Downy mildew disease is present in cucurbits like squash and cucumber around South Florida and is getting worse.
University of Georgia/Downy mildew disease can destroy plant foliage and cause the leaves to curl and die. Without healthy leaves and vines, a plant is vulnerable to blisters and sunscald during hot days.
According to the South Florida Vegetable Pest and Disease Hotline, respondents report that the disease is showing up in most watermelons and infections have increased in areas hit hard by rainfall.
“Around Manatee County, respondents report that downy mildew really kicked into high gear after the last rains and has been quite aggressive in some situations,” the hotline report stated.
Downy mildew also remains active on cucumber and some squash on the East Coast.
According to University of Georgia Cooperative Extension plant pathologist Bhabesh Dutta, downy mildew can destroy plant foliage and cause the leaves to curl and die. Without healthy leaves and vines, a plant is vulnerable to blisters and sunscald during hot days. The pathogen thrives in wet, humid conditions and needs moisture on the surface of the plant for successful spore germination and further infection.
Cucurbit crops — like cucumbers, melons, squashes and pumpkins — are susceptible to the disease. Dutta ranks downy mildew among the top diseases in cucurbit crops, along with Fusarium wilt and Phytophthora fruit rot.
How to Recognize Downy Mildew
For those vegetable farmers unfamiliar with what symptoms look like, focus on the leaves themselves. On cucurbits besides watermelon, small yellowish spots appear on the upper leaf surface away from the leaf margin. A yellow coloration later occurs with the internal part of the lesion turning brown. Lesions are usually angular as leaf veins restrict their expansion.
On watermelons, yellow leaf spots may or may not be angular and will later turn brown to black in color.
To control downy mildew, fungicide sprays are recommended for all cucurbits. Spray programs for downy mildew are most effective when initiated prior to the first sign of the disease. Once a plant becomes infected, it becomes more and more difficult to control with fungicides.
Florida vegetable farmers are struggling to manage high whitefly pressure amid trying to produce this year’s crop. According to the South Florida Vegetable Pest and Disease Hotline, tomato growers in central Florida are really struggling with heavy whitefly pressure.
It noted, “Some growers have already experienced whitefly and virus issues in spring crops and have pulled up entire first plantings due to very high incidence of Tomato Yellow Leaf Curl Virus. Respondents indicate that whiteflies are also increasing in melons. Whitefly pressure is also high in green beans.”
Around Southwest Florida, in the Immokalee, Florida area, pressure has been extreme for the acreage that remains to be harvested. These include for watermelons and other cucurbits.
On the east coast, respondents report that whitefly have become out of control in many tomato and eggplant fields. They’re also high in cucumber and pepper.
The South Florida Vegetable Pest and Disease Hotline is in its 23rd year and reaches more than 1500 individuals and businesses and covers more than 120,000 acres representing all major South Florida vegetable production areas.
Already in Georgia
Whiteflies are already a concern in Georgia. University of Georgia Cooperative Extension vegetable specialist Stormy Sparks confirmed the pest has been observed in vegetables in the South Georgia area.
The mild winter is a key reason why whiteflies are already a problem. While colder temperatures don’t eliminate whiteflies, they do kill many of their wild hosts. They also slow population development in cultivated hosts. Warmer temperatures this winter allowed for larger whitefly populations to overwinter and become mobile earlier.
Whiteflies cause feeding injury issues in vegetables and transmit two viruses: cucurbit leaf crumple virus and cucurbit yellow stunting disorder virus. Vegetables like squash, zucchini, cucumber, cantaloupe and snap beans are highly susceptible to these viruses. Commercial cultivars that have resistance or tolerance to these pathogens are not available.
For additional information about whiteflies, see UGA CAES News.
Weather conditions are an important factor when it comes to growing peaches in Florida.
Florida’s mild winters and fluctuating temperatures in the fall continue to be challenges for peach production. Because peach trees are deciduous, they require a certain amount of cold weather to become dormant. Once the cold weather requirement for dormancy is met, the warm spring weather ends the dormancy period, resulting in floral bud break.
The number of chill hours needed to end dormancy depends on the peach variety. In the past several years, the required chill hour accumulation to achieve uniform bud break was often not achieved until late January.
“Since our winters are so mild in Florida, we are seeing that the trees are not going into proper dormancy, which means the trees are never sleeping in the winters. You always see some amount of flowering which is a concern because you’re losing those buds and potential fruit, since they won’t be harvested” says Tripti Vashisth, an assistant professor of horticulture at the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS).
Hydrogen Cyanamide Trials
Hydrogen cyanamide is a plant growth regulator used worldwide in fruit crops to break dormancy. The chemical is known for promoting uniform flowering, which is beneficial for growers because a uniform fruit set requires fewer passes to plant and harvest the crop. To ensure that hydrogen cyanamide works well for low-chill peach cultivars under Florida conditions, researchers at UF have been testing the effects of hydrogen cyanamide on peach production in Florida over the past three years.
“We have found that hydrogen cyanamide is very effective in Florida conditions,” Vashisth says.
According to Vashisth, most growers are applying hydrogen cyanamide at a rate of 1.2 or 1.25 percent. However, research results have proven that hydrogen cyanamide at a rate of .75 to 1 percent is highly effective in inducing bud break and is also more economically beneficial for growers.
Timing is Key
When using hydrogen cyanamide as a management tool, it is critical to apply it at the right time.
According to Vashisth, from the time of application in North Florida, it took about six weeks for uniform bud break to occur. However, it only took about three weeks in Central Florida.
“Right timing is very critical because if it is applied too late you can lose a lot of crop,” says Vashisth. “It needs to be a very educated decision that growers make.”
Adam Brannen, a student worker on the UGA Tifton Campus, weighs tomatoes at the Blackshank Farm.
Clint Thompson
July 16, 2014
Farmers and food processors take routine steps to reduce the likelihood of foodborne pathogens, like Salmonella and E. coli, contacting our food and causing illness. The procedures that our food industry takes on a daily basis are also effective in reducing the chances that the coronavirus responsible for COVID-19 will come in contact with the food we eat.
There is currently no evidence that the coronavirus is spread through contaminated food. This is in part because the virus primarily targets cells in the respiratory tract (lungs) rather than organs in the gastrointestinal tract (stomach and intestines), and because acids in the stomach likely inactivate ingested virus before it can cause harm.
During the current pandemic and other viral outbreaks, there are further considerations that farms and agricultural businesses must take in order to protect their workers and customers despite the usual safety of our food supply.
Farms, packinghouses and food processors
Sick workers should never be allowed to come to work, and they should understand that there is no punishment for them if and when they call in sick.
Encourage distancing of at least 6 feet between workers at all time, including on buses transporting groups of workers to the field and on the packing line when possible. Only one employee should be in the cab of a truck, and frequently touched surfaces like the steering wheel or door handles should be cleaned and disinfected when passengers leave or enter a vehicle.
Frequently touched surfaces within the farm or facility should be cleaned and disinfected throughout the day and between shift changes. The U.S. Centers for Disease Control recommends a list of U.S. Environmental Protection Agency-approved disinfectants that are effective against coronavirus. A solution of 5 tablespoons of bleach in 1 gallon of water may also be used.
U-pick operations, farmers markets, farm supply stores and CSAs
Post signs stating rules to be followed at the entrance. Keep them short and easy to read. Rules should include washing hands (or using hand sanitizer if washing is not possible) upon arrival; wearing a mask, bandana or scarf; maintaining 6 feet of distance between other patrons; and requesting vendor assistance to select items instead of handling items themselves.
Indoor markets may consider putting vendors or high-demand items outside so that patrons do not have to enter the building. For items inside, consider posting a price list outside and having an employee retrieve items, or set a reasonable limit on the amount of time each customer may stay inside to do business.
Have one person dedicated to handling payments. Conduct transactions online or over the phone when possible, and require credit or debit cards for in-person transactions, since paper money cannot be sanitized.
U-pick operations should clean and disinfect all picking baskets and equipment between customers. When in the field, customers must only touch fruit they plan to pick.
University of Georgia Cooperative Extension has further guidance, in English and Spanish, including materials for farms, packinghouses, community gardens, farmers markets, food banks, agribusinesses and consumers on its emergency resources page at extension.uga.edu/emergencies.
Picture submitted by Alan Chambers/UF: Shows a collection of different mangoes.
By Clint Thompson
Florida mango lovers will soon be able to sample this year’s crop, according Alan Chambers, University of Florida Assistant Professor/Genetics and Breeding of Tropical Fruits.
“The mangoes are just beginning to ripen now,” he said. “Fresh mangoes from Florida will soon be available. We had multiple mango blooms this year in response to multiple cold spells. As a result, we have fruit at multiple maturity levels on the trees at the same time. This will complicate harvesting.”
Mangoes are grown commercially in Florida in Dade, Lee, and Palm Beach Counties, according to University of Florida/IFAS Extension. Mangoes are grown in tropical and subtropical lowlands throughout the world.
As part of his research responsibilities, Chambers focuses on the quality of the mango. He has mature trees established at the station in Homestead, Florida. He samples individual aroma compounds. He determines how sweet the fruit are, the size they are and how much they weigh. Its essential information for local growers who want to produce a desirable fruit for consumers.
“It really helps our growers who are looking for, ‘Which one should I grow? Which ones are the best that consumers like? Which ones are they willing to pay more for?’” Chambers said. “Most of the domestic mango industry is based on imports. In South Florida, there’s higher costs of production for land, inputs and labor. Our growers make their money based on specialty products, so offering something with a higher quality or that’s safer or that’s different than what you can get in the grocery store.”
Marketing for mangoes is mostly done locally. Chambers said some of the product does get sold and shipped up the east coast.
GAINESVILLE, Fla. — As University of Florida economists cross the halfway point in their surveys of Florida’s agriculture and marine industries related to the impacts of COVID-19, initial reports indicate that impacts vary widely across industry types in terms of business closure rates, operations changes, and impacts to sales revenues and employment.
In one of the five surveys of the Assessment of COVID-19 Impacts on Florida, 200-plus charter/for-hire marine professionals responded to questions on the effects of the pandemic to their businesses, with 60% reporting business closures. The participants of this survey represent 33 counties around the state, with the largest number of responses so far coming from Monroe County.
For a separate survey on commercial fishing businesses, nearly two-thirds reported a shutdown of operations. More strikingly, nearly all of the 100 business owners representing 26 counties indicated their commercial fishing businesses had been affected by the pandemic and that the average length of that impact goes back to early March, even before many efforts to mitigate the spread of COVID-19 were in full effect.
“We’ve only gotten a glimpse at the impacts so far, but the responses have been telling as to which areas of the economy are largely unable to continue their normal operations,” said Christa Court, an assistant professor of food and resource economics and director of the Economic Impact Analysis Program, who is leading the survey effort.
Court said the survey for agriculture and aquaculture producers, processors, and transporters encompasses a larger variety of commodities and operation types, so it’s harder to give a broad overview at this early stage. Still, nearly one-fifth of the more than 400 respondents, representing all 67 counties, reported no impact to their operations, with only 10% reporting closures.
“Both positive and negative impacts to sales revenues are being reported by different operations across all commodity groups,” said John Lai, a UF/IFAS assistant professor of food and resource economics who is also part of the data analysis team. “As we gather additional data, we can dig into what characteristics seem to be driving increases versus decreases. For example, whether this is dependent on markets served, commodity type, input supply disruptions, or location – we don’t have all the information yet.”
Andrew Ropicki, a UF/IFAS assistant professor of food and resource economics who is leading the marine industry analysis portion of the survey, agrees that more participation is key to getting the best overall view of the impacts to these sectors of Florida’s economy.
“We’ve received a good number of responses overall, but at current response rates, the surveys are not yet able to give us clear insights into each individual segment of the agriculture, aquaculture and marine industries,” Ropicki said. “We encourage business owners involved in any agriculture or marine industry to participate in the survey and help us most accurately illustrate the effects of the pandemic.”
The surveys opened on April 16 and will close on May 15. The five questionnaires are specific to the type of business and include background information about the business (operations, revenues, employment, and market channels); current status (open or closed, business changes if open, or reasons for closure if closed); impacts (change in revenues, employment, customer base, products/services offered); and willingness to participate in potential follow-up or similar surveys related to COVID-19 or other disasters.
University of Florida post-harvest plant physiologist Jeff Brecht cautions consumers about putting some fruit and vegetables in their refrigerators. Quality commodities like tomatoes, melons, avocados and peaches are chilling sensitive. Consumers need to be wary that too much cooling can affect the quality of certain produce.
“I hear complaints about all of those where people say, ‘They’re tasteless. They’re not like I remember in the garden when I grew up. They don’t have flavor.’ What it really is, those are all chilling sensitive, and they’ve been exposed to low temperatures for too long. They stop producing the aroma,” Brecht said. “The aroma is a super important component of flavor. That’s what it really is when you hear people complain about tasteless tomatoes is because they’ve been chilled. It’s a big problem that we have.”
Clearing Up a Misunderstanding
Brecht said there is a misunderstanding on the part of consumers about how best to handle different fruits and vegetables when they have them in their possession. Many of the vegetables can be injured by exposure to temperatures that are too low. Sensitivity is especially a concern for immature produce.
“You can keep them too long in your refrigerator because you’ll actually start to compromise the quality,” Brecht said. “Even though I preach cooling, cooling, lower the temperature to maintain the quality, there’s a whole lot of fruits where you can’t go too far with that. That limits what you can do to keep them in good shape after harvest. You can’t cool them right down to 32 degrees or something like that, which you can do with a strawberry.”
He also encourages consumers to buy local as much as possible. They’re not only providing much-needed business for producers amid tough financial times, they’re also getting fresher fruit.
“Consumers are getting even better quality that way because they’re going to pick it up at the farm, take it home and probably eat it within a day or two. I would encourage people to patronize the direct sales farming operation to whatever extent they can,” Brecht said.
David Riley/UGA: Picture shows cowpea curculio and its damage.
By Ashley Robinson
Southerners love cowpeas, also known as southern peas or black-eyed peas. Unfortunately, so do cowpea curculios, a weevil that wreaks havoc on peas grown in the Southeast. University of Georgia (UGA) researchers are working to eliminate the pest.
History of the Pest
David Riley, professor of Entomology at UGA, has been researching cowpea curculio for the past 10 years.
At the turn of the 20th century, Southern peas covered approximately 6 million acres across the Southeast. According to Riley, they were the primary legume grown for livestock feed until World War II, when soybeans took over.
“There’s a very interesting history behind the crop,” Riley says. “One hundred years ago, cowpeas used to be a massive crop, more like cotton. They were considered an agronomic crop, grown for legume grain for animal forage and feed as well as a vegetable crop.”
After the emergence of soybeans, the cowpeas that were used for livestock production disappeared. What was left of the peas was grown for food.
When Riley began working with UGA as a vegetable entomologist in 1996, he discovered that as cowpea acreage declined, so did cowpea curculio populations. As curculio issues died down, cowpea acreage made a comeback, peaking in 2015 at about 7,600 acres, according to UGA’s 2015 Farm Gate Value Report. As acreage made a comeback, though, so did curculio populations.
Research Progress and Management Options
Unfortunately, the cowpea curculio has become tolerant to pyrethroid insecticides which was the primary means of control during the flowering stage of the crop. However, in the 10 years that Riley has studied the pest, a lot of progress has been made.
“When all of your insecticide options are gone, then you have to start thinking outside the box,” Riley said.
“The most recent, big discovery that has been made is that cowpea curculio is very similar to the boll weevil in that is diapauses,” Riley says. “Diapause is a state of hibernation. During this process, the female weevils don’t develop eggs. They put on fat to survive the winter instead. This is something tropical weevils do because they don’t have any food to survive on during the winter.”
Riley recommends growers plant their crop for a late September pod set, to avoid damage.
New World Beans
Another recent discovery is that New World beans are not as affected by the weevil.
Five years ago, Riley came across a professor in Australia who was working on another cowpea project in Africa. The professor, T.J. Higgins, noticed that the New World bean, Phaseolus vulgaris (snap bean or pinto bean), wasn’t affected by this weevil. He tracked the reason down to a gene called alpha-amylase inhibitor. Amylase is the enzyme used to digest starch. An inhibitor stops that normal enzyme from working, so it’s harder to digest.
Higgins took the alpha-amylase inhibitor gene from the New World bean and put it into the Old World bean (cowpea). His results from this genetically modified pea show reduced weevil damage.
“The New World Beans have a natural resistance to weevils. They grew up together,” Riley said. “Cowpeas aren’t from the New World, so they don’t have the natural resistance.”
Although weevil-resistant peas would be ideal, it will be difficult to get them approved as the crop isn’t expensive enough and there isn’t enough acreage to warrant a big company getting involved.
“There is a practical consequence of just knowing the biology and knowing how these crops are,” Riley says. “If you use traps in the spring to see when the weevils are coming out of their overwintering sites, those weevils are very starved. Although they would prefer a cowpea, they will go after snap beans if that is all that is available.”
Since snap beans aren’t a good reproductive host for the pest, Riley suggests that growers set up traps for their area. They can determine when the weevils are on the move out of their overwintering sites. Then growers should plant snap beans first as a trap crop. Give it a month or so and force those weevils to try to lay eggs in the snap beans. Since it’s a crop with natural resistance, most of the eggs won’t develop.
GAINESVILLE, Fla. — University of Florida researchers have discovered another possible solution to the plague of citrus greening that is impacting Florida’s citrus groves. This new information adds to the growing portfolio of knowledge that UF scientists are amassing to fight the disease.
Led by UF Institute of Food and Agricultural Sciences microbiology and cell science professor Claudio Gonzalez, a team of plant pathologists, horticulturists and citrus breeders identified new management practices that slowed the spread of the damaging bacterium and supported increased fruit yield.
“Our findings present another solid block of information in the foundation of finding solutions to citrus greening,” said Christopher Gardner, a biological scientist who was a member of the research team.
The three-year project funded by the United States Department of Agriculture’s National Institute of Food and Agriculture division included greenhouse and commercial field trials. Researchers injected solutions of benzbromarone (benz), tolfenamic acid (tolf) and a combination of both benzbromarone and tolfenamic acid into trees of varying ages in both environments. Results showed that the treatment decreased infection in the roots of citrus trees compared to the control trees and increased fruit production (15%) following twelve months of treatment with benzbromarone and tolfenamic acid.
Two field trials were conducted in Florida, where benz, tolf and the combination of benz and tolf were evaluated for effectiveness against the greening bacterium in sweet orange and white grapefruit trees, ranging from 8 to 12 years old. Treatments were delivered by trunk injections.
The amount of C. paradise fruit classified in categories of higher marketable value significantly increased after the treatments; the combined benzbromarone and tolfenamic treatment was the most effective. Trees that received injections formulated with the combined treatment (Benz and Tolf) were found to produce 15% more fruit (by fresh fruit weight), when compared to the control group. C. paradisi trees that received tolfenamic acid trunk injections had seven percent more fruit at the time of harvest, when compared to controls that received buffer only.
“Considering that treatments were only administered for one season, we found these results to be remarkable, as reduced fruit size is one of the primary adverse effects of citrus greening disease,” said Gardner.
The treatments did not compromise tree viability or the soil surrounding the trees. Nor did the treatment create any negative long-term effects that would inhibit the safety of the fruit. The chemical treatments included in the project have not been assessed or approved by the FDA or USDA for use in agriculture. Researchers will continue testing compounds with similarities to those we have already identified (Benz and Tolf), to find chemicals with higher efficacy against Liberibacter asiaticus. While more research is needed, the findings contributed to the growing portfolio of knowledge on fighting citrus greening.
The research was recently published in Nature Scientific Reports.
The mission of the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) is to develop knowledge relevant to agricultural, human and natural resources and to make that knowledge available to sustain and enhance the quality of human life. With more than a dozen research facilities, 67 county Extension offices, and award-winning students and faculty in the UF College of Agricultural and Life Sciences, UF/IFAS brings science-based solutions to the state’s agricultural and natural resources industries, and all Florida residents.
University of Georgia photo/Creating a compost pile keeps unnecessary waste out of landfills, as landscape refuse, such as leaves, grass clippings and trimmings, accounts for up to 20% of landfill waste.
By Maria M. Lameiras for CAES News
With more time at home on many people’s hands these days, lots of yard work is being tackled, making this year’s International Compost Awareness Week, May 3 through 9, a perfect time to create a home composting system.
For the new composter, first find an ideal spot on your property to locate your composting pile or receptacle, says composting expert and Agriculture and Natural Resources Program Development Coordinator Amanda Tedrow, who represents University of Georgia Cooperative Extension’s Northeast District.
“If you are just starting out, go for the pile. The ideal minimum size for a compost pile is four by four by four (4 feet wide by 4 feet long by 4 feet deep). That is the right size to reach the temperatures needed for decomposition. A smaller pile will decompose at a slower rate due to lower temperatures,” Tedrow said.
Locate the compost pile downhill and away from vegetable gardens to prevent potential runoff from the compost pile, which could transmit plant diseases to the garden.
While heat is an important element to composting, the heat is generated within the composting pile, so it is not necessary to locate a composting system in direct sun. A compost pile located in direct sun may need additional supplemental water during the heat of the summer months.
Next, it’s important to add the right mix of materials to the pile.
“The general recommendation is to do two-thirds to three-quarters browns and one-third to one-quarter greens,” she said. Brown materials — such as dried leaves, sticks and old mulch — are a source of carbon, while green materials — such as grass clippings, vegetable and fruit scraps, coffee grounds and egg shells — are sources of nitrogen, both important for proper composting to occur.
Avoid adding any kitchen waste that contains meat, dairy products or greasy substances, Tedrow warns.
“Vegetable peelings, fruit rinds, stalks from broccoli, things like that are all fine. Something like peach pits might take a long time to compost, but they are perfectly fine to put in,” she said.
Moisture is essential, but a compost pile should only stay “as wet as a wrung-out sponge,” Tedrow said.
“In an ideal world, a compost pile should be turned when the temperature in the center of the pile starts dropping (below the ideal temperature of 130 to 160 degrees Fahrenheit). Most people don’t have a compost thermometer, so many composters will turn their pile every week to two weeks to keep the process moving,” Tedrow said. Compost thermometers are available in stores or online starting at about $20, she added.
If wildlife is a possible concern, an enclosed composting bin may be a better option, she said.
If you have a free-form compost pile and you are having a hard time keeping compost materials together, consider using a piece of fencing or other material to make a hoop around the pile to keep it contained, Tedrow added.
While creating a compost pile can, in time, produce material usable for gardening, the best thing about a compost pile is keeping unnecessary waste out of landfills, as landscape refuse, such as leaves, grass clippings and trimmings, accounts for up to 20% of the waste being placed in landfills.
For more detailed information on composting, visit extension.uga.edu/publications and search for UGA Extension Circular 816, “Composting and Mulching.” For further assistance or to check for local composting week events, locate your local UGA Extension office at extension.uga.edu/county-offices.
