A pot trail was conducted in order to study the influence of four organic acids i.e. salicylic , citric , oxalyic and
humic acids at two concs.0.1& 0.05% in comparison with oxamyl against Meloidogyne incognita infecting tomato
cv.9065FI under greenhouse(24±2C◦).Results indicated that all tested treatments clearly improved tomato plant
characters and reduced nematode development. Among the organic acid tested, salicylic acid at the two concs. surpassed
other application in values of percentage increase of plant length (23.37&40.54%), number of leaves (28.03&55.3%),
number of branches (16.7&54.2), total plant fresh weight (32.3&57.23%) and shoot dry weight (25.2&33.84%), and
achieved the highest percentage reduction values of final nematode population(78.08%), number of egg- masses
(89.47%), respectively. In the mean time, oxalic acid applications gave the least values in this respect comparing to the
check. Salicylic acid and humic acid at 0.05% since their eggmasses indices were in par (2) vs (4) for nematode alone.
Among tested concentrations , 0.1 g/L of such organic acids was higher in values of N, P , K , C , O.M and total
chlorophyll as compared to nematode alone , whereas the concentration of 0.05g/L of the four organic acids ranked first
in percentage increase values of total phenol which were amounted to 8.39 , 6.36 , 4.43 and 2.68% for salicylic , citric ,
oxalic and humic acids comparing to nematode alone , respectively.
Keywords: Salicylic , citric , oxalyic, humic, acid, Meloidogyne incognita, nematode , oxamyl.