Cassava brown streak disease (CBSD) remains a major threat to cassava production in Mozambique. Breeding for CBSD resistant varieties that are also preferred by farmers is an integral part of managing the disease. The main objective of the study was to determine the genetic relationship between farmer-preferred varieties from Mozambique with those from Tanzania whose resistance to CBSD is known and some of which are being used as parents in quantitative trait loci (QTL) detection studies. To achieve this, 103 genotypes collected from farmers’ field in three provinces of Mozambique were genotyped together with five varieties from Tanzania whose CBSD response is well known. Thirty-five single nucleotide polymorphism (SNP) markers with a high minor allele frequency in East African landraces were used. Results indicated that seven Mozambican genotypes were genetically similar to either one of the four Tanzanian CBSD resistant genotypes while Xino Nn'gole was genetically identical to Namikonga a CBSD resistant variety, based on the SNPs used here. Little genetic differentiation was observed in cassava between provinces, with the majority of genetic variation distributed within individual genotypes (98%) rather than among provinces (2%). Both observed (Ho) and expected (He) heterozygosity in three provinces were generally high (Ho = 0.496) and (He = 0.455). There is a high likelihood that the eight genotypes similar/identical to those from Tanzania may share the same QTL associated with CBSD resistance thus should be further evaluated for agronomic traits as well as response to CBSD.

The objective of the current research was to evaluate the fermentative characteristics of silage made with the upper third section of cassava (Manihot esculenta) plants with added condensed tannin levels of 0, 25, 50 and 75 g/kg dry matter (DM). The experimental design was a complete randomized design, with treatments arranged in a 4 × 7 factorial (tannin addition levels × days of ensiling). The loss of gas and the presence of moulds observed in the opening days had increased linearly. Fermentative characteristics were decreased by the addition of tannin. Acetic acid content showed a linear increase. Tannin levels had a quadratic effect on gas production at 28 days of ensiling. After 56 days, however, tannin levels had no significant effect on silage gas production. After 28 days of ensiling, the degradability of potentially degradable fraction ‘b’ demonstrated quadratic effect. The same occurred with the fractions ‘a’, ‘b’ which were undegradable after 56 days of ensiling. The addition of condensed tannin lengthened the fermentative stage and caused the silage to stabilize after 56 days of ensiling.

Cassava germplasm collection is important for the preservation of genetic variability, allowing the development of improved cultivars with desirable traits such as drought and disease tolerance, better starch quality and yield. Therefore, the assessment of diversity in cassava germplasm maintained by farmers is important for maintaining biodiversity and crop improvement. Herein, we report genetic diversity relationships of 52 farmer-preferred cassava landraces from the eastern zone of Tanzania based on morphological descriptors and single nucleotide polymorphisms (SNPs). Cluster analysis was performed for both morphological traits (genetic distance 1.18–0.15) and SNPs (genetic distance 0.078–0.002). The analysis revealed that there were a total of 17,393 variant positions, and that several of the SNPs were distributed across all the chromosomes. The abundance of SNP varied remarkably among the 18 cassava chromosomes, with chromosome 2 having the highest number of SNPs (1335) and chromosome 18 having the lowest number of SNPs (734). The power of SNPs in distinguishing morphologically similar landraces was shown. Both analyses did not group landraces according to geographical locations, suggesting that farmers were moving cassava germplasm to different areas. Their diversity was mainly due to adaptation and preferential selection by farmers. This further implied that within a geographical location, the cultivars were more diverse and there was no misnaming of cassava cultivars by farmers. The collection revealed a wide range of genetic diversity, and represented a valuable resource for trait improvement, allowing the capture of farmer-preferred traits in future cassava breeding programmes.

Cassava (Manihot esculenta Crantz) is one of the most important staple crops for small farmers in the tropics, feeding about 800 million people worldwide. It is currently cultivated in South and Central America, Africa and Asia. The genus Vatiga is widespread throughout the Neotropical region. Its species are sympatric and feed exclusively on cassava. The main objectives of this paper are: (1) to assess the potential distribution of Vatiga, one of the most relevant pests of cassava; (2) to project the resulting models onto the world; (3) to recognize areas with suitable and optimal climates (and thus, high probability) for future colonization, and (4) to compare this model with the harvested area of cassava analyzing the climatic variables required by both the host and the pest species. Species distribution models were built using Maxent (v3.3.3k) with bioclimatic variables from the WorldClim database in 2.5 arc min resolution across the globe. Our model shows that Vatiga has the potential to expand its current distribution into other suitable areas, and could invade other regions where cassava is already cultivated, e.g., Central Africa and Asia. Considering the results and the high host specificity of Vatiga, its recent appearance in Réunion Island (Africa) poses a serious threat, as nearby areas are potentially suitable for invasion and could serve as dispersal routes enabling Vatiga to reach the continent. The present work may help prevention or early detection of Vatiga spp. in areas where cassava is grown.

Inadequate supply, exorbitant prices and diversion towards using cereal grains for biofuel production, particularly maize, has led to a constant search for alternative energy sources for poultry and other non-ruminant species. The abundant availability of cassava in certain regions makes it a good alternative to maize and other cereal grains. Cassava root meal is rich in carbohydrate but low in protein and all other nutrients, whereas, cassava leaf meal is a moderate source of protein. Results of studies to evaluate the replacement of cereals with cassava products in poultry feed show wide variability due to differences in origin, variety, plant maturity at harvest, ecological conditions of plant growth and processing methods. Cassava products contain a wide range of cyanogenetic glycosides, particularly linamarin and lotaustralin. The level of hydrocyanic acid released from the cyanogenetic glycosides limits the utilization of cassava, but with proper processing, the dietary inclusion level of cassava meal can be increased for economic poultry production. This paper reviews the nutrient composition of cassava and its uses as a substitute for more conventional ingredients in poultry diets.

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.

Introduction. A study was conducted in India to assess the efficiency of 32P uptake and the feasibility of intercropping using land-use efficiency parameters in a banana-based intercropping system. Materials and methods. Absorption of 32P applied to plants in five-crop, two-crop and sole-crop systems involving banana Musa AAB (‘Mysore’), ginger (Zingiber officinalis Rosc.), turmeric (Curcuma longa L.), cassava (Manihot esculenta Crantz.) and elephant yam (Amorphophallus campanulatus Blume.) was studied in field trials. The experiment was conducted for two years. During the first year, the main crop was planted during October, the main planting season for banana in India, and the intercrops were planted in early May of the next year. In the second year, both the main crop and intercrops were planted in May. Results. Radiophosphorus applied in the active root zone of one of the component species in the mixed crop system was found to be absorbed not only by the treated plant but also by the neighboring plants. Absorption by banana was prevalent. Differential effects of competition were manifested as observed by the relative uptake of 32P. Lower relative uptake of 32P was observed in the main crop banana when simultaneous planting of intercrops was done. Ginger and turmeric were not affected in relation to planting at different stages of the main crop, whereas cassava and elephant yam showed lesser relative 32P uptake when planted later, confirming that different crops in the mixed crop system react differently. Conclusions. The efficiency of different crops in terms of uptake varied with the system of planting. The higher relative efficiency of 32P uptake in a multiple cropping system points to an improved efficiency of uptake and higher dry weight on a per plant basis. It confirms the efficiency and feasibility of the cropping system. Economic analysis emphasizes the concept and proves the viability of the system.

The aim of the present study was to determine, by a field experiment, whether the seasonal variations in the levels of cyanide and rutin in the phloem, secondary compounds potentially implicated in cassava resistance to the cassava mealybug (Phenaccocus manihoti), could be influenced by different kinds of soil fertilisation (manure, NPK, KC1, lime, mulch). It was found that mean cyanide and rutin contents varied significantly with season, soil treatments and infestation. For each soil treatment, the highest contents of these compounds on uninfested plants was registered in the main dry season (Jul-Aug) for cyanide and at the end of the dry season (Jul-Aug) and beginning of the rainy season (Oct-Nov) for rutin. The infestation factor induced an increase in cyanide and rutin contents for 43 combinations of period and soil treatment among 48 in total. For cyanide content (phagostimulant function in mealybug), this increase appeared significant at the end of the rainy season (Apr-May) and in the main dry season (Jul-Aug) for control and KC1 fertilisation. For rutin content (an unfavourable substance for the insect) significant increase was induced by infestation in each period for manure and mulch and especially in the main dry season (Jul-Aug) and at the beginning of the rainy season (Oct-Nov) for other soil treatments. Concerning the seasonal variations in the level of rutin, these results showed that mulch and manure are the best fertilisers to increase cassava resistance against mealybugs.

A laboratory study of the dietary preferences and duration of food plants in the gut of Zonocerus variegatus was carried out using three plant species, namely Manihot esculenta, Vernonia amygdalina and Chromolaena odorata. Whole or cut up plants were offered to the grasshopper in the experiments. Overall, whole V. amygdalina was the preferred diet of Z. variegatus, while the insect ate cassava pieces better than whole plant. Chromolaena odorata was the least preferred diet of the three. The duration of the food plant within the insects' gut was shortest for V. amygdalina, which was consumed all at once soon after being offered to the insects. The insects consumed cassava in two successive sessions and C. odorata in three. The total time spent eating was similar for V. amydalina and cassava, which were significantly shorter than that spent eating C. odorata. Evidently, V. amygdalina could serve as a good bait plant for Z. variegatus. However, its status as a human food plant precludes its use as a bait followed by chemical control; it may be used with, for example, fungal biocides such as Metarhizium.

The various pests of the cassava plant, Manihot esculenta Crantz, were reviewed with particular reference to the two exotic pests viz: cassava mealybug,Phenacoccus manihoti, Mat-Ferr, and cassava green mite, Mononychellus tanajoa Bondar which were accidentally introduced into Africa without their natural enemies in the early seventies.

Classical biological control programme for these two pests initiated and championed by the International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria was also reviewed and both successes and limitations of the programme highlighted. Suggestions on how to improve the efficiency of the programme are made.

Catantops spissus spissus were reared in groups of 10 using Calapogonium mucunoides, Zea mays, Elaeis guineensis and Manihot esculenta separately. The proximate compositions of these various food types were analysed and energy contents calculated. This was to establish how food types can influence the rate of development of the insects.

The results showed that insects reared on C. mucunoides and Z. mays had the fastest maturing period in days while insects reared on E. guineensis and M. esculenta developed much later. The rate of food consumption could not be related directly to the amounts of individual nutrients nor the total energy content of the food. On the other hand the rate of development of the insect appeared to be directly related to total energy derivable from the overall food consumed. In addition, differences in the rate of development were noticed at the various instar stages. This was also related to the amount of energy consumed from the food types at the particular instar stage.

A major cause of yield loss in cassava, Manihot esculenta Crantz in tropical Africa is African cassava mosaic virus, transmitted by the whitefly, Bemisia tabaci (Gennadius). Investigations into the epidemiology of the disease and the ecology of the insect vector at the Kenya coast demonstrated that the serious loss of yield caused by the virus could be greatly reduced if simple changes in husbandry practices were adopted. The regular rogueing of infected plants greatly reduced the incidence of African cassava mosaic virus.

Population studies of the whitefly, Bemisia tabaci, carried out in the field indicated that whiteflies were present in cassava all year round and that there were marked seasonal fluctuations in the population levels. Possible explanations for these fluctuations are discussed. It was found that the interaction of atmospheric temperature and relative humidity was highly correlated (r = 0.924) with the development of the whitefly. Results of the studies suggested that rainfall has an indirect effect on whitefly population. Whether B. tabaci behaves in the same way in mixed cropping system has not yet been established.