PLANTING TIME,  SPRAY REGIME, DISEASE EXPRESSION AND THEIR  IMPACTS  ON SIX CUCUMBER LINES IN A DERIVED  SAVANNA AGROECOLOGY OF NSUKKA, SOUTHEASTERN NIGERIA.

ABSTRACT

Cucumber  (Cucumis sativus L.)  belongs to the Cucurbitaceae  family.  It is a major  vegetable  crop worldwide and develops rapidly, with a shorter time from planting to harvest than most crops. It is a monoecious annual climber or creeper that has been cultivated for over 3,000 years and is still widely cultivated  today.  The  fruit  is  soft,  succulent  with  high  water  content,  roughly  cylindrical  and elongated  with tapered  ends.  The plant  shades  one another,  being allowed to creep on the ground thereby  having  a direct  contact  with  some  soil inhabiting  disease  causing  organisms.  Its creeping nature, pre-disposes the plant to pest and disease infestation.   However, the production of cucumber fruits in Nigeria is very low due to some constraints such as incidence of diseases which reduces fruit yield.  Presently,  they are produced mainly in the northern states of Nigeria.  Studies were conducted on the production of cucumber in south eastern Nigeria, in order to supplement the high consumption rate in the region.  Planting in April had the lowest disease incidence (3.48%) and severity on leaves (1.20)  and  fruits  (1.06),  followed  by    September  with  lower  disease  incidence  (3.60%),  disease severity on leaves (1.22) and fruits (1.17) while July had the highest disease incidence (6.27%) and disease  severity  on  leaves(l.56)  and  fruits  (1.74).    The  yields  during  the  April  and  September plantings were significantly (p<0.05) higher than other months.  April and September had 481.60 and

483. 60 tonnes per hectare respectively  while July had  19 .10  tonnes per hectare.  The spray regimes were significant (p<0.05)  on the disease incidence and severity.  The plants that received two weekly spray regime had the lowest disease incidence and severity on leaves and fruits (4.10%, 1.31 and 1.21 respectively)  followed by those that received three and four weekly spray regimes.  Those that were not sprayed had the highest disease incidence and severity on leaves and fruits. The plants that were sprayed  fortnightly  gave the  highest  yield  of 216.90  tonnes  per hectare.  The  cucumber  lines  also showed  significant  (p<0.05)    response  to  disease  incidence  and  severity  with  the  Supermarketer having  the  lowest  disease  incidence  (4.15%)  and  severity  on  leaves  (1.39)  and  fruits  (1.17)  and Poinsette Holland had the highest disease incidence (5 .15%) and Poinsette 7 6 Holland had the highest severity both on leaves and fruits (1.45 and 1.35).  The supermarketer gave the highest yield of 221.10 tonnes per hectare.   The best planting time remains April and September receiving  fungicide spray fortnightly.  Supermarketer  have  also  proven  to  be the  best  variety  to  withstand  diseases  and the weather condition of a derived savannah agro ecology.

INTRODUCTION

Cucumber  (Cucumis sativus L.) belongs to the Cucurbitaceae  family.  It is a major  vegetable crop worldwide  and develops rapidly,  with a shorter time from planting to harvest than for most crops (Wehner and Guner,  2004).  The crop is the fourth most important vegetable crop after  tomato,  cabbage  and  onion  in  Asia  (Tatlioglu,  1993);  the  second  most  important vegetable crop after tomato in Western Europe (Phu,  1997) and is the fourth most cultivated vegetable  in the  world  after  tomatoes,  brassicas  and  onions  (Wehner,  2007).  In tropical Africa,  the crop has not been ranked because  of limited use.  Cucumber  is grown widely in different  parts of the world.  It is an all year round out door vegetable  in the tropics and an important greenhouse vegetable especially in Northern Europe and North America (Mingbao,

1991).  Phu (1998) stated that cucumber  could be cultivated  in the field during the summer and winter  in greenhouses  using  artificial  heating.  Jizhe  (1993)  opined that cucumber  is a typical vegetable of warm temperate and cool tropical areas that can be cultivated at any time of the year. At present;  cucumber is cultivated as a field crop in most areas of the world under frost free conditions. Nu  (1998) stated that cucumber  is a warm season crop which can be cultivated at any time but has little or no tolerance to frost and that growth and development are favoured by temperatures  above 20C.  In Nigeria, cucumber can be cultivated at anytime of the year. During the rainy season,  the crop is grown under rain fed conditions and during the dry season using irrigation  facilities; as a result the crop can be seen in most vegetable markets  in Nigeria  throughout  the  year.  Many  varieties  of cucumber  exist  with  varying shapes,  skin colour and carotene content (Simon,  1992)  . The variation  in the performance  of cucumber varieties has been widely documented by many scholars (Manyvong, 1997; Ajisefinanni,   2004),  which  could  be  as  a  result   of  environmental   factors   or  genetic composition.  It is also  known  for its edible  fruits  because  it is delicious,  crispy,  high  in nutrients,  low in calories and excellent source of fibre needed for a healthy digestive system. In  addition  to  its palatability  and  fairly  good  calorific  value,  it is reported  to be  highly important to human for its medicinal value.  It is very useful for natural Diuretic and thus can serve as active drug for secreting and promoting the flow of urine. Cucumber is a dependable laxative  food  for  those  who  suffer  constipation.  The  juice  of cucumber  is  a  valuable medicinal food in the treatment ofhyperacidity gastric and duodenal ulcers (Ernestina, 2001).

In Nigeria,  Cucumber  production  and utilization  have not been a viable  option to farmers despite the numerous  benefits and economic importance  of this crop.  This might be in part due  to  the  declining  soil fertility  in conjunction  with  disease  infestation,  which  prevents optimum yield and the short shelf life of cucumber fruits which leads to early deterioration.

Cucumbers are susceptible to viral, fungal and bacterial diseases. They are mostly affected by fungal diseases and this causes significant losses to cucumber crops and currently requires  a high  chemical  use  for their  control.  Among the  fungal  diseases  is the phytophtora  blight disease caused by Phytophtora  capsici  (Babadoost  ,  2005),   which is prevalent  in the south eastern Nigerian.  It can develop on cucurbit plants at any stage of development; the pathogen can infect seedlings, vine,  leaves and fruits.  The infection usually appears first in low area of the fields where soil remains wet longer. It causes pre- and post- emergence damping-off  in cucumber under wet and warm (20-30 °c) soil condition.  Soil-borne diseases have led some growers to rely upon pesticides treatments.  Besides the high annual cost of these treatments, poor  application  practices  and easy re-introduction  of pathogens  due  to poor  hygiene  and sanitation  have  resulted  in frequent  disease  outbreaks.  Furthermore,  they are highly  toxic chemicals that pose a significant risk to farm workers and neighbours.

This problem is exacerbated  by the fact that there are no chemicals registered  for most soil• borne pathogens  in cucumbers. Similar problems exist for some foliar diseases (e.g. Botrytis blights and rots).  There has been a rapid development  and availability  of biological  control products  worldwide,  yet many  of these  products  have  not  been  objectively  evaluated  for efficacy.   Similarly,  many  products  have  not  been  validated   as  part  of integrated   crop management  systems for Nigerian conditions.

The way the product is applied makes a significant difference to its efficacy. The objectives of this research therefore are to:

1.     Evaluate the effect of planting time on cucumber production.

2.     Determine the effect of fungicides spray regime on the control of cucumber diseases.

3.     Determine the response of cucumber lines to disease manifestation.

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