*4.1.1.1 Management of Root knot disease*

*Cucumber Economic Values and Its Cultivation and Breeding*

Members of the genus *Pseudomonas* are pathogenic aerobic bacteria that are naturally widespread in the environment [63]. Their wide occurrence has been attributed to their great deal of metabolic diversity and as a result, ability to colonise a wide range of niches. One of the most studied members of the group is *Pseudomonas syringae*. Angular leaf spot caused by *Pseudomonas syringae* pv. *lachrymans*, is common to almost every cucumber growing area of the

Angular leaf spot is one of the serious diseases which primarily affects cucumber. The infection can affect the quality of fruit produced by inflicting up to 37 and 40 per cent reduction in fruit number and fruit weight, respectively in addition to rendering some fruits totally unmarketable [65]. At the initial stage, the symptoms appear on leaves in form of small, water-soaked lesions which later enlarge. Older lesions become angular as they enlarge and encounter veins. The infected tissues often dry and fall. The leaves are left with torn-irregular-shaped holes. In Africa, angular leaf spot disease was identified on cucumber seedlings raised from infected seeds in Egypt, with disease incidence of 98 per cent [66]. Different isolates of *P. syringae* pv. *lachrymans* from Egypt are also reported to induce wilting, besides the

Angular leaf spot disease can be effectively managed by planting disease-free seeds. Additionally, planting field should have good drainage system to avoid any form of contact from neighbouring cucurbitaceous fields. Crop rotation with non-

Members of the genus *Meloidogyne* have gained worldwide recognition as one of the major plant parasites constraining crops of primary economic importance [68]. *Meloidogyne* spp. are considered among the top five major plant pathogens and the first among the ten most important genera of plant parasitic nematodes in the world [18]. *M. arenaria*, *M. incognita* and *M. javanica* are reportedly dominant in Africa [69]. *Meloidogyne* spp. were among the nematodes found on cucumber field in Libya [70]. Aminu-Taiwo and Fawole [71] identified the effect of *Meloidogyne incognita* on cucum-

Root-knot is caused caused by *Meloidogyne* spp. All members of Cucurbitaceae family are susceptible. Typical symptoms observed on affected plants include stunted growth, pale green to yellow leaf colouration and wilting during the hot periods of the day [72]. This is due to reduced water uptake. Yield and quality of the fruit are greatly reduced. In heavy infections, plants will completely wilt and die as the nematode populations increase. When infected plants are removed from the

cucurbits and complete removal of crop remains after harvest are helpful.

typical angular leaf spots, within 3 to 6 days of inoculation [67].

*3.2.1.1 Management of Angular leaf spot*

**4. Nematode diseases of cucumber**

ber in Nigeria bringing about remarkable yield reduction.

**4.1 Genus:** *Meloidogyne*

*4.1.1 Root Knot disease*

**3.2 Genus:** *Pseudomonas*

world [64].

*3.2.1 Angular leaf spot*

**186**

Measures that have been used to manage root knot disease include the use of chemically formulated nematicides, crop rotation, soil fumigation, practice of fallow period and using plant extract with nematicidal property.
