by PAUL CATALA

On May 10, Florida Gov. Ron DeSantis signed into law Senate Bill 1718, legislation for immigration policy requiring employers to use the E-Verify system — a database that tracks whether individuals are legally able to work in the U.S. — when hiring workers and imposing criminal penalties on people who provide transportation of undocumented immigrants into Florida. The law takes effect July 1, 2023. However, those against the legislation say the law could cost Florida billions in revenue.

For immigrants and employers, the list of penalties for those who violate new employment mandates is particularly worrisome.

Across Florida, various growers — including blueberry growers on the state’s approximately 5,700 acres of blueberry farmland — are wary of the logistical impacts involved with following or enforcing the new immigrant-related legislation. 

The Florida Farm Bureau concedes the federal immigration system is faulty and has yet to be fixed. The farm bureau worked with the Florida legislature to protect the smallest businesses from having to take on more government requirements and reduce any punitive consequences of SB 1718. However, the bureau will continue to work with  the federal government to help develop and initiate long-term solutions to national immigration issues pertaining to Florida-grown products.

Those products include Florida blueberries, of which 15.66 million pounds were harvested in the 2023 season on Florida farms from March to early May. There are about 90 blueberry farms across Florida, employing approximately 2,500 workers generating an annual economic impact of about $295 million – enough to focus attention on SB 1718 and its effects.

Samuel Vilchez Santiago is the Florida director of the American Business Immigration Coalition, based in Orlando. That coalition promotes immigration reform that “boosts our economy, creates jobs, eases the labor shortage, and supports families,” according to its website. 

Santiago says immigration is federal, not state, law and admits the immigration system is “broken,” but the “path forward is not to demonize migrants.” He said cooperation between members of congress and senators needs to be better to create bipartisan solutions. He says E-verify takes away the burden from employees to prove work eligibility and places it on the employer.

“The agriculture industry that relies so heavily on undocumented migrants, and their work is going to be affected,” he says.

Santiago says he thinks the law will significantly affect the state’s agriculture industry, as well as the construction and hospitality sectors.

The Florida Policy Institute, a nonprofit policy research group, estimates that without undocumented workers, the state's most labor-intensive industries would lose 10 percent of their workforce and could lead to a drop of $12.6 billion in Florida's Gross Domestic Product in a single year.

“What’s going to happen if even 10 percent of the state’s 800,000 undocumented migrants leave with their families? We’re going to have incredible worker shortages that are going to impact our different industries. Consumers across the state…will see the price of goods, including blueberries, go up because we won’t have the labor needed in order for employers to carry out their jobs,” says Santiago.

Alyssa Houtby, director of affairs with the North American Blueberry Council, says nationwide, there’s a need for comprehensive reform for agriculture workforce programs, whether H2A, which allows foreign national workers into the U.S. for temporary agricultural work, or domestic workforces. 

She says it’s unfortunate the bill was signed at a time when farmers don’t have the tools and programs to secure reliable workforces. 

“It’s very disappointing the governor signed this bill. It’s unfortunate that the crisis at the border has become an impediment to making necessary reforms to our ag workforce and immigration policies in this country,” she says. “This piecemeal approach, it doesn’t do anyone any good – it hurts the farmers, it hurts the workers. It really needs to be looked at more comprehensively.” 

In the short term, Houtby says growers may not have the workforce needed to pick. 

“We’re not at peak blueberry harvest time now, so the crunch isn’t as bad now as other crops currently being harvested,” she says. “It’s interesting to see how this plays out next year when blueberry season picks back up and we’re in need of those employees and if this will still be a challenge at that point.” 

One grower anticipating those challenges is Leonard Park, president of the Florida Blueberry Growers Association and general manager of the 150-acre Frogmore Fresh blueberry farm near Dade City.  

Park says he has about 150 to 300 H2A workers harvesting the fields on average, and he’s currently uncertain about the impacts of the bill. He says he does know of some migrant workers already leaving the state due to the legislation.

Park says he does not think his company will be affected much.

“For our firm, particularly, I don’t think (SB 1718) is going to have a lot of impact,” he says. “I know a lot of people that have a lot of domestics and they’re very worried about it. There’s going to be a range of impacts on different farmers.”

Summer in Florida is wet, humid, and hot—great conditions for plant disease. Blueberries suffer from a range of summer problems caused by algal, fungal, and water mold pathogens. This article is meant to be an overview of some of the most important problems and ways to tie together management strategies over the summer that will cover the bases. Knowing what the typical symptoms of these diseases are and how to scout for them are critical first steps toward effectively managing healthy bushes through the summer months.

Time to Hedge and Protect Roots: Stem Blight and Phytophthora Root Rot

Summer kicks off right around the time most growers do a post-harvest pruning to rejuvenate bushes and spur on a flush of new growth that will ultimately produce the next year’s crop. The first post-harvest application of fungicide that growers may want to consider is at or just after hedging. Captan mixed with Abound is one option to help slow or prevent Botryosphaeria stem blight from occurring on the fresh pruning wounds. Some growers use hedging equipment that can also put the fungicide out at the same time and others follow the hedger with a sprayer the same day. There are many other options for fungicide products to consider as well.

Hedging is typically followed by the start of regular rains, and then the hurricane season follows. A banded, or through-drip irrigation application of a fungicide with mefenoxam (example: Ridomil Gold) into the root zone before all the rain can help protect from Phytophthora root rot, our most important root disease of Florida blueberries. On well-drained farms with sandy soils and elevated growing beds, root rot applications may not be needed across entire fields but can be beneficial for low or poorly drained areas that are prone to flooding, heavier soils, and particularly prior to tropical weather systems capable of producing large amounts of rainfall.

Follow up applications of fungicides with mono- and dipotassium salts of phosphorous acid including Agri-Fos™, K-Phite™, and ProPhyt™ (potassium phosphite) (aka “phytes”) throughout summer on a monthly interval can further help with root rot and provide some leaf disease suppression if sprayed on leaves. Where bacterial wilt has been an issue on farms, drenching the products into the bed is a better option that targets roots. Drenching is a term used to describe applications of pesticides that target the root zone; directly applied to the bed in a high delivery volume, or watered in after application. Some fungicide products can be applied through the drip irrigation system, also delivering product directly to the roots. 

Summer Maintenance: Algal Stem Blotch

Algal stem blotch is a significant disease on southern highbush blueberries (SHB) in Florida, caused by a parasitic green alga. This disease often results in mottled to very pale leaf yellowing (Figure 1), stunted growth, and increased susceptibility to Botryosphaeria stem blight. Stunting is the result of a reduction in plant vigor, and can appear as poor regrowth following summer pruning. Over time infected canes and stems may crack, which can lead to Botryosphaeria stem blight susceptibility and plant death.

Figure 1. Algal stem blotch leaf symptoms

Credit: D. Phillips, UF/IFAS

The alga is thought to enter the plant through natural wounds and openings, pruning cuts, or by direct penetration of the cuticle. Once inside the plant, the alga forms colonies beneath the stem cuticle and red blotchy raised lesions develop. During hot, humid, and wet conditions, bright orange felt-like mats or tufts of algal growth (sporangiophores) appear from the blotchy lesions on young stems and older cane surfaces (Figure 2). These reproductive structures are dispersed by wind and water splash, with peak spore production typically occurring between May and September. Plants that are stressed by abiotic or biotic factors are more susceptible to infection and subsequent disease development.

Figure 2. Algal stem blotch sporulation

Credits: D. Phillips, UF/IFAS

There is currently limited information about effective management practices for algal stem blotch. Certain cultural practices may help reduce the spread of disease, including good horticultural inputs and practices (irrigation, fertilization, sanitation, and disease and pest control) which will help reduce plant stress and related disease susceptibility. Overhead irrigation should be avoided if possible when disease is present to help minimize the spread of algal reproductive structures. In addition, removing and destroying infected canes and eliminating weeds improves air circulation in the canopy and can help to slow disease development. Disinfection of pruning equipment where symptoms are present and the use of disease-free planting stock are also recommended.

No pesticide products (including fungicides, since this pathogen is an alga) have been found to date that will kill the algae living underneath the plant epidermis, so prevention is key. Spray applications of copper-containing fungicides can help to reduce algal sporulation and disease spread. However, these products only kill the algal reproductive structures present on the plant and protect healthy canes from infection for a few days after application; they do not treat existing symptoms or eliminate the disease. Copper product sprays with good coverage should begin after harvest and continue through September, on a regular schedule prior to infection. 

The specific spray schedule and rate will vary by label instruction of product chosen with reapplication intervals ranging from 7 to 28 days. These applications can be made 14 days after the phyte applications for root rot and bacterial wilt (above), but should not be combined because some phyte products are acidic, and when mixed with copper can burn plants. More frequent applications are recommended when weather forecasts are favorable for disease development and when the disease is known to occur on the farm. Follow all label instructions and be cautious when considering tank-mixing products that contain copper with anything else. Specific issues with tank mixes of acidic products or acidifying adjuvants and copper are well-documented and can result in plant burn. Tank mixes of copper products and products with penetrants or spreader sticker type formulations also can be problematic in some conditions (Bravo Weatherstik is an example). For specific product rates, timings, and additional details on this disease, see the 2022 Florida Blueberry Integrated Pest Management Guide (https://edis.ifas.ufl.edu/publication/HS380) and Algal Stem Blotch in Southern Highbush Blueberry in Florida (https://edis.ifas.ufl.edu/publication/pp344). 

Fungal Leaf Diseases

There are several fungal leaf diseases that can be problematic for Florida blueberry growers during summer and early fall. These include anthracnose, rust, Phyllosticta, Septoria, target spot, and several others. 

Anthracnose

Anthracnose leaf spot can cause premature defoliation, poor floral bud development, and subsequent loss of yield. Symptoms are typically circular to irregularly shaped lesions beginning at the edges of leaves, expanding from 1/4 inch to more than 3/4 inch in diameter, with brown to dark brown centers and concentric circles of damaged tissue (Figure 1). Anthracnose leaf disease is common after harvest in Florida and persists through summer. 

Figure 1.  Anthracnose leaf spot lesion. 
Credit: P. Harmon, UF/IFAS

The pathogen overwinters in infected leaves and stems from the previous season. In spring, when the weather gets warmer and more humid, the fungus produces reproductive spores, which are spread by splashing water (rain or overhead irrigation), workers, and equipment. 

Many registered fungicides are labeled for anthracnose on blueberry in Florida. Applications work best before symptoms become severe. On susceptible cultivars, applications should begin after post-harvest pruning, with reapplications according to label instructions through September. Demethylation inhibitor (DMI) fungicides (FRAC 3) such as Indar™, Orbit™, Quash™, Quilt Xcel™, and Proline™ are options to be used in rotation or in tank mixtures with compatible products from another group to help prevent fungicide resistance. Fungicides with different modes of action such as Luna Tranquility™ (FRAC 7 & 9), Abound™ (FRAC 11), Pristine™ (FRAC 11 & 7), Switch™ (FRAC 9 & 12), and captan (FRAC M4) are suitable for rotation with DMI fungicides. Single applications of Bravo™ (FRAC M5) are also recommended after harvest. Anthracnose resistance to Abound™ and other FRAC group 11 fungicides has been confirmed in Central Florida, so these should be used in a premix product with two active ingredients or tank-mixed with another fungicide like captan to ensure efficacy. Fungicides with mono- and dipotassium salts of phosphorous acid including Agri-Fos™, K-Phite™, and ProPhyt™ (potassium phosphite) have shown some effectiveness against anthracnose, so when they are used as above for phytophthora root rot management, you may also see foliar disease suppression. Where the anthracnose still remains severe, consider one of the fungicides above to replace or tank mix with the foliar phyte.

Rust

Rust can result in premature defoliation, a decrease in floral bud differentiation, and a corresponding reduction in yield. Symptoms begin on the upper leaf surface as small, somewhat angular yellow spots that turn reddish brown to black over time. Multiple lesions can occur on the same leaf, eventually turning the leaves yellow and red (Figure 2) and causing defoliation. Brightly colored yellow/orange spores emerge on the underside of the leaf, opposite the lesions on the upper leaf surface, and are the distinguishing characteristic of this disease (Figure 3). 

Figure 2.  Rust lesions on the upper leaf surface. 
Credit: P. Harmon, UF/IFAS

Figure 3.  Rust reproductive spores on the leaf underside. 
Credit: P. Harmon, UF/IFAS

Rust spores are spread by wind. New leaf infections can begin in spring during or just after harvest, and disease activity typically increases again in early fall. In Central Florida, the fungus survives on evergreen Vaccinium plants, and in weeds or other plant hosts next to production fields. The disease is favored by overhead irrigation and/or frequent rains. In evergreen production in Central and South Florida, the pathogen can survive in infected leaves that remain on the plants throughout winter. Rust has recently become a significant disease concern in evergreen blueberry production. 

Applications of fungicides are the best method of control, although they work best as a preventative measure. Although systemic fungicides can move into the infected leaves and potentially stop some rust development, most products will only reduce or delay the amount of sporulation because fungicides do not effectively kill the fungus inside the leaf. Fungicides do a better job protecting against new infections, so making repeated applications to maintain a protective residue on the leaves is key to preventing the disease. Fungicides such as Proline™, Quilt Xcel™, Quash™ (FRAC 3) and Propulse™ (FRAC 3 and 7), have very good to excellent effectiveness against rust. Tilt™, Indar™ (FRAC 3), Bravo™ (FRAC M5), and Abound™ (FRAC 11) have good effectiveness. Applications should begin after harvest where leaf rust is found to be problematic and continue through late October on susceptible cultivars. In the evergreen system applications may need to continue through the winter months. Fungicides with different modes of action should be used in rotation or in a tank mix, and as part of an integrated post-harvest foliage management strategy. A sprayer capable of good canopy penetration and leaf coverage should be used to get maximum benefit from the fungicides used. 

Phyllosticta

This disease is more commonly observed later in the summer (August–September) than anthracnose. Symptoms are dark brown leaf spots with irregular borders, surrounded by a dark brown to purple margin (Figure 4). These lesions range from less than 1/4 inch to larger than one inch, and can ultimately lead to defoliation. A distinguishing feature of this disease is the presence of tiny black fungal pimples that develop within the lesions and can be seen with a hand lens. However, other fungi, including some that do not cause disease, can also produce small black structures on dead or decaying leaves. This disease is common in Florida, but it is considered to be of minor importance.

Figure 4.  Phyllosticta leaf spot symptoms. 
Credit: P. Harmon, UF/IFAS

Although there are no published fungicide recommendations for Phyllosticta leaf spot management on blueberry in Florida, it has been managed with Bravo™ (FRAC M5) in other crops. General maintenance applications of contact fungicides like Bravo™ or captan are recommended after harvest as needed or approximately every two weeks (for up to 6 weeks).

Septoria

Septoria leaf spot is a common disease in the southeastern United States. Significant infections can decrease yield due to defoliation, reduced floral bud production, and lower levels of photosynthesis. Symptoms are observed as numerous small, circular leaf spots (about 1/8 inch in diameter) with light-brown to gray centers and broad purplish margins (Figure 5), usually present more often on older leaves. These lesions can coalesce into larger necrotic areas, followed by defoliation. Septoria typically occurs from mid to late harvest through June, and may return during mild wet periods during fall. Reproductive spore germination and infection are favored by mild wet weather (75°F–82°F), and are spread by water splash (rain and overhead irrigation).

Figure 5.  Septoria leaf spot. 
Credit: P. Harmon, UF/IFAS

Applications of protective and systemic fungicides with different modes of action can help to reduce Septoria leaf spot severity. Fungicides of FRAC group 3, such as Tilt™, Indar™, Quash™, Quilt Xcel™ and Proline™, and fungicides of other FRAC groups, such as Luna Tranquility™ (FRAC 7 & 9), Abound™ (FRAC 11), Switch™ (FRAC 9 & 12), Pristine™ (FRAC 11 & 7), and Bravo™ (FRAC M5), are effective against this disease. Systemic phosphite fungicides such as Agri-Fos™, ProPhyt™ and similar phosphonate products are also effective against Septoria; however, they must be applied after harvest to avoid possible fruit damage.

Target Spot

Target spot was first reported in blueberry in the United States in 2014. Some Florida growers have observed severe defoliation on many SHB cultivars since then. Symptoms are 1/3- to 3/8-inch angular to irregular reddish-brown lesions with color varying in concentric rings, resulting in a “target” or bull's-eye pattern (Figure 6). Symptoms can appear similar to the early symptoms of anthracnose leaf spot, and both diseases can occur simultaneously on susceptible varieties. However, target spot lesions tend to remain smaller, and fewer target spot lesions are required before defoliation occurs compared to anthracnose.

Figure 6.  Target spot symptoms. 
Credit: D. Phillips, UF/IFAS

Environmental conditions such as high humidity, temperatures between 79°F–84°F, and moderate rainfall favor abundant fungal sporulation and rapid disease development. Spores can be spread by wind or water splash (rain or irrigation).

Some growers have reported difficulty managing target spot after symptoms appear and become severe. Preventive fungicide applications where the disease is known to occur or careful scouting for the first disease symptoms are encouraged. Limiting periods of leaf wetness and high humidity within the blueberry canopy also may help reduce disease severity. This can be accomplished by avoiding overhead irrigation, maintenance pruning to open canopies, and weed management in beds and row middles to increase air flow. Specific products to rotate postharvest for target spot and other foliar fungal diseases include chlorothalonil (Bravo™ and others – FRAC M5), Proline™ (FRAC 3), Abound™ (FRAC 11), and Quash™ (FRAC 3). Copper-containing products applied in summer for algal stem blotch control also have some efficacy. Rotating between the copper and other fungicide applications starting when regular summer rains begin can provide a good foundation for a fungicide application program. Supplement these applications by adding additional sprays and/or tank-mixing fungicide products (where permitted under label instructions) when target spot symptoms are noted between applications. 

Summary

Those are some of the most important summer diseases to consider for Florida blueberry production. Taken individually, that adds up to a lot of fungicide applications, but not all diseases occur each year on every farm, and there are many products that offer protection for multiple diseases from each application. When problems arise, send a sample to a UF IFAS diagnostic lab and reach out to local Extension resources for additional help tailoring a management plan to address your specific disease concerns. 

CREDIT

Dr. PHIL HARMON, Professor, UF/IFAS

& DOUG PHILLIPS, Blueberry Extension Coordinator, UF/IFAS