Double dose

The tomato moth is considered the most important pest of tomato crops. The larvae undermine the leaves and pierce the fruits, making them unusable for consumption. Various insecticides are used to control it and, when the population is high, up to three sprays are usually made per week.

The large borer, another tomato pest, is considered secondary. The larvae destroy the pulp and, in the absence of control, can cause losses of up to 80% of production. Currently, this insect has little economic importance, since the insecticides used to control the tomato moth normally also control the borer.

As the number of insecticide applications for pest control in tomatoes is exaggerated and this practice has caused several problems such as insecticide residues in food, intoxication of applicators and environmental pollution, methods that eliminate or reduce the use of these products have been sought.

is an egg parasitoid of tomato moth and large borer. When associated with bioinsecticide

has significantly reduced tomato moth damage. However, the constant use of

may lead to the selection of moth populations resistant to the bioinsecticide. Therefore, it is necessary that efficient insecticides to control this pest, with low toxicity and low impact on

, are available.

In an evaluation of the efficiency and selectivity of the insecticides chlorpyrifos, methoxyfenozide, thiacloprid and triflumuron, carried out at Embrapa Hortaliças, it was found that all insecticides controlled the large borer. While non-sprayed plants had 20% of their fruits damaged, sprayed plants had less than 5% of damaged fruits. The insecticide methoxyfenozide was selective to the parasitoid

, as the percentage of parasitized large borer eggs was not significantly affected (Figure 1 -

).

The neonicotinoid thiacloprid and the growth regulator triflumuron significantly reduced the percentage of borer eggs parasitized by

, and are therefore not considered selective (Figure 1). It is worth mentioning that thiacloprid is an efficient product for controlling whiteflies in tomatoes. Therefore, in areas where

is being released for tomato moth control, the possible application of the product for whitefly control must be carefully evaluated.

None of the insecticides evaluated were efficient in significantly reducing tomato moth damage. The percentage of brocaded fruits in the control treatment was 33%, while for the insecticide treatments, this percentage varied from 31% (methoxyfenozide 144) to 54% (chlorpyrifos 675). The causes of these results may be several, including: a) resistance of the pest to the products used. In the Federal District, it has already been observed that commercial doses of phosphorus insecticides and growth regulators did not control the pest; b) limited access of the insecticide to the pest. This may be due to areas of the plant that are not covered by the insecticide, or even due to the lack of translaminar action of the insecticide, as in the case of triflumuron and methoxyfenozide, where larvae inside the mines would not be reached.

In summary, it was found that all insecticides tested were efficient in controlling the large borer, but none were efficient in controlling the tomato moth. The insecticide methoxyfenozide did not affect the parasitism rate of large borer eggs by

, therefore being considered selective.

Embrapa Vegetables

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