Pests,diseases and weeds of Napier grass,Pennisetum purpureum: A review

Napier or elephant grass ( Pennisetum purpureum Schum.) is an important fodder crop in East Africa, particularly in Kenya, where it is used almost exclusively for feeding dairy cattle in cut-and-carry systems. A smut pathogen ( Ustilago kamerunensis P. & H. Sydow) was recently reported as being in the country, causing serious losses in biomass. A preliminary investigation of the grass/smut pathosystem revealed very little information on worldwide pests and diseases of the host. Data were not easily accessible and there was no central reference. This review attempts to address this gap in the literature, particularly with regard to the outbreak of U. kamerunensis, which may focus attention on the pest management of a valuable but comparatively neglected crop.     

Farmers' knowledge and perceptions of the stunting disease of Napier grass in Western Kenya

Production of Napier grass, Pennisetum purpureum, the most important livestock fodder in Western Kenya, is severely constrained by Napier stunt (Ns) disease. Understanding farmers' knowledge, perceptions and practices is a prerequisite to establishing an effective disease management approach. Using a random sample of 150 farmers drawn from Bungoma, Busia and Teso districts of Western Kenya, this study sought to: (i) assess farmers' perceptions and knowledge of Ns disease, including its effects on the smallholder dairy industry; (ii) record farmers' current practices in managing Ns disease; and (iii) identify Ns disease management challenges and intervention opportunities in order to develop an efficient integrated disease management approach. The majority (86·7%) of the farmers were aware of Ns disease and observed that it was spreading rapidly in the region, which was perfectly predicted by farmers' access to agricultural information (marginal effect = 0·164), indicating a need for extension platforms for knowledge sharing among the industry stakeholders. The disease had affected Napier grass yields so most farmers could not feed their livestock on the amounts they produced, and they were buying Napier grass. Those who relied on income from selling Napier grass received less due to loss in productivity. Milk production had reduced by over 35%. The cause of the disease was unknown to the farmers, with no effective disease management strategy available to them. An integrated disease management approach needs to be developed to fit within the mixed farming systems, supported by simple decision aids.     

Insect Pests and Mites

Abstract

Weeds are major components of agro-ecosystems and they affect the biology of pests and beneficial insects in several ways; provision of flowers, presence of neutral insects, modification of crop microclimate, production of chemical stimulus, alteration of colonisation background, etc. The more relevant beneficial crop–weed–insect interactions are discussed. The role of weeds in regulating pest populations is illustrated by studies on bean (Phaseolus vulgaris L.) cropping systems, in which chemical interactions between Empoasca kraemeri Ross &; Moore and two grass weeds were identified. It is proposed to continue and develop this kind of research in order to incorporate weeds into pest control strategies.     

Current status of the rice water weevil Lissorhoptrus oryzophilus in Italy: eleven‐year invasion

The rice water weevil Lissorhoptrus oryzophilus (Coleoptera: Curculionidae: Brachycerinae) was detected in Northern Italy in 2004. As Italy is the major European rice producer, and the rice water weevil is considered to be one of the major pests of rice in the world, a multiyear study was carried out to determine the spread of the pest in Northern Italy, to evaluate its establishment potential and to improve the knowledge on its biology in this new habitat. The survey allowed the distribution of the insect in Italian rice areas to be evaluated and confirmed that L. oryzophilus behaves as a monovoltine parthenogenetic species in Northern Italy. Information about the phenology of the insect and its management are also provided.     

Biological Control of the Hibiscus Mealybug, Maconellicoccus Hirsutus Green (Hemiptera: Pseudococcidae) in the Caribbean

The hibiscus mealybug, Maconellicoccus hirsutus Green, was first reported in the Caribbean in 1994 in Grenada. This was the first record of the insect as a major pest in the New World. By the beginning of 2001, the pest had spread to over 25 territories from Guyana and Venezuela in the South to Bahamas in the North. The pest has also extended its distribution to Central America (Belize) and North America (California, USA). Early attempts to control the pest using pesticides resulted in failure and a classical biological control approach was adopted. Several exotic natural enemies were introduced but control was attributed to Anagyrus kamali Moursi and Cryptolaemus montrouzieri Mulsant. In all countries where biological control was implemented, this resulted in success. This paper reviews the remarkable success story. Information is provided on the distribution and factors leading to rapid spread of the pest, its pest status and resultant economic losses, and implementation of the biological control effort.     

Studies on the apple fruit moth,Argyresthia conjugella Zeller (Yponomeutidae: Lepidoptera): Identification,distribution and extent of damage in India

Abstract

A fruit‐damaging insect on apple in the Kinnaur district of Himachal Pradesh has been identified as the apple fruit moth/miner, Argyresthia conjugella Zeller, a common pest of apple in Asian, European and American countries. It seems to be native to India, where its primary host, the sorb tree, Sorbus aucuparis Linn. is present. Studies on the distribution and extent of damage during 1983 and 1984 revealed that the pest was distributed in the Kinnaur district at altitude between 2445 to 2900 m and in yearly isotherms of 0 to 10° C. The damage varied from zero to above 50%. Its spread to other apple growing areas of the state is unlikely due to unsuitable agroclimatic conditions.     

Pathogenicity of <Emphasis Type="Italic">Stemphylium vesicarium</Emphasis> from different hosts causing brown spot in pear

Stemphylium vesicarium (teleomorph: Pleospora herbarum) is the causal agent of brown spot disease in pear. The species is also able to cause disease in asparagus, onion and other crops. Saprophytic growth of the fungus on plant debris is common. The objective of this study was to investigate whether isolates of S. vesicarium from different hosts can be pathogenic to pear. More than hundred isolates of Stemphylium spp. were obtained from infected pear fruits, dead pear leaves, dead grass leaves present in pear orchard lawns as well as from necrotic leaf parts of asparagus and onion. Only isolates originating from pear orchards, including isolates from dead grass leaves, were pathogenic on pear leaves or fruits in bioassays. Non-pathogenic isolates were also present in pear orchards. Stemphylium vesicarium from asparagus or onion, with one exception, were not pathogenic to pear. Analysis of the genetic variation between isolates using Amplified Fragment Length Polymorphism (AFLP) showed significant concordance with host plants. Isolates from asparagus or onion belonged to clusters separate from the cluster with isolates from pear or grass leaves collected in pear orchards. Multilocus sequencing of a subset of isolates showed that such isolates were similar to S. vesicarium.     

Farmers' knowledge,perceptions, and management practices of the new invasive pest,fall armyworm (Spodoptera frugiperda) in Ethiopia and Kenya

This paper reports for the first time on farmers’ knowledge, perceptions and management practices of the fall armyworm (Spodoptera frugiperda) in Ethiopia and Kenya. A survey of 343 smallholder maize farmers was conducted. Most farmers in Ethiopia and Kenya had knowledge about fall armyworm; they could identify it mainly during its larval stage. Furthermore, most farmers in Ethiopia (93%) and Kenya (97%) encountered damage by fall armyworm in their farms. They estimated an average of 32% crop damage in Ethiopia and 47.3% of crop damage in Kenya, with an estimated yield reduction between 0.8 to 1 tonnes/ha. Nearly half of the farmers relied on chemical insecticides to control this pest. The majority (60%) of the farmers in Kenya perceived that insecticides were not effective in controlling fall armyworm as compared to most farmers (46%) in Ethiopia who perceived that chemical spray is effective for the control of fall armyworm. In Ethiopia, 26% of the farmers combined handpicking larvae with insecticide sprays, whilst 15% of the farmers practiced only handpicking. The present study highlights the need to develop management strategies for fall armyworm based on farmers’ needs and priorities.     

Coffee Berry Disease

Abstract

Coffee Berry disease is caused by a mutant pathogenic strain of Colletotrichum coffeanum Noack which has spread throughout tropical Africa from its point of origin in Kenya. Fruit is attacked in all stages, and total destruction of the crop can be caused. The disease was confined for many years to the higher altitudes, because suitable conditions of temperature and humidity were infrequent in the lower ones. Following the inception of a wetter and cooler climatic phase in E. Africa in 1961, coffee in the lower altitudes is now attacked.

Infection of the fruit is initially by infective conidia produced on the maturing wood of the twigs, where the pathogen “overwinters”. When one crop only is on the tree, this inoculum is more important than that from lesioned fruit; but where a series of over-lapping crops is present, the reverse is the case. In the former situation control can be based on reduction of inoculum from the twigs: in the latter, however, this is ineffective, and control can only be achieved by a series of protective sprays.

Varieties of coffee vary greatly in susceptibility to berry disease. No commercially acceptable variety is, however, completely resistant, although genetic material embodying resistance is available.     

Effect of cassava mosaic disease,soil fertility,plant spacing and their interactions on cassava yields in Zanzibar

Improvement of farmers' decision-making has been recognised as critical for the implementation of IPM, yet practitioners lack sound knowledge on the 'how and why' of farmers' decision-making processes. This study explored the perceptions, pest management practice, decision tools and sources of information of smallholder farmers growing cotton in India and vegetables in Kenya. Farmers trained under an Insecticide Resistance Management and two IPM Farmer Field School projects were compared with untrained farmers from the same localities, using individual interviews and participatory group analysis methods. Trained farmers' decision-making was enhanced, by the use of more decision tools and new sources of information and technologies and they were generally more confident in their pest management strategies than untrained farmers. As a result, trained farmers reduced their pest management costs but did not always obtain higher gross margins. Issues of gender, sustainability, economics and group action are discussed, along with recommendations for research and extension to take a closer look at farmers' decision-making processes in cash and subsistence crops.     

Willingness to pay for area-wide management and sterile insect technique to control fruit flies in Australia

Abstract

Fruit flies are a biosecurity threat to international trade of horticultural produce around the world. Area-wide management (AWM) of fruit flies offers a promising solution to coordinate farmers’ activities to fight against the spread of this pest. The incorporation of the sterile insect technique (SIT) may increase the effectiveness of AWM and lead to greater suppression and possible eradication of the fruit fly pest. This article presents findings from a choice experiment survey to ascertain the willingness to pay (WTP) for the benefits of a suite of AWM features and SIT. These features include the benefits from (1) coordinated fruit fly monitoring, (2) coordinated on-farm male annihilation of fruit flies, (3) management of fruit fly in residential areas, and (4) coordinated release of sterile flies. This is the first study of its kind to assess the WTP for AWM and SIT in a developed country. Results suggest that growers are willing to pay for SIT and coordinated fruit fly management in residential areas but are not willing to pay for other coordinated services that they are already practicing on their farms.     

Distribution,biology, ecology and control of the psyllid Diaphorina citri Kuwayama,a major pest of citrus: A status report for China

Abstract

The Asiatic citrus psyllid Diaphorina citri Kuwayama (Hemiptera: Psyllidae) is a major pest of citrus in China. Its status derives, not from the damage it causes, but from its role as the only known vector in China of huanglongbing, a phloem-limited bacterial disease of international importance. The disease can devastate orchards within a few years of planting. It also poses a major threat to endangered indigenous citrus germplasm in Asia and Australasia. The distribution, biology, ecology and control of the psyllid in China are reviewed in these contexts. Constraints and challenges related to control of the vector in China are discussed.     

A review of investigations to improve pest managemet of stored maize in smallholder farms in Kenya

A 4-year project in Kenya to develop management strategies for the larger grain borer (Prostephanus truncatus) in smallholder maize stores is described. The entomological investigations included behavioural and ecological studies of pest activity in experimental and farmers' maize stores and the natural environment, the use of insecticides to protect maize stored as grain and cobs and the release of a biological control agent. The latter was a predatory beetle; this marks the first release of a biological control agent against a storage pest in East Africa. The operation of a national trapping network to assess the extent and future spread of the pest and predator and target control campaigns is outlined. Recommendations for the control of the stored product pests, resulting from these investigations, were tested for likely adoption and modification in the light of socioeconomic surveys and a cost-benefit analysis. A decision tree approach to managing stored product pests is suggested which allows extension workers and farmers to decide the necessity of pesticide application when assessing how best to protect stored maize.     

Potential spread of kiwifruit bacterial canker (Pseudomonas syringae pv. actinidiae) in Europe

Pest risk analyses (PRAs) are conducted to determine whether an organism is a pest and whether and how it should be regulated. Estimation of the potential area of establishment and pest spread are key factors of this analysis. Tools for modelling and mapping of these key factors have to be quick and easily applicable for a wide variety of organisms with limited data for parameterization. For this purpose, a dispersal kernel model based on a 2Dt‐distribution had been developed in a European Union project (PRATIQUE). The aim of the present study was the evaluation of this spread model hitherto tested on insects, plants, fungi and nematodes in order to determine its applicability to bacterial pests. Therefore, the potential distribution and spread of kiwifruit bacterial canker Pseudomonas syringae pv. actinidiae in Europe was investigated based on climatic suitability and host plant availability. The results of the modelling were compared with the spread history of the pest in Europe. It is shown that this generic spread model can also be applied to a bacterial pest.     

Modelling the establishment,spread and distribution shifts of pests

Abstract

During the last century increasing human trade networks have interacted with other global changes – such as land use and climate change – to accelerate the range expansion of pest species worldwide. In this special issue, we present a series of articles that model the risk of establishment and spread of non-native harmful species, as well as shifts in the distribution of native pest species. We also provide a state-of the art review of the available literature on species distribution models for pests, weeds, and pathogens. Recent advances in modelling approaches have allowed us to significantly improve our abilities to predict changes in species distribution, and these tools have been widely used to enhance biosecurity planning and pest management. We expect that this special issue contributes toward and integration of the scientific knowledge and the development of novel approaches to model pest species distribution, as well as to better understand the factors that influence their expansion in the context of a rapidly changing world.     

Spread of the spotted wing drosophila – Drosophila suzukii (Diptera,Drosophlidae) and new distribution records in Dalmatia region of Croatia

A specific survey for the detection of Drosophila suzukii Matsmura 1931 (Diptera, Drosophilidae) in Dalmatia region of the Republic of Croatia during 2013, confirmed that the pest is present and widespread. Adults were detected in traps suspended in Prunus cerasus L. (sour cherry), Prunus persica L. (peach), Ficus carica L. (fig) and Morus alba L. (mulberry) orchards and individual trees, during the fruit maturation period, in 16 (of the 51 locations) where traps were placed in Dubrova?ko–neretvanska, Splitsko–dalmatinska, ?ibensko–kninska and Zadarska counties. This confirmed the rapid spread of D. suzukii in Croatia and this pest is a great concern for areas that are not yet infested that have favourable conditions for the pests’ development. The results of the survey highlight the importance of the development and implementation of long‐term sustainable control.     

Tackling fall armyworm (Spodoptera frugiperda) outbreak in Africa: an analysis of farmers’ control actions

Abstract

Since its emergence in Africa in 2016, fall armyworm (FAW) has spread rapidly and poses a severe threat to the food security and livelihood of millions of smallholder farmers in the continent. Using survey data from Ghana and Zambia, we examined FAW prevention and control methods implemented by farm households and their impacts on maize output and household consumption of self-produced maize. The main control methods used included pesticide application and handpicking of larvae, while access to information on FAW was a key driver behind the implementation of the control methods. Results from an endogenous switching regression showed that the implementation of a FAW management strategy significantly enhanced maize yield and households’ own maize consumption. When disentangling the impacts of the main control methods, we found that the combination of pesticide application and handpicking of larvae produced the highest yield gain of 125%. We concluded that the current interventions put in place by farmers to tackle FAW infestations are providing positive outcomes, but successful management of the pest will require more actions, including raising awareness to enhance the adoption of control interventions and exploring other control options.     

Distribution and biology of the yellow‐spotted longicorn beetle Psacothea hilaris hilaris (Pascoe) in Italy

The Asiatic yellow‐spotted longicorn beetle, Psacothea hilaris hilaris, was found for the first time in Northern Italy in 2005. As this xylophagous insect is considered one of the most important pests of Morus spp. and of Ficus carica in its countries of origin, a multi‐year study was carried out to determine the spread of the pest in Northern Italy, to evaluate its establishment potential and to improve knowledge on its biology in the new habitat. The survey confirmed that P. hilaris hilaris has established in Italy and has colonized an area of about 60 km². The species overwinters as eggs or larvae. Adults are present from June to October. Damage has been recorded mostly on Ficus carica plants, and very rarely on Morus alba. Both young and older plants, healthy and weakened hosts can be attacked by the pest. Severely attacked plants become weakened and eventually die.     

Insect Mobility and the Philosophy of Crop Protection with Reference to the Sudan Gezira

Abstract

Mobility results in movement of insects from their birth place (emigration) to another site (immigration). The scale, both in time and in space, on which such migration occurs may determine rates of increase or decrease in numbers in a fixed geographical area or plot. This is self evident in the case of mobile insects, such as locusts. Other documented examples include the spruce budworm in Canada and the Queensland fruit fly.

In the Sudan Gezira the distribution of the major insect pest of cotton, Heliothis armigera Hb., was found to conform to a common temporal pattern over probably some thousands of square kilometres, and other major pests, Empoasca libyca de Berg and Bemisia tabaci Gen., are considered to be similarly distributed, suggesting that their occurrence in damaging numbers may be dominated by transport and concentration by major windfields rather than by natality and mortality within a field or area. This posibility was investigated using a Pilatus Turbo-Porter aircraft fitted with Doppler Navigator equipment and an insect collecting net, and densities of flying insects monitored by a ground-based Marine-type Radar.

The results of this study will make it possible to determine the spatial extent of a threatening population and the time during which that population is present, so that control action may be taken on a commensurate scale. Such matching of scale of operations to insect mobility is of particular importance when repeated invasions occur during periods of rapid crop growth, because it enables non-persistent insecticides to be employed, thus providing potentially better utilisation of parasites and predators than can be achieved by maintaining the crop as an environment lethal to insects. These procedures, connoted ‘synoptic survey’ and ‘synchronous control’, require that the control is applied on a scale determined by pest mobility rather than by the boundaries of fields or other artificial constraints. Evidence is accumulating regarding the importance of insect mobility, in particular adaptive dispersal, in population dynamics and this may require re-assessment of farmer and government responsibilities in crop protection.     

TaqMan real-time PCR method for detection of <Emphasis Type="Italic">Discula destructiva</Emphasis> that causes dogwood anthracnose in Europe and North America

Dogwood anthracnose, caused by the asexual filamentous fungus Discula destructiva Redlin, is a disease of several Cornus L. species. First reported in the 1970s in the United States, the pathogen has devastated North American dogwood populations causing widespread loss that has greatly impacted forest ecosystems. In the early 2000s, the disease was discovered in Italy and Germany, spread probably through the ornamental nursery trade. The origin of D. destructiva in North America remains a mystery. To facilitate studies on its origin and dispersal, a fast and accurate method using real-time PCR was developed in this study to detect and quantify D. destructiva. The assay was validated with samples from the U.S., Italy, and Switzerland as well as phylogenetically closely related fungal species, and other fungi and oomycetes commonly found on Cornus. This method allows for fast and sensitive detection of D. destructiva in host tissue and should be useful in disease management and pest interception to prevent further spread of the pathogen.