Eggplant Integrated Pest Management AN ECOLOGICAL GUIDE

__________________________________________________________________________________Major Diseases of EggplantOnce disease symptoms are found:• Infected plants, including all roots, should be removed and burnt outside the field. This will noteliminate the nematodes from the field but it will reduce population growth.• Antagonistic fungi may be available for control of rootknot nematodes. See section on naturalenemies above. Check with local extension service for details.• Grafting is sometimes practiced to overcome rootknot and other soil-borne diseases such asbacterial wilt. The eggplant variety can be placed on a rootstock of the “wild” eggplant varietySolanum torvum, which is resistant against rootknot nematodes and bacterial wilt. See section 3.13.• There are pesticides that can kill nematodes. These are called nematicides. Efficacy of thesepesticides is doubtful as the nematodes can be present in deeper layers of the soil and they can beprotected by plant roots, reducing the effect of nematicides.Points to remember about rootknot nematodes:1. Rootknot nematodes cause problems in many (vegetable) crops due to their broad host range.2. A number of cultural practices are effectively preventing or reducing infestation, the main onesbeing use of resistant varieties, and the incorporation into the soil of fresh organic matter.3. There are several antagonistic fungi that work against rootknot nematodes. These may becomeavailable over the next years.Related exercises from CABI Bioscience/FAO Vegetable IPM Exercise Manual:3-D.1. Pot experiment to test whether root diseases are soil-borne3-D.2. Use of subsoil to manage root disorders in the nursery3-D.3. Steam sterilization of soil for the nursery3-D.4. Soil solarization to manage root diseases in the nursery3-D.5. Test effect of soil solarization in the field3-B.12. Test different cultivars for resistance to wilt diseases8.2 Leaf spot, blight, leaf deformation and fruit rotThe cause of blight, spots, leaf malformations, and discoloration….“Blight” implies sudden and extensive damage to the leaves. In many leaf diseaseshowever, the affected area is limited which gives the appearance of spots. Thesespots may be big or small depending upon the organism responsible for causingthem, and the environmental conditions. Blight and leaf spots can be caused bydifferent pathogens such as fungi, bacteria, and viruses. Leaf spots can also becaused by unfavorable water relationships or temperatures, mineral deficiencies orexcesses, insects or pesticides.In the field, the difference between the various causes for blights and leaf spots is notalways easy to make, especially with early symptoms. It is stressed that for a properdecision on the management of leaf spot caused by pathogens, it is not alwaysnecessary to be able to distinguish the different causal organisms. Most fungal andviral leaf spots will need similar management practices, mainly reduction of thesource of infection by sanitation. See sections on individual diseases and check thekey table in chapter 10.It is necessary, however, to distinguish between spots and blight caused by pathogens and those causedby other factors such as unfavorable water relationships or temperatures, mineral deficiencies orexcesses, insect damage or pesticide injury to the plant. See section 7.6 for a list of questions that mayhelp finding the cause of the “blight”.138Eggplant Ecological Guide