Pests and Diseases Cause Worldwide Damage to Crops

Pests and Pathogens Place Global Burden on Major Food Crops

By Pam Kan-Rice, UC Agriculture & Natural Resources

Scientists survey crop health experts in 67 countries and find large crop losses caused by pests and diseases

Farmers know they lose crops to pests and plant diseases, but scientists have found that on a global scale, pathogens and pests are reducing crop yields for five major food crops by 10 percent to 40 percent, according to a report by a UC Agriculture and Natural Resources scientist and other members of the International Society for Plant Pathology. Wheat, rice, maize, soybean, and potato yields are reduced by pathogens and animal pests, including insects, scientists found in a global survey of crop health experts.

At a global scale, pathogens and pests are causing wheat losses of 10 percent to 28 percent, rice losses of 25 percent to 41 percent, maize losses of 20 percent to 41 percent, potato losses of 8 percent to 21 percent, and soybean losses of 11 percent to 32 percent, according to the study, published in the journal Nature, Ecology & Evolution.

Viruses and viroids, bacteria, fungi and oomycetes, nematodes, arthropods, molluscs, vertebrates, and parasitic plants are among the factors working against farmers.

Food loss

“We are losing a significant amount of food on a global scale to pests and diseases at a time when we must increase food production to feed a growing population,” said co-author Neil McRoberts, co-leader of UC ANR’s Sustainable Food Systems Strategic Initiative and Agricultural Experiment Station researcher and professor in the Department of Plant Pathology at UC Davis.

While plant diseases and pests are widely considered an important cause of crop losses, and sometimes a threat to the food supply, precise figures on these crop losses are difficult to produce.

“One reason is because pathogens and pests have co-evolved with crops over millennia in the human-made agricultural systems,” write the authors on the study’s website, globalcrophealth.org.  “As a result, their effects in agriculture are very hard to disentangle from the complex web of interactions within cropping systems. Also, the sheer number and diversity of plant diseases and pests makes quantification of losses on an individual pathogen or pest basis, for each of the many cultivated crops, a daunting task.”

“We conducted a global survey of crop protection experts on the impacts of pests and plant diseases on the yields of five of the world’s most important carbohydrate staple crops and are reporting the results,” McRoberts said. “This is a major achievement and a real step forward in being able to accurately assess the impact of pests and plant diseases on crop production.”

The researchers surveyed several thousand crop health experts on five major food crops – wheat, rice, maize, soybean, and potato – in 67 countries.

“We chose these five crops since together they provide about 50 percent of the global human calorie intake,” the authors wrote on the website.

The 67 countries grow 84 percent of the global production of wheat, rice, maize, soybean and potato.

Top pests and diseases

The study identified 137 individual pathogens and pests that attack the crops, with very large variation in the amount of crop loss they caused.

For wheat, leaf rust, Fusarium head blight/scab, tritici blotch, stripe rust, spot blotch, tan spot, aphids, and powdery mildew caused losses higher than 1 percent globally.

In rice, sheath blight, stem borers, blast, brown spot, bacterial blight, leaf folder, and brown plant hopper did the most damage.

In maize, Fusarium and Gibberella stalk rots, fall armyworm, northern leaf blight, Fusarium and Gibberella ear rots, anthracnose stalk rot and southern rust caused the most loss globally.

In potatoes, late blight, brown rot, early blight, and cyst nematode did the most harm.

In soybeans, cyst nematode, white mold, soybean rust, Cercospora leaf blight, brown spot, charcoal rot, and root knot nematodes caused global losses higher than 1 percent.

Food-security “hotspots”

The study estimates the losses to individual plant diseases and pests for these crops globally, as well as in several global food-security “hotspots.” These hotspots are critical sources in the global food system: Northwest Europe, the plains of the U.S. Midwest and Southern Canada, Southern Brazil and Argentina, the Indo-Gangetic Plains of South Asia, the plains of China, Southeast Asia, and sub-Saharan Africa.

“Our results highlight differences in impacts among crop pathogens and pests and among food security hotspots,” McRoberts said. “But we also show that the highest losses appear associated with food-deficit regions with fast-growing populations, and frequently with emerging or re-emerging pests and diseases.”

“For chronic pathogens and pests, we need to redouble our efforts to deliver more efficient and sustainable management tools, such as resistant varieties,” McRoberts said. “For emerging or re-emerging pathogens and pests, urgent action is needed to contain them and generate longer term solutions.”

The website globalcrophealth.org features maps showing how many people responded to the survey across different regions of the world.

In addition to McRoberts, the research team included lead author Serge Savary, chair of the ISPP Committee on Crop Loss; epidemiologists Paul Esker at Pennsylvania State University and Sarah Pethybridge at Cornell University; Laetitia Willocquet at the French National Institute for Agricultural Research in Toulouse, France; and Andy Nelson at the University of Twente in The Netherlands. 

UC Agriculture and Natural Resources researchers and educators draw on local expertise to conduct agricultural, environmental, economic, youth development and nutrition research that helps California thrive. Learn more at ucanr.edu.

Greensmith APN Expanding Services

Greensmith APN Ensures the Best of Both Worlds for Biological Control

By Mikenzi Meyers, Associate Editor

Integrated Pest and Crop Management, otherwise known as IPM, is a critical component of all forms of crop production. Perhaps one of the most important aspects of IPM is the practice of biological control, which includes the control of any pests or invasive plants by using other organisms to monitor their populations.

Lee Tecklenburg of Greensmith APN (Advanced Plant Nutrition), works with both conventional and organic operations in order to help maximize biological control.

Greensmith APN is currently working to put together and market products that work simultaneously with biocontrols on the nutrient side of things.

“We’re trying to create a situation where the plants can thrive and become more tolerant and more resistant,” Tecklenburg explained.

This includes integrating all parts of production, whether it be organic or conventional, in order to tie the entire system together.

“It’s all-encompassing. If you can register something organically today, a conventional grower can use it as well, and it’s not the reverse,” Tecklenburg added. “This approach ensures that everyone is able to benefit from the program Greensmith APN is creating.”

Oriental Fruit Fly Quarantine in Portion of Los Angeles County

A portion of Los Angeles County has been placed under quarantine for the oriental fruit fly (OFF) following the detection of nine adult OFF in an unincorporated area of Los Angeles County near the City of Inglewood.

The quarantine zone in Los Angeles County measures 81 square miles, bordered on the north by Avalon Boulevard; on the south by E Victoria Street; on the west by S La Cienga Boulevard; and on the east by California Avenue.  A link to the quarantine map may be found here: www.cdfa.ca.gov/plant/go/offq.

To prevent the spread of fruit flies through homegrown fruits and vegetables, residents living in the fruit fly quarantine area are urged not to move any fruits or vegetables from their property.  Fruits and vegetables may be consumed or processed (i.e. juiced, frozen, cooked, or ground in the garbage disposal) at the property where they were picked.

To help prevent infestations, officials ask that residents do not bring or mail fresh fruit, vegetables, plants, or soil into California unless agricultural inspectors have cleared the shipment beforehand, as fruit flies and other pests can hide in a variety of produce.  It is important to cooperate with any quarantine restrictions and to allow authorized agricultural workers access to your property to inspect fruit and oriental fruit fly traps for signs of an infestation.

“Our system to detect invasive species like the oriental fruit fly is working well and according to design,” said CDFA Secretary Karen Ross.  “The key is to respond quickly and take action before the pests can spread.”

Following the principles of Integrated Pest Management (IPM), CDFA uses “male attractant” technique as the mainstay of its eradication effort for this pest.  This approach has successfully eliminated dozens of fruit fly infestations from California.  Trained workers squirt a small patch of fly attractant mixed with a very small dose of pesticide approximately 8-10 feet off the ground on street trees and similar surfaces; male fruit flies are attracted to the mixture and die after consuming it.

The male attractant treatment program is being carried out over several square miles surrounding the sites where the oriental fruit flies were trapped.  A map of the treatment area is available online at:  www.cdfa.ca.gov/plant/go/ffmaps-peps.

On or near properties where fruit flies have been detected, additional measures include removal of host fruits and vegetables, fruit cutting to detect any fly larvae that may be present, and treatment of host trees and plants with the organic-approved material spinosad.

The oriental fruit fly is known to target over 230 different fruit, vegetable, and plant commodities.  Damage occurs when the female fruit fly lays her eggs inside the fruit.  The eggs hatch into maggots and tunnel through the flesh of the fruit, making it unfit for consumption.

While fruit flies and other invasive species threaten California’s crops, the vast majority of them are detected in urban and suburban areas.  The most common pathway for these pests to enter the state is by “hitchhiking” in fruits and vegetables brought back illegally by travelers as they return from infested regions around the world or from packages of home grown produce sent to California.  The oriental fruit fly is widespread throughout much of the mainland of Southern Asia and neighboring islands including Sri Lanka and Taiwan.  It is also found in Hawaii.

Residents with questions about the project may call the department’s Pest Hotline at 1-800-491-1899.

Ranchers Concerned About Invasion of Medusahead Weed on Foothill Rangeland

Source: Jeannette E. Warnert

One of the worst rangeland weeds in the West is aptly named after a monster in Greek mythology that has writhing snakes instead of hair.

Medusahead, an unwelcome transplant from Europe, is anathema to the cattle living off rangeland grass. The weed’s three-inch-long bristles poke and sometimes injure the animals’ mouths and eyes.

The weed is also low-quality forage for livestock. When medusahead takes over rangeland, it reduces the forage value by 80 percent.

When Fadzayi Mashiri, UC Cooperative Extension advisor in Mariposa, Merced and Madera counties, was appointed in 2013, she became the first natural resources and rangeland expert to hold the position since the retirement of Wain Johnson more than a decade before.

She polled local ranchers to determine their most pressing problems. They said weed management, and in particular, medusahead.

Medusahead is relatively easy to identify on the range. It has distinctive stiff awns and a seed head that does not break apart as seeds mature. Patches of medusahead are obvious when spring turns into summer.

“Medusahead stays green after most of the annual grasses have dried off,” Mashiri said.

Medusahead has high silica content, making it unpalatable to cattle. The silica also protects the plant from decomposition, so a thick thatch builds up on the rangeland, suppressing more desirable species, but not the germination of the next year’s medusahead seedlings.

Over the years, UC scientists have discovered a number of medusahead control strategies:

  •  Corral cows on medusahead before the plant heads out or employ sheep to graze medusahead patches. It’s not sheep’s favorite forage either, but they will eat if left with no other option.
  • Prescribed burning in late spring or early summer. However, this strategy poses air quality and liability issues.
  • Apply nitrogen fertilizer to medusahead to improve palatability before it flowers, which is showing promise for controlling the weed and boosting the value of infested rangeland.
  • Chemical control.

In spring 2014, Mashiri conducted a demonstration field trial in Mariposa County of medusahead control with the herbicide Milestone, which was developed by Dow AgroSciences mainly to control broadleaf weeds like yellow starthistle.

The trial followed rangeland weed control research done by scientists including Joe DiTomaso, UC Cooperative Extension specialist in the Department of Plant Sciences at UC Davis. DiTomaso found that the density of medusahead in treated areas declined and concluded that Milestone prevents medusahead seedlings from thriving.

Unfortunately, Milestone treatment of large rangeland areas is expensive.

“But if the value of forage declines, the productivity of livestock is compromised,” Mashiri said. “When you look at it that way, the chemical treatment might be useful.”

Massive Ant Hunt Launches Across 7 O.C. Cities

Source: Scott Martindale; Orange County Register

Susie Federico peered through her glasses at the dozens of ants swarming a tiny plastic trap she’d staked in the ground.

Federico, an agricultural technician for the state Department of Food and Agriculture, used a pair of tweezers to inspect all sides of the plastic basket, filled with one of ants’ favorite foods – Spam canned meat.

Unless they were big-headed ants, Federico let them go free.

“I’m looking for the larger head,” Federico said as she flicked off ants that had crawled up her hand and arm.

“There is not a sample as of now.”

Assigned to a residential neighborhood in northwestern Santa Ana, Federico was part of a team of state agricultural technicians that began setting ant traps Monday across a 79-square-mile swath of Orange County.

State officials are looking for the aggressive Pheidole megacephala species of big-headed ants, which were discovered last month in the front yard of a Costa Mesa home near the Santa Ana River.

“Knowing the extent of the infestation is an important consideration,” said Steve Lyle, a spokesman for the state Department of Food and Agriculture. “We’re still evaluating what this means. Is it something that needs to be taken care of? Is it something we can take care of?”

Named after their disproportionately large heads, big-headed ants are considered an agricultural pest and one of the world’s most invasive insects. They aren’t dangerous to humans.

In all, state officials plan to place Spam traps at 1,570 locations in seven Orange County cities in the coming days – the equivalent of 20 per square mile.

A team of up to eight state workers will spend at least a week systematically placing traps in neighborhoods up to 5 miles from where the original colony was discovered, Lyle said.

The study area encompasses all of Costa Mesa and parts of Huntington Beach, Fountain Valley, Westminster, Santa Ana, Irvine and Newport Beach.

Once officials know how far the ants have spread, they can decide whether to move forward with extermination, Lyle said.

Although California is home to native varieties of big-headed ants, the species discovered in mid April in Costa Mesa was the first documented sighting of the aggressive Pheidole megacephala species in its natural environment in California. It can displace other ants and eat beneficial insects, authorities say.

The Costa Mesa colony was first spotted by amateur entomologist Gordon C. Snelling of Apple Valley, who was visiting a friend in mid April.

The friend had been complaining about aggressive ants invading his house and winding up dead in his swimming pool, Snelling said.

Snelling said the big-headed ants had likely traveled to his friend’s home inside potted plants or sod, and that they had probably been there at least a year.

“I knew the state and the county would get in an uproar as soon as I let them know,” Snelling, 55, told the Register last week.

“It’s one of those things that gets the adrenaline pumping and your brain churning,” added Snelling, who runs the website armyants.org and has published scientific papers on ants. “It’s certainly caused more response than anything else I’ve done.”

Seminar on Sustainable & Organic Practices in Southern California

An all day seminar for growers and crop consultants focusing on sustainable and organic farming practices for pest management and plant health in Southern California will be held on June 19.

Subjects include: County of San Diego Department of Agriculture Regulatory Update, BioControl of Pests, Micronutrient Use, Essential Plant Nutrition, Soil Testing, Mycorrhizal Inoculants, Soil Amendments/Compost, Organic Weed Control, Optimizing Organic Fertilizer Application and an Organic Grower Panel Discussion.

Also exhibits by firms providing products acceptable for organic and sustainable production.  CEUs are offered for Certified Crop Advisers (6.0 hours) and licensed Pest Control Advisers (6.0 hours).

WHO: Presented by the San Diego County Chapter of California Association of Pest Control Advisers and Organic Fertilizer Association of California.

WHEN: Thursday, June 19, 2014, 8:00 am – 3:00 pm.

WHERE: Pala Mesa Resort, 2001 Old Highway 395, Fallbrook, CA

INFO: Contact Steven Beckley, (916)539-4107, sbeckley@aol.com.

Program and Registration is available at https://capcaed.com/continuing-ed-seminars/june-19-2014-fallbrook-sustainable/organic-practices-in-southern-california