May Growing Tips

By Raintree Horticulturist Theresa Knutsen

• Planting in Hot Spring Weather
• Guideline For Choosing Which Plants Will Work for You
• Insect and Disease Control  Apple maggot/Coddling moth  Caterpillar control  Suzuki Fruit Fly   Fungal Disease Control
• Weed Management
• Mason Bee Late Spring Care
• Check to See if Blue Honeysuckle Fruit Are Ripening
• Irrigation
• Container Plants Care
• Spring Bud Grafting Tips
• FAQs: My Recently Planted Bareroot Plant Has Leafed Out But Not Grown Any Shoots. Will It Be OK?

If you live in the Pacific Northwest, and other cool spring locations, there is still time to plant out bare root plants before the on-set of summer heat. Potted plants are also still OK for most locations. Remember, Raintree bare root trees are kept in cold storage and are dormant and in ideal shape to dig in and grow for you.

However, if your day time temperatures are generally 75- 80° F you will need to take special precautions to ensure success with your new plants, particularly the bare root. (Or you may choose to call us and pre-order bare root plants to be shipped to you at your optimal planting time next year). Following are some precautions that will help your new bare root plants thrive.

If you choose to plant in the ground in a permanent location right away; soak the plants in water 1-2 hours just before planting, apply little or no mulch after planting ( to allow the soil to warm up), irrigate regularly to keep the soil evenly moist, not soppy wet, and provide shade or mist daily in the morning, until the plants are well-established. Warm air temperatures encourage faster shoot growth than root growth in the still cool soil, creating water stress in the tree; shade helps to reduce the water needs of the plant and give the root system time to catch up with the top of the plant. Another technique you can use, taught to us by a Southern California grower, is to whitewash the dormant tree before planting out. Use a 50/50 mixture of white interior latex paint and water, and apply to the entire tree above the roots. If you use a brush, apply it with an upwards motion, so you do not knock off the buds. Once the paint dries follow the planting instructions above. The buds will be delayed a little bit, and the trunk and branches will stay cooler, giving the roots some time to start growing and doing their job before the leaves start demanding water and nutrients. When the trees have pushed good new growth, 6-14", then apply a good mulch to suppress weeds and maintain soil moisture through the summer.

Or you may choose to plant your new plants in the ground in a temporary, shady location. Mulch and water them regularly through the summer. In the fall, when the worst of the summer heat has passed, dig and move the plants to their permanent location. By the following spring they will be well-established and ready to grow.

A third choice is to plant your new bare root plants into containers. Maintain your potted plants in a protected location, and plant in their permanent location in the fall when the worst of the summer heat has passed.

Our potted plants have been held in a greenhouse and are out of dormancy now, so will benefit from hardening off before planting out. Expose the plants to indirect sun for a few hours the first day, then gradually increase the number of hours and the amount of direct sun over the next few days to get then used to direct sun and wind. If you prefer to wait until fall to plant your potted plants in a permanent location they would probably benefit from potting up to a slightly larger container. 4" to 1 gallon, 1 gallon to 3-5 gallon (depending on vigor).

Please see our Plant Owner’s Manual for more late planting instructions.

APPLE MAGGOT/ CODLING MOTH:  

If you haven’t done so yet, install and monitor both apple maggot (#T161) and codling moth (#T163) traps to determine when populations of each insect are increasing, so you can apply control measures when they are needed and will be most effective. Apply Surround or Spinosad (both are organic and OMRI approved), or the insecticide of your choice, when the number of flies or moths trapped increases. Sprays will need to be re-applied periodically throughout the fruit ripening season. Read package labels for instructions. Instead of spraying multiple times you can do a one-time installation of apple maggot control bags, see below for more details.

Expect the first flight of adult codling moths about 14-30 days after bloom, with the largest numbers when evening temperatures stay above 60°F. Put out your codling moth traps just prior to bloom, so you know when adults are starting to emerge. See the Plant Owners Manual page 16 for spray suggestions, or ask for control recommendations at your local co-operative extension service (find yours in the useful links page, click on 'Useful Links' at the bottom of the page.
Learn more about codling moths at the following web site.  http://jenny.tfrec.wsu.edu/opm/displayspecies.php?pn=5
Do not put out extra codling moth traps as a control measure such as can be done with apple maggot traps. The exception is large orchards in which the traps are located around the perimeter. Extra codling moth traps in small orchards have been shown to attract and increase codling moth populations, not decrease.

You don’t like spraying? The new heavier weave Apple maggot control bags (#T167) we are offering this year may also help prevent codling moth larva from entering the fruit; if the bags go on the fruit early enough (with or before the increase in adult numbers), and the little caterpillar can’t chew its way in. According to the Home Orchard Society of Oregon there is a way to improve codling moth control using the apple maggot control bags. Before you install the bags soak them in Surround® , a kaolin clay based insecticide. Here are their instructions:

Materials needed:  4 quart pan, colander to hold apple maggot control bags, another pan (similar volume) to catch the fluid, two pkgs of apple maggot control bags (#T167) so you have 288 bags.

1. Put 3 tbsp of Surround® in 3 quarts of water. Start with a small amount of water to make a slurry, then add the rest of the water.
2. Stir until the Surround® is fully dissolved.
3. Place 288 apple maggot control bags in the mixture-stir to soak the bags.
4. Pour the apple maggot control bags and mixture into the colander, with the second container underneath to catch the fluid.
5. Stir the collected mixture and pour over the bags in the colander, with the empty container beneath.
6. Repeat step 5 until the fluid runs clear.
7. Dry the bags by spreading on a wire mesh, the table, etc.
8. Install the bags over the little fruitlets before the codling moth starts depositing eggs. (See the installation instructions below in the apple maggot section).

Biological codling moth controls, such as Trichogramma wasps, are available through Arbico Organics (arbico-organics.com). Trichogamma wasps deposit their eggs in the eggs of codling moths and other harmful moths.  Put some cards out 7-14 days after you start seeing codling moth adults in your traps, and again every 7-10 days until you no longer see adult moths. An image search on the internet will provide you with pictures if you are not sure what codling moth or apple maggot adults look like.

There are several strategies you can use for Apple Maggot Control; combining strategies can improve your results.

Put out Apple maggot traps with pheromones (#T163) to monitor when the apple maggot flies are present, so you know when to apply sprays. Use 1-3 spheres per tree, increase the number to 5-10 per tree (more in larger sized trees) to trap more adult flies and reduce the apple maggot fly population in your trees.

Thin apple and Asian pear fruit when the fruits are about the size of a dime to a nickel to one fruit every 6-8 inches along the branch and install apple maggot control bags (#T167) to prevent apple maggot flies from depositing their eggs on the fruit. Slip a bag over the little fruit and twist the mouth of the bag around the fruit stem to secure. Each fruit will grow inside the nylon mesh bag and be protected.

If you had a lot of apple maggot flies last year you might try controlling them before they emerge from their over-wintering stage. Treat the ground under your fruit trees with predatory beneficial nematodes available through Arbico Organics. Predatory nematodes actively seek and feed on apple maggot larvae, codling moth larvae, and other harmful grubs in the soil, reducing the number of adults that can emerge and deposit eggs on your fruit. Apply the nematodes in late spring before the adults have emerged, or in fall after fruit harvest. The ground must be moist and night temperatures consistently above 40°F when the nematodes are applied.  

Sanitation is an important cultural tool for reducing the over-all insect population of both apple maggot and codling moth in your orchard, or other types of insects that deposit their eggs in fruit. Pick up any fruit that falls to the ground (within a couple days of falling) and discard or destroy it, before the developing maggot or larvae is mature enough to crawl out of the fruit and continue its life cycle. Compost piles do not get hot enough to destroy the larvae or pupae, feeding to animals does not always destroy them either. The first fruit drops of apple and pear in May and June are the most important to pick up. The more isolated your orchard is the more effective picking up the fruit will be. If your neighbors are not picking up their fallen fruit you might consider putting up extra monitoring traps between your orchard and theirs, to trap some of the migrating insects before they arrive in your orchard.  


Caterpillar Control: Spinosad, a quick acting broad spectrum natural insecticide spray derived from the metabolites of a common soil bacterium, and BioNeem, a natural insecticide derived from the Neem tree, are both effective against codling moth, plum curculio, and currant worm caterpillars before they enter the fruit. Use Spinosad for heavier infestations, and follow label instructions on timing to avoid damage to beneficial insects, up to 6 sprays per year. Use BioNeem when you prefer a more gentle approach. The first spray is applied 2-4 weeks after bloom, or when you start seeing pin hole scars in the fruit (from the little caterpillars chewing their way into the fruit). Applying spray in August is helpful in controlling second or third generations of these pests. Start looking for the scars a week or so after catching increased numbers of adults in your monitoring traps, when you start seeing new scars it is time to spray.

Spotted Wing Drosophila, Drosophila Suzuki, is a new pest of concern along the west coast of the United States. First identified in California in 2009, it has now been identified from California to B.C. Canada in many locations along the I-5 corridor. Hot dry summers are expected to limit its spread into the interior portions of the country. It is a type of fruit fly, or vinegar fly is another common name. Unlike other types of vinegar fly which deposit their eggs in fully ripe fruit, this one deposits her eggs in the fruit just prior to the full ripe stage. The larvae are mature and ready to pupate in 6-10 days, when the fruit is just ripe and ready to pick, depending on temperature. This fruit fly infests many types of soft fruit, from blueberries to strawberries, plums to cherries, domestic or wild, and many others in between. At this point the insect is not widespread, but is expected to become more established over the next few years. Learning to monitor and identify this insect will be your first best step to dealing with it. Currently, Spinosyn based insecticides, such as Spinosad, are the recommended spray if they are present in your fruit plantings. Go to this web page  to learn more about the life cycle, identification, and monitoring of SWD (Spotted Wing Drosophila) https://ir.library.oregonstate.edu/xmlui/bitstream/handle/1957/20883/em9026.pdf.   Contact your local co-operative extension service to see if the SWD fruit fly has been reported in your area, or they have more local information available on management or control.

Fungus Control continues in the Pacific Northwest. Spring time warm wet rains encourage the germination and growth of fungal infections in our fruit trees. Continue applying fungicide sprays for scab or powdery mildew in your apples or pears, or brown rot or coryneum blight in your stone fruits if you noticed problems last year. If you are not sure what the problem was take a sample to your local co-operative extension office for identification help. Applying fungicide sprays prior to infection can help keep fungal diseases under control. Fungal diseases are generally more difficult to manage after infection has occurred. Lime sulfur, wettable sulfur, or fixed copper are possible products to use (always follow label instructions), see the Raintree Plant Owners Manual page 16-22 for more specific information, and pages 23-24 for a helpful calendar.

Apple and Pear Scab control usually requires several applications of fungicide at two week intervals for complete effectiveness, starting at the green tip or pre-pink blossom stage, or when day time temperatures are above 45°F. The most critical time to apply preventive sprays for apple and pear scab is from the breaking of the cluster buds until leaves are fully expanded. However, new infections can still occur until the weather is warm and dry.  A mixture of delayed dormant (light weight) oil, lime sulfur, and Dipel (a Bt thuriengensis bacterial insecticide) applied as the first leaves start to pull away from the flower clusters will serve as your first spray for scab, powdery mildew, and leaf rollers control. If your spring continues to be wet and cool additional sprays of lime sulfur at the pink stage and petal fall will be needed. You can reduce the number of sprays required to control scab, or increase the effectiveness of your sprays, by paying attention to temperature and moisture patterns, which allows you to forecast when it is time to spray. For more details you can read about this approach in “The Apple Grower” by Michael Phillips (#S005), or ask about a bulletin at your co-operative extension office.

Brown rot and coryneum blight infections occur in stone fruit (apricot, peach, plum, cherry) as buds are swelling. Apply lime sulfur, wettable sulfur, or copper sprays at the ‘popcorn stage’ (flower buds look like kernels of popcorn), petal fall, and one week later if the weather continues to be quite wet. Spray times will vary by type and variety, so keep an eye on each tree.

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Weed Management

Keep grass short and weeds under control. Regular shallow (2-4” deep) cultivation around newly planted trees will help keep weeds under control, keep a loose layer of soil on the surface that helps reduce moisture loss, and encourage the new roots from your tree to go deep. Don’t try this with shallow rooted plants like blueberry and other small shrubs though.

If your blueberries have a lot of weeds under them you might try cutting the weeds to the ground, putting down a ½-1” layer of peat moss, several layers of newspaper or a layer of cardboard, and then wood chips on top. Most weeds will be smothered. More persistent perennials that eventually come back through the mulch, can be repeatedly cut off (every 10-14 days) until their roots starve out.

New plantings of ground covers, such as cranberry, lingonberry, or wintergreen, need regular weeding. Even after they have filled the space, some weeds may still come through. Putting down cardboard or layers of newspaper covered with mulch between the new plants will help reduce weeds as well as contribute to building the soil organic matter.

Permanent weed barrier fabrics may seem to be a good solution for controlling weeds, but only if used for just a year or two, or only just near the trunk of the tree. Longer use in the active root zone area of the plant interferes with organic matter rebuilding in the soil, which can have a negative impact on the general health of your trees. Instead, try using a bio-degradable ground cover product or several layers of cardboard or paper topped with bark or compost that will decompose in 1-3 years, allowing you to control weeds in the short run and encourage healthy decompostion in the long run.

Remember to dig or roto-till around your raspberry rows to keep those vigorous spreaders where they belong.

Weed killers can be harmful to your fruiting plants. Avoid using broadcast weed and feed lawn products within the root zone area of your fruit trees, which can be harmed by the herbicides. The typical spread of an established trees root system is 3-5 times the width of the canopy. Spray drift from glyphosate (in Roundup and other products) can cause dieback, stress, or death when it lands on thin bark; or bark lesions in stone fruits if absorbed through the roots. Symptoms may not be present until the following year. The pre-emergent dichlorbenil (in Casoron) leads to stunted yellow leaves and death if over-applied or used repeatedly. A quick search on the internet for organic herbicides shows several products that could be useful substitutes for the standard chemicals usually available. I have not researched or tried any of them, but you may wish to.