Evaluation of Integrated Management Approaches against Citrus Nematode (Tylenchulus semipenetrans) in Pakistan

Present study was conducted to explore the nematicidal potential of different synthetic chemicals, biopesticides and antagonists against citrus decline. Effect of eleven chemicals, seven biopesticides and two antagonists on juvenile mortality was evaluated in vitro. Four concentrations (2S, S, S/2 and S/4) of each chemical were prepared on the basis of recommended dose for each chemical. Juvenile mortality of citrus nematodes was calculated after 24, 48 and 72 hour of exposure to chemicals. Rugby expressed maximum percentage of juvenile mortality at 2S, S, S/2 and S/4 concentration. Mortality percentage observed by Rugby, Furadan, Match and Cartap after 72 h at 2S concentration was (100, 100, 95.44, 88.23%) whereas at S/4 concentration mortality percentage was (76.32, 81.18, 62.15, 55.28%) respectively. Among biopesticides maximum percentage mortality observed by Proclaim and Cure after 72 hours at 2S concentration was (83.87, 80.44%) while at S/4 concentration it was (59.87, 57.38%) respectively. Cultural filtrates of two antagonist Trichoderma harzianum and Trichoderma viridi were evaluated at S, S/2 and S/4 concentration under lab conditions. Maximum mortality (88.42%) was observed when both antagonists were applied in combined treatment at S concentration after 72 hours of exposure. Two best performing chemicals, one biopesticide and one antagonist were evaluated under greenhouse against T. semipenetrans on Citrus jambhiri Lush (rough lemon) and their effect on plant growth and nutrient uptake was measured. Nitrogen uptake was measured by following micro Kjeldahl method. For phosphorus and potassium uptake absorbance of samples at 720 nm was measured with the help of spectrophotometer. Phosphorus was calculated by comparing standard curve already prepared while potassium uptake was assessed by flame photometer method after digestion. All the treatments were found significantly effective against citrus nematode but maximum plant height, stem diameter, number of leaves, root length, root weight, shoot weight, and number of feeder roots (90 cm, 2.4 cm, 102, 48.3 g, 12.1 g, 48.8 g and 70) as compared to control when Rugby, Furadan, Proclaim and T. harzianum were applied in combination. Similarly maximum uptake of Nitrogen (3.14) Phosphorous (2.44%) and Potassium (1.95%) was observed when all the treatments were applied in combination. The results of present study will be helpful in selecting the suitable chemicals for growers having problems of citrus nematodes in orchards.