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By: Erdal Ozkan, Professor and Extension State Specialist, Department of Food, Agricultural and Biological Engineering-OSU
In contrast to field crops, vineyards and orchards exhibit significant canopy size and structural diversity. Interplanting vines of various ages within the same vineyard is a common practice that creates gaps between them. Additionally, canopy density can range from no canopy at all to a very dense canopy throughout the growing season, as shown below in pictures of the same vineyard in early season (left), mid-season (middle), and late season (right).
Unfortunately, with today’s conventional fixed-rate sprayers, the sprayer operator cannot turn nozzles on or off when there are gaps between grapevines. Similarly, operators lack the ability to deactivate some nozzles on the go when vine sizes vary from fully grown tall ones to short, small vines planted only a year ago. Under these conditions, much of the sprayed material is wasted, particularly during early-season spraying when there is minimal canopy cover. As a result, excessive pesticide use raises production costs and increases the potential for environmental contamination. An air-assisted, “intelligent sprayer” was developed in Ohio for variable-rate pesticide application in orchards, vineyards, and nurseries to tackle these issues. It detects canopy presence, measures size, shape, and foliage density, and then independently adjusts the spray output of individual nozzles to match canopy volume and travel speed in real-time. Field tests showed that this sprayer technology could reduce airborne spray drift by up to 87% (depending on the growth stage of the canopy and leaf density), decrease ground spray loss by 68–93%, and lower spray volume by 47–73% while maintaining effective control of insects and diseases. The “Smart Guided Systems” company has commercialized this technology in the U.S. The company offers components to retrofit existing constant-rate conventional “airblast” sprayers used in vineyards and orchards, enabling them to apply pesticides at a variable rate. This allows growers to modify their existing equipment and convert their constant-rate sprayer into a variable-rate sprayer at a fraction of the cost of a new sprayer.
Another recent technological development is the use of drones for spraying pesticides in vineyards. Drones are becoming increasingly popular, especially in areas where using conventional spraying equipment is neither safe nor practical. Currently, several factors—such as rapid advancements in drone technology, insufficient data on the effectiveness of drone applications compared to traditional ground sprayers, and Federal Aviation Administration (FAA) restrictions on drone operations—are hindering the adoption of drone spraying among fruit growers. However, given the substantial interest in and popularity of drone spraying, these limitations will likely be eased and addressed in the future. I will feature an article on the use of spray drones in an upcoming issue of this newsletter.
Detailed information on recent advancements in technology for effective spraying in orchards and vineyards is provided in the Ohio State University Extension publication (FABE-538) “Advancements in Technology for Effective Spraying in Orchards and Vineyards” (https://ohioline.osu.edu/factsheet/fabe-538).
Both the intelligent sprayer for variable-rate application and the spray drone will be demonstrated in a workshop on August 12, 2025. In addition to these new technologies, best practices for spraying with conventional vineyard sprayers will be discussed and demonstrated at this event. Additional information about this workshop, including registration details, can be found at this website https://ohiograpeweb.cfaes.ohio-state.edu/events/new-sprayer-technologies-and-best-spraying-practices-workshop.
By: Maria Smith, HCS-OSU
May weather:
Precipitation is the story so far.
Rain is an expected feature of spring in Ohio, and that’s not much of a debate. In fact, the 30-year average cumulative precipitation for May in Wooster is 3.73”. This year, we’ve received nearly 1” above that average with 4.59” of total cumulative precipitation (https://newa.cornell.edu Wooster Hort 2 station). The real uncanny part to me is the number of days that it has rained this month: 22 of 31 days. That’s right, we logged measurable precipitation for 71% the month.
…and the fun hasn’t stopped. June to date has logged an additional 2.18” across 4 total days of rainfall so far, which is nearly 57.6% of the 30-year average monthly rainfall, with more forecast over the next 7 days.
Temperature and Growing Degree Days (GDD)
Not only was May rainy, but it was also cool. The average daily temperature in May was 57.6 F, which is 2.6 F cooler than the 30-year average. Despite below average temperatures, cumulative annual GDD (720, base 50 F, January 1 to June 12) remains similar to, albeit slightly below, the 30-year average (787).
Phenology
Reports across the state place phenology anywhere from pea-size (Southeast Ohio) to pre-bloom and early bloom (Northeast Ohio).
In Wooster, we are moving through bloom this week, with some early hybrid cultivars (e.g., Itasca) near fruit set, while others (e.g., Cab Franc) are just beginning bloom (Figure 1, Table 1).
Figure 1. Clarion approaching post-bloom (top) and Regent at trace-bloom (right). 10 June 2025.
Table 1. 50% bloom date and GDD for select cultivars at Hort 2, Wooster, OH.
|
Cultivar |
50% bloom date |
GDD |
|---|---|---|
|
Cabernet Franc |
12-Jun |
720 |
|
Chardonnay |
13-Jun |
-- |
|
Regent |
12-Jun |
720 |
|
Albariño |
12-Jun |
720 |
|
Aromella |
13-Jun |
-- |
|
Traminette |
10-Jun |
681 |
|
Chambourcin |
13-Jun |
-- |
|
Marquette |
9-Jun |
674 |
|
Itasca |
5-Jun |
613 |
|
Petite Pearl |
9-Jun |
674 |
|
Clarion |
9-Jun |
674 |
|
Jupiter |
9-Jun |
674 |
Canopy management
With the rain and recent warming temperatures, shoots have reached nearly 3’ in length (Figure 2). Shoot and wire positioning Vinifera for VSP and suckering/thinning have been ongoing over the past several weeks. We are waiting to comb the high-wire shoots on the hybrids until the fruit starts to weigh the shoots down and shoot tips become less prone to breaking (Figure 3).
Figure 2. Regent canopy, VSP, 10 June 2025
Figure 3. Clarion canopy, High-wire cordon, 10 June 2025.
Disease updates
Cool, rainy conditions in May meant Phomopsis in several cultivars at Unit 2 (Figure 4). In more southern regions, many are also seeing Anthracnose stem and leaf infections (Figure 5). Reminder: we are still well-within the critical window for flower and fruit protection for all major diseases. This period over the next several weeks are the most important time of the season to ensure broad spectrum coverage using your best fungicides for preventative protection. For fungicides registered for grapes and disease efficacy, see: Midwest Fruit Pest Management Guide.
Figure 4. Phomopsis on shoots and leaves, Clarion, 27 May 2025
Figure 5. Anthracnose on Vidal blanc. Note how the lesions are gray in the center and sunken compared with Phomopsis. Leaf lesions of Anthracnose also fall out as the leaf tissue dies, leading to a “shot hole” appearance. June 2025. (Photo used with grower permission)
Insect management
It is right about time to start turning our attention to Grape Berry Moth (GBM). This is one of the handful of insects that can cause direct crop loss from fruit damage (Figure 6).
The other major insect to begin to start monitoring for is Japanese beetles. These foliage feeders can get out of hand quickly if allowed to accumulate large populations.
Some minor pests to monitor for include gall makers (grape cane gallmaker, grape tumid gallmaker), flea beetle larvae, and leafhoppers.
Scouting and monitoring (using GDD-based tools and traps) are the best means for deciding when insect control is warranted. In Wooster, we typically use fewer than 5 insecticide applications all season (this includes pre-harvest sour rot management sprays) by regular monitoring and providing well-timed and appropriate insecticide applications. Excessive use of insectcides may cause secondary pest infestations, including mites and mealybugs.
Figure 6. Berry damage from GBM in July 2024 (and some more Phomopsis on the stem).
Figure 7. Japanese beetle adult (top). Foliar feeding damage from Japanese beetles (bottom). July 2023.