Eggplant Integrated Pest Management AN ECOLOGICAL GUIDE

___________________________________________________________________________________Major Agronomic Practicesfermentation, several degradation products are formed and after some time, a biogas, methane, isformed in addition. Also, the concentration of carbon in the soil increases. The fermentation products, thebiogas methane and the carbon are thought to play an important role in the suppression of some soilpathogens and nematodes. The effects are better at higher temperatures.In small scale field trials in the Netherlands, the effect of this method was studied on survival of the soilbornefungus Fusarium oxysporum. The organic matter used was grass (40 tons/ha) or broccoli. Resultsshowed that good control was achieved in the soil layer where plant material was present. Below thislayer, the effect disappeared. It is planned to test the method on larger scale production fields.Similar studies showed that biological soil sterilization was effective against the many soil-borne fungi:Fusarium oxysporum, Rhizoctonia solani and R. tuliparum, Verticillium dahliae, Sclerotinia sclerotiorumand different nematode species (Meloidogyne and Pratyenchus).This soil sterilization method can be combined with solarization (see section 3.10.1.2). Under the Dutchtemperate conditions (with low amount of sunshine), the plastic used was non-transparent to preventweeds from germinating under the plastic and produce oxygen, thus reducing the sterilization effect.However, when using transparent plastic under tropical conditions, the expectation is that the soiltemperature rises enough to kill weed seeds. When incorporating organic matter into the soil beforeplacing the plastic sheets, three effects may be obtained:• Soil sterilization by fermentation processes caused by degradation of organic material by microorganismsunder anaerobic (no oxygen available) conditions,• Soil sterilization by rise of soil temperature due to sunshine and plastic sheets,• Addition of organic material through the green manure crop to improve soil structure and soilfertilization.(Blok, 1998; pers. comm. Dr. W. Blok, Wageningen Agr.Univ., 1999).3.10.1.6 Boiled waterAlthough not proven, the use of boiling water for soil sterilization may be an option for soil sterilization. Afarmer from Bangladesh used this method: he boiled water and pored it one to three times over thenursery soil to kill pathogens and possibly insects and/or nematodes in the seedbed. He let the soil drainand cool down before sowing the seed (pers.comm. farmer Chittagong, Bangladesh, 1998).It would however be advisable to set up an experiment (possibly with pot trials) to test if this methodwould be appropriate for your area.To see if any of these soil sterilization methods work in your field,set up an experiment to compare the method against the common practice!3.10.2 SowingEggplant can be sown directly in the field or sown in a nursery and transplanted later. Usually,transplanted eggplants show earlier ripening and give higher yields than directly seeded ones. Therefore,most commonly, eggplant is sown in a nursery. This nursery should be located at a sunny place wherethe soil is not too wet. High humidity may provoke diseases like damping-off which can destroy allseedlings in a very short time. If possible, the nursery should be sited on land which has not grownsolanaceous crops like eggplant, tomato, pepper or potato for 3 years or more. This is the most effectiveprecaution against the occurrence of (soil-borne) diseases.3.10.2.1 Flat field and raised seedbedsProper drainage and aeration are necessary to prevent soil-borne diseases like damping-off. A goodoption is to prepare raised seedbeds which will dry up more quickly than flat-field plantings.Compost can be mixed in the seedbeds to get a fine soil structure with sufficient nutrients. Make sure theseedbeds are properly leveled. Dig trenches between the seedbeds to facilitate drainage of the nursery.When nursery beds are prepared, it is best to leave the beds for about 10 days to allow the soil to settle.After 10 days, the seeds can be sown.35Eggplant Ecological Guide