MMSU researchers find plant extracts effective in controlling pests, diseases

Batac CITY—Researchers at the Mariano Marcos State University (MMSU) have found an easy way to make pesticides and fungicides from plant extracts which are effective in controlling common insect pests and diseases attacking high value commercial crops.

Leticia A. Lutap and her co-workers found that extracts derived from snake weed, yellow ginger, betle, banana bush, Mexican poppy, lantana, sticky spider flower, aloe vera, garlic wastes, and tibak leaves contain substances effective in controlling tomato fruitworms, thrips, mites and beetle pests; and diseases like tomato blight, purple blotch  and cercospora leaf spot on garlic.

These pests and diseases, according to the researchers, are known to reduce the yields of farmers by as much as 40 to 90 percent. Tests showed that compounds present in these extracts have ovicides, insecticides, and anti-feedants properties. Ovicides kill eggs of insect pests, while anti-feedants destroy the pest’s appetite on the host plant.

When applied as biological pesticides and fungicides, the plant extracts have markedly reduced the pest’s growth such as the number of larval and pupal days and the premature mortality of treated larvae. The formulated products are as effective as the commercial chemical pesticides and fungicides commonly used by farmers.

Tomato is usually attacked by fruitworms. Although foliage feeding of the newly hatched larvae in tomato may not cause any significant damage, yet the holes they cause in fruits will result in yield loss up to 70%. Thrips and mites, which are known vectors of viruses also cause damage to sweet and finger peppers. High population of these pests produces leaf curls, distortion of plant growth, lower deformation, and wilting.

Beetle is now becoming a major pest in eggplant and the most prevalent pest of other high value commercial vegetables especially towards the onset of rainy seasons. Both the larva and adult damage the plants by eating the leaf tissues between the veins causing the skeletonized leaves to dry up. Also, tangle top disease infestation caused by mites can reduce garlic yield by as much as 40-50%, and thrips by as much as 50%.

On the other hand, the Ilocos garlic industry is slowly collapsing due to low yield caused by purple blotch and cercospora leaf spot diseases. Tomato production is also being adversely affected by blight disease which is being triggered by hot and humid weather. Unless controlled, the disease can cause 90-100% yield loss.

Generally, farmers use synthetic chemical pesticides to abate pest incidence in the absence of alternatives. Moreover, its use has been an important part of pest management for many years, but with known disadvantages and risk. Some synthetic pesticides leave unwanted residues in food, water and the environment. Some are suspected carcinogens and low doses of many insecticides and fungicides are toxic to mammals.

This predicament has resulted in the researchers’ search for less hazardous alternatives to conventional synthetic insecticides – and they found the plants’ extracts. Thus, the researchers recommend the commercial production of these biopesticides and biofungicides to have alternative solutions to the unabated increase on the prices of chemical outputs in agriculture.

“This breakthrough will not only provide leads in synthesizing new structural types of pesticides and fungicides that are relatively safe to man and environment, but can also veer away the use of expensive and limited supply of these chemicals,” the researchers said.

“With the increasing concern for environmental safety and human health, development of alternative control methods for crop production such as the use of biopesticides against major pests of vegetable crops is necessary,” they added.

To produce biochemical pesticides and fungicides, the plant extracts -- which have pheromones, plant hormones, and natural plant-derived regulators – are mixed with clay, potassium bicarbonate and enzymes which serve as active ingredients.

The researchers said that for every pest and disease that attacks their crop, there is a corresponding combination of plant extracts and an amount of formulation that will be used. The following are combinations of plant extracts and their usage:

To control tomato fruitworm, use the extracts derived from sticky spider flower, Mexican poppy, snake weed, banana bush and goat manure tea (GMT). As repellant and anti-feedant, use the combined extracts of snake weed, yellow ginger, betle, banana bush, and tibak leaves, while aphids and sucking insects can be controlled by extracts of yellow ginger, and garlic wastes.

Mix 10 to 15 tbsp. of the extracts with 16 liters of water, a volume just enough for one knapsack sprayer tank. Spray the solution evenly preferably during late hours in the afternoon. Mix thoroughly before application. Repeat application every 5 to 7 days if necessary. Frequency of spraying can be increased or decreased depending upon the pest infestation.

To control early symptoms of plant diseases such as tomato blight, combine the extracts of garlic wastes, yellow ginger, and aloe vera. Mix 15 to 20 tbsp. of the combined extracts with 16 liters if water and spray it to the plants at 30 days after planting (DAP) at 5 to 7 days interval.

For purple blotch and cercospora leaf spot on garlic, combine the extracts of tibak leaves, yellow ginger, lantana, and aloe vera. Mix 15 to 20 tbsp. of the combined extracts with 16 liters if water and spray it to the plants at 30 days after planting (DAP) at 5 to 7 days interval. The best time to spray the solution is during the late hours in the afternoon.

The researchers clarified that these biopesticides and biofungicides are used primarily as preventive measures, so they may not perform as quickly as some synthetic chemical pesticides do. However, these are generally less toxic to farmers and non-target organisms, making them desirable and sustainable tools for pests and diseases management. The findings will help reduce the incidence of pests and diseases and the health hazards caused by the adverse residual effects of commercial synthetic pesticides and fungicides.

Results also showed lower disease intensity and higher marketable yields by the crops sprayed with plant extracts. Shelf life of the reformulated products also showed potency until six months of storage at room temperature.

In October planting of garlic, for instance, the crop gave 2.94 to 3.10 tons per hectare when sprayed with biofungicide, which was comparable with those sprayed with chemicals which gave 2.89 tons per hectare. Also, disease severity was reduced which rendered the plants to produce bigger and quality bulbs.