Mir1-CP in combination with Bt toxin provide ultimate protection

A cocktail of insecticides containing a plant protein and a common insecticide may be more lethal to crop pests than either ingredient used alone, according to biologists. The one-two punch also inhibits the insects’ growth rate and reduces their chance of developing resistance. “We found a synergistic effect, where the two insecticides together decreased the growth rate of caterpillars more than either one did alone,” said Dawn Luthe, professor of plant stress biology at Penn State. “The insect mortality rate was also much greater than the sum of mortality rates when only one insecticide was used.” One of those insecticides, Bt, is commonly used around the world. When insects feed on plants genetically modified to produce Bt, the toxin binds to chemical receptors lining the insects’ midgut. This disrupts the receptor’s function, eventually killing the insects. But researchers say some insects always survive the ordeal and over time subsequent populations could develop resistance to the toxin. Luthe and her colleagues Srinidhi Mohan and Peter W. K. Ma, post-doctoral student and professor at Mississippi State University, and W. Paul Williams, research geneticist at the U.S Department of Agriculture studied a unique plant-based insecticide known as Mir1-CP.

Their goal is to see if Mir1-CP, when used in tandem with other biological pesticides, such as the Bt toxin, can prevent pests from developing resistance and make the toxin more effective. “This protein, which we developed from certain strains of corn from Antigua, breaks down other proteins and peptides in the insects’ gut,” said Luthe, whose findings appear in the current issue of PLoS One. Unlike Bt, Mir1-CP breaks down proteins in a protective membrane covering the midgut. This membrane acts as a barrier that protects the caterpillar from toxins in the diet, and cycles nutrients to the midgut. “It is the caterpillar’s first line of defense against toxins and chemicals in its diet,” said Luthe. The researchers fed insects a sub-lethal dose of the two insecticides to test the effectiveness of both insecticides on the pests.

They found that when used alone, a concentration of Bt at five parts per billion killed four percent of all corn earworms and five per cent of tobacco budworms. Mir1-CP, when used at a concentration of 60 parts per billion, killed eight percent of the corn earworms and three percent of the tobacco budworms. But when researchers added the two insecticides together, the mixture killed 61 per cent of corn earworms and 57 percent of tobacco budworms, which is more than 10 times better than either by itself. Researchers saw similar results against the fall armyworm and the southwest corn borer, when the insecticides were used at slightly different strengths. In addition to a high mortality rate among the insects, the study indicates a significant decrease in the growth rate of the survivors.
“We think that Mir1-CP is making holes in the membrane, which in turn is making it easier for the Bt toxins to reach the insects’ midgut,” explained Luthe, whose work is funded by the National Science Foundation.

The Penn State researcher says the findings have important implications for agriculture because each year insects cause major losses to farmers. Nearly 20 per cent of major crops worldwide are lost to insects. Genetically modified crops that produce the Bt toxin have managed to check the insects to some extent but Luthe says insects may be winning the fight. “Researchers in the Mississippi delta have found resistance to Bt among some insect populations in the region,” Luthe noted. “There is a chance that some time in the future Bt will not be as effective against pests as it is now.” The Penn State researcher suggests strains of corn that naturally produce Mir1-Cp could be cross-bred with other strains of corn that produce Bt to develop new varieties that are more effective against pests. “If you have two mechanisms of attack, it will take much longer for an insect population to develop resistance to both modes of attack, and help slow the development of resistance,” Luthe added. Credit: Sciencedaily and TAMU.

How good is the sterile moth plan, questions scientists

The plan to substitute sterile moths for aerial spraying as a way to combat the light brown apple moth has mollified many anti-spraying activists, but some pest-control experts have cast fresh doubt on how effective the program would be, based on the moth’s mating habits. Starting in 2009, state officials will begin releasing sterile male moths into the environment — as many as 20 million moths per day by 2011 — to out-compete wild male light brown apple moths in the race to mate with females. At $37 million per year, the sterile breeding program is supposed to provide a definitive solution to the moth problem, which has spread to eight counties and put hundreds of square miles under quarantine. At issue is whether the female moth mates more than once in her lifetime, which would expose her to multiple opportunities to lay eggs. The California Department of Food and Agriculture says the female moth mates only once and is basing its plan on this premise.

But independent pest control experts and entomologists say the female light brown apple moth can mate several times in the one-to two-week period preceding the period in which she lays her eggs. “Within a few days, 100 percent of them have mated, and they can mate up to five times. Most won’t mate that many times, but all you need is a few who don’t mate with sterile males, and the system doesn’t work,” said professor Andrew Gutierrez, an entomologist and integrated pest management expert at UC Berkeley. Herb Fong, Stanford University’s arborist and a certified pest control adviser, agreed with Gutierrez’s assessment, based on his own knowledge of light brown apple moth behavior in New Zealand. “She will keep going until she finds another mate to impregnate her or she has viable eggs,” he said. He disagreed, however, with the assertion that the plan wouldn’t work.

“It should be an effective means of control, as long as there are enough sterile males to out-compete the fertile male. You have to swamp the population,” said Fong. That’s the plan, said Department of Food and Agriculture spokesman Jay Van Rein. It’s not known how long the sterile moth program will last, but the moths will be released from airplanes every month. “You’re releasing enough moths that the odds of mating successfully are way down. The wild males and females are not able to find each other to mate,” he said. The program will be supplemented by painting a sticky mixture containing a pesticide and the moth pheromone onto trees and telephone poles in an effort to kill the male moth in heavily infested areas. Pheromone-infused “twist ties” have been distributed in the branches of trees in more rural zones throughout the Bay Area, along with thousands of moth traps that also contain the pheromone.

But the main part of the campaign is the sterile moth program, and the delayed schedule for releasing the moths has led some anti-spraying crusaders to question the ongoing state of emergency declared by both state and federal agriculture officials in 2007. The U.S. Department of Agriculture has since spent $100 million on eradication efforts in California. The emergency status also allowed the state Department of Food and Agriculture to take action before an environmental impact report was complete. “What happened to the emergency? What happened to the ‘months’ left to eradicate this?” asked Santa Cruz resident Glen Chase, an advocate with California Alliance to Stop the Spray. Van Rein said the emergency status had nothing to do with a timeline and everything to do with being allowed to spend money on distributing traps and inspecting nurseries under quarantine. Those actions have already yielded strong results. “The evidence is pretty clear at this point that we’ve contained the infestation with activities already in place. The infestation now is essentially where it was when we found it in March of 2007,” Van Rein said.

“The infestations have been more intense, but they’ve been limited to the areas that were originally infested.” While the Department of Food and Agriculture will comply with two recent court orders in Monterey and Santa Cruz counties, which ordered officials not to spray pheromones until an environmental impact report has deemed it safe, the agency is still not ruling out aerial spraying in hard-to-reach places with tall tree barriers and ridge lines that block the sterile moths from finding females. Source: Julia Scott.

Novel ideas to counter approaching water crisis

As growing demand for clean water stretches even the resources of the world’s largest industrialized nations, scientists and engineers are turning to new technology and novel ideas to find solutions. Mark Shannon of the University of Illinois at Urbana-Champaign joined a slate of world leaders in water resource research to address this crisis in a review paper in the March 20, 2008, issue of Nature. “As dire as the growing problems are with a lack of enough clean water in the world, I have a great deal of hope that many of these problems can be solved by increasing research into the science and technology of water purification,” said Shannon, who also serves as director of the National Science Foundation (NSF) Center of Advanced Materials for the Purification of Water with Systems (WaterCAMPWS).

Photo: New class of synthetic antimicrobials that disinfect by inducing negative curvature in bacterial membranes, generating pores. With an emphasis on environmentally friendly tools for killing microbes, membrane bioreactors, nanoscale filtration, and a host of other advanced technologies, the review paper addresses how these systems can be used for disinfection, decontamination, reuse and reclamation, and desalination of water supplies across the globe. “Clearly, a coordinated, multi-faceted approach is needed to deal with complex water issues,” said Geoffrey Prentice, the NSF program director supporting the WaterCAMPWS center and currently on detail to the U.S. Mission to UNESCO in Paris. “Ours is one of several agencies working to address the water crisis before it grows worse. Working with the U.S. Mission to UNESCO, we are highlighting the international dimensions of inadequate water supplies, which lead to millions of deaths each year, primarily in the developing world,” Prentice added.

One example is a June 27 international water forum at the Department of State at which NSF, UNESCO and a number of agencies and international organizations will be joining Shannon and other technical experts to confront some of the most pressing global water needs. Source: Gerard Wong, University of Illinois at Urbana-Champaign/NSF.

Water: The forgotten crisis

This year, the world and, in particular, developing countries and the poor have been hit by both food and energy crises. As a consequence, prices for many staple foods have risen by up to 100%. When we examine the causes of the food crisis, a growing population, changes in trade patterns, urbanization, dietary changes, biofuel production, and climate change and regional droughts are all responsible. Thus we have a classic increase in prices due to high demand and low supply. However, few commentators specifically mention the declining availability of water that is needed to grow irrigated and rainfed crops. According to some, the often mooted solution to the food crisis lies in plant breeding that produces the ultimate high yielding, low water- consuming crops. While this solution is important, it will fail unless attention is paid to where the water for all food, fibre and energy crops is going to come from.

A few years ago, IWMI (the International Water Management Institute) demonstrated that many countries are facing severe water scarcity, either as a result of a lack of available fresh water, or due to a lack of investment in water infrastructure such as dams and reservoirs. What makes matters worse is that this scarcity predominantly affects developing countries where the majority of the world’s under-nourished people– approximately 840 million — live. The causes of water scarcity are essentially identical to those of the food crisis. There are serious and extremely worrying factors that indicate water supplies are steadily being used up. Essentially every calorie of food requires a liter of water to produce it. Thus those of us on western diets, use about 2500-3000 liters per day. A further 2.5 billion people by 2030 will mean that we have to find over 2000 more cubic kilometers of fresh water to feed them. This is not any easy task given that current water usage for food production is 7500 cubic kilometers and supplies are scarce.

According to the recent report “Water for Food, Water for Life” of the Comprehensive Assessment of Water Management in Agriculture, which drew on the work of 700 scientists, unless we change the way we use water and increase “water productivity” (i.e. more crop per drop) we will not have enough water to feed the world’s growing population (This population is estimated to increase from 6 billion now to about 8.5 billion in 25 years.) Compared with the lengthy agenda to combat climate change, this is a very short time indeed and yet the impacts of water scarcity will be profound. However, very little is being done about it in most countries. Since the formulation of the UN Millennium Goals in 2002, much of the water agenda has been focused around the provision of drinking water and sanitation. This water comes from the same sources as agricultural water and as we urbanize and improve living standards there will be increasing competition for drinking water from domestic and other urban users, putting agriculture under further pressure. While improving drinking water and sanitation is vital with respect to health and living standards, we cannot afford to neglect the provision and improved productivity of water for agriculture. There are potential solutions. Better water storage has to be considered. Ethiopia, which is typical of many sub-Saharan African countries, has a water storage capacity of 38 cubic meters per person. Australia has almost 5000 cubic meters per person, an amount that in the face of current climate change impacts may be inadequate. While there will be a need for new large and medium-sized dams to deal with this critical lack of storage in Africa, other simpler solutions are also part of the equation.

These include the construction of small reservoirs, sustainable use of groundwater systems including artificial groundwater recharge and rainwater harvesting for smallholder vegetable gardens. Improved year- round access to water will help farmers maintain their own food security using simple supplementary irrigation techniques. The redesign of both the physical and institutional arrangements of some large and often dysfunctional irrigation schemes will also bring the required productivity increases. Safe, risk free reuse of wastewater from growing cities will also be needed. Of course these actions need to be paralleled by development of drought- tolerant crops, and the provision of infrastructure and facilities to get fresh food to markets.

Current estimates indicate that we will not have enough water to feed ourselves in 25 years time, by when the current food crisis may turn into a perpetual crisis. Just as in other areas of agricultural research and development, investment in the provision and better management of water resources has declined steadily since the green revolution. I and my water science colleagues are raising a warning flag that significant investment in both R&D and water infrastructure development are needed, if dire consequences are to be avoided. Source: International Water Management Institute.

Don’t let volunteer corn report for duty

Bt could stand for “big trouble” in the years ahead if farmers aren’t careful in their use of biotech corn, said a Purdue University entomologist. Corn varieties containing Bacillus thuringiensis, or Bt, genes to control corn rootworms and corn borers, and genetically modified to withstand Roundup herbicide, could become more susceptible to rootworms unless growers keep soybean fields free of volunteer corn and continue planting refuge acres, said Christian Krupke. “We need to stay a step ahead of rootworm resistance development,” Krupke said. “If there’s one thing we know about insects, it’s that they figure out a way to adapt to whatever we throw at them.”

Rootworms are a major threat to corn crops, costing farmers about $1 billion a year in yield losses and control expenses. About 30 percent of Indiana’s estimated 6.45 million corn acres were planted to multi-trait biotech varieties this year, including the Bt/Roundup “triple stacks.” While transgenic varieties have helped growers boost corn yields, those varieties could unintentionally produce stronger, tougher-to-control rootworms when farmers rotate their cornfields to soybeans the following year, Krupke said. Rootworms feeding on volunteer corn – maverick plants that grow from seed produced by the previous year’s crop – are exposed to Bt but at less-than-toxic levels.

“What we found was that in areas where triple stack corn was planted in 2006 and soybeans in 2007, we had a great deal of volunteer corn in some of those fields,” Krupke said. “Most of that volunteer corn showed up as being Roundup Ready and as having the Bt gene for rootworm. “The problem is that the Bt, for whatever reason, isn’t expressed at the same level as Bt that you’d get in off-the-shelf corn. So you get a lot of rootworm larvae eating that volunteer corn, and they are able to survive on it. That’s a concern because now you’re getting insects exposed to sub-lethal doses of Bt that survive to mate and lay eggs and possibly develop stronger offspring. That is exactly what we don’t want.”

Volunteer corn is considered a weed and is usually controlled with herbicides. Controlling that corn becomes more difficult when it is both resistant to glyphosate, the active ingredient in Roundup, and growing in Roundup Ready soybeans. In recent years about 90 percent of Indiana soybean acres have been planted to Roundup Ready varieties. “Most soybean growers have relied on Roundup as their No. 1 – and sometimes only – weed control for a long, long time,” Krupke said. Farmers have several herbicide options for controlling volunteer corn, said Bill Johnson, Purdue Extension weed scientist.

“To control volunteer Roundup Ready corn in soybeans, farmers should use Assure II, Select Max, Fusion or Raptor tank mixed with glyphosate,” Johnson said. Another factor that could hasten rootworm resistance to Bt corn is improper or insufficient planting of refuge corn. Planting refuges alongside Bt corn crops is required by law.
“A refuge is anything that is not Bt corn,” Krupke said. “So when you plant Bt corn for rootworm or corn borer, for every 80 acres you plant of the Bt you have to plant 20 acres of the refuge. “The thought behind the refuge is that you have some insects in that refuge that are never exposed in their lifetime to Bt. They never have an opportunity to develop resistance to it. The only way insects develop resistance is by exposure. The more you expose them, the greater the pressure is for them to be resistant. So you want to generate some insects that are never exposed to Bt so that they will mate with the ones that are exposed to Bt to dilute the chances of those offspring being resistant.”

Killing all rootworms by planting 100 percent of acres in Bt corn is neither the objective, nor is it possible, Krupke said. “If you expose the entire rootworm population at the same time to Bt, the insects will either have to become resistant or go extinct,” he said. “We have made zero species of insects extinct, so you can figure out which way it is going to go.” Even in cornfields where refuge acres were planted, Krupke and fellow Purdue entomologists have found troubling signs.

“We’ve looked at the relative sizes of rootworm beetles coming out of the transgenic and refuge corn and found some large females coming out of the transgenic blocks,” Krupke said. “That is important because large females tend to lay more eggs and are preferred by the male beetles because they lay more eggs.” Farmers need to remain vigilant when they plant Bt corn to ensure the technology is around for a long time, Krupke said.

“If we don’t do the things that we need to do, then we’re eventually going to have products that are not effective against rootworm,” he said. “The two primary things would be to continue planting the refuge and, in areas where you are rotating corn with soybeans, clean up any volunteer corn that you have in the field. You need to do the latter because volunteer corn is a host, and that’s where rootworms can develop. There will be a lot of eggs in those first-year soybean fields that were in corn the year before.” Source: Purdue Univ.

Record breaking heat badly affecting bees

The record-breaking triple-digit temperatures are not only wreaking havoc on humans, but on honey bees. On days when temperatures exceed 100 degrees, bees collect more water to cool the hive to protect the brood (immature bees) and ward against a meltdown, said UC Davis, bee specialist Susan Cobey. She said bees reduce their flight activity for nectar and pollen, but collect more water. They spread droplets of water and then fan their wings to ventilate and cool the hive. “When the heat is really intense, the worker bees rev up the fanning and water circulation,” said Cobey, a bee breeder and geneticist at the Harry H. Laidlaw Honey Bee Research Facility, part of the UC Davis Department of Entomology.

Beekeepers know to locate their hives in shade and near ample water, such as a drippy faucet. “Beekeepers will often crack a hive to provide more air flow and if the bees don’t like it, they’ll plug it (the hole) with propolis (plant resins collected by bees that serve as a cement or bee glue),” Cobey said. UCD entomologist Lynn Kimsey said that honey bees must keep the temperature inside the hive around 92 to 94 degrees. “That’s a real problem when the temperature outside reaches 100 or 105 or more,” Kimsey said. “You’ll see honey bees collecting water everywhere, from around leaky faucets, and in puddles, bird baths, fish ponds and swimming pools – anywhere there’s water,” Kimsey said.

Worker bees do all the work to maintain the hive. In addition to gathering nectar, pollen, propolis and water, they serve as air conditioners, architects, construction workers, nurses, dancers, guards and undertakers. However, bees don’t work in foul weather: rain, heavy fog, or in a wind of more than 15 miles per hour, and they don’t like the heat. Source: Daily Democrat.