AgNet DEMO

Category: Vegetables

  • Shade Nets Show Benefits for Peppers

    Figure 1. Shade nets can prevent crops from receiving too much light.

    By Juan Carlos Díaz Pérez

    Vegetable growers know well about the importance of light to plants. Light is necessary for the process of photosynthesis through which plants convert light energy into chemical energy (sugars) needed for plant growth and development.

    LIGHT AND HEAT

    Light is electromagnetic radiation that comes from the sun. The portion of the electromagnetic spectrum that can be seen or perceived by humans, the “visible light,” is within 400 to 780 nanometers (nm). (A nanometer is a billionth of a meter.) Photosynthesis also occurs within this visible range.

    In addition to the visible light, infrared is an important region of the electromagnetic spectrum that is for plant growth. The infrared light covers the range from 780 nm to 1 millimeter. A little more than half of the electromagnetic energy received from the sun is in the form of infrared radiation. Objects such as plants, animals and the soil emit heat as infrared radiation.

    Heat is energy that flows because of differences in temperature. Although visible light and other electromagnetic radiations may produce heat, the majority of heat at the Earth’s surface is associated with infrared radiation. Thus, plant heat stress due to excessive light and temperature are related to high exposure to infrared radiation.

    Although not all scientists agree with the concept of global warming, most climate experts believe that Earth’s temperature has been increasing since the time of the Industrial Revolution. The rise in temperature affects agricultural crops and may increase incidences of pests and diseases. New pests and diseases have been detected in the last decades that have been linked, at least partially, to changes in climatic conditions.

    Vegetable crops are particularly sensitive to high temperature and high light intensity conditions. Vegetables typically require soil moisture availability to reach high fruit yield and quality. Under conditions of high light and high temperature, crops such as pepper plants show drought stress, reduced fruit yields and high incidences of fruit physiological disorders such as fruit sunburn and blossom-end rot.

    PROTECTIVE TOOL
    Figure 2. Bell pepper plants are grown under shade net supported with a metallic cable and posts forming a pyramidal structure at the University of Georgia in Tifton.

    Shade nets are a type of technology used extensively to protect vegetables and other horticultural crops from damage by high solar radiation, wind, birds and hail. Black nets are the most common and the least expensive (Figure 1).

    Shade nets help reduce the heat load on crops by absorbing a portion of the solar radiation (visible light and infrared) and may reflect or refract some of the radiation, depending on the color and chemical composition of the net. The percentage of the solar radiation reduced by the net (called the “shade factor”) may vary from as low as 15% to as high as 80%. The type of net shade factor to use depends on the crop.

    RESEARCH RESULTS

    A study at the University of Georgia (UGA) in Tifton was conducted to determine the response of bell pepper plants to nets with different shade factors. Bell pepper plants (cultivars Camelot, Lafayette, Sirius and Stiletto) were grown in the field following the recommendations of the UGA Extension Service. Plants were planted in the field during the spring season of two years.

    Table 1. Bell pepper fruit yield under field conditions in Tifton, Georgia, as influenced by shade factor of black nets. Values are the means of four cultivars (Camelot, Lafayette, Sirius and Stiletto).

    Plants were grown in unshaded conditions (0% shade factor) and under nets with 30, 47, 63 and 80% shade factors (Figure 2). Results showed that fruit marketable yield of the four cultivars was highest under nets with 30 and 47% shade factors (Table 1). The yield of nonmarketable fruit decreased with increasing shade factor, indicating that reduced light levels were associated with diminished incidences of fruit physiological disorders (sunburn). The fruit size also increased with higher shade levels. See doi.org/10.21273/HORTSCI.49.7.891 for a more detailed report of this study.

    In conclusion, shade nets with shade factors between 30 and 47% resulted in the following benefits:

    • Increased fruit marketable yield
    • Improved fruit size
    • Decreased incidences of fruit sunburn

    Juan Carlos Díaz-Pérez (jcdiaz@uga.edu) is a professor in the Department of Horticulture at the University of Georgia in Tifton.

  • Beware: Fungal Foliar Diseases Alive and Well in Alabama

    Figure 1. Anthracnose fruit rot of strawberry © Catherine Eckert / shutterstock.com

    Weather conditions are conducive to certain plant diseases being a problem this year. Joe Kemble, Alabama Extension vegetable specialist, cautions Alabama producers about certain fungal diseases that could become problematic.

    “One of the things that’s important this time of the year is there are a lot of foliar fungal diseases. They cause problems in strawberries, but they also cause problems in vegetable crops,” Kemble said. “I’ve seen quite a bit of scattered anthracnose around the state. It’s a common fungal disease. It also goes to strawberries, different species of the disease. Basically, if the weather conditions are favorable for one, they’re favorable for all the different versions of that disease.”

    While diagnosing the disease is not an issue, managing it can be a problem if you’re an organic producer. They don’t have the same options to control diseases as a conventional grower would.

    “If you’re a conventional grower, there’s herbicides that work quite well to manage these. But if you’re growing organically, you’ve got a bit of a mixed bag in terms of what you need to do. There aren’t any products out there that are curative. It’s really a preventative measure,” Kemble said. “If I’m an organic grower, this time of the year, I think it’s safe to assume that you’re going to have these diseases. It’s a good idea to put on any type of protectant sprays that you’d like to use. If the spray’s not there, you’re not going to get any type of control. It’s very hard after the fact once you see the disease.”

  • USDA Vegetable Outlook

    Fresh cucumber prices were down 44% in the first quarter of 2020.

    Fresh vegetable production value in the United States was down 11% in 2020, according to the USDA Vegetable and Pulses April Outlook.

    Spinach experienced the biggest decline, dropping 28.7% a year after increasing 49.8%. Cauliflower dropped 25%. A year after increasing 22.8%, cabbage production dropped 18.2%. Bell peppers dropped 11.2%, while Carrots declined 7.1%. Dry onions also dropped 14.5%.

    Sweet corn experienced the biggest increase with an 18.5% jump from 2019. Sweet potatoes also increased 9.7%

    First Quarter 2021 Prices Down

    The Producer Price Index (PPI) reveals fresh vegetable producer prices decreased by 8% through the first quarter of 2021. Lettuce was down 23%; sweet potatoes down 8%; tomatoes down 46%; and broccoli down 8%.

    Consumer Preference

    Consumers also demanded more organic vegetables. First quarter non-organic prices for fresh cucumbers were down 44%, while organic cucumber retail prices rose by 138%. Prices for organic white round potatoes increased by 151% from 50 cents to $1.25 per pound. However, prices for non-organic white round potatoes increased by just 1.9%.

    Imports Increased, Exports Decreased

    The U.S. continues to import vegetables, increasing by 3% in 2020. However, exports were down 4% in 2020. The U.S. imported 4.05 billion pounds of tomatoes in 2020, a 1% increase from 2019. There were 2.19 billion pounds of cucumbers imported in 2020, a 2% increase from 2019. Bell peppers also increased 3% to 1.66 billion pounds in 2020.

    Broccoli imports increased by 10% to 542 million pounds in 2020. Lettuce imports also increased by 4% to 821 pounds.

    Stormy Impact

    The National Oceanic and Atmospheric Administration (NOAA) reported $22 billion weather events, which cost the U.S. $95 billion. Wildfires in California, Oregon, Washington and Colorado were devastating.

    Excessive rains at the end of the growing season in 2020 hurt sweet potato yields in North Carolina, the largest producer of the crop.

    A record-breaking number of hurricanes in 2020 affected sweet potato production in Louisiana as well. More than 660 acres of sweet potatoes were lost in the state due to hurricanes/tropical depressions and excessive moisture/rain.

  • Biological Control of Sweetpotato Whiteflies With Predatory Mites in Squash

    Adult sweetpotato whitefly Photos by L. Lopez

    By Lorena Lopez and Oscar E. Liburd

    The sweetpotato whitefly (Bemisia tabaci) is one of the most problematic pests in vegetable production in the world and it is a key pest in squash. Most significant damage caused by this pest is due to the transmission of viral diseases and its ability to rapidly develop resistance to pesticides.

    Sweetpotato whiteflies can develop from egg to adult in two to three weeks under optimal environmental conditions (77 to 91°F, 50-70% relative humidity). Adult whiteflies are ~0.03- inch-long, yellow insects with two pairs of iridescent white wings.

    Females can live up to 24 days and lay up to 300 eggs. Eggs are oval, pearly white to yellow, and darken as they mature.

    Whitefly nymphs disperse briefly within the same leaf and then attach permanently to the leaf while continuously feeding on its contents. Before turning into adults, nymphs are less flattened and have big red eyes.

    THE DAMAGE DONE

    Sweetpotato whiteflies are usually found living and feeding on the lower side of squash leaves. Nymphs excrete honeydew that accumulates on leaves, flowers and fruit when populations reach high numbers. This results in sooty mold (fungus) development, reduction in photosynthesis and fruit losses.

    A) Silvered squash leaves. B) Healthy fruit (top) and fruit with discoloration due to viral infection (bottom)

    Feeding of nymphs is also associated with the development of squash silverleaf disorder in pumpkins, winter and summer squash, and some types of butternut squash. Squash silverleaf causes the newly developing leaves to turn silver due to proteins in the nymph’s saliva. Decreased photosynthesis and yield reductions result from high silvering of the squash leaves.

    Additionally, sweetpotato whiteflies transmit multiple viral diseases to squash. These include cucurbit leaf crumple virus, cucurbit yellow stunting disorder virus and squash vein yellowing virus. Common symptoms of viral diseases in squash include plant stunting, leaf and fruit malformation, yellowing and discoloration.

    In Florida, squash is grown mostly during the fall from mid-September to mid-November. Some growers may also plant squash in the spring from mid-March to mid-April. It is common to have higher whitefly pressure during the fall compared to the spring season. The combination of whitefly-transmitted diseases with high pest infestations can cause up to 50% reduction in marketable yield during the fall compared with the spring season when fewer viral diseases and low whitefly infestation levels are observed. 

    WHAT TO DO

    The management of plant viruses is best achieved when resistant varieties are available. However, there are no squash varieties resistant to whitefly-transmitted viruses yet. Therefore, squash plant viruses are mainly managed by suppressing the vector.

    Sweetpotato whitefly populations are usually managed using insecticides that are applied on a weekly basis. However, the development of resistance against these insecticides is always a major concern. Entrust (spinosad) is a low-risk pesticide commonly used in vegetable crops, but it is not effective against whiteflies. Other low-risk pesticides such as M-Pede® (soap concentrate) or Azera® (azadirachtin + pyrethrins) are effective against whitefly populations and can be used together with biological control agents like predatory mites.

    A) Adult predatory mite (Amblyseius swirskii) females guarding eggs. B) Larvae (left) and nymph (right) of A. swirskii

    The predatory mite Amblyseius swirskii is an effective predator of major pests found in Florida squash including sweetpotato whitefly and thrips. A. swirskii feeds mostly on whitefly eggs and small whitefly nymphs. Data from University of Florida biological control field studies showed that the predatory mites released onto squash leaves can rapidly disperse to other plants and suppressed whitefly populations as early as four weeks after planting. Additionally, squash silvering can be significantly reduced when this predatory mite is released.

    Data from field trials also indicate A. swirskii can disperse regardless of the squash cultivar. Moreover, squash cultivars exhibit different levels of sweetpotato whitefly attraction and susceptibility to silvering. Gold Rush is a sturdy squash cultivar that showed fewer silvered leaves compared to high-yielding squash cultivars such as Zephyr and Cash Flow. Additionally, Zephyr and Cash Flow seemed more susceptible to squash silverleaf.

    Zephyr squash is very attractive to farmers and consumers due to its green-yellow tone, but it was observed to be highly attractive to whiteflies as well. This is probably due to the light green color of the leaves that make the plants easily detected by whiteflies.

    No significant reductions in yield were observed despite high levels of silvering. However, plants were observed to be stunted and deformed when infested with high numbers of whiteflies and in the presence of whitefly-transmitted viruses. Thus, early management of sweetpotato whiteflies is recommended to avoid risking fruit quality.

    It is important to combine the use of predatory mites with other practices such as intercropping flowering plants in row middles or at the edges of the squash crop to attract other predators and parasitoids that can complement the release of predatory mites. Additionally, low-risk pesticides can be used to lessen severe whitefly infestations three to five days before the release of the predatory mites. It is best to release the predatory mites early in the morning or late in the afternoon to avoid the hottest hours of the day, during days with low winds and when there is no forecast for rain.

    Lorena Lopezis a postdoctoral research associate and Oscar E. Liburdis a professor at the University of Florida in Gainesville.

  • New Normal? Vegetable, Fruit Sales Up Amid Pandemic

    Increased food consumption at home amid COVID-19 means potentially more sales of fresh fruits and vegetables for Alabama producers, says Wendiam Sawadgo, Alabama Extension economist.

    “There was about a 50% increase in consumption at home in (last) March compared to before the pandemic. That sort of tapered off a little bit. But it’s still much higher than it was before,” said Sawadgo during the Alabama Extension Commercial Horticulture Facebook Q&A session on Friday. “What that means for a lot of our fruit and vegetable producers is sales have gone up. Fruit sales have been up 7% compared to before the pandemic. Vegetable sales about 12%.

    Restaurants closing amid the onset of the pandemic meant a drastic increase in families eating at home. But as states continue opening up and vaccines are administered around the country, does that mean a return to the pre-COVID days? Not necessarily.

    “We have data from a company that’s been tracking what’s going on with grocery sales since last March. Now they have data from the first two months of the year. There’s the thought that maybe we’ll start to come back down to where we were before the pandemic,” Sawadgo said. “We’re still up 5% to 10% from where we were. The question moving forward, are we going to keep having these high sales for the next several months, which is what I think is most likely. I don’t think it’s quite as likely that consumer behavior is going to immediately return to how it was before March of 2020.

    “The next few months will be exciting to look at, especially as vaccine rollouts increase and more parts of the country get out more, to see if we can still have sustained vegetable sales.”

  • Best Laid Plans? Georgia Vegetable Producer Adjusting Following Winter Rains

    Sometimes a farmer’s best laid plans go awry. Just ask Georgia vegetable producer Ricky Powe.

    File photo shows fumigation being applied in a vegetable field.

    “I was going to have plastic laid and ready to go by Feb. 10 and be waiting on the plants. But with farming, the best laid plan isn’t always what it is,” said the Grady County grower.

    What stopped this Georgia vegetable producer? How about a deluge of rainfall throughout February? That delayed Powe and other South Georgia farmers from laying plastic in preparation for the upcoming season. Some growers have also had to make a judgement call on whether to fumigate or not.

    Why is Fumigation Important?

    Fumigation protects crops from nematodes and other pests and diseases. The gas can linger under ground longer and prevent the plants from being put in the ground on time if the soil is too wet when fumigation is applied.

    “Normally this time of year, 21 to 28 days is plenty. Normally, 21 days, it does what it’s supposed to do and gets out of there. But I’ve got some (plastic) that I’ve laid on Feb. 15, laid a little too wet and gas levels are still extremely high in those right now,” said Powe, who produces tomatoes, peppers, pickles, yellow squash, zucchini and half runner beans. “I chose (Tuesday) to lay a little bit and just have to leave the fumigant out just because the plants were ready. Here in Georgia, we’re on a very tight market window. Either we hit that market, or it’s gone.”

    Powe would rather hit the market with potentially reduced yields compared to hitting it with maximum yields but have no one to sell to.

    “It’s kind of a two-edge sword where you get cut on both sides. I guess the best way for me to say it is, if I had put gas out and make 3,000 boxes to the acre and it got here July 4, nobody’s going to be in the market for Georgia pepper on July 4. I made the decision to get 1,600, 1,800 boxes of pepper in the right time slot,” Powe said.

  • Ant Control: Alabama Extension Encourages Farmers to Protect Crop

    Alabama Extension photo/Shows fire ants on okra.

    Vegetable crops are vulnerable to ant pressure this time of year. Alabama Extension encourages vegetable producers to implement management tactics as they begin planting this year’s crops.

    According to Alabama Extension, fire ants can protect aphids and other honeydew producers on vegetables, which makes their effects worse on the plants. Fire ants can also interfere with natural enemies. Ultimately, though, fire ants can damage crops like okra, potatoes, sunflowers and hemp.

    Cultural Controls

    It is important to control fire ant mounds around or outside the production area to prevent them from moving into the garden. It is also essential to manage excessive plant residue on the soil. This will aid in the detection of foraging ants. It provides ants fewer places to stay out of sight and makes it easier to apply bait insecticides on open ground.

    Insecticide Options

    The best time to apply baits is from April 15 to Oct. 15. Mound treatments can be done any time of the year on warm, sunny days above 65 degrees Fahrenheit when fire ants are active. Apply products close or on the mound after checking for foraging ants.

    For more information on fire ant control, read Managing Fire Ants with Baits located on the Alabama Extension website. More information is available in Fire Ant Control: The Two-Step Method and Other Approaches on the eXtension Foundation website.

  • Vegetable Assessment: Georgia Growers Approve

    citrus expo

    Georgia vegetable growers have made their voices known: The Georgia Vegetable Commission marketing order has been extended for an additional three years.

    Producers overwhelmingly voted to extend the assessment of one cent per marketing unit by producers with more than 50 acres crops that include green beans, bell pepper, specialty pepper, carrots, broccoli, beets, eggplant, cabbage, sweet potatoes, cantaloupes, cucumbers, greens, squash and tomato.

    The balloting period for the market order was conducted from Feb. 1 through March 2, 2021, and 87.67 % of the eligible ballots returned voted yes.

  • Wacky Weather: Alabama Planting Season Nears Amid Excessive Rainfall, Drought

    The most recent US Drought Monitor shows parts of Alabama in a moderate drought.

    Planting season nears for Alabama vegetable producers. Once again, weather will play a key role as farmers prepare to plant this spring’s crops.

    Joe Kemble, Alabama Extension vegetable specialist, implores producers to wait until soil temperatures increase above a certain level and stay that way for several days straight. That will be a better environment for seed to germinate and transplants to grow.

    “We like to plant by the calendar but unfortunately that just doesn’t work out really well sometimes. So, the best way to do that is to measure your soil temperature. For small and large growers, you want your soil temperature to be above 60, 65 degrees Fahrenheit for several days in a row,” Kemble said. “That’s actually a better indicator of when it’s time to put in your squash planting or your tomatoes. Anything below that, it can hamper seed germination and stand establishment. It can also knock back some of the warm season crops that go in as transplants.”

    Excessive Moisture

    Some growers may not have much choice than to wait for soil temperatures to warm. Parts of the state have experienced excessive rainfall this month. Some growers are still waiting for fields to dry out.

    “Between Alabama and South Georgia, we’ve gotten a lot of rain over the last couple of weeks. That’s hampering a lot of growers getting in the field and getting things prepared,” Kemble said.

    Moderate Drought

    But then there is a portion of southwest Alabama that could use some rainfall. According to the US Drought Monitor, Dallas County, Lowndes County, Marengo County, Monroe County, Wilcox County are classified in a moderate drought why surrounding counties are abnormally dry.

    “They’re definitely drier than the rest of Alabama. Most of Alabama got a lot of rain over the last couple of weeks. A little dry is okay,” Kemble said. “You still need a little bit of moisture though to plow effectively. If it’s too dry, you end up plowing and you create soil clots. You can sort of create a real mess for yourself.”

  • What’s Next? Georgia Producer Concerned About Future of American Farmer

    Georgia vegetable producer Sam Watson may not be a blueberry farmer, but he had a vested interest in the International Trade Commission’s recent decision regarding the impact of blueberry imports.

    Watson

    Watson, like his farming brethren, was disappointed that the ITC did not find that imports do have a significant injury to the domestic industry.

    “It’s just really frustrating and disheartening. We all know what’s happening,” Watson said. “I’m just afraid corporate America, these corporate farms and politics have played a big role in it.”

    The decision was made despite staggering statistical evidence of how the rise of imports in previous years from countries like Mexico has led to diminished prices.

    Another ITC Hearing

    Watson, managing partner of Chill C Farms in Colquitt County, Georgia, produces squash, zucchini, bell pepper, cabbage, eggplant and cucumbers. Squash and cucumbers are scheduled for a similar hearing with the ITC on April 8.

    The future of the American farmers is at stake with these hearings. With all of the competitive advantages that Mexico has, how can Southeast farmers compete? They can’t, says Watson.

    “When you go to talk about the regulatory side, the labor side, the subsidy side, the fact that they can just outright do it cheaper than we can … it doesn’t matter how much is coming because they’re just going to eventually put us out anyway. They can just do it cheaper,” Watson said.

    The USITC is currently seeking input for two additional investigations regarding the impact of imported cucumbers and squashes on the U.S. seasonal markets. The U.S. Trade Representative (USTR) requested the investigations in a letter. The USITC will hold a public virtual hearing regarding the investigations on April 8 at 9:30 a.m.