Abstract: Zonocerus variegatus (Orthoptera: Pyrgomorphidae) is known as an agricultural pest in West and Central Africa. In this study, the effects of 13 single and eight mixed host plant diets on the survival, post-embryonic development and morphology of Z. variegatus in the laboratory were investigated. In each cage, 20 one-day larvae were provided with these diets and their survival monitored every two days, from August 2000 to September 2002, until all individuals died. Results showed that the number of larval stages varied from six to eight according to the diet. Six larval stages were most frequent. Development to the adult stage (complete development) was only noted with 52% of diets. All the mixed host plant diets induced complete development of Z. variegatus except that of Cajanus cajan + Synedrella nodiflora + Chromolaena odorata. Complete development was observed with four single host plant diets: Lablab purpurea, C. cajan, Manihot esculenta and S. nodiflora. Compared to leguminous species and Asteraceae, M. esculenta (Euphorbiaceae) was the species that resulted in the highest level of survival and development of Z. variegatus. Chromolaena odorata and S. nodiflora (Asteraceae) induced late appearance of the different Z. variegatus nymphal instars and the appearance time was shorter on legumes. The supernumerary stage 7 has the same color as the larva in stages 1â6, but this larva was significantly larger than stage 6 and smaller than the adult stage. These results indicate that legumes for short fallows affected the survival and post-embryonic development of Z. variegatus in the laboratory.
Abstract: Zonocerus variegatus (L.) is known as an
agricultural pest in Central Africa. Since legumes are
introduced in the Chromolaena odorata fallows in the
southern Cameroon as short fallow improvement strategies,
we evaluated the abundance of Z. variegatus in short fallows
(natural versus planted leguminous fallows) and
adjacent fields. Existing Randomized Completed Block
Design were used, with three treatments (C. odorata,
Calliandra callothyrsus and Pueraria phaseoloides) and
three replicates, split in two sites (land cleared from forest
and land cleared from chromolaena fallow). Research was
carried out from February 2000 to February 2002 by captures
(every 14 days) in each fallow and adjacent cropped
fields. Within 30 min, 24 ± 75 (SD) individuals were
captured in the fallows, while only 10 ± 20 (SD) were
captured in adjacent cropped fields. The abundance was
greater in fields after forest clearing than in fields after
chromolaena clearing. More individuals were captured in
C. odorata fallows in both sites. Z. variegatus abundance in
planted fallows depended on the site. After forest clearing,
Z. variegatus abundance was highest in the P. phaseoloides
and lowest in C. callothyrsus fallow, while after chromolaena
clearing the abundance in P. phaseoloides fallow was
lowest. Z. variegatus abundance between cropped fields
adjacent to C. odorata, C. callothyrsus and P. phaseoloides
fallow was not significantly different, but significant linear
relationships were found between Z. variegatus abundance
in 2 years old fallows and the adjacent cropped fields.
These results indicate that in areas where chomolaena
dominates the fallow, planted P. phaseoloides could be
useful in managing Z. variegatus.
Abstract: A cross-sectional transversal study on the malaria transmission was carry out in the Mangoum village, situated in the Mountain western region of Cameroon in October 2005 and May 2006. The parasite and spleen rates, biting habits and entomological inoculation rate of parasites and Anopheles species were investigated during dry and rainy seasons. Mosquitoes were collected by night landing catches on volunteers and indoor pyrethrum spray catches. Members of the An. gambiae complex and molecular forms were identified using PCR method. Infection intensity was determined by counting the number of infected red blood cells against 200 leucocytes. A total of 1195 Anopheles was collected, 183 and 1012 respectively in the dry and rainy seasons. Two Anopheles species were identified; An. gambiae s.l. and Anopheles funestus. An. gambiae s.s. was the only member of the An. gambiae complex found and the main malaria vector in this region. The sporozoïte rate of An. gambiae was higher in the rainy season (9%). The average inoculation rate was 90 infective bites per man per year. A total of 699 children were examined. Two parasites species were identified: Plasmodium falciparum and P. malariae. The mean parasite rate was 41, 3%. In the age range of 2â9 years, the parasite rate were respectively 49% in the dry season and 34, 7% in the rainy season. The mean spleen rate of the age range (2â9 years) was 24, 7% with 26, 7% in rainy season and 22, 3% in the dry season.
Abstract: This study assesses the abundance of Zonocerus variegatus in 2 natural herbaceous fallow and 2 planted forest types of the forest reserve of Mbalmayo (Cameroon) with the aim of testing the hypothesis that the high abundance of the grasshopper is linked to the presence of C. odorata. In each of 3 replications of each treatment, we carried out once every 14 days (from February 2002 to December 2003), regular collection and observation with sweep netting for a period of 30 mn. The results showed that, Z. variegatus is found in herbaceous fallows, but is extremely rare in the Inga edulis planted fallow. Within natural herbaceous fallows, it is significantly more abundant in those with, than in those without C. odorata, only in the dry season. No individuals were observed in the type I planted forest (without C. odorata) while 0.29 individuals were captured in the type II (with C. odorata). These data suggest that the type of vegetation has an important effect on Z. variegatus abundance.
Abstract: Weekly captures from January 2000 to January 2002 enabled us to study the abundance and life cycle of
the variegated grasshopper, Zonocerus variegatus (Orthoptera: Pyrgomorphidae), in the humid forest zone
of Southern Cameroon. We found that Z. variegatus was present throughout the year in the forest reserve
and the human-influenced zones of Yaounde and Mbalmayo in two univoltine populations, which had
unequal abundance and durations. The separation of the two populations was clearer in the Yaounde and
Mbalmayo developed zones than in the Mbalmayo forest reserve (undeveloped zone). The abundance of
Z. variegatus varied according to the post-embryonic stage, sex, year and season. Hatching and coupling
took place during the dry and rainy seasons, whereas oviposition occurred only in the rainy season. In
Cameroon, the type of life cycle of Z. variegatus observed in the humid forest zone of the south is different
from that of the âSudanian and Sahelianâ zones.
Abstract: Background: Zonocerus variegatus (Linnaeus, 1758) (Orthoptera: Pyrgomorphidae) is known as an
agricultural pest in West and Central Africa. However, its importance in the agricultural production
system in Cameroon has not been investigated. The study assesses farmers' perception on the
importance of Z. variegatus in the agricultural production systems of the humid forest zone of
Southern Cameroon.
Methods: Research was carried out in 5 villages of each of three Agro-Ecological, Cultural and
Demographic Blocks (AECD-Blocks) of the Forest Margin Benchmark Area (FMBA). In each village,
a semi-structured survey was used; male and female groups of farmers were interviewed
separately.
Results: Z. variegatus is present throughout the humid forest zone of Southern Cameroon, where
it is ranked as the third most economically important insect pest of agriculture. In the farmers'
opinion, Z. variegatus is a polyphagous insect with little impact on young perennial crops. The length
of the pre-farming fallow does not affect Z. variegatus pest pressure in the following crops. The
increased impact of the grasshopper observed today in the fields, compared to what existed 10
years ago is as a result of deforestation and increase in surface of herbaceous fallow. The damage
caused by Z. variegatus is higher in fields adjacent to C. odorata and herbaceous fallows than in those
adjacent to forests and shrubby fallows. The fight against this grasshopper is often done through
physical methods carried out by hand, for human consumption. The farmers highlight low usage of
the chemical methods and a total absence of biological and ecological methods.
Conclusion: Farmers' perception have contributed to understanding the status of Z. variegatus in
the humid forest zone of Southern Cameroon. The results are in general similar to those obtained
in other countries
Abstract: Group surveys were conducted in five villages in each of the three resource-use zones of the humid
forest zone of Southern Cameroon, to assess insect pestsâ incidence and the variation due to forest
landscape degradation in the agricultural production systems. 389 farmers were interviewed. The
results show that: (1) In annual crop systems, insect pests in general rank together with vertebrate
pests and diseases amongst the most important agronomic constraints. No differences were found
between the intensification zones, except for weeds, which appeared to be a greater constraint in the
slightly degraded area. Within the insect pest, the greatest damage to crops according to farmers
originated from borers and scales, followed by variegated grasshopper. Only the termites showed a
difference between zones - the problem being greatest in the high-degraded areas. (2) In the young
perennial crop systems, all the categories of agronomic constraints were equally important. Within the
insect pest, mirids were identified as the greatest constraint, followed by borers and caterpillars. There
were more variations in the responses according to zones compared to annual crops. Termites and
scales were relatively more important in the high-degraded area. In term of control strategy, we
recommended an integrated pest management.
Abstract: The economic exploitation of timber and the practice of slash and burn agriculture are the major causes of the transformation of the forest landscape in tropical Africa. This paper reviewed the consequences of deforestation on the diversity and status of grasshoppers. In addition, the threat to food security was discussed. It is known that, globally, grasshopper infestation is most likely to affect countries with drier climates. Because of transformation of the forest landscape, forest zones will likely become vulnerable in the future. The substitution of trees by herbaceous plants supports the reduction of grasshopper diversity, but the increase of herbaceous fallow can enhance the environment for locusts. The damage from grasshoppers significantly decreases agricultural output and constitutes an important threat to food security. To reduce the risks related to this deforestation, it is important that the forest policies of each affected country should emphasize strategies that focus on a) reinforcement of artificial forest regeneration, and b) research on the effects of short fallow stabilization.
