Asian Innovations in Insect Control

Innovations in Insect Control in Asia date back almost 2,000 years to when ancient Chinese farmers learned the art of biological insect control. China’s ancient orchardists annually introduced colonies of predatory ants to cultivated trees to control caterpillars and other pests of crops such as citrus. Ancient Chinese biocontrol practices included constructing bamboo bridges between trees, so predatory ants could easily wander from tree to tree foraging for pests.

Fast forward to the twenty-first century: Tea is arguably the second most widely consumed beverage, after water. Tea production occupies 2.7 million ha (6.7 million acres) in 34 countries, with 78% of production in Asia and 16% in Africa. Sustainable tea production practices emphasize displacing pesticides with cultural and biological control practices to control spider mites and other pests in tea plantations.

“The application of natural enemies in tea pest control aroused a large amount of investigations in the tea producing countries,” reported Yang Yajun and colleagues at the Tea Research Institute of Chinese Academy of Sciences at the 2005 International Symposium on Innovation in Tea Science and Sustainable Development in Tea Industry. “In South India, investigations showed the introduction of three species of entomophagous fungi in the control of tea spider mite (Oligonychus coffeae). In Japan, the use of pesticide-resistant predatory mite resulted in successful control…In Japan, one fungal preparation and one bacterial preparation were registered and used in control of tea diseases.” In China and Japan, viruses stop pesky leafrollers and loopers. Japan also has five fungal biocontrol products, one bacterial biocontrol preparation, and several kinds of parasitic and predatory natural enemy preparations to control tea insect pests.

“Great achievements in the application of physical and agricultural control methods in controlling the tea pests were advanced,” said Yajun et al. In Japan, China, and Malawi (Africa), yellow sticky traps and reflective films (near ultra-violet light) help control tea aphids, thrips, and leafhoppers (70-80% pest reduction). “A special mist wind insect-sucking machine was developed in Japan,” and it reduces tea leafhopper, whitefly, and spider mite populations.

Sex pheromones have been used for mating disruption in Japanese tea gardens since 1983 to control a pesky tea leafroller. Sex pheromones are also being used against other tea pests in Japan and China. Natural volatiles from the tea plant that attract natural enemies but not pests are also under development. For example, the April 2004 Chinese Journal of Applied Ecology (15(4):623-626) reported that beneficial lady beetles, green lacewings, and hover flys (syrphids) controlling tea aphids were attracted by natural compounds such as nerol from tea flowers, n-octanol from intact tea shoots, and geraniol, methyl salicylate, benzaldehyde, and hexanal from aphid-damaged tea shoots.

At Entomological Society of America (ESA) annual meetingss, California Department of Food and Agriculture (CDFA) officials report that T. Kanzawa’s 1939 translation of Professor Dr. Shonen Matsumura‘s 1931 book, 6000 Illustrated Insects of Japan-Empire, is still used to help with identification and control of invasive insect pests like the dusky-winged fruit fly (Drosophila suzukii). Oregon entomologist Jana Lee told the ESA that the Japanese get 100% fruit fly protection by placing 0.98 mm (0.04 inch) mesh over blueberries 20 days pre-harvest. After the harvest, 100% of fruit fly eggs and newly hatched larvae on cherries are killed by holding the fruit at 1.6-2.2 C (29-36 F). In Japanese experiments, fruit fly egg laying in cherries was reduced 30-60% with botanicals such as eucalyptus, neem, and tansy. In other promising Japanese research, Kotaro Konno and Hiroshi Ono told the ESA that latex from the same mulberry leaves used to safely grow silkworms since ancient times could be an effective botanical insecticide against other pests.

Since the 1920s, the USDA has been importing Japanese and Korean biocontrol organisms, like Tiphia wasps to control Oriental beetles and Japanese beetles attacking golf courses, turf, crops, and landscape ornamentals. Japan is currently patenting decoy tree technologies to help stop an explosive outbreak of oak wilt fungus (Raffaelea quercivora), caused by mass attacks of ambrosia beetles (Platypus quercivorus), said Masahiko Tokoro of the Forestry and Forest Products Research Institute (FFPRI) in Ibaraki, Japan (See earlier blog post: The Asian Invasion -Insects in Global Trade).

In South Korean greenhouse tests, Sangwon Kim and Un Taek Lim of Andong National University told the ESA of greenhouse tests showing the superiority of yellow circles against a black background versus conventional rectangular yellow sticky traps for capturing pesky whiteflies and thrips. “In laboratory behavioral studies using different backgrounds and shapes, yellow sticky card with black background was 1.8 times more attractive than sticky card without background, and triangle attracted 1.5 times more sweetpotato whitefly (Bemisia tabaci) than square,” said Kim. Black sticky cards with small yellow circles caught 180% more sweetpotato whitefly than cards with larger circles.

Lacewing Silk

GREEN LACEWING consumption of moth eggs, small caterpillars, spider mites, aphids and other pests promotes sustainable biological pest control in farms, gardens, greenhouses, zoos, malls, conservatories and other landscapes. Sustainable cotton farmers around the world have long utilized green lacewings for biocontrol, but few ever had an inkling that both cotton AND lacewings could be fiber crops. Indeed, biocontrol companies like Rincon-Vitova Insectaries, which has a green lacewing logo, may one day be garbed in garments woven from organic cotton and green lacewing silk.

Not that green lacewing silk is likely to make a major fashion splash anytime soon or displace traditional mulberry-reared silkworm cocoon threads. Rather, adding another insect silk to the textile design palette is just another milestone marker from several decades of studying the chemistry, genetics, biology, physics, acoustics, ecology, etc. underlying biocontrol by green lacewings. The latest technical details from Australia’s Commonwealth Scientific Industrial and Research Organisation (CSIRO) on the superior textile properties of green lacewing egg-stalk silks is just one more brick in the ecological edifice.

Ecologically, besides finding shelter from the elements and locating nourishment, the real world for an insect is also a constant struggle to avoid being prey to natural enemies. Even pest natural enemies like green lacewings are preyed upon by their own set of natural enemies (e.g. spiders, bats, parasitic wasps, ants). Lacewings adapt by eavesdropping on bat echolocation signals (a form of radar used for navigation and prey detection) and flying evasive flight patterns. Green lacewings trapped in silken orb spider webs have their own almost ritualistic behaviors for chewing themselves free, and tiny wing hairs are designed to smoothly slide free from sticky spider webs.

Thin tough silken egg stalks that are strong yet flexible loft green lacewing eggs safely out of the reach of marauding ants. For extra protection, the high-protein silk egg stalks are also coated with oily ant repellent chemicals. Interestingly, the egg stalk silks are very different from green lacewing cocoon silks. Textile buffs are intrigued, as egg stalk silks rapidly solidify after being secreted as liquid droplets that are extruded into thin strong fibers swaying like palm tree trunks topped with lacewing eggs.

From an engineering standpoint, these green lacewing egg stalk silk properties suggest the possibility of new industries and biological silk factories. In a future decade, green lacewing silk may be woven along with silkworm silk and cotton into apparel and furnishings. An unexpected dividend from years of research related to green lacewings and biocontrol.