*2.1.1.1 Management of PVMV*

Capsicum

(PepLCV), *Tomato yellow leaf curl virus* (TYLCV), *Cucumber mosaic virus* (CMV), *Alfalfa mosaic virus* (AMV) and *Tomato spotted wilt virus* (TSWV) while other viruses of minor importance include *Pepper vein yellows virus* (PeVYV) and *Potato virus X* (PVX) [8]. These viruses are mainly vectored by aphids, whitefly or thrips during feeding probes. However, mechanical transmission and seed transmission are efficient means for the spread of infection. Typical symptoms induced by viruses infecting *Capsicum* spp. include stunting, curling and mottling of foliage and fruits. Symptoms can vary significantly with cultivar, plant age, virus isolate and environmental condition. In recent years, co-infection of previously non-

The increasing outbreaks of virus species infecting *Capsicum* spp. have become a major problem for growers in many countries including Ghana, Uganda, Mali, Cameroon, Morocco and Nigeria [9, 10]. This is due to a combination of factors, including expansion and intensification of pepper cultivation, availability of volunteer hosts, abundance of insect vectors and climate change [6, 11]. Many techniques are used to minimize viral infections in *Capsicum* spp., but are successful when they begin prior to planting of the crop. Current management options for virus infection in *Capsicum* spp. is by the integration of several approaches. These include use of protected nurseries, cultivation of disease resistant varieties and ensuring adequate

Generally, eco-friendly management measures are needful to reduce occurrence

of virus diseases in *Capsicum* spp. and decrease the rate of spread of same into unaffected regions. This is important because of the need for increased international movement and exchange of pepper germplasm. This will also facilitate the selection and breeding for improved *Capsicum* spp. adapted to local conditions and uses. Therefore, there is need for a review of viruses infecting *Capsicum* spp., their

The genus *Potyvirus* consists of a large group of plant viruses that are widespread, infecting economically important crops like tomato, potato, eggplant and pepper [12]. Members of this genus have non-enveloped flexuous filamentous single-stranded RNA (ssRNA) particles about 680–900 nm long and 11–15 nm wide [13]. The symptoms induced by potyviruses include mottling, mosaic, curling, vein banding or clearing, chlorosis, blistering and severe stunting of the whole plant. Severity of these symptoms depends on the *Capsicum* variety, virus strain and presence of other viruses. The major potyviruses infecting *Capsicum* spp. in Africa

*Pepper veinal mottle virus* (PVMV) was first reported in Ghana in 1971 and has since then spread to other regions in Africa including Ethiopia, Kenya, Tanzania, Uganda and Rwanda [14] causing yield loss ranging from 70 to 100 % [15]. Infection of PVMV also occurs in other solanaceous crops, including eggplant and tomato [16]. Eight species of aphids have been shown to transmit the virus in a non-persistent manner, of which *Myzus persicae*, *Aphis craccivora*, *A. gossypii* and *A. spiraecola* are rated as efficient vectors [17]. Mechanical transmission also occurs through contact with infected sap, but not via seeds. Several symptoms associated with

existent virus strains is most devastating [7].

phyto-sanitary conditions after transplanting.

**2. Viruses of pepper**

**2.1 Genus:** *Potyvirus*

symptoms, mode of transmission and management options.

include PVMV, ChiVMV, PepMoV, PVY and TEV [12].

*2.1.1* Pepper veinal mottle virus *(PVMV)*

**74**

Plastic mulches have been reported to reduce insect infestation and the concurrent damage associated with the insect transmission of viruses [10]. Intercropping *Capsicum* spp. with maize can also reduce the incidence of the disease compared to sole cropping [17]. The use of resistant varieties, raising of seedlings in insect-proof nursery and roguing of infected plants once detected are also crucial to reduce PVMV incidence and spread in the field. These are recommended as integrated ways for managing PVMV infection in the field [7].

### *2.1.2* Chilli veinal mottle virus *(ChiVMV)*

*Chilli veinal mottle virus* (ChiVMV) has been reported in various countries of West and East Africa including Ethiopia, Uganda and Tanzania [19]. The virus is not transmitted through seeds but is acquired mechanically and is transmitted by several species of aphids in a non-persistent manner. These vectors (*Myzus persicae*, *Aphis gossypii*, *Aphis craccivora*, *Aphis spiraecola*, *Rhopalosiphum maidis*, *Toxoptera citricida* and *Hysteroneura setariae*) retain the virus for not more than1 hour after virus acquisition [20]. The winged aphids are generally the most efficient vectors to transmit the virus from field to field and are the most difficult to control [21]. Typical symptoms caused by ChiVMV include leaf mottle and dark green vein-banding.

### *2.1.2.1 Management of ChiVMV*

The effective management strategies for ChiVMV include early identification and timely disposal of infected seedlings, application of mineral oil-based insecticides in controlling aphid populations early enough during planting, careful handling of diseased-free seedlings and use of resistant varieties. In addition, removal of solanaceous weeds, which serve as alternate hosts, can reduce incidence of ChiVMV in pepper gardens [21].

### *2.1.3* Potato virus Y *(PVY)*

*Potato virus Y* (PVY) is common among solanaceous crops including pepper, potato, tomato, tobacco and many weeds [22]. It has been reported in many African countries including Zimbabwe, Zambia, Kenya, Tanzania, Malawi, Madagascar, Ethiopia and Nigeria [23]. Isolates of PVY from pepper do not infect potato and vice versa [24]. Strains of PVY infecting sweet pepper are classified by their ability to overcome resistance genes based on differential host reactions. They cause yield reductions of 20–70% in pepper production [25]. The virus is transmitted in a non-persistent manner through several species of aphids, but the green peach aphid (*Myzus persicae*) is considered generally to be the most important vector. Infection of PVY can spread during grafting, handling of plant and use of unsterilized farming equipment. The symptoms of PVY include stunting or dwarfing of plant, systemic vein clearing and banding, leaf mosaic and small deformed fruit with a mosaic pattern making them unmarketable [26].

#### *2.1.3.1 Management of PVY*

Management of PVY is successful through the use of resistant varieties, elimination of solanaceous weeds and adjoining volunteer host plants, scheduling the time

of planting to conform with period of least aphid population, careful handling of plant seedlings especially during nursery and farming operations. Early detection and roguing of infected plants are the effective measures to reduce incidence of PVY. Additionally, intercropping pepper with maize has been found helpful in the management of potyviruses in pepper fields [27].
