**6.1 Pest and disease management in ginger (***Zingiber officinale***)**

Ginger cultivation is affected by both biotic and abiotic factors. Biotic factors are viruses, bacteria, fungi and nematodes [112, 113] with bacteria being the most important causing wilt and soft rot. The next major pathogen after bacteria is fungi which causes rhizome rot, soft rot, sclerotium rot and yellows disease. Nematode causes root-knot disease while viruses causes mosaic and chlorotic fleck in ginger plants leading to reduction in rhizome yield of the plants. In River State of Nigeria, a survey was conducted by [114] and it was reported that the most abundant arthropods in stored ginger was mites then *Lasioderma serricorne*. Reports have it that *Aspergilus flavus, Aspergilus niger, Fusarium oxysporium* and *Rhizopus* sp. were fungi pathogens isolated from dried ginger samples with high occurrences *of A. flavus*. According to a survey in Rivers State, Nigeria, stored ginger has no immunity against arthropod pest infestation and fungal infection. It was also observed that population dynamics of arthropod *Nigeria Root Vegetables: Production, Utilization, Breeding, Biotechnology and Constraints DOI: http://dx.doi.org/10.5772/intechopen.106861*

pests of stored ginger was affected by seasonal variation. The four main diseaseS and pestS of ginger as reported by THE National Agricultural Advisory services (NAADS) Uganda are rhizome rot, soft rot, root-knot nematode and rhizome scale.

#### *6.1.1 Rhizome rot*

It is a partly/completely decomposition of rhizome tissue; root may dry, wet, soft or slimy and color turns black. This rot is caused by the fungus (*Fusanum Oxysporum*) both in the field and post-harvest when ginger is washed in dirty (recycled) water, poor aeration and storage in contaminated sheds where rotten piles of reject ginger is allowed to accumulate.

#### *6.1.2 Soft rot*

Soft rot is caused by fungus *Pythium gracile*, either alone or in combination with a bacterium *Erwinia* species. The fungus *Pythium* is a water-mold and develops maximally in moist conditions when temperatures are favorable. Prolonged wet weather, therefore, creates ideal conditionS for development of soft-rot disease in ginger.

#### *6.1.3 Root knot nematode*

It is caused by the nematode (*Meloidogyne incognita*) which attacks both the root and ginger rhizome, resulting in warty overgrowth on them. The nematode normally burrows themselves into the soil and form knots on the roots and rhizome. In this way, they attack the plant by feeding on the food and nutrients which should be used by the plant for growth and production. Therefore, because of starvation with nutrients and food, the plant dies.

#### *6.1.4 Rhizome scale*

The size and shape of this scale insect is about 0.5–2 mm in diameter and usually circular in shape. They normally have a shell color brown on top which act as coverage and protection. It attacks the rhizome of the plant by sucking out the juice from it thus resulting in wilting and death of the plant. It is hard or difficult to treat this pest (using insecticides or even hot-water treatment) because of the shell forming on top which protects the insect from dying.

Apart from these major pest and diseases, others include Fungi and bacteria such as Thread blight *Ceratobasidium* sp.; *Corticium* sp., Stem rot (*Athelia rolfsii*), Leaf spot (*Magnaporthe Grisea*).

#### *6.1.5 Nematodes*

Burrowing Nematode—*Radopholus similis* (associated with rhizome rot); Reniform nematode- *Rotylenchulus reniformis* (yellowing leaf drying and stunting); Pin nematode *Criconemoides onoensis*

#### *6.1.6 Yellow leafspot of ginger*

Over the years, ginger yellow leaf spot disease has posed a serious challenge to increased ginger production in Nigeria [115]. The most susceptible stage which is

three- to four-leaf stage coupled with high humidity has been observed to be conducive for the disease spread. Ginger plants of up to 6–7 months old are also susceptible to this disease. Grasses have been reported as reservoir hosts while agents of dispersal are rainwater and wind [116]. This disease spread widely in ginger-growing areas with resistance to benomyl (Benlate 50wp), mancozeb (Diathane m-45), and Kocide 101 (copper hydroxide) treatments. In the rainforest agro-ecology of Nigeria, though there may be appearance of early signs of the disease but severity is usually noticeable towards the end of vegetative growth.
