The effect of the weaver ant,Oecophylla smaragdina (Hymenoptera: Formicidae), on the mango seed weevil,Sternochetus mangiferae (Coleoptera: Curculionidae), in mango orchards in the Northern Territory of Australia

Abstract

The mango seed weevil, Sternochetus mangiferae (Fabricius), is one of the major mango insect pests in northern Australia. A reasonable level of control can be obtained with insecticide sprays together with orchard sanitation, but the only option available for organic growers is the latter. Weaver ants, Oecophylla smaragdina (Fabricius), are effective in controlling the main insect pests in citrus, cashew and mango orchards. To determine whether weaver ants, which are usually abundant in non-sprayed mango orchards, have the potential to control the mango seed weevil, field experiments together with regular monitoring programmes at six orchards in the Northern Territory of Australia were conducted from 2001 to 2003. Data from two conventional orchards showed that the treatment with weaver ants plus soft chemicals produced lower levels of downgraded fruits (<0.5%) compared to the treatment with chemical insecticides (1.4 – 2.1%). In three organic or insecticide-free orchards, fruits were much less damaged on trees with weaver ants (<1%) than on trees without the ants (2.5 – 15.7%). In the sixth orchard, that had much higher mango seed weevil populations than the others, levels of downgraded fruits were lower on trees with abundant weaver ants than on trees with fewer weaver ants. We conclude that weaver ants are efficient biocontrol agents of the mango seed weevil, and that for successful control of the pest it is important both to maintain the ants at high levels and to destroy excess fruits.     

中国水稻害虫治理对策的演变及其展望

本文简要回顾了中国水稻害虫的变迁、相应的对策演变,从中了解、总结害虫发生与人类治虫对策之间的因果渊源,指出只有师法自然、通过生态工程实施生态治理技术才能持续双赢。     

蝗虫综合防控技术研究进展

蝗灾是世界性生物灾害,给农牧业生产造成巨大经济损失.2020年初沙漠蝗Schistocerca gregaria再次暴发,严重影响自然生态系统和社会经济的发展.进入21世纪以来,蝗虫防治的新技术和新策略不断发展.本文概述了我国蝗虫主要成灾种类、分布及其危害,总结了近年来蝗虫监测预警及防控技术相关研究进展,重点介绍了以生...     

Effects of cultivar resistance and fungicide application on stem canker of oilseed rape (Brassica napus) and potential interseasonal transmission of Leptosphaeria spp. inoculum

Phoma stem canker is a damaging disease of oilseed rape (Brassica napus) that causes annual yield losses to UK oilseed rape growers worth approximately £100 million, despite the use of fungicides. In the UK, oilseed rape is sown in August/September and harvested in the following July. The disease epidemics are initiated by ascospores released from Leptosphaeria spp. pseudothecia (ascocarps) on stem stubble in the autumn/winter. Control of this disease is reliant on the use of cultivars with “field resistance” and azole fungicides. This study investigated the effects of cultivar resistance and application of the fungicide prothioconazole on the severity of stem canker before harvest and the subsequent production of pseudothecia on the infected stubble under natural conditions in the 2017/2018, 2018/2019, and 2019/2020 cropping seasons. The application of prothioconazole and cultivar resistance decreased the severity of phoma stem canker before harvest, and the subsequent production of Leptosphaeria spp. pseudothecia on stubble in terms of pseudothecial density. Results showed that stems with less severe stem cankers produced fewer mature pseudothecia of Leptosphaeria spp. on the infected stubble. This investigation suggests that the most sustainable and effective integrated control strategy for phoma stem canker in seasons with low quantities of inoculum is to use cultivars with medium or good field resistance and apply only one spray of prothioconazole when required.     

Responding to Economic Crisis in Sub-Saharan Africa: New Farmer-Developed Pest Management Strategies in Cocoa-Based Plantations in Southern Cameroon

Cocoa is a key or source of income and poverty reduction in the humid forest of Southern Cameroon. Cameroon like other African countries went through a major economic crisis in the early 1980s with a decline in international commodity prices and significant changes in macroeconomic policies. Structural adjustment reforms following the economic crisis led to removal of fertilizers and pesticides subsidies, cocoa price liberalization and the overall withdraw of Government interventions from the cocoa sub-sector. Cocoa input price increases have been compounded by the devaluation of the CFA Franc, which doubled the prices of the imported pesticides which were considered key to the control of cocoa pests. This overall economic shock led to changes in cocoa producer's production decisions as a response to minimize cost. Among the changes the use of alternatives to imported chemicals for cocoa pest control. Farmers responded to the high prices of pesticides by developing, from local botanical knowledge and pest management strategies, which include plant extracts and plant extracts mixed with pesticides at different proportions. This is a major decision given the importance of imported chemical in the cost of production of cocoa. Valuable indigenous knowledge from farmers could be used also as an effective support system for communicating and diffusing modern knowledge and technologies to farmers. The paper describes the farmer knowledge-based alternatives to chemical pesticides for pest control in cocoa fields as a response to high pest control costs. Pest management specialists are urged to take advantage of this shift in practice and assess their effectiveness for further use. Two sets of questions are posed: (1) were the conventional insecticides, with all their problems, really necessary? and (2) are the materials derived from locally grown plants effective pest management agents or are they, in some way, placebos?     

Improving local technologies to manage speargrass (Imperata cylindrica) in southern Benin

Abstract

Speargrass (Imperata cylindrica) is difficult to control in the tropics. Farmers allocate most of their time and labour to weeding speargrass. We investigated in a joint experiment concluded with farmers, how effectively grain legumes suppress speargrass, and the relationships between speargrass suppression, legume grain yield, and subsequent maize yield. Without management, speargrass shoots and rhizomes increased with 31 and 17% per month, respectively. The integration of deep ridging, deep hoe weeding and shading suppressed speargrass more effectively than farmers' practices. Creeping varieties of cowpea that produced most biomass were most successful in suppressing speargrass and in enhancing subsequent maize yields, but erect cowpea cultivars produced more grain. Farmers traded off cowpea yield against speargrass suppression to bridge the hungry gap. They preferred the erect cowpea cultivar wan. The need to forego a harvest and the fact that pigeonpea is not consumed in the area makes pigeonpea presently unsuitable for integration into the cropping system.