How to stop deadly tomato moth before it destroys crop
A teacher who does not know the bullies in his class will not be able to control the students. Likewise, a farmer who does not know the pests in his farm will not be able to prevent damage on his crops.
Effective crop protection starts with timely and correct identification of the pests in the field. For a farmer to effectively control Tuta absoluta, he must detect the pest early. Detection of weeds, diseases and pests is often referred to as “crop scouting”.
Scouting of pests can be done visually by inspecting the crop. With Tuta absoluta, however, this might be a challenge because the adult moth is only active during the night. In addition, the eggs are only 0.5mm, therefore, it may be difficult to see with naked eyes.
When you notice the destructive stage of the Tuta absoluta -the caterpillar stage – it is already too late as the damage is done.
Thus, to detect the presence of Tuta absoluta early, it is necessary to trap the moths before they start causing problems.
You can use pheromones to lure them and then catch them using a delta-trap. When a female moth wants to mate, it will send out specific pheromones that attract only male Tuta absoluta moths.
A pheromone-based trap makes use of a copy of chemicals stored in a rubber lure. Once outside its original packaging, the lure will start emitting pheromones over a six week period, which will attract male Tuta absoluta moths to the trap and they will be caught on the sticky surface at the bottom of the gadget.
It is highly unlikely that additional moths will come into the field due to the trap’s limited attraction range. Early in the season, two traps should be placed per acre of tomatoes. The farmer should count on a daily basis the amount of moths that are caught in the traps. It is important to keep a record of the counts.
When three moths or more are caught in one trap in a week, the farmer should start control measures like use of pesticides.
At this moment, the amount of traps should be increased to about eight to 10 per acre. Those eight can be delta-traps or water traps. The latter, which a farmer can construct himself, use water with some soap to catch the pests.
If catches are above 30 moths per trap a week, the number of traps should be increased to 20 an acre. Lures should be replaced after six weeks, water traps should be refilled with water and soap twice a week during hot periods.
When buying lures, it is important to note the amount of active ingredients each contains. Most lures in the market contain 0.5mg active ingredient. Stronger lures that contain 0.8mg can give up to three times as many catches.
The lures used by the Ministry of Agriculture to determine the presence of Tuta absoluta in Kenya were called “Tutrack lures” and also contain 0.8mg of active ingredient.
To get a good control, it is also important to target more than one stage of the Tuta absoluta. With the trapping system, the farmer already targets the moth stage of the caterpillar. By using spray insecticides, the farmer targets the caterpillar and there are products that kill the pests in the egg stage.
The more stages targeted, the more effective the control will be. When using spray insecticides, it is important to keep note of the Pre-Harvest Interval (PHI) period of the used products. PHI refers to the number of days that must lapse after the pesticide application before the farmer can harvest the produce.
RESISTANT TO CHEMICALS
To target the caterpillar stage of Tuta absoluta, the farmer might use Runner (methoxyfenozide), Radiant (spinetoram) and Coragen (chlorantraniliprole) pesticides. Runner has a PHI of 14 days, Radiant three days and Coragen a day.
Several weeks before the first harvest, a product such as Runner with a longer PHI can be used.
After two weeks, if catches in the traps are not going down, the amount of traps should be increased to 20 per acre, and also a product with a shorter PHI such as Radiant can be used. When catches are still high closer to the start of harvest, it is important to use insecticides with very low PHI such as Coragen.
Tuta absoluta often develops resistance to chemicals. It is, therefore, important to interchange insecticides.
Moths will not develop resistance against pheromone traps, these can thus be used continuously, including during harvest. It is even advisable to keep using traps up to three weeks after harvest to reduce the amount of Tuta absoluta for the next planting of tomatoes.
Koppert Biological Systems Ltd
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