AgNet DEMO

Category: Corn

  • The Challenges of Controlling Silk Flies in Florida Sweet Corn

    Corn silk fly maggots injure sweet corn silks and kernels. Photo by Julien Beuzelin, UF/IFAS

    By Julien Beuzelin

    Corn silk flies are the most damaging insects of sweet corn in southern Florida. Adults of three species(Euxesta stigmatias, Euxesta eluta and Chaetopsis massyla) are commonly observed in commercial fields where they lay eggs on sweet corn silks. Maggots feed on silks and kernels before leaving the ear and falling onto the soil surface, under which they pupate. Adults emerge from the soil ready to mate and lay eggs within days, thus completing the pest’s life cycle.

    Corn silk fly maggot infestations and associated injury are responsible for crop losses every year, particularly in the spring. Losses occur because a small proportion of sweet corn loads might be rejected, but also because growers forgo harvest of portions of fields and sometimes entire fields when infestations are expected to lead to load rejections. These losses occur in spite of intensive pest management. In addition, corn silk flies have become increasingly challenging to manage over the past 20 years.

    Research conducted at the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) has focused on determining why corn silk flies are challenging to control and on developing improved management tactics.

    PYRETHROID RELIANCE AND SUSCEPTIBILITY

    Pyrethroids have become the cornerstone of corn silk fly management because effective alternatives in other insecticide classes have been phased out. Chlorpyrifos, methomyl and spinetoram also play a role currently. However, chlorpyrifos, which might lose its registration in the near future, can only be applied at a reduced rate within 21 days of harvest when sweet corn is susceptible to flies. In addition, methomyl has limited residual activity, and spinetoram is extremely expensive. Thus, chlorpyrifos and methomyl are frequently co-applied with pyrethroids to increase efficacy, and spinetoram is seldom used.

    Corn silk fly control is challenging because available insecticides are effective only if the insects are exposed to sprays or treated surfaces. Thus, only adults are the targets of management. Maggots and pupae are protected within ears and under the soil surface, respectively. Female adults escaping insecticide control or moving into sweet corn fields from adjacent habitats can lay eggs on susceptible ears, resulting in maggot infestations that cannot be further controlled.

    Repeated use of a single insecticide mode of action may lead to the development of insecticide resistance in pest populations. Therefore, pyrethroid resistance is a concern and may contribute to difficulties in controlling corn silk flies.

    Graduate student Eric Schwan Resende at the UF/IFAS Everglades Research and Education Center in Belle Glade has recently developedan adult vial assay for corn silk flies. This method involves coating the inner surface of small glass vials with a pyrethroid and introducing adults into the vials for 24 hours to record mortality as affected by different insecticide concentrations. It has been used to determine pyrethroid susceptibility for populations occurring in Florida sweet corn fields.

    Seven corn silk fly populations collected in sweet corn fields of the Everglades Agricultural Area and Homestead region in 2020 were evaluated using beta-cyfluthrin as a representative pyrethroid. The LC50, which is the estimated concentration killing 50 percent of the population, was determined for each population.

    In the laboratory, researchers are studying corn silk fly adults in vials to learn the effects of insecticide ingestion. Photo by Victoria Dunkley, UF/IFAS

    Two E. stigmatias populations from non-treated experimental fields had LC50s of 0.4 and 0.8 microgram (µg) per vial. Four E. stigmatias populations from commercial fields had LC50s between 1.5 and 3.5 µg per vial. One E. eluta population from a commercial field had an LC50 of 0.2 µg per vial. In addition, one E. eluta population maintained in the laboratory and serving as susceptible reference had an LC50 of 0.02 µg per vial.

    These results provide further evidence that E. eluta is more susceptible to pyrethroids than E. stigmatias. Thus, management should be more aggressive if E. stigmatias is present. Results suggest that E. stigmatias populations in non-treated fields are more susceptible to pyrethroids than populations in commercial fields that were intensively treated with insecticides. However, there is little variability in E. stigmatias pyrethroid susceptibility among populations in commercial fields. Thus, difficulties in controlling E. stigmatias are likely the result of high population levels, environmental conditions and the selection of less susceptible individuals in field populations.

    THE SEARCH FOR ALTERNATIVES

    Laboratory protocols were developed in 2020 to determine corn silk fly mortality associated with contact and ingestion exposure to insecticides including non-registered active ingredients. Preliminary experiments using E. eluta adults showed that whereas pyrethroids are effective via topical exposure, alternatives including neonicotinoids, diamides, abamectin and indoxacarb do not cause observable lethal effects. Via ingestion of insecticides at 1 percent of high field rates, the non-registered neonicotinoids thiamethoxam, clothianidin and dinotefuran caused 60 to 90 percent mortality.

    Although results need to be confirmed, these experiments show that potential alternatives to pyrethroids are not effective via topical exposure. However, some neonicotinoids are effective via ingestion. Thus, these insecticides cannot be direct replacements for pyrethroids, but they should be considered with baits forcing corn silk fly ingestion of insecticides.

    CONCLUSIONS

    High levels of pyrethroid resistance do not appear to be the main reason why corn silk flies are extremely challenging to control under current sweet corn production conditions. However, observations suggest reduced susceptibility in commercial field populations. Thus, adult vial assays are a newly developed method that will be used routinely to test field populations and monitor for pyrethroid resistance.

    With large corn silk fly populations building up, additional insecticides and new modes of insecticide delivery are needed. The use of baits and neonicotinoids have potential to control silk flies and will be further evaluated. In addition to insecticides, UF/IFAS entomologists will continue studying corn silk fly ecology, in particular the role of habitats adjacent to sweet corn fields to reduce or even prevent adult movement from adjacent crop and non-crop habitats.

    Acknowledgments: Corn silk fly research is partially supported by Florida Department of Agriculture and Consumer Services Specialty Crop Block Grants. Crop consultants and Dak Seal (UF/IFAS Tropical Research and Education Center, Homestead) assisted with insect collections.

    Julien Beuzelin is an assistant professor at the UF/IFAS Everglades Research and Education Center in Belle Glade.

  • What to Look for With Corn Earworm

    According to a University of Florida/IFAS blog, the corn earworm is especially concerning to corn and tomato growers. It causes serious damage when it feeds on corn silk and kernels and tomato fruit.

    Corn earwom adult. Photo credit: J. Capinera, University of Florida

    In corn, eggs are laid on silk and the caterpillar hatches and feeds on silk and kernels. In tomato, eggs are laid on leaves, flowers or fruit. The caterpillar feeds by burrowing into tomato fruit. The corn earworm prefers warmer climates. Adult moths migrate north from southern states and can overwinter as far north as Ohio and Kansas.

    Caterpillars are a common pest of vegetable plants. They can reduce fruit quality and yield by feeding on leaves or fruit. One important caterpillar pest is the corn earworm (Helicoverpa zea). This caterpillar develops into a relatively harmless nondescript moth, but the caterpillar causes major crop damage in corn and tomato. It is also known as the tomato fruitworm, cotton bollworm, soybean podworm, and sorghum headworm. Some experts consider it one of the most damaging pests in the United States.

    Identification

    Identification of caterpillars can be difficult and may require the assistance of an expert. Caterpillar body color is variable and can change as it grows older. They can be brown, green or even pink. There is usually a pair of narrow stripes that run down the back. There is also usually a white net pattern on the head. Adults are also difficult to identify. They have brown to yellow forewings with a dark spot in the center.

    Lookalike

    The corn earworm is established in the United States, but it looks identical to the old world bollworm (Helicoverpa armigera) which is considered an invasive pest. In order to distinguish the two species, DNA molecular analysis or dissections must to be performed by an expert. If you find a caterpillar that you are unsure is the corn earworm or the invasive old world bollworm, contact the FDACS-DPI help line at: DPIHelpline@FDACS.gov or 1-888-397-1517.

    By Benjamin Waldo

  • Severe Drought in Alabama Having Little Impact on Produce

    By Clint Thompson

    A severe drought in Mobile County, Alabama and Baldwin County, Alabama is not negatively influencing fruit and vegetable production, says Joe Kemble, Alabama Extension vegetable specialist.

    “Most of the veggies down there are irrigated,” Kemble said. “I don’t know anyone that doesn’t irrigate, frankly, in that area.”

    Irrigation is important in that area right now. In the most recent release of the U.S. Drought Monitor, parts of both counties are classified as ‘D2’ status or a severe drought.

    “Mobile and Baldwin Counties, they’re opposite each other, Mobile Bay. They are definitely well under. I think there was a trending hashtag of #mobilethedesert or #desertmobile. Guys were saying how dry it is down there,” Kemble said.

    There’s cause for concern, especially considering how much produce is grown in that area. Growers cater to a lot of road-side produce stands and farmers markets in that area.

    “In that area, it’s pretty diverse, production wise. Large acreage wise, sweet potatoes are still a pretty important crop in that area, and to a lesser extent, some irish potatoes as well. After that it’s tomatoes, watermelons, corn are probably the staples in that area, as well as peppers,” Kemble said. “There’s a lot of road-side stands in those areas, farmer’s markets in that area. They tend to feed a lot of product into those. They’re always looking for a diverse background of crops. But I would say the major ones are still going to be the tomatoes, watermelons and sweet corn.”

    Kemble said the crops are progressing well.

    “I was speaking to a regional agent down there. He was saying things are on track,” Kemble said.

  • Irrigation and Nitrogen Fertility Rate Strategies to Reduce Leaching

    By Ashley Robinson

    Irrigation in a corn field.

    Excessive nutrients in waterbodies, such as nitrate-nitrogen (N), have been one of the major issues in unconfined regions underneath the Upper Florida aquifer. This can be attributed to farmers applying excessive N fertilizer with the hope of obtaining higher yields. Therefore, the implementation of Best Management Practices (BMPs) such as proper irrigation and N management is required to avoid N leaching from soil profiles.

    RESEARCH RECOMMENDATIONS

    A field experiment was conducted in Live Oak, Florida to evaluate different irrigation strategies and N fertilizers in corn production. The goal was to improve strategies that could reduce N leaching from fields.

    Scheduling can increase irrigation efficiency by decreasing runoff, deep percolation and soil evaporation losses. It also manages soil water content to reduce evapotranspiration during crop stages that require less water. According to Maria I. Zamora-Re, a Post-Doctoral Associate at the University of Florida, soil moisture sensors and soil water balance sheets are recommended methods of irrigation scheduling.

    “The soil water balance sheet is a very easy spreadsheet that growers can put their inputs into, and the spreadsheet will allow them to know when irrigation is required in their fields,” says Zamora-Re.

    In addition to reducing the amount of nutrients leaving the fields, irrigation scheduling tools can save growers input costs by applying less irrigation and fertilizer while potentially increasing crop yields.

    “The data may be seen as overwhelming by some growers, and just one added to-do thing to their list. So we’re hoping to provide the tools and teach them that these technologies can be a very simple and cost-effective adaption. Another concern some growers share is the cost of soil moisture sensors. However, cost-share programs are now available through the grower’s water management district, which would provide them with a great opportunity to try this technology,” Zamora-Re says.

  • The Day South Florida Agriculture Changed

    florida

    Submitted by Gene McAvoy, Regional Vegetable Extension Agent IV Emeritus with UF/IFAS

    “Up to the end of Feb our growers were having a banner year and it looked like this season would be one of those homeruns that come around every 5-6 years.”

    Here is a report that I prepared on the state of S Florida ag and shared with officials. (Long read but may shed some light on how COVID-19 is impacting agriculture in our area.)

    Markets

    On Tuesday, March 24, a local broker says, everything changed. From brokers, orders stopped and everything got quiet. On Wednesday, March 25, it got super quiet.

    Since then tomato volumes are down 85%, green beans are like 50% and cabbage is like 50%.

    R.C. Hatton has plowed under 100 acres of green beans, around 2 million pounds, and 60 acres of cabbage, or 5 million pounds.

    Florida’s tomato growers target 80% of their production to restaurants and other food service companies, rather than to supermarkets. In this sector, growers are walking away from big portions of their crop.

    Tony DiMare estimates that by the end of the growing season, about 10 million pounds of his tomatoes will go unpicked.

    Some crops like potatoes and oranges are faring well, whileother produce isn’t selling like it used to.

    With a lot of people staying home and buying mostly comfort foods, products like peppers, tomatoes and cucumbers have actually slowed down incrementally,” said Chuck Weisinger, president of Weis-Buy Farms, Inc.

    “The biggest challenge we have right now is getting the stores to start buying,” said John Stanford, farm manager at Frey Farms.

    As you know. produce is highly perishable and three weeks into this, many companies around Immokalee, Florida have already had to empty their coolers and dump produce. One dumped 20,000 pounds a day last week, let that sink in… 20,000 pounds of tomatoes a day. They dumped a total of 100,000 pounds so far. This is from one farm.

    Three weeks in, most farms have exercised triage dumping and emptying coolers and are terminating fields for which they have no foreseeable markets. They are concentrating on maintaining fields that they still have demand for, unfortunately, depending on the crop – this is only 20-50% of the total planted.

    Impacts on Ranchers

    The cash market and futures prices are lower than anyone can remember. One local rancher sold calves this week and averaged $250 per head at the Arcadia auction barn. A few weeks ago he would have received $450 per head average, and that constitutes below breakeven.

    In normal times, strategy would be to hold calves until the crisis is over, and hope prices will take an upswing. But there is huge uncertainty about how long this will last. A major compounding problem is the dry conditions, and lack of reserve forage. These weather patterns would normally dictate early weaning of calves. Hay costs, when available, and low market prices are a formula for hardship.

    The extended impact on ranchers will be the cows not breeding back on schedule. Holding calves longer in hot and dry conditions puts a strain on a cow’s reproductive system. This has been well-documented by University of Florida researchers.

    Many growers are exploring alternative methods of moving product.

    Sam S. Accursio and Sons Farms’ in Homestead packing house opened direct sales to consumers, selling boxes at $10 in each of the past two weekends. They had cars stretched for half a mile in front of the packing house and were able to move 120,000 pounds of Redland-raised squash, tomatoes, beans and cukes. They also partnered with a farmer out of Mount Dora, Florida who had 30,000 flats of unsold blueberries and sold these at 12 pints for $20. Similar efforts were conducted by Alderman Farms in Bonita Beach, Florida, Farmers Alliance in Immokalee and others.

    Martin County, Florida opened a pop-up drive-thru market that saw 500 cars in one day. Traditional commercial farms in South Florida have been overwhelmed by the support for the sales at their packinghouses – all fruit that would have otherwise gone unsold if waiting on traditional markets to purchase.

    Growers are still concerned that a large amount of produce seen in the supermarket comes from Mexico.

    According to Bill Braswell, since March 1, the start of the Florida blueberry season, Florida has produced 6.1 million pounds through last Thursday April 2. In that same time period, Mexico has imported 17.4 million pounds into the U.S., according to a USDA report. Mexico market price is $12 for a 6-ounce flat delivered to Chicago which translates to $2.60 per pound.

    Labor

    Growers are taking aggressive steps to protect workers from COVID-19, including keeping truckers separate from on-farm labor.

    They have been taking advantage of training resources and posters supplied by IFAS Extension and others.

    Agents have also shared information on essential services exemption and supplying growers with template essential services exemption letters to facilitate movement of their essential staff and labor.

    Labor shortages – reports indicate that COVID-19 has delayed the U.S. government’s processing of H-2A work visas. This will impact growers in central and north Florida and up the coast.

    Food banks

    Last week, growers in Immokalee alone donated more than 3 million pounds of vegetables to Harry Chapin food bank, overwhelming their ability to store, transport and distribute the produce – they had to call a halt.

    Farm Share, which partners with more than 2,000 food pantries, churches, schools and other nonprofits throughout Florida, is running at maximum capacity, despite having 25 refrigerated trucks, six warehouses of between 10,000 to 35,000 square feet and 40 to 50 drop sites from Jacksonville, Florida to Florida City, Florida. They usually help more than seven million pounds of food reach the hungry and now are faced with moving a lot more.

    Over the past two weeks, Wish Farms has donated 220,000 pounds of fresh strawberries — equivalent to 241 pallets or nine semi-trailer loads — to feeding Tampa Bay.

    Growers are having a tough time adapting because everything is happening so quick. Faced with a highly perishable product, growers are struggling to survive right now, with picking, packing and shipping everything that they can. Because of the coronavirus, things have changed. Buyers are demanding tight security, heavier sanitation, distancing and more.

    We have heard many ideas and suggestions from the public and even local officials – what many people fail to realize is that picking, packing, cooling, storing and transporting vegetables costs money, and growers who have already lost millions of dollars are understandably reluctant to throw good money after bad. It also costs money to maintain fields with no hope of sales in sight. Growers are disking up fields and maintaining just what they feel they have markets for. Unfortunately, this is only about 20% to 30% of the total acreage. Each acre of tomatoes costs $10,000 to $12,000 to grow and $5,000 to $6,000 to pick and pack. Unmaintained fields rapidly succumb to pests and diseases and soon become a breeding ground threatening the health of nearby fields that growers are trying to save for their remaining markets.

    It is not only veggies, as of yesterday about 7.7 pounds of milk has been dumped by one Central Florida co-op (there are a few in Florida). Milk is sold by the pound so that is 900,000 gallons.

    While I don’t have the exact amount from the other co-op I would expect their numbers to match ours in north Central Florida and South Georgia. Unfortunately, we can easily say that 10 million pounds of milk has been dumped throughout Florida.

    There are efforts to help farmers all over our state. In the dairy industry, there is a grassroots group of passionate producers, processors, promotion people, school representatives and Extension agents trying to get more milk moving. This group includes people from Florida and Georgia, that in normal times might view each other as the competition (different co-ops and different promotion boards). These efforts range from delivering school lunches, buying and delivering milk to food banks and those in need; contacting schools to increase their milk in each meal, contacting legislators to allow whole milk in school lunches (we need help with this), and asking stores to stop limiting the purchase of milk.

    People really have no concept of the amount of food we are taking about – Immokalee alone ships approximately 400 to 500 semis of vegetables a day from March through mid-May. This is 15,750,000 pounds of vegetables headed to market every day. Add to this Belle Glade, Palm Beach Co, Homestead and the amounts are staggering. I know of one grower in Belle Glade who is disking up 1 million pounds of green beans every three days.

    South Florida vegetable growers supply more than 150 million people in the eastern U.S., from Miami to Chicago, from late October to mid-May.

    Here is a resource a producer may be interested in sharing – this is a clearing house for finding food – donating food etc.

    Find Food Now – Florida’s Food Bank Network – http://www.feedingflorida.org/taking-action/find-food-now/

    Support local growers and food systems and eat fresh!

    About the Author:

    Gene McAvoy

    Associate Director for Stakeholder Relations
    University of Florida IFAS Southwest Florida Research and Education Center

    Regional Vegetable Extension Agent IV Emeritus

    President – National Association of County Agricultural Agents

  • FDACS Agricultural and Seafood Availability Notice

    fdacs

    (HCCGA) — FDACS has created the attached form for producers to fill out with their product availability. Once submitted, FDACS will utilize to forward to their Fresh From Florida contacts, as well as the Florida Department of Corrections, food banks and make connections with other State Departments of Agriculture in hopes of providing market opportunities to move product during the Coronavirus pandemic.

    Producers, please download the attached Ag and Seafood Availability form and submit

    Source: Highlands County Citrus Growers Association