Pesticides and Neem Seed Kernel Extract on Blights and Tuta absoluta at Different Phenological Stages of Tomato in Hamelmalo Agricultural College, Eritrea

Abstract

Tomato in Eritrea is affected by nearly 30 diseases and insect pests among which blight, leaf curl virus, root-knot nematodes, powdery mildew, Tuta absoluta, Helicoverpa armigera, aphids, whitefly and red spider mites are the most important. In the field, experiments were conducted in Hamelmalo Agricultural College for two consecutive seasons (2015 and 2016) in a Randomized Complete Block Design with three replications. Treatments used were pesticides (mancozeb, dimethoate, deltamethrin) and aqueous Neem seed kernel extract and their combinations. Disease incidence (DI), Disease severity (DS) of blights and infestations of Tuta absoluta [Lepidoptera:Gelechiidae] were assessed at different phenological stages of the crop. Mancozeb alone was not so effective to reduce either DI or DS or damage of plants but it causes declining the number of larvae of T. absoluta at flowering stage. T11 showed the highest control of DI, DS and reduced the larval population of T. absoluta per plot and minimized the damage level. Among all the treatments, T11 and T9 were the most effective to reduce the damage of plants and minimizing the larvae of T. absoluta at fruiting stage. Neem extract had the least effect than all treatments.  Mancozeb (T1) and combinations of Mancozeb + Dimethoate + NSE (T11) gave significantly higher marketable yield than other treatments. The overall Cost-Benefit Ratio (CBR) was similar for all treatments during the two crop seasons, but the average CBR was higher for T11 whereas it was least for T3.