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|Title:||BIOECOLOGY AND CHARACTERISATION OF TROPICAL WAREHOUSE MOTH, Ephestia cautella WALKER (LEPIDOPTERA: PYRALIDAE) ON STORED COCOA BEANS IN SOUTHWESTERN NIGERIA|
|Other Titles:||A THESIS IN THE DEPARTMENT OF CROP PROTECTION AND ENVIRONMENTAL BIOLOGY, SUBMITTED TO THE FACULTY OF AGRICULTURE AND FORESTRY, IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE AWARD OF THE DEGREE OF DOCTOR OF PHILOSOPHY OF THE UNIVERSITY OF IBADAN|
|Authors:||OYEDOKUN, A. V.|
|Abstract:||The Tropical Warehouse Moth (TWM), Ephestia cautella is a major insect pest causing severe damage to stored cocoa beans (CB). The most popular control with chemical fumigants is being discouraged due to human and environmental hazards. There is paucity of information on the ecology and biotypes of this pest. Therefore, the bioecology and characterisation of populations of TWM in southwestern Nigeria were investigated. Sixty-four warehouses/storage bins from sixteen randomly selected cocoa producing communities in four Southwest States, Nigeria were surveyed for insects associated with stored cocoa beans (CB) in two years using standard indices to identify species diversity and evenness (E). The populations of TWM were characterised by whole genome sequence using specific primers with standard genetic sequence statistics to identify biotypes. Biology of TWM was studied on CB Variety-N38 and Cocoa–Soy artificial Diet (CSD) in the laboratory and developmental period (days), body morphometrics (mm), sex ratio, fecundity and longevity were assessed. Dried CB (Variety-N38) fermented for different durations (0 - 7days) by standard procedures were analysed for mineral constituents and each treatment infested with 10 larvae/100g cocoa beans and mortality, Total Adult Emergents (TAE) and Days to Adult Emergents (DAE) were assessed. Also, dried fermented beans of 14 cocoa genotypes and four potential food hosts: wheat, maize, soya and okra were evaluated using standard choice and no-choice assay in six replicates to identify resistant donor and suitable hosts and oviposition, damage (holes/bean or seed), F1 adult emergents, developmental period (days) and weight loss (g) were assessed at 120 days. Data were analysed using descriptive statistics, regression analysis and ANOVA at p=0.05. Six insect species comprising two primary-; Ephestia cautella and Cocyra cephalonica, three minor-; Lasioderma serricorne, Ahasverus advena and Carpophilus obsoletus and one secondary-; Tribolium castaenum pests were associated with stored CB in southwestern Nigeria. TWM was the most persistently occurring (6.00±0.82-28.00±3.43) across locations while T. castaenum was the most abundant (8.00±1.83-46.50±4.32). Species diversity (0.28) was low while the Evenness index was high (E=1.28). Genomic clusters of TWM populations indicated occurrence of two biotypes in southwestern Nigeria at 0.4 similarity level. Developmental period from egg (4.70 days); 1st (5.70 days), 2nd (5.50 days), 3rd (4.90 days) and 4th instar (6.40 days); pre-pupa (4.93 days); and pupa (6.50 days) to adult totaled 38.63 days. Mean fecundity increased significantly in mated female fed 10% sugar (131.05±31.73) than in mated male and female (21.95±7.82) fed on natural diet. Sex ratio (male: female) was 1: 1.28. There were significant correlations between mineral constituents of fermented cocoa beans and TAE (r=0.53) and DAE (r=0.57). The most resistant cultivar was Genotype-21 (damage=<5%; F1 Emerged=0%; weight loss=0.73g) compared to control. TWM completed development on maize and wheat only with comparatively higher percentage F1 emergent (60-120%) than cocoa beans and were considered suitable hosts. There are two distinct biotypes of the tropical warehouse moth, Ephestia cautella in southwestern Nigeria. Wheat and maize are suitable hosts along with cocoa beans and therefore; should not be stored together in same warehouse to avoid cross-infestation.|
|Appears in Collections:||Academic Publications in Crop Protection and Environmental Biology|
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