Extent of pesticide use by crucifer farmers in Benguet and Mountain Province [Philippines] against Plutella xylostella L. and other insect pests of cabbage

The study showed that among vegetable growers in Benguet and Mountain Province [Philippines] and elsewhere in the country, crucifer farmers used the highest amount of pesticides. Some studies also showed that pesticide use on cabbage even surpasses cereals, fruits and vegetables, rice, corn, banana, pineapple, potato, onion, and even tobacco. Before biological control agents were introduced in these provinces, cabbage farmers solely relied on synthetic pesticides in controlling diamondback moth (Plutella xylostella L.). Resistance to virtually all potent and hazardous insectides available in the market was observed due to farmer's misuse and abuse of pesticides in terms of the frequency of application, volume and intervals between applications. These farmers used a total insecticides of 18.79 kg a.i./ha in wet season and 17.70 kg a.i./ha during the dry season in 5 years with an annual average of 1.697 kg a.i./ha (around P14,866) and 4.697 kg a.i./ha (around P41,147.52/ha) during the rainy and dry seasons, respectively. Now cabbage farmers in the areas where Diadegma had been introduced control DBM through this parasitoid and supplement with biological-based insecticides like Dipel, Thuricide, and other Bacillus thuringiensis (Bt) insecticides. They also sprayed with an average frequency of 17 times at weekly intervals during the rainy season; while in dry season when the population of DBM is high, they increased the frequency to 20 times and shortened at 5 days intervals. However, after the Diadegma were well etablished in the areas, the above frequency decreased to 5 and 8 times in wet and dry sry season, respectively; with longer intervals of about 20 days or more. Similar trend is also evident on other pesticides like fungicides and herbicides. The reduction of pesticide use of cabbage farmers from 1991 to 1994 is also reflected on pesticide volume imported and sold in Benguet and Mountain Province which declined to 20 percent, 23 percent, and 33 percent in 1992, 1993, and 1994, respectively. In contrasts, the price of pesticides have been increasing as chemical companies try to compensate the loss of marginal revenues caused by the decreased sales of pesticides. On the other hand, the cabbage production in terms of cultivated area and volume in Benguet province have also improved with its average harvested area of 6, 129.42 ha/yr. The average production volume is 105, 453 tons/ha during the dry season and wet season, respectively. This has reached 18.15 tons/ha, although few farmers reported to have harvested up to 25.2 tons/ha.