Abstract
Incidence and severity of phomopsis blight and fruit rot of eggplant (Phomopsis vexans) in Bangladesh varied with location, soil type and environmental factors. Incidence and severity of the disease ranged from 2.00% to 56.66 % and 0.65% to 12.62%, respectively in 23 locations where the eastern and south eastern areas of the country appeared to be more prone than the western parts. The disease is favoured by moderate air temperature (24.8 - 25.5 °C), slightly acidic soil (pH 5.3 5.8), moderately high RH (65% to 75%), sandy loam soil, low soil temperature (16 - 20 °C) and low soil moisture (45 - 65%). Incidence of P. vexans on farmer's seeds collected from different growing areas of Bangladesh varied from 0.0% to 7.5%. Variation exists among the isolates of P. vexans collected from core eggplant growing areas of the country and the isolates were grouped into five distinct groups based on their cultural properties. Eggplant cultivars/entries showed differential reactions against P. vexans. Percent disease index (PDI) of fruit ranged from 0.0% to 68.49% among the 42 accessions where 11 cultivars were found highly susceptible (HS), 15 cultivars susceptible, 7 cultivars moderately susceptible while cultivar Katabegun and wild accession were resistant (R). Seed selection had a significant impact on the incidence of P. vexans and use of apparently healthy seed was found effective in controlling damping off, tipover and seedling blight of eggplant caused by P. vexans. The least incidence of P. vexans (0.75%) and the highest germination (86.75%) were recorded in apparently healthy seed as against 6.5% seed infection and 58.00% seed germination recorded in farmer's seed. Hot water seed treatment at 56 °C for 15 minutes completely controlled P. vexans and increased seed germination by 53.8% over control. Out of 11 botanicals, garlic (Allium cepa L) bulb and allamanda (Allamanda cathertica L) leaf extracts were found promising arresting mycelial growth and inhibiting spore germination of P. vexans in invitro and controlled phomopsis blight and fruit rot of eggplant in the field significantly. Among 14 bioagents, Trichoderma harzianum CP, Trichoderma harzianum T22 and Trichoderma sp EP-1 were found effective against P. vexans in invitro and in the field condition. Field spray of T. harzianum CP and T. harzianum T22 reduced 82.35 83.33% leaf infection and 75.82 79.25% fruit infection, respectively in eggplant cultivars Dohazari and Laffa S over control. For multiplication of Trichoderma spp., peat soil based formulation combined with black gram and water in 1:1:2 ratio was found suitable for maximizing CFU/g and minimizing the time of sporulation. Bavistin (50% carbendazim) even at 50 ppm concentration completely inhibited mycelial growth of P. vexans in the laboratory and effectively controlled phomopsis blight and fruit rot of eggplant in the net house and in the field at 0.1% concentration. Combinations of apparently healthy seed (T2), seeds treated with garlic bulb extract (T3) and soil treated with T. harzianum CP (T11) completely controlled damping off, tipover and seedling blight in the nursery bed in the net house and increased germination by 48.83% over control. For the integrated effect of IPM components in the field, spraying of either garlic bulb extract (1:1) or allamanda extract (1:1) or Bavistin (0.1%) in combination with soil treatment with T. harzianum CP or T. harzianum T 22 was the suited approach in controlling phomopsis blight and fruit rot of eggplant that reduced considerable leaf infection, flower infection, and fruit infection by 89.35%, 83.62%, 93.50%, respectively and increased yield up to 292.68% in cultivar Laffa S over control.