Informatics Publishing Limited

Abstract

Tobacco is one of Zimbabwe’s most valuable crop. It accounts for about 26 % agricultural gross domestic product and 61 % of agricultural exports. It is therefore important to review the main attributes governing yield and quality of the crop.Good progress has been made regarding the development of best tobacco management practices with the aim of achieving maximum economic yields. Nitrogen is one of the major nutrients that affects and influence tobacco yield and quality because it is part of all proteins, chlorophyll and enzymes. Topping stimulates the production of secondary plant products that accumulate in the leaves. These products give the cured leaf improved quality and smoking characteristics. A good sucker control program is necessary to ensure high yields of acceptable quality. The removal of primings from the tobacco plants in the field can improve the yield and quality of the harvested tobacco leaves especially that of the first reaping. This paper has reviewed the importance of Nitrogen, topping and leaf priming in tobacco management. However, there is still need to establish the best nitrogen and priming levels, which might vary with place and variety.

Keywords

Full Text

Abstract

Cereals are very important crops grown in Africa for human consumption. Our review confirms that of the various insect pests attacking cereals crops in Africa, lepidopteran stem borer,B.fusca and C.partellus are by far the most injurious causing maize yield losses in many African countries.B. fusca is indigenous to Africa and C.partellus invaded the continent from India. Severe damage is caused by the larvae that feed on the plant from early stage up to maturity causing a devastating impact on maize yield. Increased damage in young plants is due to tenderness of leaves and stem since aged and toughened leaves are unsuitable for newly hatched larvae.Their distribution follows a define pattern with B.fusca dominating the high elevation (˃ 1200 m) while C.partellus is most abundant and widely distributed species occurring at all sites, but predominantly in the low elevation (<600 m). C.partellus distribution is highly influenced by altitude and moisture gradients. This article is an attempt to summarize the status of knowledge about economically important cereal stem borers in Africa with emphasis on their distribution, host plants, general damage and larval behavior, yield loss in Africa, pest management and conclusion. B.fusca and C.partellus are given special attention as they are most important pests of maize in Africa.

Keywords

Full Text

Abstract

The maize stem borers, Busseola fusca and Chilo partellus cause qualitative and quantitative losses on green mealies as they attack maize from seedling up to harvesting. A study was conducted to evaluate stem borer damage and management in green mealies on maize varieties SC 608, PHB 30B50 and SC 513. Two field trials similar in set-up and treatments were conducted. The first trial was planted on the 4th/August/2014 and the second was planted on the 4th/ October/ 2014. The essence of staggering planting was to determine whether B. fusca and C. partellus were problematic in the first part or second part of the dry season before the onset of the rain. For each variety, four treatments were applied, namely; whorl applications of ammonium nitrate (AN), Bulldock® 0.05GR (beta- cyfluthrin), Dipterex® 2.5 GR (trichloforn) and untreated control. The treatments were applied at 6 and 4 weeks after crop emergence (WAE) in the first and second trials, respectively and subsequently at 14 day intervals up to tasseling. The parameters assessed were; plant heights, number of plants with windowed leaves, number of plants with dead- hearts, plant biomass (t/ha), fresh cob weights (t/ha), number of damaged cobs and stem borer parasitism and predation. Results showed that the October planting was less infested with B. fusca and C. partellus than the August planting. Dipterex® 2.5 GR and Bulldock® 0.05 GR were effective to manage B. fusca and C. partellus infestations in green mealies. The effectiveness of the two granular insecticides was not significantly different (P˃0.05) on the assessed parameters. A stem borer larval parasitoid recorded in the August planting was Schembria eldana Barraclough (Diptera: Tachinidae) with 5.9% parasitism on both stem borer species. For the October planting, the parasitoids that were recovered from both stem borer species were S. eldana Barraclough and Cotesia sesamiae Cameron (Hymenoptera: Braconidae) with parasitism levels of 13.5 and 21.6% respectively. Recovered species preying on stem borer larvae and pupae included earwigs (Dermaptera: Forficulidae), wasps (Hymenoptera: Vespidae) and ants (Hymenoptera: Formicidae) Overall, applying AN in the funnel was not effective in managing B. fusca and C. partellus. Farmers are therefore encouraged to use Dipterex® 2.5 GR and Bulldock® 0.05 GR with other IPM methods such as planting period manipulation, to manage B. fusca and C. partellus infestation in green mealies. 

Keywords

Full Text