Invasive Insect Damages US Ash Trees

A beetle invasion in the United States has killed at least twenty million ash trees. The invasion of the emerald ash borer was first discovered near Detroit, Michigan, in 2002. Experts believe the small green insects arrived in the 1990s in shipments of goods from China.

The emerald ash borer has destroyed trees in the Midwest and as far east in the United States as Maryland. The insects have also spread as far north as Ontario, Canada. Emerald ash borers are attacking tree farms and can also spread when logs and firewood are transported.

Ash trees are popular. They grow well in heavy clay soils, and they can survive ice storms well. They produce many leaves, so they provide shade protection from the sun. And in the fall the leaves turn a beautiful gold and purple.

Ash trees can resist many diseases. But they cannot resist the emerald ash borer. It lays eggs on the bark. Then the young larvae drill into and feed on the inner bark. This harms the ability of the tree to transport water and nutrients.

The United States Department of Agriculture is working to save the ash tree. So are agriculture departments and university extensions in a number of states.

In some places, farmers are using "detection trees." These have an area where bark has been cut away. The area circles the tree and is called a girdle. The girdling process weakens the trees. It makes them easier targets for borers, and shows if the insects are nearby.

Efforts to stop the spread of the emerald ash borer include cutting down affected trees. A tree farmer in Maryland, for example, recently faced the loss of hundreds of trees.

There are worries that the ash tree might disappear unless the invasion is controlled. To prepare for such a possibility, a government laboratory is collecting seeds from ash trees.

David Burgdorf works in East Lansing, Michigan, for the Natural Resources Conservation Service; the service is part of the United States Department of Agriculture. He is asking people to send in ash seeds. The laboratory examines and x-rays the seeds to make sure there are no living borer embryos.

The best seeds are then sent for storage in a seed bank in Fort Collins, Colorado. There, they are dried and frozen at the National Center for Genetic Resources Preservation. Should the seeds ever be needed, the hope is that scientists might someday develop an ash tree that could resist the little green attackers.

Source:
VOA News Service

Genetically Engineered Rice Varieties Cut Use of Pesticides

A study in China suggests that two kinds of genetically engineered rice can reduce the costs, and dangers, of using pesticides.

One kind of rice includes a gene found in the bacterium known as Bt. Bt lives in soil and on plants; it is a natural insecticide. It is poisonous to some kinds of insects. Bt maize is commonly planted in the United States. The other kind of rice was engineered to resist insects with a gene from the cowpea plant.

The two-year study involved tests of Bt rice in Hubei province and cowpea rice in Fujian. Scientists collected information from small farms already testing insect-resistant rice without technical aid. Some farmers are growing both insect-resistant and traditional rice.

The scientists found that the Bt rice produced six to nine percent more grain than other kinds of rice. The cowpea rice, based on fewer observations, did not appear to increase productivity.

Still, the findings show that resistance to insects improved for both kinds of rice. The study says farmers used eighty percent less insecticide than usual.

Science magazine published the findings. Jikun Huang led the study. He is director of the Center for Chinese Agricultural Policy, in the Chinese Academy of Sciences.

The study notes that no country has yet released a major food grain crop that has been genetically changed. Engineered crops are now used mostly for animal feed and products like cotton.

The Chinese farmers in the study made their own decisions about when to use insecticides. Those with traditional rice crops used chemicals almost four times per growing season on average. But farmers with the insect-resistant rice used insecticides an average of less than once per season.

Less insecticide meant fewer sick farmers. The study says the farmers growing insect-resistant rice did not report any health problems from the use of poisons.

China has not approved genetically engineered rice for market. But a report from Hubei last month said insect-resistant rice appears to have been sold illegally for the last two years. That report came from the environmental group Greenpeace, which oppose genetic engineering. China says it is investigating the Greenpeace report.

Some countries will not import genetically engineered foods. Not everyone is sure that such products are safe for people or the environment.

Source:
VOA News Service
Author: Mario Ritter
First published: May 9, 2005

Protecting Crops with Pest-Controlling Plants

There are a variety of ways that farmers and gardeners can use plants to protect their crops from pests and diseases without resorting to chemical controls. For instance, some plants provide food and protection for insects that help control harmful insects.

Ladybugs are beneficial beetles that like crimson clover and hairy vetch. They find food, water and a resting place in the clover and vetch. Ladybug larvae eat harmful aphids, tiny insects that feed on many different kinds of crop plants.

Plants also help each other through their root systems. For example, scientists say the roots of the marigold flower reduce harmful nematode populations in the soil. Nematodes are tiny worms. There are more than ten-thousand different kinds of nematodes. And some of them feed on corn.

Wild mustard is another plant that releases a poison through its roots. This poison kills nematodes. It also kills some kinds of fungi.

A researcher at the University of California, Santa Cruz, said the wild mustard should be cut close to the ground after the first fifteen days. After that, it should be cut once a month. If left to grow freely, wild mustard will compete with the corn for nutrients in the soil.

Canadian researchers discovered that the dandelion weed can protect tomato plants from fusarium disease. Fusarium attacks the plant roots. It reduces the number of tomatoes that the plant produces.

Dandelion roots produce cichoric acid. This acid prevents the disease from getting iron from the soil. Fusarium needs iron to survive.

There are, however, plants that should never be grown together. The roots of the black walnut tree, for example, produce a poison that kills potatoes, peas, tomatoes and peppers.

Dying parts of the brassica family of plants produce a poison that prevents the seeds of some plants from growing. Brassica plants include broccoli, cabbage and cauliflower.

Plants with small seeds, such as lettuce, are especially affected by the brassica poison. A professor at the University of Connecticut said brassica plants should be removed from the soil after they have produced their crop.

Related topics:
Plants Invite Insect Allies to Dine on Pests
Try Natural Pest Control with These Insect-Repelling Plants

Source:
VOA News Service
Author: Bob Bowen
First published: April 1, 2005

Pests and Diseases

The following posts cover topics related to plant pests, pest control, plant diseases, and disease prevention and treatment.

• Protecting Crops with Pest-Controlling Plants


• Plants Invite Insect Allies to Dine on Pests
  
  
• Insects Devouring Your Garden? Call in the Ladybugs
  
  
• Try Natural Pest Control with These Insect-Repelling Plants
  
  
• Tips for Choosing a Lawn Care Service
  
  
• Western Redwoods Endangered by Killer Microbe
  

Plants Invite Insect Allies to Dine on Pests

Students are taught at an early age about how insects help plants reproduce. Schoolchildren learn that plants release sweet juices, or nectar, through small openings inside the flower. These small openings are called nectaries.

The sweet-smelling nectar appeals to bees and other insects so they go to the plant. While the bee is drinking the sweet nectar, the hairs on its legs become covered with pollen. The bee flies to another flower and drops some of the pollen there.

During a flight, the bee usually visits several male and several female flowers. In this way, flowers are able to reproduce.

Many plants, however, release nectar for another purpose. Scientists have known about it for more than one hundred years.

The second way plants release nectar does not involve flowers. The nectar is contained in extrafloral nectaries. They are found on the tops of leaves, where the leaf and stem come together.

Trees that have extrafloral nectaries include the peach, poplar, viburnum, black locust and wild cherry.

Extrafloral nectaries are often smaller than a grain of salt. Researchers say the sweet juices released in them are not used to help the plant reproduce. Instead, they are used to get some insects to come to the plant to help control harmful insects.

Scientists have known for many years that tiny ants feed on the sweet juices released by the extrafloral nectaries. But only in more recent years did they make discoveries involving other insects.

Back in 1984 there was a report about extrafloral nectaries in Agricultural Research magazine. The magazine is published by the United States Agriculture Department. It reported that two government scientists, Robert Pemberton and Jang-hoon Lee, had studied extrafloral nectaries for two years. They looked for ways to control gypsy moths.

They did their research in forests near the South Korean capital, Seoul. During their research, they discovered that two helpful insects liked the extrafloral nectaries.

In fact, the insects killed two times more gypsy moths on trees that had the extrafloral nectaries than on those that did not. The insects are the Cotesia melanoscelus wasp and the Parasetigena silvestris fly.

A third insect, the Blepharipa schineri fly, also improved its control of gypsy moths on trees with extrafloral nectaries.

Source:
VOA News Service
Author: Bob Bowen
First published: November 7, 2005

Insects Devouring Your Garden? Call in the Ladybugs

There are plenty of insects that farmers hate. But there also are some they like. These protect crops against damage from other insects. A good example is the lady beetle, also known as the ladybug.

Lady beetles are a natural control for aphids. Aphids are tiny insects that develop colonies on plants and eat plant fluids. Aphids can also spread crop diseases. Adult lady beetles can eat fifty aphids a day. The young beetle larvae can eat hundreds of aphids.

Lady beetles are red, orange or black. They often have black spots, though some have light colored spots. Different kinds of lady beetles have different numbers of spots. There are lady beetles with four, five, seven and fourteen spots.

Many of the well-known kinds of lady beetles come from Asia or Europe. They now are common throughout the United States.

American scientists imported one kind of lady beetle, the multicolored Asian lady beetle, as early as nineteen sixteen. They released them as an attempt to control some kinds of inspects. Over the years, the beetle has become established, possibly helped by some that arrived with imported plants on ships.

Experts say over four hundred fifty kinds of lady beetles are found in North America. Some are native to the area. Others have been brought from other places. Almost all are helpful to farmers.

The Asian lady beetles now in the United States probably came from Japan. The Asian lady beetle eats aphids that damage crops like soybeans, fruits and berries.

In the southern United States, Asian lady beetles have reduced the need for farmers to use pest-killing poisons on pecan trees. This popular tree nut suffers from aphids and other pests that the beetles eat.

But some people say the Asian lady beetle has itself become a pest. Lady beetles have no food after crops have been harvested. It is time for them to prepare for winter. Normally this is in the ground, but it can also be in someone’s home. Some farmers also worry that the beetles may eat their late-autumn fruit crops.

Experts say Asian lady beetles may appear in large numbers in some years. But they say the insects are too helpful to consider pests.

Source:
VOA News Service
Author: Mario Ritter
First published: April 10, 2006

Western Redwoods Endangered by Killer Microbe

A microscopic pathogen, introduced to the United States about 1995, is wiping out a relative of the oak tree called the tanoak in the western states of California and Oregon. Only about ten percent of known tanoaks remain. At a slower rate, the same organism is also attacking 15 other deciduous, or leaf-bearing, trees and plants. And there is alarming evidence that the world's tallest tree, the soaring California redwood, may be next.

The awe-inspiring redwood, which can live 2,000 years and top 100 meters in height, is such a signature symbol of the northern California coast that the area is called "the Redwood Empire." Logging almost wiped out that empire until harvesting was regulated.

Today, more than 250,000 hectares of redwood forest remain in timber production. And safe havens for the trees were established in state and national parks. No wonder scientists and preservationists are worried about the recent discovery that the deadly Phytophthora ramorum organism has migrated from broadleaf trees to the redwoods, which are needle-bearing conifers.

Plant pathologists Matteo Garbelotto at the University of California in Berkeley, and David Rizzo at the university's branch in Davis, California, have found DNA evidence of the pathogen in dead redwood branches.

Dr. Garbelotto says Phytophthora, which is a microscopic cousin of the algae that form ocean kelp, is especially virulent because it is carried by the wind as well as moving through soil and water. So far in bushes like rhododendrons and huckleberries, it invades and kills only selected leaves and small branches. But in oaks and tanoaks, it produces enzymes that disintegrate the tree trunk's bark.

"And then once it's gone through the bark, it colonizes the cambium, which is the live part of the tree," Dr. Garbelotto said. "And by doing so, it basically kills it. It destroys the cambium, and once it's done girdling the whole circumference of the tree, the plant is dead."

Dr. Garbelotto says that while blotching has been found on redwood needles, and Phytophthora DNA has been confirmed in small, dead redwood branches, he and Dr. Rizzo have not yet confirmed that entire redwood trees have been killed by the organism.

"The branch that we're looking at is dead, but the branch could be dead for different reasons - many different reasons," he said. "What it may do - it may take out every single branch, one at a time. But that may take, you know, a long, long time. We could talk tens or even hundreds of years for a redwood."

Ken Bovero is an arborist in Mill Valley, California. He first identified Phytophthora in oaks and coined the term "sudden oak death." He says he's cut into three dead redwoods in the forest, seen other distressed redwoods, and found evidence of Phytophthora deep inside the giant trees.

"I saw dark, vertical staining between the sapwood and the heartwood. I also found a heavy odor of fermentation," he said. "It smells as if you had freshly uncorked a bottle of wine, and if you smell the cork, you smell that fermentation. That's what alarmed me. So I sent samples to a laboratory in Davis, California, and they confirmed that Phytophthora fungus was present in the samples that I sent them."

Scientists can do little to stop a blight in the areas where an outbreak has already occurred. In the late 1800s, a blight introduced to the New York Botanical Garden wiped out the entire East Coast population of chestnut trees. About the same time in Australia, a pathogen similar to Phytophthora killed a thousand native species.

Dr. Garbelotto says the spread of disease can be better controlled today than in the days of the chestnut blight. If it's confirmed that Phytophthora is threatening redwood trees, affected stands can be quarantined. Then other redwoods could be sprayed with copper sulfate, which would kill attacking spores and, hopefully, save the Redwood Empire.

Source:
VOA News Service
Author: Ted Landphair
First published: January 15, 2002

Try Natural Pest Control with These Insect-Repelling Plants

If you're plagued by garden pests but want to avoid using pesticides, one natural pest control option is to choose plant species that repel pesky bugs. The following plants have their own chemical defense systems, and when planted among flowers and vegetables, they help keep unwanted insects and other garden pests away.

Pest	Plant Repellent
Ant	mint, tansy, pennyroyal
Aphids	mint, garlic, chives, coriander, anise
Bean Leaf Beetle	potato, onion, turnip
Codling Moth	common oleander
Colorado Potato Bug	green beans, coriander, nasturtium
Cucumber Beetle	radish, tansy
Flea Beetle	garlic, onion, mint
Imported Cabbage Worm	mint, sage, rosemary, hyssop
Japanese Beetle	garlic, larkspur, tansy, rue, geranium
Leaf Hopper	geranium, petunia
Mexican Bean Beetle	potato, onion, garlic, radish, petunia, marigolds
Mice	onion
Root Knot Nematodes	French marigolds
Slugs	prostrate rosemary, wormwood
Spider Mites	onion, garlic, cloves, chives
Squash Bug	radish, marigolds, tansy, nasturtium
Stink Bug	radish
Thrips	marigolds
Tomato Hornworm	marigolds, sage, borage
Whitefly	marigolds, nasturtium

Source:
U.S. Department of Agriculture