Eggplant Integrated Pest Management AN ECOLOGICAL GUIDE

__________________________________________________________________________________Major Diseases of Eggplant• Grow seedlings in pots to avoid injury to roots while transplanting.• Use of compost may reduce bacterial wilt. This may be due to sanitation (removing all crop residuesfrom the field for composting – including all diseased materials and weeds) and due to improving thesoil structure and fertilization. High organic matter in the soil improves conditions for micro-organismsincluding antagonistic organisms that may work against Ralstonia bacteria. In USA, experiments attwo sites in Florida showed that (amongst other treatments) mushroom compost also reducedbacterial wilt disease incidence of tomato compared to controls (Peet, www1).Effects of compost on bacterial wilt: experiments from VietnamIn Vietnam, farmers found that adding compost (19 tons/ha) to the planting hole of cucumber reducedwilt incidence and increased yield by 80%! Pesticide applications were reduced from 9 to 5 perseason. This resulted in an astronomical increase in profits! ☺Potting experiments on the effect of compost on bacterial wilt in tomato, showed that compost couldsuppress disease development and spread. ☺(FAO – PAR on soil-borne diseases in tomato, March 2000)• Soil amendments: The effect of adding dry powders and crop residues of onion, and garlic cropresidues as soil amendments for the control of bacterial wilt has been studied by the AVRDC,Taiwan. They found that adding 1% dry Welsh onion powder (not including roots) to the soil of pottedtomato plants significantly reduced bacterial wilt. The effect in field trials, however, was no sodistinct. It may be an interesting option for testing in your own field. Effect of crop residues of onionor garlic may also be tried.Good suppression of bacterial wilt has been achieved by incorporation of mustard green manure inthe soil (see section on biofumigation 3.10.1.4). In Dhaka region, Bangladesh, good results havebeen obtained with incorporation of mustard oil cakes and with poultry refuse in both seedbeds andmain field (pers. comm. Md. Atiur Rahman, 2001).Once disease symptoms are found:• Control of bacterial wilt is extremely difficult because the pathogen can remain viable in the soil formany years. In some areas, soils could not be used for solanaceous crops due to heavy bacterial wiltinfection.• Pull out infected plants including roots and attaching soil, remove them from the field and destroythem. This may reduce further spread of the bacteria.• Crop rotation may be useful for soils with bacterial wilt. However, the wide host range of bacterial wiltincludes all solanaceous crops and peanuts which severely limits crops that can be used in rotations.In Sri Lanka, crop rotation of tomato with paddy rice effectively controlled the bacterial wilt becausethe wilt is unable to survive in a field that has been flooded. In India, the following rotations reducedbacterial wilt incidence in eggplant: maize-okra-radish; maize-Vigna sp.-maize; okra-Vigna sp.-maize; or Eleusine coracana-eggplant (wilt-resistant cv. Pusa Purple Cluster)-Phaseolus vulgaris.(Sohi, 1981)Effect of crop rotation on bacterial wilt infection of tomato: a demonstration from VietnamIn Tan Tien village, Hai Phong province, a demonstration plot was established to show the effect ofcrop rotation in a bacterial wilt infested field. The crop grown previously was potato and it had beenaffected by bacterial wilt. The field was split into two: one half was planted with sweet potato (not asolanaceous crop), the other half with tomato. The sweet potato plot looked very healthy. Thetomato plot was severely affected with about 40% (visual estimation) of the plants lost due tobacterial wilt.This demo-plot clearly showed why it is necessary to rotate crops of different families!(pers.observation F.Praasterink, April 2000)• A fallow period of several months, including weed control, was reported to be effective in somecountries.148Eggplant Ecological Guide