Recent Blog Posts

They say history doesn’t repeat, rather it rhymes. And right now, it’s feeling much like January 2014-2015 over here:

• Jan. 7, 2014: The term “polar vortex” enters the public lexicon with extreme damaging cold temperatures. A similar historic event would repeat Feb. 20, 2015.
• Jan. 15, 2015: OSU defeats Oregon in the first 2014 CFP national title, 42-20. 

Ten years later in 2025, OSU wins the first expanded CFP national title and this evening’s forecast tonight calls for lows throughout the state anywhere between 1F and -11F (Figure 1), with cold temperatures (< 0F) expected to persist from 8pm through 10am.

Figure 1. Forecast nighttime low temperatures Jan 22, 2025. Figure from https://weather.gov.

Some key differences from 2014-2015:

• Vine cold acclimation is much better than in 2014-2015. A late first fall freeze aided in improving winter hardiness through extending wood maturation, carbon and nutrient reassimilation. 
• Sustained below-freezing temperatures through January (Figure 2) have aided in achieving maximum cold hardiness while minimizing deacclimation and freeze/thaw cycles, which often leads to more extensive bud/tissue injury.

Figure 2. Average temperature departure from long-term mean from 22 Dec 2014 through 20 Jan 2025. Figure from https://climate.osu.edu. 

• Persistent snowpack provides an insulating layer that helps protect the base on the vine trunk.
• Our most recent estimates of LT50 (e.g., minimum temperatures that result in 50% bud injury) from cultivars at Unit 2 suggest many Vinifera cultivars have attained cold hardiness to approximately -10F and hybrids < -15F. These values are similar to reported LT50 estimates from Cornell University. 

We will be following up in the coming week with temperature minimum descriptions, incidence of bud injury, and recommendations for adjusted pruning. 

In the meantime, stay warm! 

By: Maria Smith, HCS-OSU

Semisonic’s 1998 hit, “Closing Time”, an anthem to endings, encapsulates the take-home message of this post: "every new beginning comes from some other beginning’s end." A chapter ends, and the next begins, each building on the one before. The same applies to vineyards; the success of the 2025 season begins with how we end 2024.

Over the past few weeks, I have received several calls regarding routine preparation and clean-up operations relevant to fall, which finally arrived last week in Wooster (FIG 1). Below are a few that I will highlight relevant to vineyard winterization and preparation for 2025:

Figure 1. Leaf yellowing during senescence in Vitis hybrid ‘Regent’ at Hort Unit 2, Wooster, 21 October 2024.

Q: When should I remove grow tubes?

A: Grow tubes, the blue or white cylindrical tubes placed over the vine in new vineyards (FIG 2), provide deer and herbicide protection on developing, tender new shoots. They also retain heat and moisture, which is beneficial for promoting quicker shoot development in the spring but can be detrimental for cold acclimation and wood health in the fall and winter. Grow tubes should be removed approximately one month prior to the first date of fall freeze.

Figure 2. Grow tubes installed at a new vineyard planting, June 2024.

Q: I harvested my vines, but do I still need to apply fungicides?

A: It depends. Protecting foliage through leaf fall is important for cold acclimation and maximizing winter vine hardiness, as foliage returns nutrients and carbohydrates to perennial storage tissues (roots, trunks, cordons). If your vines are harvested in August or September, and there are still months before leaf fall, then it would be prudent to continue protecting the vine foliage, especially from downy mildew, which can rapidly defoliate shoots in severe cases. Reverting to Mancozeb (at least for now) can protect foliage post-harvest and is an effective multi-site mode of action fungicide with low disease resistance potential. Mancozeb, along with other options for disease management, can be found in the Midwest Fruit Pest Management Guide. Remember, disease resistance is a key issue for powdery and downy mildew, and we should be using best practices to minimize resistance (think: combine with Mancozeb or Captan if using such fungicides as Ridomil, Ranman, Revus Top for more residual control of downy mildew)

However, if your vine varieties have low susceptibility to downy mildew, the forecast does not favor disease development (temps < 55F, dry), or the vines are very late harvest, then it’s possible that you may not require continued post-harvest fungicide use.

Q: How late is too late for sowing ground cover during new vineyard site preparation?

A: You can still sow ground cover through October into early- to mid-November (especially this year), to help stabilize soil and reduce erosion potential. One of the better options for November planting is cereal rye. Resources on cover crop options for Ohio can be found at https://cfaes.osu.edu/features/ohio-cover-crops. Choice of cover crop prior to vineyard establishment depend on your goal (soil organic matter, nitrogen, compaction, etc.) and timing of cover crop establishment.

Q: What do I need to do for fall vineyard weed control?

A: How effective is your current weed management program? For annual weed situations, contact herbicide (Rely 280, Gramoxone, Venue, etc.) application combined with a pre-emergent herbicide is effective for suppressing weeds through winter.

For perennial weed issues, Glyphosate (Round Up) is best applied at this time, since it acts systemically to kill root systems. However, glyphosate should not contact living grape tissues, as this can cause significant injury that may not be visible until growth resumes next spring. You may also consider waiting until after leaf fall to apply glyphosate. Glyphosate can similarly be combined with pre-emergent herbicides for improved weed suppression. It is important, however, that pre-emergent herbicides reach the soil surface, so earlier (now) passes of burn down/contact herbicides may be useful to clear vegetation if weed pressure was high this past year.

A note on pre-emergent herbicides: Selection should consider vine age and target weed species. For more information on grape-registered herbicides, see the herbicides section of the Midwest Fruit Pest Management Guide. Temperature and rainfall are important components of pre-emergent herbicide success, so ensure that the timing of application is appropriate based on label guidelines.

Are your soils mounded for graft union protection? This practice helps control weeds through mechanical disturbance and may mean you do not require as much reliance on herbicides as own-rooted vineyards where weeds are not mechanically disturbed. If hilling, pre-emergent herbicides should be applied after hilling has been completed.

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Winterization in Wooster vineyards is underway now that our harvest has wrapped. This also includes activities like storing netting and removing wire clips. It can also mean taking assessments of the vineyards for possible vine issues such as crown gall that could require trunk replacement in the next year (FIG 3). Now is also a good time to winterize and prepare to store your vineyard sprayer and other equipment. Lastly, now is also an excellent time to sample soils, apply lime, non-nitrogen fertilizers, or organic fertilizer sources (e.g., compost) that slowly break down over winter.

Figure 3. If foliage is not yellow in the fall, that is an indication that there may be other issues with the vine. In the case of this ‘Regent’ vine, crown gall infection is causing die back of the older cordon on the right-hand side of the vine. We will need to replace that trunk and cordon from suckers emerging from the base of this vine in 2025.

By Melanie L. Lewis Ivey, Associate Professor, Extension Fruit Pathologist, Department of Plant Pathology

In June, the EPA completed the proposed interim registration review for mancozeb. Mancozeb is a broad-spectrum fungicide widely used by fruit, nut, and vegetable growers to control many fungal diseases. Mancozeb is a multisite fungicide, which means it targets several biochemical pathways in fungi. This mode of action makes it more difficult for fungi to develop resistance compared to fungicides that target a singlesite. However, the EPA has identified risks of concern to human health and non-target organisms from the use of mancozeb and thus proposed the following measures specific to fruit crops to “ensure mancozeb use does not present unreasonable adverse effects for human health or the environment.”

• Cancellation of mancozeb use on all types of grapes (including table, wine, juice, and raisin).
• For aerial applications to orchards that are adjacent to residential area a 25-foot buffer zone from the edge of the treated field will be required.
• Closed-cab equipment plus gloves will be required for the airblast applicator scenario for the airblast applicator scenario for all formulations for orchards and vineyards.
• The use of an APF10 respirator and closed loading systems for aerial, chemigation, and ground-boomapplications utilizing dry flowable, wettable powder, and water-soluble packet formulations.
• Increase in restricted entry intervals (REIs) for pome fruit from 24 hours to 4 days for all activities.
• Prohibition of hand-thinning pome fruit crops.
• Mandates on droplet size.
• Spray drift buffers for fields adjacent to aquatic habitats and conservation areas depending on the application method:
  • Aerial applications – 50 ft
  • Ground boom applications – 15 ft
  • Airblast applications – 15 ft

The proposed deadline to submit comments to the EPA is September 16, 2024. This leaves very little time for the fruit industry to put together a strong argument for the retention of the registration of mancozeb for grapes and the retention of a 24- hour REI for apple and pears. The grape and tree fruit industries arestrongly encouraged to write a letter of request to extend the public comment period so that the industries have adequate time to develop a strong public comment. Requests can be emailed directly to Dr. Jean Overstreet (see contact information below). It is recommended that Mr. Ben Tweed be copied on the email.

A copy of the proposed interim registration review can be found at u.osu.edu/fruitpathology/fruitnews-2/.

By: Erdal Ozkan, Professor, Extension Pesticide Application Technology Specialist, FABE-OSU

For many reasons, including production costs, safety, and the environment, it is important to maximize pesticide deposits on the target when spraying. Spray drift is a major challenge to pesticide applicators trying to achieve this goal. Although complete elimination of spray drift is impossible, it can be significantly reduced by awareness of its major causative factors, and by taking precautions to minimize their influence on the off-target movement of droplets. Extensive information related to factors influencing spray drift is in the Ohio State University Extension publication (FABE-525) “Effect of Major Variables on Drift Distances of Spray Droplets”.

The risk of drift is considerably higher when spraying in orchards and vineyards compared to spraying in field crops for three main reasons:

1. The target being sprayed in field crops is relatively uniform, it’s a short distance from the nozzles, and the droplets are directed downward. The target in orchards and vineyards is not uniform in size and shape (there may be gaps in canopy), there is a much longer distance from the nozzles, and the droplets are directed in an upward trajectory.
2. The type of sprayer used in field crops releases the droplets downward just over the target. The sprayer used in orchards and vineyards uses a powerful fan that blows droplets in a horizontal and upward trajectory, making the droplets much more susceptible to drift.
3. The type of nozzle and droplet size used in field crop spraying is most often a flat-fan nozzle that discharges relatively large droplets. Orchard and vineyard sprayers are generally equipped with hollow-cone nozzles that produce very fine to fine category droplets.

Therefore, more precautions should be taken to reduce the drift risk when spraying in orchards and vineyards.

Strategies to Reduce Spray drift

Some factors that affect drift, such as weather conditions, are out of the control of the pesticide applicators spraying in orchards and vineyards. However, many of the factors affecting drift are under the control of the applicators. Here are some of the key cost-effective and practical strategies to reduce spray drift:

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• Keep drift in mind when selecting your sprayer. Although the air-assisted (airblast) sprayer type shown in Figure 1 (with radial spray discharge) is used by most fruit growers in the U.S., many other less drift-producing types of air-assisted sprayers, such as the one shown in Figure 2 (with horizontal spray discharge) are used in other parts of the world. Sprayers producing horizontal air and spray flow generally produce less spray drift. Take a look OSU Extension publication (FABE-533) “Sprayers for Effective Pesticide Application in Orchards and Vineyards”, which provides a discussion of all major types of sprayers used in orchards and vineyards.

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• Consider switching to low-drift nozzles. In the U.S., the typical sprayer used in orchards and vineyards is an airblast sprayer equipped with hollow-cone (most often) or conventional flat- fan nozzles (less common). Both nozzle types produce extremely fine, very fine, and fine droplets, which are highly susceptible to drift. Hollow-cone nozzles operated at high pressure are especially susceptible. In recent years, nozzle manufacturers have introduced new nozzles that significantly reduce the number of extremely small, drift-prone droplets. In other parts of the world— especially Europe— most growers are gradually switching to these low-drift air-induction nozzles to spray fruit trees.
• Spray pressure affects the size of droplets released from a nozzle. Higher pressure produces smaller droplets. Therefore, avoid operating the sprayer at high pressures. Although 200 to 300 psi is the norm for manU.S. growers when operating airblast sprayers, a pressure of 100 to 150 psi is more than adequate to generate the fine to medium size droplets that improve penetration and coverage on the target.
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• Spraying in high winds, high temperatures, and low relative humidity increases the risk of spray drift. If weather conditions are not favorable, and there is a concern about spraying that might result in drift, wait for more favorable conditions. Review the forecast and schedule spraying accordingly. Use apps that provide current, local weather conditions and use that information to make sound decisions on when to spray. Be aware that wind speeds shown in apps display data taken from nearby weather stations that may not reflect the wind speeds in your specific spraying location. Therefore, it is best to carry a small hand-held, battery-powered wind meter (anemometer) to check the wind speed several times before and during spraying. The price of a wind meter is usually less than one-third the hourly fee a lawyer can charge a client sued for drift-related damages.
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• Adjust the sprayer fan air-flow rate and volume so that the air being directed into the canopy replaces the air already in the canopy but dies down significantly as it reaches the other side of the canopy. A proper air adjustment results in very little spray droplets escaping the canopy. As a side benefit, reduced air assistance results in lower fuel consumption.
• The travel speed of the sprayer also influences spray drift. Even when adjustments are made to restrict air intake into the fan, too much air may reach the canopy if the travel speed is extremely low. Slow travel speeds allow the canopy to be exposed to the air flow for a much longer time, thus contributing to drift.
• When spraying the outer side of the last row, turn off the nozzles on the side of the sprayer that are pointed away from the canopy. In addition, if you are using a conventional airblast sprayer with radial air discharge, cover the air exit port on the side of the sprayer facing away from the canopy. Both actions further reduce the risk of spray drift.
•  
• Carefully direct the air from the fan towards the canopy to ensure that the sprayed droplets are intercepted by the canopy. With conventional, radial discharge airblast sprayers, deflector plates must be installed on both the top and the bottom of the fan, and on both side of the sprayer, to guide the spray plume toward the canopy and at a level equal to the canopy's height. The size of the deflectors should be big enough to effectively direct the air at the canopy.

A successful spray operation in orchards and vineyards achieves maximum efficacy from the pesticide applied while minimizing the off-target (drift) movement of pesticides. Spray drift poses health risk to nearby people and animals, increases the risk of polluting natural resources like air and water, and wastes pesticides that could have been used to treat pests in orchards and vineyards. A brief discussion on practical ways to reduce spray drift is discussed in this article. More comprehensive information on this topic is given in the Ohio State University Extension publication (FABE-535) “Strategies to Minimize Spray Drift for Effective Spraying in Orchards and Vineyards”.