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M. Devi ¹, R. F. Niranjana ², N. Kalieswari ³

Affiliations
1 Department of Agricultural Entomology, Tamil Nadu Agricultural University, Coimbatore (T.N.), IN
2 Department of Agricultural Biology, Eastern University, Chenkaladi, LK
3 Department of Plant Pathology, Tamil Nadu Agricultural University, Coimbatore (T.N.), IN

Abstract

The sweet potato weevil, Cylas formicarius, constitutes a major constraint to sweet potato production and utilization in Africa. Host plant resistance/tolerance, mulching and varying harvesting dates could provide an approach that fits well into an integrated pest management programme of this insect pest. In this study, a trial was conducted to evaluate the effect of host plant, mulching with freshly harvested, dried and chopped up aerial parts of elephant grass (Panicum maximum), and the manipulation of harvesting date, on crop damage by the sweet potato weevil. Cylas formicarius incidence was observed to decrease with increase in mulching level. Also, significant cultivar variation with respect to Cylas formicarius tuber damage and the total number of tubers produced were recorded. Karur local (White) and Arun (White) were observed to be significantly less susceptible to the sweetpotato weevil. Harvesting date was also significantly different, with respect to the number of damaged tubers. More tubers were damaged when harvesting was delayed. Hence, using Karur local (White) or Arun (White), coupled with mulching at the rate of 3-5t/ha and harvesting at 104 DAP resulted in increased number of tubers and reduced sweetpotato weevil infestation in the field.

Keywords

Cylas formicarius, Sweet Potato, Mulching, Harvesting Date, Tuber Damage.

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N. Kalieswari ¹, I. Yesu Raja ¹, M. Devi ¹

Affiliations
1 Department of Plant Pathology, Centre for Plant Protection Studies, Tamil Nadu Agricultural University, Coimbatore (T.N.), IN

Abstract

A Leaf spot disease was caused by Alternaria alternata ten isolates were collected from the ashwagandha growing different regions of Tamil Nadu. The virulence of the isolates were tested based on the Per cent Disease Index (PDI) and symptom expressed on the foliar surface. The maximum disease intensity of 65.13 PDI was recorded in Chempatti (I₆) isolate. The minimum disease intensity was recorded in I₁₀ from Cumbum (36.83 PDI). Seven fungicides viz., carbendazim(0.05%), mancozeb (0.2%) copper oxy chloride (1%), chlorothalanil (0.2%), fosetyl (0.1%), Ridomil MZ (0.05%) and dithane M 45(0.05%) were tested against A. alternata. Among the fungicides, the minimum diameter of mycelial growth of A. alternata (0.75cm) and maximum percentage of inhibition (91.34%) were recorded in mancozeb (0.2%).

Keywords

Per Cent Disease Index (PDI), Fungicides, Alternaria alternata, Leaf Spot, Ashwagandha.

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