Eggplant Integrated Pest Management AN ECOLOGICAL GUIDE

___________________________________________________________________________________Major Agronomic Practices3.11.3 Planting densityPlanting density varies according to variety, soil fertility, soil moisture and farmer’s objectives.The planting density has an effect on crop production and susceptibility to diseases. Wider crop densitiesresult in more space and nutrients to one plant, which will usually result in more fruits and a higher fruitweight per plant. In a study with tomato, it was found that the fruit numbers and fruit weight per plantincreased more with wider plant spacing than with wider row spacing (AVRDC, 1987). However, highyields can also be a result of high plant population and high fruit numbers.Planting density also has an effect on the climate within the crop. In a close planting, wind and sunshinecannot reach to the soil level and as a result, the lower leaves of the crop stay wet longer. This canstimulate disease infection because many diseases need water to infect the plant. When seriousproblems are present with a pathogen, for example early blight, an option would be to plant at a widerspacing. This will keep the plant dryer and this prevents spores (the ‘seed’ of a fungus) from germinatingand infecting the plant.In addition, pest insects such as red spider mites (Tetranychus sp.) can easily walk from one plant to thenext when leaves of adjacent plants touch.For example, data from Agro Ecosystem Analysis during a Farmers’ Field School in Negros Occidental,the Philippines (1998/1999), showed that more insect pests and more mechanical damage from fieldoperations were observed in the “high density” eggplant field (pers.comm. Carlito Indencia, 2001).Some factors related to spacing are listed in the table below.Narrow spacingmore plants per area = higher initial costssmaller plantsmight increase disease incidencemore plants = (possibly) more fruits, butsmaller sizeWide spacingfewer plants per area = lower initial costslarger plantsmight reduce disease incidencelower plant numbers but fruit numbers and fruitweight per plant may increaseEggplants are typically established in 60 – 90 cm rows with 45 – 60 cm between plants, depending onthe variety (smaller growing or larger growing type) and the planting method (single row or double-triplerow planting). The time required to reach maturity depends on variety and climatic conditions.Spacing: space for variationSpacing is much determined by local tradition and varieties grown. In Bangladesh for example,spacing of eggplants varies with area:Mymensingh practice 60 x 60 cmRangpur and Delampar 75 x 60Chittagong 100 x 75Jessore 100 x 100(pers. comm. farmer Yousuf, Jessore, Bangladesh, 1998)3.11.4 MulchingMulching means keeping the soil surface covered with non-transparent material. Mulching reduces weedgermination and it will keep the soil cool and moist because the sun cannot shine directly on the soil.Organic mulch can provide shelter for predators such as ground beetles and spiders. Mulching can bedone both on the nursery after sowing (also to prevent birds from eating the seed) and after transplantingin the main field. Mulch on the nursery usually needs to be removed once the first seedlings havegerminated.39Eggplant Ecological Guide