issues and constraints related to the development of cashew nuts ...

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4ability to move long distances, and could well become a pest in a new place in the future. Inaddition, as the area of cashew expands and increases, pest dynamics also change, often for theworse.Sucking pestsHelopeltis sp (Hemiptera: sub-order Heteroptera: family Miridae)Helopeltis was present at many of the sites visited throughout Guinea, Guinea Bissau and Coted’Ivoire. Helopeltis was also present in Ghana, but there Anoplocnemis curvipes damage wasanother common feature at some sites (see next section) and it was difficult to distinguish therelative importance of Helopeltis. In Nigeria Helopeltis was present but damage levels were verylow.Helopeltis was responsible for significant loss of yield at a number of sites, most notably inGuinea.Helopeltis sucking pest leaf damage can take the form of black lesions on petioles or on the leafmidrib, or black angular spots on the leaf surface. Typical feeding damage on stems appears as adiscoloured, necrotic area or lesion; similar lesions also occur on fruits and developing nuts. (Peopleencountered during the course of the surveys were often identifying this type of damage as beingcaused by anthracnose.) When Helopeltis feeding pressure is sufficiently intense, the whole shoot diesand this damage is typically called ‘Dieback’ (see Photograph 1). In very serious cases, the entire treelooks burnt.In East Africa, the sucking pests Helopeltis anacardii, H. schoutedenii and Pseudotheraptus wayiBrown (Hemiptera: Coreidae) are the main insect pests of cashew and studies there have shownthat sucking pest damage can be very variable from year to year and place to place (Boma et al.1998 and Topper et al, 1998). It is therefore, highly likely that Helopeltis damage in West Africacould vary in intensity from year to year and place to place, depending upon environmentalfactors, age and attractiveness of cashew and other host plants in the vicinity. In India, Helopeltisantonii (the tea mosquito) is the main production constraint.Anoplocnemis curvipes (Hemiptera; sub-order Heteroptera; family Coreidae)Damage symptomsA. curvipes are in the same sub-order of insects as Helopeltis and they feed in a similar way, bypenetrating the living tissues of plants with their piercing mouthparts and imbibing the sap. (seePhotograph 2).A. curvipes damage (see Photographs 3 and 4) was found to be widespread in West Africa andwas particularly serious in Cote d’Ivoire and Ghana, where farmers often wanted to spray in orderto protect their cashew trees, but resources were not available.According to Hill and Waller (1988), A. curvipes is distributed throughout Africa, where theysuck the sap of a variety of plants including both sesame and coffee.Thrips (Thysanoptera: Thripidae).Many species of thrips exist and it is likely that more than one species could attack cashew inWest Africa. The Plant Protection department in Guinea Bissau had identified Selenothrips sp. asone candidate.
5The severity of attack by thrips usually varies from year to year and place to place and normallythey are only dry season pests; as soon as the heavy rains start they disappear.Damage symptomsThe vast majority of thrips species derive their nutriment by penetrating the living tissues ofplants with their piercing mouthparts and imbibing the sap. Loss of sap can result in yield lossand some thrips species can transmit viral diseases. As a result of such feeding, mainly on themore mature cashew leaves, they turn a bronze colour and eventually drop off.Thrips were widespread throughout the 5 countries surveyed; usually damage was minor and ofno economic significance. However at a few places in Guinea and Ghana in particular, thripswere responsible for serious levels of defoliation and yield loss.At the MIM Estate in Ghana, thrips and other sucking pests were a major problem. They have tospray 3 or 4 times every year to control the thrips; without this, the trees would be completelydefoliated. Tractor-drawn sprayers were used, since backpack motorised blowers could not dothe job. Interestingly, the trees from Indian seed were apparently more susceptible to damagefrom thrips than the local trees.Trunk borers and girdlersEvidence of trunk boring insects was seen at various places throughout the survey but the numberof trees affected was small.Apate terebrans (Coleoptera, family Bostrychidae)The most spectacular example of borer damage was found in Seguela district, Cote d’Ivoire. Inone 6 year old tree, 37 adult borers were found causing extreme damage and the death of the tree.The following information was provided by the Natural History Museum (UK): “This species iswidespread throughout Africa and Madagascar and has been introduced into Central and SouthAmerica. The larvae develop in a variety of timbers, including living trees and constructionwood. The adults also feed in the wood and they can damage young trees, causing death. Thelife cycle is usually 1 to 3 years depending on the condition of the wood, moisture content, extentof infestation, etc. Adult beetles will disperse naturally by flight but they have also been spreadfurther by trade”.A. terebrans is polyphagus and Hill and Waller (1988) record A. terebrans as attacking coffee,citrus, cocoa, guava, cotton and other plants.Cultural control is usually recommended, whereby a flexible wire (e.g. a bicycle spoke), ispushed into the tunnels to kill the larvae or adults. Insecticide-soaked cotton wool can also bepushed into the holes to kill the insect. Borer damage is usually restricted to a small number oftrees, and with vigilance and the appropriate cultural control knowledge, it can be kept undercontrol quite easily.Analeptes trifasciata (Coleoptera, Cerambycidae)Damage by this pest was mainly seen in Nigeria, but it has been reported as being a problem inall the countries surveyed.
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Page 9 and 10: 9Powdery Mildew Disease (PMD)During
Page 11 and 12: 11In addition to the direct impact
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Page 15 and 16: 15 GhanaThe germplasm collection of
Page 17 and 18: 17reflects the relative ‘newness
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Page 21 and 22: 21substantial loss of investment we
Page 23 and 24: 23Use of cashew applesIn all countr

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