Eggplant Integrated Pest Management AN ECOLOGICAL GUIDE

__________________________________________________________________________________Major Diseases of EggplantRelated exercises from CABI Bioscience/FAO Vegetable IPM Exercise Manual:3-A.1. Study of symptom development of leaf spots: classroom exercise3-A.2. Study of symptom development of leaf spots: field exercise3-A.3. Effect of infection of the seed bed3-A.4. Effect of the use of infected planting material3-A.9. Test effect of infected crop debris in the field3-A.10. Effect of rain on the spread of leaf spot3-A.14. Restricted fungicide use to manage leaf spots3-C.1. Symptom development of fruit diseases: classroom exercise3-C.2. Symptom development of fruit diseases: field exercise3-C.3. Use of healthy seed3-C.4. Test of seed health3-C.5. Test effect of hot water seed treatment3-C.6. Transfer of a fungal fruit disease3-C.7. Transfer of a secondary bacterial fruit disease3-C.8. Test different cultivars for resistance to fruit diseases8.3 Wilt8.3.1 Bacterial wilt - Ralstonia solanacearumSee photo 19 (page 177).Causal organism: bacterium – Ralstonia solanacearum also calledPseudomonas solanacearum.Other names for this bacterial disease are southern bacterial wilt,brown rot and blight.The disease affects several plant species, mainly family of theSolanaceae (tomatoes, potatoes, eggplants, tobacco, peppers) andpeanuts. There are also several weeds that can be affected bybacterial wilt.Signs and symptomsThe disease is characterized by sudden plant wilting without leafyellowing. Stem centers and roots become water-soaked and laterturn brown. Sometimes, the stem centers become hollow. Also rootsare formed on the stem. As the browning and root decompositionprogress, the amount of wilting and dying of the leaves increasesuntil the plant is killed. This process may go very quickly. Whenrecently infected stems or roots are cut crosswise and squeezedtightly, a dingy gray to yellowish fluid appears. This fluid is calledooze and contains many bacteria. Woody stem tissue turns brownand roots may start to form on the stem. Soft rot bacteria may enteraffected plant parts.Tolerant plants may show only dwarfing or slow decay of the roots.Bacterial wilt: the arrows show twopossible entry sites for bacteria intomato(from: Blancard, 1992)Source and spreadThe bacterium is soil-borne. It can survive for a long time in the soil. The bacteria can also survive in cropresidues, some weeds, and in water. The bacteria can be spread by infected seed, transplants andcutting knives or other field tools. It can also spread from infected higher level fields to lower level field inirrigation or ground water. Nematode infections increase the severity of wilt.The bacteria enter plants through wounds made by tools, soil insects, broken roots on transplants andthrough natural openings where secondary roots emerge. Several nematode species that suck on theroots of plants such as the rootknot nematode (see section 8.1.3) can increase the incidence of wiltbecause they create entry points for the bacteria. Symptoms appear within 2 to 8 days after infection,depending on temperature, plant age and susceptibility of the variety. The bacteria reach the vessels and146Eggplant Ecological Guide