Strawberry Renovation Revisited

Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu

As strawberry season winds down in June, it will be time to consider renovation options depending on the production system

Matted Row Systems
In matted row strawberries, the goals in renovation are to reduce plant numbers by narrowing the rows, remove old foliage (reduces diseases), control weeds, reduce insect and mite pests, and promote new runner development (production of daughter plants). After renovation, regular irrigation and weed control are essential. High yields next year depend on having large, healthy, vigorous plants when fruit buds are initiated in late summer.

With matted rows, renovation starts with an application of 2,4-D amine herbicide (Weedar 64) after the last harvest. If grasses are a problem a sequential application of sethoxydim (Poast) or clethodim (Select) may be necessary (do not tank mix with the 2, 4-D). After the last herbicide application, wait 3-5 days and then mow off the strawberries to just above the crown (do not damage the crown). Apply nitrogen fertilizer (25-60 lbs N/acre) at this time. Using a split N application half at renovation and half 4 weeks later is preferable. If other nutrients were low or deficient (as indicated by tissue tests prior to fruiting) then apply at this time. Subsoil fields with compaction from equipment or heavy foot traffic between the rows (U-pick plantings for example).

Next, narrow the rows with a cultivator, coulters/discs, a rotary tiller/multivator or other devices to 12-18 inches at the base. Matted row strawberries are edge bearers and benefit greatly from this narrowing. Strawberries produce new roots higher on crowns each year so try to throw about 1/2 -1 inch of soil over the row (without covering the crowns). This will also help new daughter plants root (runners produced from mother plants).

After narrowing the rows apply preemergence residual herbicides. Apply 2-4 ounces of terbacil (Sinbar). This is one half the annual rate. Sinbar can injure some varieties and attention should be paid so as not to have overlaps. If Sinbar is not used, DCPA (Dacthal) may be applied at this time. This material requires adequate rainfall or overhead irrigation for activation. Dacthal benefits from being lightly incorporated (possible in row middles). During the summer, cultivate between rows to remove weeds and to sweep runners into the row. From late summer on, cut off any additional runners during cultivation (discs or coulters work best).

Weeds in the rows must be controlled throughout the summer. Sethoxydim (Poast) or clethodim (Select) may be sprayed over the top to control grass weeds. Clopyralid 0.12-0.25 lb (Stinger 0.33-0.67 pt/A) has a 24c label for use in MD, NJ, VA, and PA for over the top control of some broadleaf weeds. Hand hoeing will be necessary for removal of remaining weeds.

Irrigate strawberries so that they receive 1.5 inches of water (combined rainfall and irrigation) each week during the summer. Irrigation during late July and August are very critical to produce large plants as flower buds will be initiated starting in August. Continue irrigation (at reduced rates) through the fall until dormancy. Strawberries may benefit from low amounts of additional nitrogen fertilizer (25 lbs of N/acre) later in summer depending on the vigor.

Plasticulture Systems
With the high cost of establishing strawberries planted on plastic mulch, many growers choose to carry them over for another year. First, evaluate the disease pressure on the planting. If anthracnose was a major problem, you should not carry the planting over. If disease pressure was low, then renovation can proceed.

The goals in renovating plasticulture strawberries are to remove old foliage, remove any runners formed, remove diseased plant material from the field, control weeds, reduce insect and mite pests, and reduce crown size of very large plants.

Mow the strawberries as close to the crowns as possible without damaging them. Remove any diseased plant material from the field. Plants with more than 5 branch crowns will benefit from thinning. Using an asparagus knife, remove one half of the crown. Apply weed control measures between plastic beds (herbicides, cultivation, or combination) being careful not to apply herbicides over the plastic beds. Irrigate strawberries so that they receive 1.5-2 inches of water each week during the summer. Fertigate with 40 to 60 pounds of nitrogen per acre in late August and add any additional nutrients as suggested by tissue tests. Continue irrigation as needed throughout the fall.

The key for carryover strawberries on plastic is not to have too many crowns going into the fall. Excessive crown numbers will reduce berry size greatly. Carry over beds should not be row covered until winter to avoid excessive growth and may not need row covers in mild winters until the frost protection period in March and April during flowering.

Day Neutral (Repeat Blooming Types) Renovation on Plastic
The decision on when and how to renovate day neutral plasticulture strawberries differs from June bearing types in that production can continue into the summer, picking up again in the fall.

With fall planted day neutrals consider renovation in July when production slows. Mow the strawberries as close to the crowns as possible without damaging them. Remove any diseased plant material from the field. Plants with more than 5 branch crowns will benefit from thinning. Using an asparagus knife, remove one half of the crown. Apply weed control measures between plastic beds (herbicides, cultivation, or combination) being careful not to apply herbicides over the plastic beds. Irrigate strawberries so that they receive 1.5-2 inches of water each week during the summer. Fertigate with 40 lbs/a N at the July renovation and fertigate again with 20-40 lbs/a N and 40 lbs/a K when first bloom appears in the fall.

With spring planted day neutral strawberries, remove runners throughout the season. If production stops, maintain plant health by regular irrigation and disease, mite and insect management. In mid-August, fertigate with 40 lbs/a N and fertigate again with 20-40 lbs/a N and 40 lbs/a K when first bloom appears in the fall.

 

Misshapen Strawberry Fruits

Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu

Most commonly, misshapen strawberries during spring result from poor pollination. Strawberries are aggregate fruits. They have multiple ovules per receptacle where the fruit is formed. The strawberry receptacle may have up to 500 ovules per berry. You will see these as “seeds” on the outside of the strawberry fruit which are called achenes. To have the largest berry possible, you need as many of these ovules to be successfully pollinated as possible. To avoid misshapen fruits the achenes need to be pollinated evenly and fully. With pollination, the receptacle tissue around the achenes will develop to form the strawberry fruit.

Strawberries have both male and female flower parts on the same flower and can self-pollinate. Wind and rain can move pollen within the flower. However this usually does not allow for full pollination of all the ovules. Bees, such as honey bees or bumblebees, are usually necessary to allow for complete pollination. Some flowers actually produce bigger berries when cross pollinated with pollen from other flowers. Incomplete pollination will often result in smaller or misshapen berries.

Strawberry flowers are not heavy nectar producers. However, bees do visit the flowers and studies have shown that where native bees are limited, adding hives of honey bees or bumble bees increased productivity. It is recommended that each flower receive 16-25 bee visits. This is particularly true of the king berries, which form from the first flower to open on a fruiting truss.

You can distinguish poor pollination from other types of damage because fruit will have variable achene (seed) size. Large seeds received pollination, while small seeds did not. Poor pollination is common when plants have been under row covers during bloom and when the bloom period has been rainy, stormy, or cold. Frost damage that does not kill the whole flower will also cause berry deformities because some achenes have been damaged.

Lygus bugs (Tarnished Plant Bugs) can also cause misshapen fruit by feeding on the flower. To distinguish between Lygus bug damage and poor pollination look at the seed size on the fruit – seeds on fruit affected by Lygus will be similar in size.

Boron deficiencies are another potential cause of misshapen strawberries.

Strawberry deformities caused by poor pollination and cold injury.

Fruit Drop in Tree Fruits

Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu

Fruit trees commonly set more fruit than they will carry and chemical, mechanical, or hand thinning is done to reduce fruit loads, increase fruit size, and limit alternate year bearing. Natural fruit drop also occurs and is often called “May Drop” or “June Drop”. This is often accompanied by some leaf drop, especially in stone fruits.

Natural fruit drop is a result of unfertilized or poorly fertilized seeds, cold injury, competition between fruits, or shading. Poor pollination may be a result of cold, rainy weather during bloom in self-fertile fruits such as peaches or poor insect pollinator activity during flowering in insect pollinated fruits such as apples. In stone fruit, some fruit that is not fertilized will remain on the plant for 25-50 days after bloom and then will drop before pit hardening starts.

Another wave of natural fruit drop occurs in late May or early June. This fruit drop is due to competition between fruit for sugars stored and produced by the tree. A tree can only carry a certain load of fruit and will naturally drop smaller and weaker fruit during this period. However, thinning should have been accomplished before this competitive fruit drop occurs. Having fruit remain on the plant until natural competitive drop will use up food reserves in the plant and reduce the size potential of remaining fruit. Fewer cells will have been produced by the fruit remaining on the plant and therefore fruit size will not be recovered.

Another cause of fruit drop is cloudy weather during the period 5 to 7 weeks after bloom. A continuous 4-day period of cloudy days during this period will also cause fruit to drop. In addition, defoliation due to disease such as peach leaf curl, chemical injury such as copper fungicide damage, or severe storms can cause fruit drop during this critical period.

Bruising on Strawberry Leaves

Jerry Brust, IPM Vegetable Specialist, University of Maryland; jbrust@umd.edu

Over the last few weeks I have been sent pictures of and have seen dark spots on the foliage of strawberry plants (Figures 1 and 2). These spots can look pretty bad at times and are thought to possibly be the start of some disease, such as angular leaf spot or anthracnose. The dark spots are usually on the upper or lower surface of the leaf, but at times can be found on both surfaces of a leaf. These damaged areas of strawberry foliage can be very disconcerting when they appear as dark spots on the stems (Fig. 3). No bacteria or fungi have ever been found associated with these dark spots. I have seen this type of discoloration in strawberry foliage early in the season many times over the years and have never seen the spots turn into any disease problem or any other type of problem. The best that we can come up with is that the plant has ‘bruised’ foliage. And as you look at the spots this is exactly what the damage looks like (kudos to Karen Rane for coming up with this description of the damage). This damage usually appears within a short time span after high winds occur. Figure 4 shows a good example of this as you can see the bruised areas of the leaves that appeared a few days after a very windy period on April 15. Also notice the tattered appearance of the leaf edges demonstrating that these leaves were knocked around a great deal. It is possible that disease organisms might enter the plant through this damaged tissue, but I have never seen this occur to any extent in the field—even during the wettest spring. Nothing needs to be done about this bruising, growers just need to be aware of the possibility occurring after wind events.

Figures 1 and 2. Dark spots on strawberry leaves often mistaken for the start of foliar diseases

Figure 3. Strawberry stem with dark spot

Figure 4. Strawberry leaf with bruises and tattered margins

 

Establishing Blueberries – Plan Now for a 2020 Planting

Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu and Emmalea Ernest, Associate Scientist – Vegetable Crops; emmalea@udel.edu

There has been an increase in interest in growing blueberries in Delaware and we have had several new plantings in Delaware in recent years.

Blueberries are very specific in the type of soil conditions in which they will grow. The ideal blueberry soil will be sandy but with high levels of organic matter, it will have a pH between 4.5 and 5.0, it will be well drained in the surface soil but will ample subsurface water. These are the conditions of southern New Jersey where blueberries are native and where there are large commercial plantings. We only have a small area of Delaware with those characteristics; the “black soils” were marshes were drained in southern Sussex County. In all other areas of Delaware, it is necessary to recreate those conditions.

There are five keys to success with blueberries:

1) Increase soil organic matter before planting

2) Drop soil pH to between 4.5 and 5.0 and bring phosphorus and potassium up to optimum or high levels prior to planting

3) Put organic material in the planting hole during planting

4) Mulch the plants well after planting

5) Install a drip irrigation system

The following are some more details on each of these keys.

A common mistake is to plant blueberries before the soil has been modified. Normal agricultural soils will have a pH around 6.0 and organic matter below 2%. Blueberries will not grow well in these conditions. Begin modifying the soil at least one year in advance of planting.

To increase organic matter, plant cover crops and consider amending the soil with additional organic sources such as pine bark fines. Do not use composts that have high pH.

The pH of the soil will need to be modified. This is done by adding elemental sulfur at recommended rates according to soil type and the amount of pH drop required. Again, the target is between 4.5 and 5.0. Blueberries are among a group of unique plants that are acid loving in contrast to most other crops, which require a higher pH. Sulfur additions to lower pH must be done the year before planting. This is because bacteria in the soil need to react with the sulfur to form an acid that lowers the pH. This only occurs when soil temperatures are warm and it takes several months for the full reaction to take place. You cannot apply sulfur in the year of planting and expect the soil pH to be in the acceptable range for good first year growth. Sulfur rates will depend upon soil types and starting pH.

During the year when you are modifying soil, add phosphorus and potassium to bring soil levels to optimum for those two nutrients prior to blueberry planting. Use Potassium Sulfate as the potassium source.

After the soil has been properly modified, you can plant the blueberries. This is normally done in the spring. Fall plantings are possible but there are higher risks of plant loss in harsh winters. When laying out plantings and deciding on between row spacing, think about how you will apply mulch and pesticides and whether you will be using netting to exclude birds. Rows will need to be wider if large equipment is used for mulching or spraying, but wide row spacing will increase costs if netting is needed to prevent bird damage.

Another key to planting blueberries is to add organic matter to the planting hole. The most common practice for smaller plantings is to use one gallon of moistened peat moss in each hole. Other organic materials can be substituted but they should be low in pH and should be at least partially decomposed. Most commercial composts are not acceptable because the pH is too high for blueberries. Also, composts made with manures as a component may have too high of salt levels and can injure the blueberry roots.

After planting, blueberries should be mulched heavily. Blueberry roots are shallow and need to be protected from high soil temperatures. In addition, the mulch will conserve soil moisture and provide additional organic matter as it slowly decomposes. Blueberries are also very sensitive to weed competition and mulch helps to prevent weed growth. The best mulch materials are high in lignin and acidic in nature. Pine bark is ideal but is often not readily available. Aged wood chips or ground yard waste that has been aged makes good mulch. Sawdust must be partially decomposed before use to avoid nitrogen deficiencies. Avoid mulches that increase soil pH.

Drip irrigation is recommended for blueberries and is best placed under the mulch. Because blueberries are shallow rooted, frequent irrigations during our hot summers will be needed to get the plants established and growing well. Two drip lines per bed, one on either side of the plants, optimizes rooting area, especially in sandy soils. Overhead irrigation can also work if designed properly.

Do not put fertilizers in the plant hole and avoid adding any fertilizer until plants are established. In the first year, blueberries will need about 20 pounds of nitrogen and nitrogen should be in the form of ammonium sulfate or urea. Do not use N sources that contain nitrate. Do not use fertilizers containing chloride (such as KCl – potash).

Place plant orders the year prior to planting. Plants may come as bare root plants, large liners, or potted plants. Large liners and pots have less risk of planting losses. Choose northern high bush varieties recommended for our region. Current recommendations can be found in the Mid-Atlantic Berry Guide. The University of Delaware has conducted trials with additional varieties (many southern highbush types). Contact Emmalea Ernest (emmalea@udel.edu) for results and additional recommendations.

Blueberries cannot tolerate standing water at any time and site selection is important. Choose well drained sites and consider raising beds or ridges to improve drainage where needed.

Extending Your Strawberry Season with Day Neutral Varieties

Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu

Plasticulture strawberry planting season is quickly approaching. Growers seeking to extend their strawberry seasons should consider planting a portion of their area to day-neutral varieties. Day-neutral strawberries start fruiting 12-14 weeks after planting and have the potential to give late fall as well as early April through July production. Currently, the three varieties that have shown the most potential for extended production on Delmarva are Seascape, San Andreas, and Albion.

Albion, in particular, has shown great flexibility for season extension. It is very flexible on when it is planted in the late summer or early fall. August plantings will yield some late fall production, particularly in high tunnels. While much less productive in the main Chandler season in the spring, it has some unique properties that make it valuable to growers. First, it will give some early production, ahead of Chandler. Second, even though production is lower, it produces evenly over an extended period of time from April through July. In general, it will give 5-6 weeks more production than Chandler. It is a large, firm berry that, while not as sweet early in the season, has good quality in May and June.

Early August plantings of San Andreas will yield more fall production than Albion and San Andreas has comparable yields to Chandler in the spring with continued production through June. Both Albion and San Andreas have good quality and are firm berries that will stand up to regional shipping.

Seascape has been around for a long time and was the first of the larger sized day-neutral berries to show commercial potential in our area; however, Seascape has a softer berry and does not ship well so is best adapted to U-pick and local sales. Some grower in the region have had luck growing Seascape with multiple spring plantings spaced about three weeks apart from March through June giving summer and fall sales. Both Albion and San Andreas can also be planted in the spring for extended summer sales. Production in the heat of July and August will decline or stop unless there is a cool summer.

Because these day-neutral varieties keep blooming throughout the season, it is critical to maintain fertility, particularly with nitrogen, potassium, and calcium through fertigation. Albion, in particular, has high nitrogen needs to produce well. Disease management is also critical because these varieties bloom for an extended season. Gray mold fungicide sprays must be applied regularly throughout the extended seasons.

USDA Offers Free EBT Equipment and Service for Farmers Markets and Direct Marketers

The USDA’s Food and Nutrition Service (FNS) recognizes that America’s farmers markets and direct marketing farmers are a great source of fresh fruits, vegetables, and other healthy foods. FNS has made it a priority to expand access to such food for Supplemental Nutrition Assistance Program (SNAP) participants by providing free electronic benefit transfer (EBT) equipment necessary to process SNAP benefits to eligible farmers markets and direct marketing farmers.

Interested in Free SNAP EBT Equipment & Service?
SNAP authorized farmers’ markets and direct marketing farmers are eligible for funding if you:

  • Have not previously received EBT equipment through the current or former SNAP EBT Wireless Grant Program, and
  • Do not currently possess functioning SNAP EBT equipment, or
  • Currently possess functioning SNAP EBT equipment, but received the equipment before May 2, 2012, and
  • In the case of a Direct Marketing Farmer, participate in at least one farmers market.

Benefits for Eligible FMs and DMFsmarke
Eligible farmers’ markets and direct marketing farmers will have the option to choose their own SNAP approved equipment from one of the participating service providers. The costs of purchasing the equipment and services (set-up costs, monthly service fees, and wireless fees) for up to three years will be covered for eligible farmers’ markets and direct marketing farmers. Transaction fees (for SNAP EBT, credit, and debit payments) will not be covered.

How to Apply for the SNAP EBT Equipment Program
Once you’ve received your SNAP Authorization Permit Number from FNS, you can start your application for free EBT equipment. Contact information, including a valid email address, FNS number, and some general information about your farm or farmers market will be required. Funding for this program is limited, and is available on a first-come, first-serve basis.

For more information, please visit the wireless SNAP EBT grant program’s website: https://www.mysnapebtequipment.com/

To apply to accept EBT, please visit the following website: https://www.fns.usda.gov/snap/retailer-apply

Editor’s Note: UD Cooperative Extension is in the process of designating people from our FCS team who will be able to assist farmers interested in applying to this program. Stay tuned for more info during Delaware Ag Week.

When to Plant Plasticulture Strawberries

Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu

Chandler has been our main plasticulture strawberry and has shown consistently high yields. For most of Delaware, the recommendation has been to plant Chandler the second week in September. However, Chandler is more sensitive to fall and winter temperatures than other varieties and in warmer conditions Chandler will put on too much growth, leading to small berries the following spring; therefore, knowing when to plant is difficult. If you could accurately predict fall and winter temperatures, you could adjust planting dates, but, of course, this is not possible.

One strategy has been to make multiple plantings of Chandler one week apart starting the second week in September. This will insure that a part of the crop will come out of winter with the proper number of crowns (not too many, not too little). Unfortunately, this means that part of the crop will be low yield and part will have small berries.

Another strategy is to switch to varieties that are less susceptible to putting on too much growth. This is where the variety Camarosa may have a fit; it is less temperature sensitive than Chandler in the fall and is not prone to putting on excessive growth. Camarosa has not performed as well on Delmarva compared to North Carolina.

Sweet Charlie, the early berry that also can put on a second late crop, is normally planted 7-10 days ahead of Chandler. It is not an option to replace Chandler. For other varieties being tried, we still do not have enough research in our region to know if they can be replacements for Chandler. Flavorfest has performed well but does not produce over as long of a season as Chandler.

Another strawberry that should be considered by growers is Albion, a day-neutral variety. It too is not sensitive to when it is planted in the fall. While much less productive in the main Chandler season, it has some unique properties that make it valuable to growers. First, it will give some early production, ahead of Chandler. Second, even though production is lower, it produces evenly over an extended period from April through early July. In general, it will give 5-6 weeks more production than Chandler. It is a large, firm berry, that, while not as sweet early in the season, has good quality in May and June. Research at Cornell and Penn State has shown that Albion needs much higher levels of nitrogen than the other common varieties and when fertilized properly will give higher yields over an extended period.

Three New Jersey Counties Under Quarantine for Lanternfly

David Owens, Extension Entomologist, owensd@udel.edu

If you have business in New Jersey, please be advised that three counties (Mercer, Warren and Hunterdon) have recently been placed under quarantine in an attempt to slow the spread of the spotted lanternfly. Quarantine means that certain restrictions may be in effect for moving materials, and that vehicles and goods will need to be examined when moving out of the quarantined area to ensure that it is lanternfly-free. Please see the following news article: https://www.nj.com/news/index.ssf/2018/07/these_three_nj_counties_are_now_under_a_spotted_la.html.

Notes from the Annual Meeting of the American Society for Horticultural Sciences (ASHS)

Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu

Each year, the ASHS has an annual meeting bringing together scientists working with specialty crops (vegetables, fruits, ornamentals). This year the meeting is in Washington DC. The following are some notes from sessions I have attended over the last 2 days that have relevance to our Delmarva growers.

  • Sweet corn planted into selected biodegradable black plastic mulches were shown to provide equal weed control, production, and earliness to standard black polyethylene mulch and eliminate mulch disposal costs.
  • Pepper production under biodegradable plastic mulch was equivalent to standard black plastic mulch again eliminating the need for mulch disposal.
  • Low rate compost application in potato (1 ton/a) reduced nitrogen needs and improved quality and yield in potato production.
  • Reduced curing temperatures and time of curing as well as delayed vine termination (mowing just before digging) reduced internal defects in ‘Covington’ sweet potato
  • Using white or reflective mulch did not improve broccoli production compared to black plastic mulch (we have a similar study currently in Delaware)
  • Progress is being made in breeding beets for lower levels of geosmin, the compound that gives beets the earthy taste.
  • Grafting tomatoes onto certain vigorous rootstocks can improve yield in high tunnel production, even in the absence of soil-borne disease.
  • From Matt Kleinhenz at Ohio State University “Commercial microbe-containing crop biostimulants are advertised to maintain or enhance crop growth. More than two-hundred such products ranging in composition (e.g., bacterial, fungal, both; cfu/ml) are currently available. To date, outcomes from standard statistical approaches common in product evaluations, variety trials, and cultural management comparisons show that significant increases in yield or quality have been rare, regardless of inoculation parameters or experimental conditions.”
  • A multistate project is underway to see if there are long term benefits to the “soil balancing” philosophy of soil management — specifically, balancing percentages and ratios of calcium, magnesium, and potassium through applications of lime, gypsum, and other materials to improve soil physics (tilth) and biology and, thereby, crop yield and quality and weed control. Past, shorter-term studies have shown no benefits to soil balancing but some growers and crop advisors disagree. This multi-state research aims at answering claims that University research on soil balancing has not been long term and thus is biased.
  • Recently, a finely ground (<0.5 micron) liquid limestone-based product (Top Flow 130; Omya, Oftringen, Switzerland) was developed for agriculture use to be injected through drip irrigation tubing. Research by Tim Coolong in Georgia showed that Top Flow 130 could be used to adjust pH in a plasticulture system, but that the effects would occur within a zone of 4 inches on each side of the drip irrigation tubing. This may be useful for situations where pH has dropped below 5.2 in plasticulture beds.
  • UV blocking plastic in high tunnel covers were shown to reduce Japanese beetle activity greatly in high tunnel raspberry production.