Review Article

Management of Field Insect Pests of Cashew- A Review

Azeez OM*

Department of Crop and Soil Science, Faculty of Agriculture, University of Port Harcourt, Choba, Port Harcourt, River State, Nigeria

Submission:March 21, 20255; Published:April 03, 2025

*Corresponding author:Azeez OM, Department of Crop and Soil Science, Faculty of Agriculture, University of Port Harcourt, Choba, Port Harcourt, River State, Nigeria

How to cite this article:Azeez OM. Management of Field Insect Pests of Cashew- A Review. Paper Recycling Ann Rev Resear. 2025; 12(5): 555847.DOI: 10.19080/ARR.2025.12.555847

Abstract

Although artificial Intelligence and its related applications are being increasingly used in innovative ways by public and private firms as part of their digital transformation efforts, there is limited knowledge sharing of their success stories in the business academic literature. Sharing studies that highlight successes (or failures) of AI deployments could help practitioners learn vicariously, leading to better decisions. Hence, our objective is to present a case study highlighting an innovative and successful deployment of machine learning applications through the lens of the Diffusion of Innovations (DOI) Theory. Specifically, our case focuses on the adoption, and diffusion of machine learning by a public transportation firm and its subsequent benefits. Findings indicate that machine learning applications were adopted and diffused across the organization without much resistance, which made it interesting. The application of machine learning algorithms reduced driver fatigue significantly, leading to many business benefits including increased operational efficiency and resource optimization. Our study shows that practitioners could deploy machine learning and other AI technologies in a similar manner using principles from DOI to drive efficiencies in their organizations and processes.

Keywords:Machine Learning; Artificial Intelligence; Digital Transformation; Diffusion of Innovations; Case study; Public Transportation

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Company Description and Market Analysis

Ingvar Kamprad the founder of the worldwide known Swedish furniture shop IKEA that was established in 1943. The company is well known for its ready-to-assemble and affordable furniture, home décor, and kitchen equipment. By 2024, IKEA will operate in more than 50 countries and have 445 shops globally with more than 217,000 employees worldwide. IKEA offers a massive range of options for diverse clients to beautify their homes, ranging from reasonably priced furniture to home design goods and snacks. The decentralized architecture of the company’s management structure facilitates prompt decision-making at the local level. With so many businesses throughout the globe and the centuries’ differences according to IKEA website, the brand unites thousands of co-workers and hundreds of companies with different owners around the world (About Ikea – our story 2024) [1]. ‘’

Being able to offer IKEA products to as many people as possible is a challenge we love’’ (How we work – ikea global 2024) [2]. IKEA is regularly viewed as the market leader in inexpensive home furnishings and enjoys a strong position in the furniture retail sector in terms of market share. Some of IKEA’s main competitors in the United State are Rooms to Go and Wayfair as well as Home Centre and Danube Home in the United Arab Emirates. With all the innovation and development IKEA went through, their vision and mission remind the same. Which is “To create a better everyday life for the many people” (About Ikea – our story 2024) [1]. that can be achieved by providing stylish, useful, and reasonably priced home furnishings. IKEA’s mission statement specifically mentions innovation, as the firm strives to continually improve its operations and product lines to satisfy the shifting demands and tastes of its clientele and the world trends. Moreover, driven by one of IKEA values they are committed to encourage innovation and fresh ideas. As proved by the fact that it employs dedicated managers for different innovations and tasks. It is the duty of this innovation manager to supervise the creation of new goods, procedures, and services that complement IKEA’s goals and objectives. Furthermore, IKEA is a major player in the retail furniture market because of its decentralized management structure and commitment to continual development and providing a large selection of sustainable products to improve the daily lives of its consumers..

Innovation Framework, Policies, and Strategies

The reviewed work was on Cashew plant affected by myriads of insect pests, their developmental stages, inadequate management and plant protection. Based on practical example of a major insect pest, the knowledge of the nature of damage and oviposition sites of Analeptes trifasciata, the use of farm sanitation method for the control of this pest which involves the removal of girdled stems containing the eggs and progenies of the pest from the plantation and destruction of developmental stages inside them by burning such stems outside the plantation. Though there are several insect pests attacking Cashew in the field, only fifteen common species of economic importance are discussed within the purview of this work. The importance of developmental (i.e. Biology/life cycle) and damage characteristics including control measures (i.e. chemical, mechanical/physical, and cultural methods, use of natural enemies and botanicals etc) were examined. Insect pests were classified as either minor or major based on the degree of damage caused to Cashew. Moreover, the studies of population dynamics in Cashew production have enhanced proper taxonomy and enable formulation of standard integrated packages for insect pest management.

Keywords: Insect pests; Cashew spp; Damage characteristics; Control measures; Field insect

Abbreviations: ENDC: Eastern Nigeria Development Corporation; WNDC: Western Nigerian Development Corporation; IPM: Integrated pest management

Generic Model of Innovation Process

Cashew, Anacardium Occidentale belongs to the genus Anacardium. It is a member of the family Anacardiaceae, the family to which also the Mango, Mangifera indica belongs. The family comprises of about 60 genera and 400 species of trees and shrubs. In Nigeria, commercial plantations of cashew started simultaneously at Ogbe in the then Eastern Nigeria by the Eastern Nigeria Development Corporation (ENDC) and Iwo, Eruwa and parts of Upper Ogun in the present Oyo State by Western Nigerian Development Corporation (WNDC). From these locations, its planting spread to other areas particularly the Northern States of Nigeria, but with the largest populations of about 8,000 hectares concentrated at Oghe, Mbala, Isuochi and Okigwe (Olunloyo and Igboekwe, 1985). Recent observation made from different agro-ecological zones of Nigeria showed that cashew is mainly cultivated by peasant farmers whose sizes of farm holdings range from 2.5-20 hectares. The total holding in Nigeria is estimated at about 15,000 hectares. These farmers contribute over 60% of the total cashew production in the country.

Although cashew is now widely grown in almost all states of Nigeria, its cultivation on plantation basis is still limited to few specific locations such as Oghe in Enugu State and Iwo, Eruwa and Upper Ogun in Oyo State. According to FAO (1988) Nigeria has no consistent and reliable production and export records for cashew. Nevertheless, Makanjuola (1978) estimated that a total of about, 3,300 tonnes are produced per year, which is about 10% of Kenya’s annual production. But in recent times, cashew commands a high price at the foreign exchange markets. In Nigeria a ton of cashew nuts sells for about N24,000-N40,000 (Ojelade, 1998), current nut production rate is 176,000 metric tonnes (Adetumbi, 2001). Research on cashew production and its uses started at the Cocoa Research Institute of Nigeria, Ibadan in 1971. The cashew trees are grown mainly for their kernels, which when roasted, have pleasant taste and flavour. A chocolate product called ‘AMCHO’ made at CRIN partly from cashew-kernel meal has been organoleptically assessed to be fair for consumer acceptability (Ojeh and Falowo, 1983). An edible oil of excellent quality has also been processed from the kernel (Ojeh, 1985). Another product from the kernel is the cashew butter, similar to peanut butter. It also finds its uses in confectionery manufacture [1-20].

Major field insect pest of Cashew

Red-banned thrips, Selenothrips rubrocintus Giard. (Thysanoptera: Thripidae)

Importance: This is a serious foliage pest of cashew, which causes severe damage to young plantations particularly in the dry season. The adults are just over 1 mm in length and dark brown to black in colour, while the nymphs are yellow with a red band around the base of the abdomen. The eggs are kidney-shaped and about 0.25 mm long.

Biology: Eggs are inserted into the leaf tissue by the female. Hatching occurs in 12-18 days and the nymphs develop over the next 6-10 days. Pupae resemble the nymph but have wing buds and do not feed but moves when disturbed. The adults emerge after 3-6 days.

Damage characteristics: The nymphs and adult thrips are sap suckers and colonize the lower surface of the leaves where they feed. Their feeding activities caused the leaves to become pale brown and slightly crinkled with roughening of the upper surface. Heavily attacked leaves will fall off and the defoliated branches give the tree a ‘stag-headed’ appearance. The plants that survive normally become stunted in growth. Although the pest seems to have a slight preference for the older leaves, they also attack young leaves, shoots, inflorescence and flower. Adults and nymphs deposit a sticky red secretion onto the surface of the leaves as they feed. This sets into shiny black dots.

Control measures:

a) Chemical method: Dioxocarb was recommended for the insect pest. Endosulfan, Cypermethrin, Lambda-cyhalothrin and Fenitrothion have been suggested for effective control of nymph of insect. Also, Chloropyrifos, Dimethoate, Fenitrothion and Triazophos effectively controlled the bug. Effective control was achieved with these insecticides by spraying them onto the undersurface of the leaves and immature pods.

b) Cultural method: It involves the removal of damaged plant parts containing the eggs and progenies of the pest from the plantation and destruction of developmental stages inside them by burning such materials outside the plantation. This farm sanitation method is encouraged for all the insect pests of cashew, cocoa, coffee, kola and tea.

Cashew stem girdler, Analeptes trifasciata Fabricius (Coleoptera: Cerambycidae):

Importance: The adult beetle is about 55 mm long and 12-16 mm wide at the base of the elytra. The head, thorax and abdomen are black. The elytra have three broad orange transverse bands separated by two black bands of irregular shape. The antennae are twice as long as the body of the insect.

Biology: The female beetle lays its eggs above the girdled portion in excavated holes made on the bark of the branch with her ovipositor. The eggs are elongated and about 0.15 cm in diameter. Up to 80 eggs could be found in a heavily infested branch. The emerging larvae burrow into the stem and feed on dead tissue for further development. The number and duration of larvae instars as well as the pupal period are not yet known. Though pupation takes place within the hollow out branch.

Damage: The adult insects make small holes and girdled portions on stems and branches of cashew plants. The symptoms of damage by this pest include the presence of small holes and girdled portions on stems and branches. The girdled stems and branches have deep grooves as a result of which the stem and branches are left with thin woody tissue at the center to temporarily support the weight of the branch. Such branches are known to snap under slight breeze, leading to loss of all the fruits the branch has yielded. Stumps of affected branches have been known to regenerate and produce many side shoots, giving an untidy appearance. Damage is usually noticed on cashew trees more than four years old that have attained flowering stage.

Control measures

a) Chemical method: Dichrotophos and Monocrotophos were found to be effective for the control of the girdler. Endosulfan, Cypermethrin, Lambda-cyhalothrin and Fenitrothion have been suggested for effective control of the girdler. Effective control was achieved with the use of persistent chemicals such as carbofuran or endosulfan by spraying them onto the undersurface of the leaves and immature pods or applied as granules to the base of the tree in the rainy season.

b) Nonchemical method: Farm sanitation is based on the knowledge of the nature of damage and oviposition sites of Analeptes trifasciata, and the use of farm sanitation method for the control of this pest has remained the best option. Farm sanitation involves the removal of girdled stems containing the eggs and progenies of the pest from the plantation and destruction of developmental stages inside them by burning such stems outside the plantation [21-40].

Zonocerus variegatus L

Importance: Zonocerus variegatus L. is found throughout West Africa, South of the Sahara spreading Eastwards of Uganda and northwards into Sudan (Page, 1978). Youdeowei (1974) has produced a map of the distribution of the two species of Zonocerus (Z. variegatus and Z. elegans), which occurs in Africa. According to Page (1978), Z. variegatus is largely distributed between the Tropic of Cancer and the Tropic of Capricorn, with a predominant occurrence in the West African Sub region. In Nigeria, they are found all over grassland areas, and Toye (1971) reported that Z. variegatus usually occurs in cultivated land with nymphs and adults sharing the same habitat and its habitat extends from the lowland rain forest zone to the Guinea savannah in the north. Two distinct populations of Z. variegatus exist in southern Nigeria (Toye, 1971; Taylor, 1972; Anya, 1973 and Youdeowei, 1974). These are typically referred to as the dry and wet season populations. In South West, Ibadan area, the populations of Z. variegatus may be found throughout the year. The population found during the wet season (April-October) is small, while the dry season population (November-March) can be very large (Page, 1978). Therefore, the occasional outbreaks of grasshopper can cause serious damage to tea crops. They are of various species, which includes; Comphosene producta Wlk (Orthoptera: Pyrogomophidae); Attractomorpha aberans Karsch (Orthoptera: Pyrogomophidae).

Biology: In South West, Nigeria, adult Zonocerus variegatus becomes sexually mature with the onset of the rains. Their eggs `are laid from the middle of march to April, with the majority of the laying occuring during the first week in April, but do not hatch until late October or November with embryonic development, which includes diapauses taking 6-7 months (Entwistle, 1972; Page, 1978; Omole, 1986). In Eastern Nigeria, there is one annual generation but two definite broods, most eggs being laid in March/April and August/ September. Each female lays 1-4 egg pods, which is 40-45 mm long, each containing 20-90 eggs. The pods are buried 5-8 cm deep in the soil. As many as 3,500 pods have been found on a site of 16 m2 (Toye, 1982). This shows that egg pods are normally concentrated in selected egg-laying sites. The egg development is dependent on high level of soil moisture and takes place at the end of the wet season. Zonocerus variegatus generally has six nymphal instars in the field although a small percentage of the insect will have only five instars (Chapman et al., 1977). The nymphal development proceeds during the dry season and adults are dead before the next rain or at the onset (Entwistle, 1972; Toye, 1982). Lee and Wood (1971) stated that as plant tissue is either directly or indirectly the source of food for termites, vegetation must be an important factor in determining their distribution and abundance [41-60].

Damage characteristics: In Nigeria, various species have been reported to cause serious damage on virtually all the economic crops across the Mangrove and Fresh water swamp forest, Rain forest, Guinea savannah and Sudan savannah (Harris, 1971; Malaka, 1973; 1983; 1996). The polyphagous pests: Zonocerus variegatus L.; Brachytrypes membranaceus Dury and Gryllotalpa africana Beauv, were not left behind as they were seen feeding on kola foliage and young stems causing excessive defoliation and death of seedling plants (Daramola, 1978a). The females deposit egg capsules in the soil during the rainy season. The eggs hatch and nymphs appear in November, while adults emerge in late January to March (Daramola, 1978a; Toye, 1982). The nymphs of the variegated grasshopper, Z. variegatus are gregarious, and often very numerous and it is at this stage that most damages are done. They are sluggish and migrate only slowly by walking and hence attack tends to be patchy. The adult grasshoppers are less gregarious than the nymphs, which eat up the leaves, leaving the veins intact, especially of seedlings. Both the nymphs and adults feed on new flushes, moving from one plant to the other after stripping the former bare. Their feeding activities always result in severe damages to young kola stands. Grasshoppers are known to feed on wide range of plants, showing preference to various annual herbs. Field observations on the damage caused to economic crops in Nigeria by Z. variegatus have been recorded by several authors (Toye,1972,1974, Anya, 1973; Youdeowei, 1974; COPR, 1975, 1976; Page, 1978; Omole, 1986). They all have illustrated accounts of the nature of damages to important economic crops such as banana, plantain, cassava, citrus, cocoa, kola, cotton, cashew, cowpea, tea etc.

Control measures

a) Cultural control: Toye (1982) however reported that control operations on grasshopper should be carried out in November and early December when young nymphal aggregations are dense. A drastic reduction of the Zonocerus population could be achieved by digging up the egg laying sites and exposing them to high surface temperatures so that the eggs are killed. If all or nearly all the sites in a large area are cleared in this way the population of the grasshoppers can be reduced well below the damage threshold at no financial cost and with very little labour (Page, 1978; Toye, 1982). According to the COPR (1977), it is possible to reduce a Zonocerus population by 90% through this method. Also, studies carried out in two egg-laying areas showed that potential hatches were reduced by 83-91% through exposure of dug egg pods to desiccation (Page, 1978).

b) Chemical method: All instars of Z. variegatus can be killed easily by the common insecticides (Fenitrothion) using solutions of 0.1% wt/vol. a.i., though 0.5% a.i. could equally achieve effective control on the target. The best time for spraying is in the early mornings or late afternoons when the insects are less active and preferably on the highly aggregated early instars of the insect. However, due to the well dispersal and high mobility of later instars of the insects, spraying them would be uneconomical unless the crop is of high economic value, in which case spraying at regular intervals according to the rate of re-invasion, would be worthwhile (Page, 1978; Toye, 1982). Ndubuaku, (1989) effectively controlled nymphal aggregations on weeds with kerosene applied using a motorised mist blower [61-75].

c) Grasshoppers (Orthoptera: Acrididae): They are gregarious and feed on young immature leaves thereby reducing their photosynthetic area and damaging the leaf quality of tea leaves. They are usually brown in colour and mature adults are about 4-6 cm long. Mature females lay their egg pods (which usually contains 80-100 eggs) in shade on abandoned farmlands. In the drier regions of Nigeria, eggs are laid at the end of one raining season and hatch at the beginning of the following year rains. The eggs are encased in a capsule made from the soil to prevent desiccation.

Crematogaster buchneri Gorel

Importance: Ants are general nuisance pests, building nests in trees, biting aggressively and making harvesting difficult.

Biology: Ant colonies have some fertile males called drones and one or more fertile females called queens.

Damage characteristics: Eguagie, (1973) reported that the ant, Crematogaster buchneri Gorel scrapes off the epidermis of the leaves and follicles of cocoa. The damage usually results in the shedding of leaves and the premature dropping of shrivelled follicles. The associated beneficial insects like scale insect, Stictococcus sjostedti CKII has large colonies whose piercing and sucking feeding injuries cause stunted growth and pod drop. Also, the feeding injury of the mealybugs, Planococcus citri Risso; Planococcus njalensis Laing; Ferrisiana virgata CKII on the cocoa flowers, flower stalk and pods, impair fruit development (Ndubuaku, 1989).

Control measures

a) Cultural method: Farm sanitation like pruning and shade management is effective in insect management.

b) Chemical method: Aldrex 40 is proven effective for the control of insect.

Ancistrotermes spp, Amitermes spp, Captotermes spp and Macrotermes spp

Importance: Ancistrtermes spp, Amitermes spp, Captotermes spp and Macrotermes spp (Termite) colonies are started by the sexual forms, which fly from the nests at the start of the rainy season and lose their wings before re-entering the soil or other hiding places (NRI, 1996). Termite, Macrotermes bellicosus, is however an emerging pest of Cocoa tree plantation.

Biology: Termites undergo incomplete metamorphosis; the younger instars of their nymphs greatly resemble the adults and take on important functions in the nest at an early stage (Kranz et al., 1978; Malaka, 1996; Pearce, 1997). Copulation is eventually accomplished and eggs laid into excavated initial cell which terminated courtship in termites. In an established colony, the queen lays egg and the eggs may be carried by the workers to other chambers or to a separate part of the royal chamber during incubation for hatching. The larvae are translucent with large setae. They can be assisted in hatching by workers who pull off, eat the eggshell and clean the larvae thoroughly to remove any remains. The larvae on hatching, remain in the brood chamber with the reproductives who look after and clean them, until the first workers develop to take on the role of foraging for food and looking after the young ones.

Damage characteristics: Termites cause damages on the field by attacking the trunks and pods of cocoa/kola tree causing the plant and the pods to dry up after severe infestations. They feed on dead vegetation and tunnel into the roots and stems of trees of any age resulting in destruction by weakening of the tree structure causing them to collapse or giving access to the entry of pathogenic organism (fungus and other diseases). The fungal pathogen is responsible for rot infection. Other insect damage activities included bark nibbling and scraping, which can cause the death of seedling and even mature plants. Damage is most severe in stands which are under severe water stress, old stands and those subjected to bad pruning which leaves dead and dying tissue on the plant (NRI, 1996).

Control measures
a) Cultural method

Crop rotation or rotational cropping system is effective in the control of the subterranean insect pest. Avoid continuous cultivation on the same area of land to prevent the termite population build up.

b) Chemical method

Termites could effectively be controlled by the application of insecticides (Methidathion,Carbofuran, Endosulfan, Pyrinex, Dursban, Termicid, Endocarp and Fenitrothion) to the soil around the base of the kola seedlings and mature plants or coppiced stems just before the outset of the dry season (NRI, 1996; Adejumo and Asogwa, 2001). Oyedokun et al., (2011) reported that the aqueous extracts of Phyllanthus amarus, Acassia albida and Tithonia diversifolia caused 40-56%, 24-60% and 42-88% mortality of termite, after 140 minutes of exposure (MOE) to the extracts. Similarly, ethanolic extracts of the P. amarus, A. albida and T. diversifolia resulted in a significantly (P<0.05) higher percentage mean mortality of 64-91%, 36.4-76% and 36-68% respectively (Table 1).

General control of insect pest damages

The following cultural, chemical, botanical, integrated Pest Management (IPM) strategy and legislative control measures have been proposed and perfected for the control of insect pests of Cashew, Cocoa, Kola, Coffee and Tea. These measures are also applicable to all economic crops Cultural control measures – These involve the use of simple cultural practices such as farm sanitation, physical removal and killing of insects, controlled burning, shifting cultivation, crop rotation, intercropping and interplanting, tillage practices, use of shade crops, use of alternative hosts, pruning and excision, timely and prompt harvesting, processing outside the farms etc. These cultural operations are very cheap and stabilize the populations of most insect pests below their economic threshold. The practices are also humane and environmentally friendly and do not have any side effects. Some of the cultural practices are as follows:

Use of shade crops – Cultural operations involving the utilization of shade plants in young and old cocoa and kola plantations have been comprehensively researched upon. Adequate provision of shade and timely removal of infested seedlings also reduce infestation and activities of root feeding termites in newly established and young cashew and other trees such as cacao, coffee, kola and tea plantations.

Physical removal

Hand picking and subsequent destruction of the later instar larvae of the pests of cashew. This method has been utilized for the control of Analeptes trifasciata, which resulted in the drastic reduction of the infestation levels in cashew plot.

Tillage practices

A drastic reduction of the Zonocerous variegatus population could be achieved by digging up the egg pods in the egg laying sites around young cashew, kola, cocoa, coffee and tea plots thereby exposing them to high surface temperatures that desiccate the eggs. If all or nearby all the sites in a large area are cleared in this way the population of the grasshoppers can be reduced well below the damage threshold at no financial cost and with very little labour. It is possible to reduce a Zonocerous population by 90% through this method.

Farm sanitation

Based on the knowledge of the nature of damage and oviposition sites of Analeptes trifasciata, the use of farm sanitation method for the control of this pest has remained the best option. Farm sanitation involves the removal of girdled stems containing the eggs and progenies of the pest from the plantation and destruction of developmental stages inside them by burning such stems outside the plantation. This farm sanitation method is encouraged for all the insect pests of cashew, cocoa, coffee, kola and tea.

Pruning and excision

Pruning is usually embarked upon to maintain a good canopy and to achieve tree structure convenient for harvesting and spraying. It usually entails removal of dead, diseased and insect damaged woods, which are destroyed to prevent further pathogen and insect development. This helps to decrease number of primary wood-boring insects and also reduces the number of sites at which termites can gain a foothold. There are two main aspects to termites control in Cashew, cocoa, coffee, cashew, kola and tea.
a) Prevention of root, collar and basal stem attack in the nursery and in young plants in the field
b) Prevention of termite establishment in wounds and dead wood on mature trees so as to avoid spread of infestation to healthy wood. Treatment should be an organized part of routine farm or plantation maintenance and consists of careful pruning of dead wood, preferably with saw cuts close to the branch origin, and the treatment of cut and damaged surfaces with paint, coal tar or copper fungicide until they are callused over. The improvement of pruning technique, routine removal of all dead plant parts and manipulation of the shade and soil moisture through intermittent irrigation during the dry season may minimize attack by termites.

Use of alternative hosts

With polyphagous insects the wild host plants may be so numerous that special eradication would be impracticable, but where insect pests have a restricted host range, their removal may be especially beneficial. Studies by various workers have produced a long list of alternative-host plants of cashew pests. These includes; Lannae humilus Oliv. (Anarcardiaceae) Spondias mombin L. (Anarcardiaceae), Terminala catappa (L) (Combretaceae) Ficus mucosa (Myrtaceae) Eucalyptus toreticornis (Myrtaceae), Adansonia digitata (Borabacaceae) and Ceiba pentandra for Analeptes trifasciata among others. Theobroma cacao and areca nut of betel nut (areca tree) have been identified as alternate host plants of Selenothrips rubrocintus, while pawpaw, mango, almond and citrus trees are notable alternate hosts of Pachnoda cordata. These host plants can be manipulated in trapping out the pests away from the main crop plantation. Alternatively, all the alternate host plants within the vicinity of the main crop plantation should be cut down so as to prevent the pests from hibernating on them during the off season in biological reports, plants which tolerate specific phases of the development stages of the insects or serves as temporary source of food and survival are often referred to as alternative host plants, whereas they are better regarded as incidental host plants, fortuitous host plants or trap plants.

Trap plants – In general, the alternative host plants of major and minor pests of cocoa, coffee, cashew, kola and tea should be avoided while intercropping their young seedlings with food crops. This deters rapid invasion and multiplication of such pest in such farms. An alternative host plant can be broadly defined as that which tolerates all facets of the insect developmental activities (from egg to adult) in addition to serving as source of food to the various instar stages. It is common in biological studies to often refer plants, which only tolerate some phases of the developmental stages of an insect as an alternative host plant.

Use of cover crops

Any rehabilitation method other than growing young cocoa under old trees increases the weed problem. The area becomes exposed and weeds and pests invade it. To avoid the ingress of grasses, cover crops, some of which may have economic value, e.g. beans, melons, could be tried. The use of cover crops will reduce soil erosion which could aggravate the soil fertility problem. Row weeding must, however, be done to keep the immediate surrounding of the cocoa plants free of weeds, thus reducing competition for nutrients. Results of experiments at Kade, Ghana revealed that no particular cover was superior to natural regeneration, although the use of Tephrosia and Indigofera Sumatrana (both legumes) encouraged early and are replaced by natural regeneration. Mulching and use of legume covers gave higher cocoa yield than natural regeneration. This was attributed to better early growth rather than the residual effects of the cover on the soil.

(2) Biological control measure – It entails the use of an organism to control another organism. The population and activity of insect species can be altered through introduction of another organism including bacteria, viruses, insects and other natural enemies may be by introduction or man’s intervention with the stable ecological factors (abiotic and biotic factors). The concept of prey-predator relationship gives an overall view of biological control. However, rearing of biological control agents is an expensive venture. In most cases, the nature enemies of the insects within their existing ecological conditions are consciously preserved by man through judicious and selective chemical applications. If need be, thus the concept of integrated pest management gives an adequate protection to the maintenance of natural enemies in their natural environments.

Chemical control measures

Chemical control method is encouraged as the last resort to complement other methods or to address major pest outbreak problem. Presently, conscious efforts are directed towards judicious and selective chemical usage. This will combat the problem of resistance to pest, toxicity to man and tainting of plant products. The pyrethroids, though costly, are considered safer than other class of chemicals including organochlorine, organophosphate, carbamates etc. The chemical control should be at the initial stage of infestation of all the foliar pests since the later stages inflict greater injuries on the plant than the early stages. Spraying of insecticides should be carried out early in the morning or by late evening. All instars of Zonocerus variegatus can be killed easily by the common insecticides (Fenitrothion) using solutions of 0.1% wt/vol. a.i. The best time for spraying is in the early mornings or late afternoons when the insects are less active and preferably on the highly aggregated early instars of the insect. However, due to the well dispersal and highly mobility of later instars of the insects spraying them would be uneconomical unless the crop is of high economic value, in which case spraying at regular intervals according to the rate of re-invasion, would be worthwhile. Termites could effectively be controlled by the application of insecticides (Methidathion, Carbofuran, Endosulfan, Pyrinex, Dursban, Termicid, Endocap and Fenitrothion) to the soil around the base of the cocoa seedlings and mature plants just before the outset of the dry season.

Pesticides considered safe for protection of tree crops

The following synthetic insecticides such as Actara 25 WG, Esiom 150 SL, Proteus 170 0-TEC, Avesthrin, Termicid, Capsida, Phostoxin, Zap, Confidor etc. were screened against attacks of kola/Cocoa weevils/mirids. This is to determine biodegradability of the insecticides with little or no residue effect that may pollute the environment (Asogwa, 2014b). Among the chemical insecticides screened, Actara 25 WG, Esiom 150 SL and Proteus 170 0-TEC passed through all the stages and considered effective, and thus recommended for use on Cocoa/Cashew tree or their products. Other chemicals aside recommended ones are still under investigation (Asogwa, 2014b). Though there is a need to check or monitor the influx of banned or adulterated insecticides in the country, equally enlighten farmers/traders on the use of currently approved insecticides and involved modern techniques (Azeez, 2015b).

Use of natural plant products (Botanicals)

Due to the hazard effects of synthetic chemicals there is an urgent need to develop an alternative form of pest control that is non-toxic, biodegradable and affordable for the management of pests of agriculture and public health. This will help to protect the environment and reduce the economic and social costs of agricultural production. Crude extracts from selected plant species and other materials of biological origin appear to offer an effective method of pest control especially when used within an integrated pest management schedule. Plant extracts can provide a simple means of control that can be used by farmers. Botanical protectants have a great deal of advantage over all other types of protectants. This is because they do not lead to the buildup of resistance by insect pests. Most of these botanicals are acquired freely in the environment. They do not pose health hazard to the local farmers, as most of them are either medicinal plants or vegetables that are consumed as food. It also can help in rural development and employment for the rural populace through the establishment of cottage industries for the processing of selected plant materials for pest control. The natural pesticides from these plants may be utilized in the form of powdery, oil or aqueous formulations and could be applied in various ways ranging from the broom sprinkling method to the use of knapsack sprayer.

Legislative control (Quarantine)

This involves the regulation of plant materials from one region to another to restrict the introduction of exotic pests, which may be accidentally transported by those plant materials. The government of each country or region enforces this law (Quarantine laws), which are prohibitive at all ports of entry into a given country. The law requires all imported plant materials to be brought in with an import permit accompanied by a phytosanitory certificate, which guarantees the state of health of imported materials. Regulatory control also prevents the spread of pests from one location to a wider area in a given zone.

Integrated pest management (IPM)

Integrated pest management (IPM) is process consisting of the balanced use of cultural, biological and chemical procedures that are environmentally feasible and socially acceptable to reduce pest populations to tolerable levels. It could also be defined as a sustainable approach to managing pests by combining biological, cultural, physical and chemical tools in a way that minimizes economic, health and environmental risks. Integrated pest management (IPM) involves the judicious utilization of two or more of the control methods to achieve a more effective control. For instance strict cultural practices can be used effectively with minimal pesticide sprays to get rid of most devastating stages of insect pests. IPM approach discourages the use of persistent pesticides (Organochlorine and organophosphates), rather Carbamates, Pyrethroids, Natural plant products (Botanicals) and Bio-insecticides (formulation based on pest pathogenic microbes) are now being favoured for use on agricultural products.

For almost two decades (1970-1990) research efforts on pests and diseases of cocoa were concentrated on bioecology and control of cocoa mirids, black pod disease and cocoa swollen shoot virus disease. By late eighties it had become obvious that most of the recommendation extended to cocoa farmers on the control of these insect pests and diseases have become inadequate and unsustainable. This was because mirids have developed resistance to all lindane-based insecticides that are widely used by farmers. These insecticides together with the copper base fungicides recommended for the control of black pod disease also became expensive and less affordable. Hence, the need to identify alternative but sustainable techniques for the management of these pests and diseases. In view of the above scenario, concerted research efforts were made to identify and evaluate various control techniques (Cultural, biological and chemical), which could be harnessed for integrated management of these most important pests and diseases in Nigeria.

Conclusion

The knowledge of ecology combined with life cycles of insect pest would enhance better understanding of the best option of pest management strategies to employ. Therefore, the sparingly use of chemical (0.025 ml) with other control options in a compatible manner would achieve effective and sustainable pest management. Some chemicals have been banned but the information is yet to reach those who buy in ignorance and apply without knowledge. In the foregoing, the approved and prohibited pesticides are provided to make producers to take right decision. Accredited sources in Nigeria have been provided so that fake chemicals are avoided and recognized (Asogwa, 2014b). Some of these chemicals must be used at specific times and locations in the value chain of the crop. Consequently, it is important to use the right chemicals so that the quality of the farm products would not be affected when used for food items (Asogwa and Dongo, 2009). It is worthy to note that irrespective of previous storage trials, there has been no categorical recommendation of chemical control of kola weevils. This is due to the fact that kola nuts need no further processing before consumption hence no level of chemical residue on it will be acceptable.

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