, for the first time, a study of the pre-imaginal stages of P. sjostedti. Its life cycle consists of an egg stage (mean length and width of 0.10 and 0.05 mm) and three larval stages (mean head-capsule width of 0.21, 0.36 and 0.49 mm for the first, second and third instars, respectively): pre-pupa, pupa and adult. The length of pupae averaged 3.10 mm and the width was 1.40 mm. The mean life cycle was 37 days. The mean pre-oviposition period was 7.7 days, oviposition period was 49.2 days and post-oviposition period was 6.5 days. Females were significantly larger than males and the sex ratio (female: male) was 1.52:1.

Studies on the larvicidal properties of extracts and fractions from Kotschya uguenensis Verdc. were done by long-term exposure of Anopheles gambiae s.s. larvae. The cumulative mean percentage mortalities and deformities at different concentrations for the extracts and fractions were recorded after every 24 h. Treatment of A. gambiae s.s. larvae with K. uguenensis extracts showed growth disruption by forming elongated guts and resulting in eventual death. Larvae treated with the methanol extracts from the stem and root barks, and fractions of the former extract attained complete mortality in 6–8 days at 50 and 100 ppm. More deformed larvae were observed from the methanol extract of the stem bark (40%) and methanol-soluble fraction (88%) than those treated with water-soluble fraction (22%) and methanol extract of the root bark (5%). The growth disruption may be associated with constituents in the plant that interfere with the normal endocrine system functions.

Upland rice is mostly at risk from soil-borne insect pests, including termites, which cause significant crop yield losses. Studies were conducted in 2005 and 2006 at Ikenne, southwest Nigeria to assess the effectiveness of two traditional practices (cow dung and red palm oil mixed with pawpaw), two plant extracts (neem seed oil and neem powder) and Furadan coated with garri (cassava flour) against termite attacks on nine rice varieties—NERICAs 1–7, LAC 23 and OS 6. In 2005, the results showed that neem seed oil was more effective than neem powder and cow dung in the control of termites. Of the five treatments in 2006 (Furadan coated with garri, neem seed oil, neem powder, cow dung and red palm oil mixed with pawpaw), two treatments—neem seed oil and Furadan coated with garri—gave the best protection against termite attack. Among the rice varieties, termite attack was significantly lower on NERICA 5 than on the other NERICA varieties in both years. NERICA 5 was apparently the least attacked by termites when unprotected, indicating that it could be used as a resistant check variety for termites. Yield losses were lower in the treated than in the control plots. These findings indicate that botanicals, such as neem seed oil, can provide effective control against termites on rice fields and can also be used as alternatives to persistent chemical pesticides. This study has far-reaching implications because neem seed oil is environmentally safe, easy to prepare, readily available and affordable by resource-poor farmers in Nigeria.

Hexane extracts of 10 different varieties of tomato (Lycopersicon esculentum Mill) obtained in the vegetative and flowering periods were studied for synomonal response of the egg parasitoid Trichogramma chilonis Ishii. Gas chromatography of leaf extracts revealed the presence of saturated hydrocarbons ranging from C14 to C29 in varying numbers and concentrations. These hydrocarbons elicited varied synomonal responses from the parasitoid. The quantity of individual hydrocarbons varied from 72 to 34,940 ppm in the vegetative period and from 4 to 46,170 ppm in the flowering period. Hexane extracts obtained during the flowering period showed a greater synomonal response compared with those obtained during the vegetative period. A better response observed for certain varieties of tomato at a particular period could be due to the presence of higher concentrations of favourable hydrocarbons relative to unfavourable ones. Synomonal activity seems to be associated mainly with tricosane, heneicosane, pentacosane and hexacosane during the vegetative period and with heneicosane and hexacosane during the flowering period. In the vegetative period, the tomato variety To-Pant-T4 elicited the highest activity as well as parasitism at the lowest concentration of 25,000 ppm, which was higher than other varieties at all concentrations. Varieties To-BT-116-32, To-BT-20-2-1 and To-Pant-T3 in the vegetative period and To-Selection-15, To-Selection-32 and To-BT-22-2-1 in the flowering period elicited higher responses than the other varieties. To-BT-20-2-1 elicited a maximum response in the flowering period, which may be due to the presence of higher relative quantities of tricosane, heneicosane and hexacosane. In view of these findings, tomato varieties with favourable semiochemicals could be exploited in an integrated pest management programme to enhance the effectiveness of the egg parasitoid T. chilonis against the fruit borer Helicoverpa armigera (Hb).

In Cameroon, the demand for hive products is growing. Honey and pollen yields are low in the country, partly because of the poor knowledge of the apicultural value of the flora. To determine the apicultural value of Dichrostachys cinerea (L.), Vitellaria paradoxa Gaertn. F., Persea americana Mill. and Securidaca longepedunculata Fres., Apis mellifera adansonii Latreille activity was observed on the flowers of these plants in Ngaoundéré, from December 2001 to May 2002 and from December 2002 to May 2003. The flowers of each plant species were prospected at least 4 days per month, between 0700 and 1800 h, for recording of the nectar and/or pollen foraging behaviour of A. m. adansonii workers. Results show that A. m. adansonii harvest nectar and pollen of V. paradoxa, P. americana and S. longepedunculata. The flowers of D. cinerea were visited for pollen only. The greatest number of workers foraging simultaneously on a plant varied from 34 (D. cinerea) to 1640 (P. americana). A. m. adansonii workers that visited flowers of a given plant species once remained with this nectar source throughout the observation period. Thus V. paradoxa, P. americana and S. longepedunculata could be cultivated and protected to increase honey production, whereas D. cinerea could enable bee-keepers to increase their pollen production as a hive product. During foraging, A. m. adansonii workers increased pollination possibilities of each of the plant species.

Parasitism rates of Bemisia tabaci (Gennadius) and searching and oviposition behaviours of its parasitoid Eretmocerus mundus Mercet were compared on two cassava varieties: a glabrous variety, Nase 4 and a hirsute variety, MM97/0245 with c. 88 leaf hairs/cm2. Parasitism was assessed after potted plants of both varieties were exposed in open fields to natural infestation by B. tabaci and its natural enemy. For the behavioural studies, naive, less than 24-h-old females were individually observed on infested cassava leaflets under a microscope for a maximum of 1 h each. The different foraging behaviours were recorded using the computer software ‘The Observer 5.0’ (Noldus Ltd, Wageningen, The Netherlands). Total per cent parasitism and parasitism by E. mundus did not differ significantly between varieties. Upon encounter with leaf hairs, the parasitoids stopped and groomed before resuming the host search. The frequency of repeat probing, host feeding and antennation after probing and host feeding were higher on the glabrous than on the hirsute variety, while the converse was observed when feeding on liquids on the leaf. The duration of host assessment, initial probing, grooming and resting on the leaf was higher on the glabrous than on the hirsute variety. Leaf hairiness at the density investigated caused some changes in the behaviour of the parasitoids, but did not have an overall effect on field parasitism. Since cassava is generally considered to have glabrous leaves and the variety MM97/0245 is one of the most hirsute varieties, we discount leaf hairiness as a factor in determining levels of parasitoid activity.

The spotted pod borer Maruca vitrata (Geyer) is known for its economic importance throughout its geographical distribution because of its destructive nature to reproductive parts of several grain legume crops including pigeonpea. In view of the importance of the pest, the present study was carried out on the association of different morpho-chemical traits with resistance/susceptibility to M. vitrata at the International Crops Research Institute for the Semi-Arid Tropics, Patancheru, India. Trichome length and density, sugars, proteins and phenols were found to be associated with resistance to M. vitrata in short-duration pigeonpea genotypes. Pod damage by M. vitrata on different short-duration pigeonpea genotypes in the field ranged from 5.8 to 68%. Laboratory studies showed less consumption of food and reduced larval and pupal weights of M. vitrata when reared on the resistant genotypes ICPL 98003 and ICPL 98008 indicating antibiosis effects of the genotypes. Trichome density on upper and lower surfaces of the leaf (390 and 452/9 mm2), and length (3.5 mm) and trichome density (442/9 mm2) and length (5.9 mm) on pods were found positively correlated with the resistant genotype ICPL 98003. High sugar content in flowers (22%) and pods (10.6%) was responsible for the susceptibility of ICPL 88034, while high phenol concentration in flowers (6.5%) and pods (9.3%) in ICPL 98003 was responsible for resistance. Protein content in pods was significantly higher (25.5%) in susceptible ICPL 88034 when compared with resistant ICPL 98003 (16.5%). Based on these results, ICPL 98003 and ICPL 98008 were categorized as highly resistant and ICPL 98012 as moderately resistant. This paper discusses the physico-chemical traits associated with resistance to M. vitrata in short-duration pigeonpea genotypes.

The biology of Typhlodromips swirskii (Athias-Henriot), Typhlodromus athiasae Porath and Swirski and Paraseiulus talbii (Athias-Henriot) was studied using Aculops lycopersici (Massee) active stages as food source. For T. swirskii, development was faster and reproduction was higher than in T. athiasae. Survival of immatures of P. talbii was low on A. lycopersici and all failed to develop to adulthood. A total of 35.4 and 30.3 eggs per female, respectively, were obtained when T. swirskii and T. athiasae were fed on active stages of the tomato rust mite. A diet of A. lycopersici provided the shortest female longevity and highest mean total fecundity, which resulted in the highest net reproductive rate (Ro = 26.785), intrinsic rate of natural increase (rm = 0.235) and finite rate of increase (λ = 1.265) for T. swirskii. The mean generation time ranged between 13.97 and 17.85 days for T. swirskii and T. athiasae, respectively.

The extent of genetic differentiation between native and groundnut-feeding forms of the groundnut seed beetle Caryedon serratus Olivier was studied. Sixteen samples (560 individuals of both sexes collected in four localities in Senegal) of C. serratus were reared from pods of four distinct host plants (Arachis hypogaea L., Bauhinia rufescens Lam., Piliostigma reticulatum (DC) Hochst and Tamarindus indica L.), and five microsatellite loci were analysed. Phylogenetic and statistical analyses indicated that host plants strongly influence the degree of genetic differentiation between sampled individuals. Within host plants, genetic differentiation was low. Genetic differentiation between hosts was highly significant (average θ = 0.374) and geographical distances between localities did not influence the genetic structuration of C. serratus populations from a given host plant. The results of this study show that C. serratus could be under a host race formation process.