Usually harmless insects, under extreme conditions, gather in massive swarms and annually destroy hundreds of thousands to millions of tons of grain. Using insecticides against them is challenging, but the problem must be addressed. Recently, scientists have proposed a new method of control that also helps increase crop yields.

Locusts: A Threat to Crops

From a scientific perspective, the term "locust" refers to several species within the Acrididae family, which, when faced with resource shortages or overpopulation, form large migratory swarms numbering in the hundreds of millions. When these swarms land on fields, they can destroy up to 80% of the crops, and sometimes even more. Across an entire country, locusts rarely destroy more than 10% of grain crops, but the local damage along their migration routes can be catastrophic.

Unlike other pests, combating locusts with insecticides is difficult: their migration routes are unpredictable, and it is hard to quickly distribute the necessary amount of chemicals across vast fields once a threat emerges.

An Alternative to Insecticides

An international team of scientists set out to find an alternative way to control locusts, particularly the Senegalese grasshopper, which regularly damages agriculture from West Africa to India. The results of their work were published in the journal Scientific Reports.

Since locusts require large amounts of carbohydrates during their migrations, the researchers attempted to alter the nutrient balance in cultivated plants. To do this, they conducted a field experiment on one hundred hectares of millet in Senegal: some fields were heavily fertilized, mainly with nitrogen-based fertilizers, while adjacent plots of the same size were left untreated. The fertilizers were applied according to a specific schedule: three treatments with NPK (nitrogen-phosphorus-potassium) and two with urea.

Experimental Results

The fields were surveyed three times: before fertilization, during, and after. The results varied across different plots, as even within the same region it is difficult to predict where locusts will be most numerous. Nevertheless, on average, the locust population on treated hectares decreased during the fertilization period, and even more so afterward (by tens of percent). Millet yields on the treated plots also increased by tens of percent. However, it is difficult to determine whether this was due to protection from locusts or simply the effect of the fertilizers.

How the New Approach Works

The protective mechanism is not related to toxicity for insects. Plants that receive more nitrogen synthesize proteins more actively, increasing their proportion in the plant's mass, while the carbohydrate content decreases. For humans, who are naturally omnivorous, an increase in protein in the diet is not a problem. However, locusts, as obligate herbivores, suffer from a lack of carbohydrates, which they need for migration.

Advantages of the Method

The new method of controlling locusts does not require the urgent application of large doses of insecticides, reducing the logistical and operational burden on farmers. Fertilizers can be applied in advance, annually, without haste or overload. Even if locusts do not appear, the costs of fertilizers are offset by increased crop yields.