Agriculture.ph Blog

Locust is an age-old insect pest. History tells us that our ancestors have been imaginative in their fight against this living scourge. But swarms of locust still unpredictably occur at anytime of year.

Locust devastation has been reported to occur in Pangasinan, Central Luzon, Masbate, Negros Oriental and Occidental, Ormoc City, Davao, Cotabato City, and General Santos City.

According to entomologists, what makes locusts difficult to control is their ability to multiply in population and transform into destructive phase. Sometimes, they are solitary or nonswarming; at other times they become gregarious or migratory. The migratory locusts are much stronger and destructive than the solitary ones. They fly in swarms, by the thousands and millions depending on the favorable growth of host plants, in their search for food. They can destroy a field of rice, corn, sugarcane, or other crops in just a few ours.

To find out the most effective and friendly environmental control measures against locusts, PCARRD has supported and coordinated a multiagency program entitled “Migratory Locust (Locusta migratoria manilensis Meyen) R&D program.”

The program which is implemented by the University of the Philippines Los Baños-National Crop Protection Center (NCPC), DA-Region III, delves into the locusts’ bioecology and

morphometrics, biological control, bionomics, and population dynamics.

Among the significant findings of the program are as follows:
# Disturbed locusts do not mate at day time. Instead, they start mating from dusk (6:00 a.m.) to dawn (5:00 p.m.). This could be useful in timing the application of control.
#  The continued presence of locusts in Zambales breeding areas is due to the numerous rivers and tributaries, and availability of food plants in the areas.
# A parasitic mite which was found to be a potent biological control agent was prevalent among grasshopper species, including locust, not only in Central Luzon but in Masbate and South Cotabato, as well.
# Locusts were observed to copulate during the day at an average temperature of 29 degree C and a relative humidity of 76.5 percent.
# Rice was the more preferred host plant where 82% locust survival was recorded.
# The number of eggs that a female locust could produce was affected by foods. Highest number of eggs produced was in corn, while percent hatchability was highest in sugarcane.
# Crowding affected the transformation from typical phase solitaria to gregaria type.
# Neem tree had a strong potential as behavioral control
# Fine rice bran + salt + molasses (FRBSM) and course rice bran + salt + molasses (CRBSM) were preferred by locust nymphs for bait. Regardless of carriers and attractants used, baits fortified with carbaryl exhibited 100% mortality of 3rd instar (life stage of an insect between two successive molts) nymphs five minutes after exposure.
# Older nymphs consumed more food than young ones; females consumed more food than males and had greater weight gain.
# Results of simulation study indicated that assuming an initial egg of 1,000 and survival rate of 50% for each nymph stage, there were 512 reproductive adult individuals after 67 days.
Meanwhile, researchers of the Oxford University in the United Kingdom discovered that a chemical sometimes found in the foam that surrounds locusts eggs could provide a key to locust control. This chemical is responsible for the nymphs or youngs to turn into gregarious and migratory locusts. When the chemical is not present, the eggs will hatch as solitary or nonswarming locusts.

The Oxford researchers found that the stimulus to produce the chemical is overcrowding. When the solitary locusts are consuming a vegetation, they tend to crowd closer. Once they start rubbing up against each other, the females are stimulated to produce a chemical into the foam to protect the eggs as they are laid into the soil. The researchers also observed that just four hours crowding was sufficient to stimulate the females into producing the chemical. (Bengie P. Gibe, S&T Media Service)

Source: www.pcarrd.dost.gov.ph