Control action threshold for Tuta absoluta (Lepidoptera: Gelechiidae) in tomato raised under greenhouse in Tunisia

A study was conducted in Saheline region of Tunisia to compare 8 alternative
strategies for the control of the tomato borer, Tuta absoluta under greenhouse during
the cropping cycle of tomato in 2010. The intervention protocols (strategies) included
(1) ST1 = density of 1-4 mines or larvae per plant , (2) ST2 = density of 4-8 mines or
larvae per plant , (3) ST3 = 8-16 mines or larvae per plant (4) ST4= superior to 16
mines or larvae per plant, (5) ST5 =systematically sprayed with chemicals, (6) ST6=
systematically sprayed with organic product (spinosad), (7) ST7 unsprayed (control)
and (8) ST8 = Sprayed alternatively with conventional chemical and plant extracts.
The alternatives were evaluated with (1) the density of T. absoluta biological stages
(eggs-pupae) in tomato leaves, (2) the percentage of larval mortality and (3) the fruit
quality (the percentage of infested fruits).
Results demonstrate the good performance of spinosad (ST6) in the reduction of fruit
infestation. There is a difference between ST1, ST2, ST4 and ST5 regarding the larval
density suggesting to shift from systematically chemical spray to spraying when
population densities reach more than 16 mines or larvae per plant (ST4). The strategy
8 (combination chemical – organic sprays) seems to be better than Strategy 5
(chemical control only) suggesting the need to integrate plant extracts as soft
insecticides in the integrated pest management of the tomato borer.