Eggplant Integrated Pest Management AN ECOLOGICAL GUIDE

___________________________________________________________________________________Major Agronomic Practices3.2.2 Resistant varietiesAnother important aspect to consider when selecting a variety is whether the variety is tolerant orresistant against certain insect pests or diseases. Growing a resistant variety is one of the best and mostenvironmentally safe methods of crop protection! Unfortunately, resistant varieties are not alwaysavailable. Also, resistant varieties are usually not resistant to all pests and diseases that may occur.And to make it more confusing: term resistance is explained differently by different researchers. Forexample, in a study in India, the eggplant Pusa Purple Cluster was considered resistant to bacterial wiltwhen less than 20% of all plants wilted (Gopalakrishnan, 1985). Other studies testing resistance to fruitand shoot borer (FSB) stated the variety was resistant with less than 15% FSB infestation (Tejavathu,1991). Others may stick to a 0% infection.Data from TOT and FFS field studies in Philippines showed that hybrid eggplant varieties were moretolerant to pest and disease infestation, and especially to the fruit and shoot borer, as compared to openpollinated varieties (pers.comm. Carlito Indencia, 2001).Resistant variety: an insect pest or disease cannot survive on the plant. Thiscan be due to long or sticky hairs on a plant that hinder an insect moving andfeeding on a plant, or due to the excretion of toxic chemicals by the plant, or theconstitution of the plant sap that make it less attractive to insects or diseases.Tolerant variety: an insect pest or disease can infect the plant but symptoms willnot be severe and the effect on yield will be none or minimal. However, infectedplants may become a source of infection for other fields!Susceptible variety: insects or diseases can attack the plant and this may resultin yield and quality loss.The following table lists a number of varieties that have been found “resistant” or “tolerant” to someinsect pests or diseases. It is emphasized that NONE of the varieties listed in this table is 100% resistant.All studies compare a number of eggplant varieties, and from this comparison, the least susceptiblevariety has been marked as “resistant” or “tolerant”. However, the difference in susceptibility betweeneggplant varieties can be considerable (e.g. 5% FSB infestation in resistant versus 60% in susceptiblevarieties!). The table gives examples of variety names as inspiration for setting up a varietal trial in yourown field. See box below.Insect/Disease Resistant/ Country VarietiesReferenceTolerant reportingLittle leaf disease resistant India Chaklasi doli, Doli-5, Pusa Jyani, 1995purple clusterBacterial wiltresistant India Surya, Swetha, Annapurna, Singh, 1998(Ralstoniasolanacearum)Arka KeshavBacterial wilt resistant India Arka Kesev, Arka Neelkanth Chaudhary, 1999Bacterial wilt tolerant Bangladesh Khotkhatia Long, KG Begun, Mondal, 1991Planpuni, Singnath,Pusakanti, Uttara, IslampuriBacterial wilt tolerant Bangladesh Jhumka pers.comm. Md. AtiurRahman,200110Eggplant Ecological Guide