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By: Dr. Maria Smith, HCS-OSU

From Ashtabula to Cincinnati, the growing season is here. Usually, budbreak is a stratified process over several weeks from the south to the north, but not this year. An unusually warm spring has heralded in the start of the season in an uncanny uniform fashion and without regards to cultivar or geographical region (Fig 1). This year’s budbreak pattern, which is anywhere from days to weeks ahead of historical averages, can largely be attributed to the abnormally warm, dry conditions that increase in intensity from south to north (Fig 2).

 

Fig 1. Phenology among several Vinifera and hybrid cultivars at Wooster, Unit 2, Apr 16, 2021 (Photo credit: Diane Kinney).

Fig 2. Temperature (left) and precipitation (right) deviation from the long-term average from March 17 through April 15, 2021 (figures from https://climate.osu.edu)

Despite the recent pleasantly warm weather, Ohio unfortunately remains at risk for below freezing conditions for another 2 to 4 weeks (Fig 3). This week will be a stark reminder of that, as both below freezing temperatures and the chance of snow accumulation are forecasted courtesy of a cold front moving across the state later this week (Fig 4).

Fig 3. Median date of last 32°F for Ohio (figure from www.mrcc.illinois.edu)

Fig 4. Forecast and minimum temperature maps for the week of Apr 19, 2021. (figures from NOAA, www.weather.gov)

Given the upcoming forecasts, let's review some lessons from the 2020 season freezes

Stay calm and optimistic!

Just because temperatures reach < 32°F does not automatically mean that all the shoots will die. Grapes are resilient when it comes to coping with environmental stress, and spring freezes are no exception. The good news over the past few days is that cooler temperatures have slowed growth and development of the vines. This is crucial since we know that buds/shoots that are less advanced can withstand colder temperatures than those which are more developed (Table 1). Additionally, grapes are comprised of compound buds, so that if there is loss of the primary shoots, secondary and tertiary shoots can emerge to resume growth. Although these secondary and tertiary shoots are less fruitful than primary shoots and are developmentally delayed, many common French American and cold-hardy hybrids grown in Ohio have highly fruitful secondary shoots that can temper potential yield losses.

Table 1. Estimated critical temperatures for Pinot noir at different stages of bud/shoot development (Gardea, 1987)

 

Swell

Bud break

First leaf

Second leaf

Third leaf

Pinot noir

26.6

28.0

28.4

28.9

30.0

Review the tools for successfully “weathering” this week’s freeze

One of the first questions that come up when a spring freeze event approaches is “What can I do to protect the vines?”. Once vines have reached budbreak, the options for protection are limited, and the efficacy of the options is highly dependent upon the type of freeze event (Table 2). For many small vineyards, the best options are those that need to be considered and used in advanced of any predicted spring freeze events.  

Table 2: Characteristics of radiation vs advective freeze events. Table from https://www.canr.msu.edu/news/what_is_the_difference_between_a_frost_and_a_freeze

Radiation freeze

Advective freeze

Winds less than 5 MPH

Winds higher that 5 MPH

Clear sky

May be cloudy

Cold air mass 30 to 200 feet thick

Cold air mass 450 to 3,000 feet thick

Inversion develops

No Inversion

Cold air in the low spots

 

White or black frost damage

 

Easier to protect

Difficult to protect

Below is a republishing of methods that can also be found from our OGEN article from APRIL 2020 - Spring Freeze Issue.  Drs. Imed Dami and Michela Centinari (PSU) also discussed these methods in a recent March webinar. Click here to view the presentation.

Methods prior to frost event

  • Delayed pruning: similar to 2020, vines have more advanced phenology than normal and buds are pushing earlier as a result of above average temepratures. Delayed pruning helps with delaying budbreak.
  • Double-pruning: the rationale is similar to delayed pruning. With 1st pruning, you leave extra buds per vine. Due to apical dominance, apical buds push earlier than basal buds. If frost occurs, basal buds (which are delayed in growing) will be less likely to be injured. With the 2nd pruning, apical shoots (injured or not) will be pruned by retaining a final bud count per vine. Note: the 2nd pruning should occur when apical shoots are less than 2" in total growth to avoid potential issues with fruitless shoots developing from the basal buds regardless if you are past the last date of freeze.
  • Row middle and cover crop: bare ground in row middles provide more heat to keep vines warm during a frost event. Mowed grass cover crop will also do the same. So, it is crucial that you mowed your grass as short as possible for added frost protection.
  • Products that delay budbreak: Some products can be effective, but it is too late to apply now if you have not already done so. Please view the recorded webinar presentation with Dr. Imed Dami (link) for an overview of the available budbreak delay products.  
  • KDL (0-0-24) fertilizer: Even though growers would like to use this product, research has shown that KDL does not protect shoots against frost injury once vines resume growth. Therefore, it is not recommended. Dr. Smith researched this product and can be contacted directly for more information.
  • Copper: has been shown to protect young shoots against frost injury by killing ice forming bacteria present on vine foliage. You may start spraying as soon as budbreak and repeat every 5-7 days (washes off easily and must be reapplied after an inch or more of rain) until you’re out of the frost threat period (2 – 3 weeks) in your vineyard. Read the label for the application rate. In CA, 0.75 actual copper per acre was used. Read the label to avoid plant injury. To avoid injury, apply when not cold or wet (slow drying) and use formulation with lime.

Methods during a frost event

  • Wind machines: wind machines, although expensive, are effective against radiative spring frost events (clear, cold nights with temperature inversions).
  • Overhead irrigation (sprinklers): None of our growers in OH has this system. Having said that, DO NOT SPRAY YOUR VINES WITH WATER USING A SPRAYER. You will cause more damage than doing nothing.
  • Heaters: same as above; not a common method in Ohio. When temperature inversion exists, heaters are effective alone and best with wind machines. However, cost of fuel and pollution are main limitations.

Although there are still a couple of days until the predicted freeze event, it is a good idea to also review the recommendations for managing the vineyard if the forecasted freeze causes shoot injury. Those recommendations can be found in the APRIL 2020 OGEN.

Posted In: Viticulture
Tags: Viticulture, Spring Freeze, 2021 Season
Comments: 0

Elizabeth Y. Long, Horticultural Entomologist, Purdue University
Adjunct Horticultural Entomologist, The Ohio State University

A natural wonder will occur in 15 states this year: the emergence of the Brood X, 17-year periodical cicadas! Also known as “17-year or 13-year locusts” the last mass emergence of these insects occurred in 2004. Now, 17 years later, the immature cicadas will emerge from the ground, molt one last time to gain wings, and “sing” loudly to find mates and lay eggs in trees and woody shrubs.

Periodical cicadas: where and when?

Many of you likely remember when the Brood V, 17-year periodical cicadas emerged in Ohio in 2016 (Fig. 1, purple shading on map). That emergence occurred in key grape-growing counties in northeastern Ohio. However in 2021, activity of the Brood X, 17-year cicadas will be heaviest in west-central and south-west Ohio (Fig. 1, yellow shading on map), with emergence taking place late May through June.
 

Figure 1. Active periodical cicada broods of the United States. Yellow-colored counties indicate areas where 17-year cicadas are predicted to emerge in 2021. Image credit: AM Liebhold, www.fs.fed.us

You will see two distinct life stages of these charismatic insects: the nymphs and the adults.

Although there is no single degree-day model to predict the emergence perfectly across regions, it’s generally agreed that when soil temperatures warm up to 65 °F or so, the nymphs will begin to emerge from the soil. The nymphs are wingless, just a bit creepy, and dark golden-brown in color (Figure 2). After emerging from the ground, nymphs crawl up tree trunks and items like patio furniture, to molt - leaving behind their cast skin (exoskeleton).

Figure 2. Periodical cicada nymph (cast ‘skin’). Photo: John Obermeyer

The adults are 1.5 to 2-inches long, with black bodies and reddish-colored legs, wing margins, and eyes (Figure 3). Newly emerged adults may appear pale or white in color until the exoskeleton has hardened and darkened (Figure 4). Adult periodical cicadas live for ~1 month, and during this time the males produce shrill “songs” to attract females using vibrating organs called tymbals - how romantic! Females cut slits into twigs of woody plants to lay eggs that hatch in 6-7 weeks. After hatching, the next generation of 17-year cicada nymphs drop to the ground and dig down into the soil, where they will remain for another 17 years feeding on sap from tree roots.

Figure 3. An adult periodical cicada on my arm

 

Figure 4. A newly emerged adult periodical cicada, before its exoskeleton has hardened and darkened. Photo: Jane Chandler

Why the mass emergence? This is a life history strategy to satiate predators (Figure 5, they can’t eat them all!) and maximize the chances that the majority of periodical cicadas will survive to mate and lay eggs.

Figure 5. Periodical cicadas have many predators, including chipmunks. Photo: Emily Keith

Damage

  • The good news is periodical cicadas do not bite or sting people, or pets.
  • The bad news is females lay eggs in 200+ woody tree species and can cause severe damage to young trees and grapevines (Figure 6).

Figure 6. Cutting/slitting egg laying damage caused by female periodical cicadas on grapevines. Photo: E. Y. Long

Apples, cherries, peaches, plums, and grapevines are at high risk, because these hosts are preferred for egg laying by female cicadas. However, any young trees and grapevines with main branches, stems, and canes between 3/16-inch and 7/16-inch in diameter are susceptible to damage and should be the main focus of protective efforts.

Egg laying physically weakens and damages branches and canes, which may turn brown, die, and break off (“flagging”). Under heavy attack, the loss of branches and canes can cause serious damage or death to young trees and grapevines. It is also possible that nymphs feeding on roots reduces vigor.

Management

Step #1: Cultural control

  • Delay new plantings in 2021, either until the emergence has ended, or next spring.
  • Plan accordingly for future emergence of periodical cicadas broods in Ohio: (Table 1, below).

Table 1. When and where 17-year periodical cicadas will emerge in Ohio in the future.

Brood number

Race

Year to appear

Where they will appear

XIV (14)

17-year

2025

South-west/south-central Ohio.

Step #2: Mechanical control (recommended for small orchards/vineyards, backyard fruit trees/grapevines, and organic production)

1. Net grapevines with mesh screening (no larger than 1/2-inch openings), when first males begin singing (before egg laying begins), to prevent females from accessing the plant to deposit eggs.
Cover grapevines and secure the netting to/near the trunk, the ground, or lower trellis wire (Figure 7). Remove after adult periodical cicada activity ends.

Figure 7. Example of netting grapevines to exclude female periodical cicadas. Photo: Wikimedia.org

Step #3: Chemical control (recommended for settings where netting is not feasible, like large/commercial vineyards)

IMPORTANT: Chemical control is not as effective as netting. While netting is applied once to exclude egg-laying females, insecticides must be applied repeatedly against “waves of cicadas” during the ~1-month activity period of adults to prevent or reduce injury to grapevines.

Insecticides are not recommended to protect mature grapevines, because these vines can tolerate egg laying damage. However, insecticide applications can reduce periodical cicada injury to young grapevines:

1. Once egg laying begins, insecticides may be applied:

  • Every 3-4 days, to help prevent injury, or
  • Every 7-10 days, to help reduce injury
  • Soil-applied, systemic insecticides are not effective against periodical cicadas.

Scout vineyards every 2-3 days during egg laying to evaluate how well insecticide applications are protecting young grapevines.

Pyrethroid insecticides are recommended against periodical cicadas because they have fast knock down and good residual activity; however, commercial producers should beware flare-ups of spider mites when using pyrethroid insecticides like Baythroid XL (active ingredient: cyfluthrin), and Mustang Maxx (active ingredient: zeta-cypermethrin) against periodical cicadas, because they also kill beneficial, predatory mites that typically keep spider mites at bay. Pyrethroids like Danitol (active ingredient: Fenpropathrin) and Brigade (active ingredient: Bifenthrin) are unlikely to cause spider mite flare-ups when used below the maximum rate.

Commercial producers can refer to the 2021-2022 Midwest Fruit Pest Management Guide for insecticide recommendations.

Homeowners can use products with active ingredients permethrin (Bonide Eight), zeta-cypermethrin (GardenTech Sevin), or gamma-cyhalothrin (Spectracide Triazicide Concentrate for Lawns and Landscapes) against periodical cicada on backyard fruit and ornamental trees and shrubs.

For your safety, always read and follow the instructions on pesticide labels.

In summary, here are some quick “take home messages:”

  • 17-year cicada emergence will occur in west-central and south-west Ohio late May through June.
  • Female cicadas damage twigs, branches, and canes 3/16-inch to 7/16-inch in diameter by cutting into them to lay eggs.
  • If you have an orchard, vineyard, or backyard fruit trees/vines: prepare to take action when you hear the first males begin to “sing.”
  • Focus protective efforts (netting, insecticide applications) on young trees and grapevines, because they are most vulnerable.
  • Select and use insecticides judiciously to reduce flare-ups of secondary pests, like spider mites.
Posted In: Insect management
Tags: Cicadas, Insects, 2021 Season
Comments: 0