Chemicals no match for lanzones pest

KORONADAL CITY — A deadly pest bedevilling lanzones trees, resulting in lower yields and sour-tasting fruits, has spread to two towns in the South. Agriculturists, however, are hoping bio-control methods such as the introduction of pest-eating beetles could solve the problem. By the middle of the year, lanzones should have already flooded local markets in the Central Mindanao region but the infestation of mussel-scale insects hardly made the fruit visible on the stands. Pepito S. Leyza, regional crop protection center head of the Department of Agriculture, said the pests have spread from the towns of Magpet, Makilala and Kidapawan City to President Roxas and Kabacan, all in North Cotabato province. In September last year, mussel-scale insect (Lepidosaphes ulmi) infestations resulted in losses of P5 million to lanzones growers in the town of Magpet alone. The pests invaded at over 200,000 trees in 20 villages of Makilala — 15 in Magpet and 25 in Kidapawan. "The pests, which are difficult to control, might now spread to the town of Arakan," Mr. Leyza said. To date, he noted the pests have invaded 550,976 trees in North Cotabato. No figure for the damage, however, was given. Mussel-scale insects attack the leaves of the lanzones, eventually rendering the fruit with a sour taste. United Kingdom-based Kendall Bioresearch Services said the insects "attack many deciduous trees and shrubs, including apples and other fruit and ornamental trees. Infestations are most severe on older trees and may impair plant growth and vigor." Mr. Leyza said that spraying the infected trees with chemicals (Malathion 5 EC and Actara 25 WG) proved ineffective. "Weekly spraying did not give positive results because of the defense mechanism [of the pests] characterized by the waxy substance which covers the body during molting of the nymphal stage," he said. "Once the nymphs settled down, insecticide spraying is not effective [even] to female adults." Trunk injection using Actara 25 WG gave a positive result in the five-month test period. The pest population in two sites was totally wiped out but this was not followed through because of a change in the weather. A team from the University of the Philippines in Los Baños (UPLB), headed by Jose R. Medina, has recommended a natural tack to eradicate the infestation. Two species of beetles — the black and orange coccinellids — were found feeding on the pests. Samples of black coccinellid (Chilocoros nigrilus) were brought to UPLB for identification and were discovered to be voracious feeders. Mr. Leyza said the regional crop protection center has adopted the natural approach by mass-producing the two beetle species at their laboratory in Tacurong City. Reproduction of the beetles involves using squash as medium and coconut scale insect (Aspidiotus destructor), as host of the predators. Kidapawan City, one of the localities ravaged by the pest, has established a laboratory for the production of the beetles, Mr. Leyza said. He urged the Agriculture main office to provide funds for the setting up of more laboratories to reproduce the beetles that can easily multiply in a week to three weeks’ time.- BusinessWorld