Tree and shrub care for mid-April

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By John Ball

SDSU Extension Forestry Specialist

Will winter ever end? Much of the state has endured more snowstorm this past week a cold weekend. Fortunately, we have not had too many days of warm weather prior to these cold snaps. Our trees and shrubs have remained dormant rather than breaking bud prematurely, which could have caused them to be killed back by the cold.

Mountain pine beetle and pine engraver beetle

The mountain pine beetle epidemic has run its course, as it has done several times during the past 120 years. These epidemics are not periodic, occurring at regular intervals, but at irregular time periods. Once an epidemic starts they run about a decade or two before declining. Forest entomologists debate as what causes epidemics to start and end. Favorable weather – hot, dry summers – and a buildup of natural enemies play a role, but the one factor all agree on is you cannot start and sustain an epidemic until you have a lot of large trees. As the average tree size and stand densities decreases, fewer beetles emerge and they have less success at mass-attacking trees. It seems that once the Black Hills forest has a significant portion of it impacted by the beetle, the epidemic comes to an end.

I looked at only one mountain pine beetle attacked tree this winter and it was last week. The tree was attacked last summer by the beetles but it was not a successful attack as evidenced by the large, white pitch masses being exuded from the tree. Only this one tree in the stand was attacked and it was the tree that had the top break out in a storm two years ago. In the interim period between epidemics, mountain pine beetle has the best chance of successfully attacking these trees and even here they are not always successful.

However, the end of mountain pine beetle does not mean we are done with bark beetles. The pine engraver beetle Ips pini is another native bark beetle to the Black Hills. It usually attacks only trees that have recently died or branches in the tops of dying or hail-damaged trees. The insect will also infest fresh logging slash during the spring and summer. However, the beetle can become a tree-killer during periods of drought which weakens pine defenses, the resin the tree uses to pitch the beetles out as they attempt to bore in.

Short periods of drought are not usually of much concern, but the lingering drought over the last few years has left many trees vulnerable to attack. I was out in the Black Hills last week and visited a number of neighborhoods in Rapid City and the surrounding area that had pines infested by the pine engraver beetle. Homeowners usually requested visits because they noticed a few of their trees were being attacked by woodpeckers. These birds will search for insects residing just beneath the bark and it was common to find pine infested by mountain pine beetle with bird pecks so dense the bark was shredded off.

These trees were heavily infested by pine engraver beetles as well as several other species of wood borers and even some Pityophthorus beetles which resemble engraver beetles. The drought had weakened the trees to the point that they have few defenses and are easy prey to a host of beetles. Unless we start getting good rains, these trees may die, but if the engraver beetles are not managed, the trees will die as well. There are quite a few home associations and individual homeowners that are planning to have their trees sprayed to protect them against new attacks.

Unlike the mountain pine beetle, which does not emerge from its host as an adult until late July, the pine engraver beetle is an adult right now. It can be found either beneath the bark of declining trees (it’s the tiny insect within the yellow circle, the oval hole above it is from a wood borer) and logging slash or even in the duff on the forest floor. They resemble a small mountain pine beetle and I used to receive calls in the spring of “mountain pine beetles” flying earlier that usual, but they were just pine engraver beetles.

The pine engraver beetle generally begins flying in mid-April depending on the location. It usually appears first at lower elevations in the southern Black Hills and later in the higher elevations of the northern Hills. The cold weather the Black Hills is experiencing right now (along with the rest of the state) is cold enough to keep the adults from flying. They generally begin their flight when we have day temperatures staying in the 60° and 70°F range. That’s sounds like the weather this week.

The adults will be flying soon and stressed high-value pines may need to be treated to prevent successful attacks by this insect. If a property has a few trees that were attacked by this insect last year, it may be worthwhile to treat them and the surrounding trees this spring. One application of an insecticide labeled for bark beetle control, applied at the proper rate, will be sufficient to protect pine trees from pine engraver beetles for the entire growing season since they will be out flying throughout the summer.

A difference between mountain pine beetle and the pine engraver beetle is engraver beetles have several complete generations per year so we tend to see adults out flying (and attacking new hosts) throughout the season, from April to September. The second generation, which usually appears in May or June, is most commonly the one that goes after stressed trees. However, a drought stressed trees can be attacked at any point during the growing season.

Finally, since pine engraver beetles infest branches as well as trunks, the entire tree must be sprayed, not just the trunk. This means a sprayer with enough pressure is needed to reach high into the canopy.

Pine shoot blight in the Black Hills

There has been a recent media report of an outbreak of ‘unexplained’ infection of pine by this disease. Pine shoot blight is more commonly called Diplodia tip blight (Diplodia sapinea). It is a shoot disease of native and exotic 2-and 3- needled pines. We see the disease on Austrian pine (Pinus. nigra) in community and windbreak plantings and in ponderosa pine (P. ponderosa) throughout the Black Hills as well as in towns and windbreaks across the state.

There is nothing new about the disease in the Black Hills. We find it in dense as well as open stands, in young trees as well as old trees. The only common denominator in many pockets of infested trees is hail. It was once thought that hail opened up wounds in a tree that permitted infection. Now we know that diplodia can exist as an endophyte in healthy pines. As long at the tree remains healthy, it does not present symptoms of the disease. However, if the tree is stressed – hail-damage, drought, old-age – the fungus begins to kill shoot tips.

The disease symptoms are dying or dead stunted shoot tips with short, hanging, discolored needles. The disease often does not kill the tree, but can disfigure it as the canopy becomes filled with these dead tips. However, over-mature trees can be killed too.

The disease is found on pines throughout the globe and its origin is unknown. It was first noted in the Black Hills in 1943 but probably was there earlier. A more extensive report on infection in the Black Hills was made in 1979. We find the disease almost everywhere we find susceptible pines in our state.

The disease can be treated, not cured, by fungicide treatments in the spring starting when the buds are just beginning to swell and continuing through shoot expansion. The timing and fungicides will be in a coming Update, closer to the treatment period.

Brookings County – What is this growth on my pine tree?

This round branch gall is from western gall rust (Peridermium harknessii). (See photo.) This fungus is a common rust disease that causes deformations in branches and stems of ponderosa pines as well as many other native and exotic pines (including even mugo pine). These galls will swell in early summer and produce white to orange pustules. A yellowish dust, the spores, will come from these pustules. The spores are carried by the wind and infect the expanding shoots and needles of nearby pines. While swellings are often the only sign of the disease, stem cankers may also occur which can break the trunks of small trees during excessive loading by wind or snow. Many trees are not highly susceptible to the disease so it seems to appear only on certain trees within a stand. If the galls are pruned from these infected trees, they often just reappear. The best management is just to remove young trees with galls.

Meade County – What is causing this growth?

This was a site visit, and the Rocky Mountain juniper (Juniperus scopulorum) had a ball composed of stunted, short shoots and dense foliage. (See photo.) This is called a witches’ broom and is commonly due to a fungus, Gymnosporangium nidus-avis, though these brooms have been associated with a phytoplasma , a bacteria-like organism, in the Pacific Northwest. The fungal disease is called juniper broom rust and as with most rust disease has an alternate host. This disease alternates between juniper (Eastern redcedar, J. virgninana, or Rocky Mt. juniper) and serviceberry (Amelanchier) a common tall shrub/small tree found in the Black Hills. The disease is not common on junipers and is more a curiosity than a threat to their health.

Potter County — How do you start succulents from seed. How long does it take for them to sprout.

Growing succulents from seed can be a lot of fun, but it does take patience. First of all, you need to use a well-drained germination mix. I like a combination of 1 part packaged potting soil to 3 parts coarse sand or better yet, use fine poultry grit. The poultry grit is available at ag stores that sell feed for poultry. Mix that together well and moisten it well. Use it to fill a pot or flat. Scatter the seed over the top, then press them into the media. Place the container in a partly sunny location. You can cover the pot or flat with a piece of glass or plastic to help keep it nice and humid around the seed. But, you have to remove it as soon as you see the very tiny seedlings emerging. Place the pot or flat in a tray of water to water it from the bottom up so you do not disturb the tiny seedlings.

When they get large enough to handle, usually after 6 to 18 months, you can carefully transplant them from the pot or flat in to their own little pots or you can use small cell packs. Cacti will usually be much slower growing than other succulents. – David Graper

Mark your calendars

The Annual South Dakota State Horticultural Society Spring Workshop will be held in Huron April 21, 2018 at the Plains Dining and Recreation Center (960 4th St. north east).

“This is an excellent opportunity to hear presentations from a nationally and internationally renowned speaker who is an authority on bulbous flowers that can help you to have a more beautiful garden, right here in South Dakota,” said David Graper, SDSU Extension Horticulture Specialist & Master Gardener Program Coordinator.

Registration for the event is due by April 11, 2018. (Registration deadline was extended.) The workshop fee is $30 for South Dakota State Horticultural Society members and $35 for non-members. Registration fee includes lunch. To register, send a check payable to S.D. State Horticultural Society or SDSHS to the organization’s treasurer, Glenda Oakley at 1241 Frank Ave SE, Huron, SD 57350.

Event information

The event begins at 8:45 a.m. (CST). The event’s speaker is Mr. Brent Heath, a noted authority on bulbs. He promotes the use of flowering bulbs of all kinds. Heath and his wife, Becky are co-owners of Brent and Becky’s Bulbs at Gloucester, Virginia.

Event agenda

• 8:45 a.m. – Registration

• 9:30 – 10:30 a.m. – Bulbs as Companion Plants

• 10:30 – 10:45 a.m. – Break

• 10:45 – 12:00 p.m. – Pest Resistant Bulbs

• 12:00 p.m. – Lunch during which time the S.D. State Horticultural Society will host its annual business meeting

• 1:30 – 2:30 p.m. – Bulb Gardens of the World

• 2:30 – 2:45 p.m. – Break and door prizes

• 2:45 – 3:45 p.m. – Lovely Long Lasting Lilies and Awesome Alliums

If you have questions or for more information, contact Glenda Oakley at 605-352-3391 or by e-mail

Sign up for 2018 Master Gardener Training today!

SDSU Extension Master Gardener Training is provided by SDSU faculty and includes access to online training materials, a resource manual, and hands-on classes. Hands-on classes will be held in three locations, over eight sessions. Each session begins at 8:30 a.m. and ends at 4:30 p.m. local time. Come join the fun!

When/Where: Participants can select one of three training locations: Huron: June 5, 12, 19, 26, July 10, 17, 24, 31; Pierre: June 6, 13, 20, 27, July 11, 18, 25, Aug 1; Rapid City: June 7, 14, 21, 28, July 12, 19, 26, Aug. 2.

Topics Include: Basic botany and taxonomy; soils and fertilizers; turf and weed management; plant pathology/composting; tree and shrub care; pest management; planting and landscape use; pesticides; insects and pollinators, biodiversity; vegetables and season extension; herbaceous ornamentals, native plants, plant propagation and more!

Cost: There are two training options:

• Training with Volunteer Commitment as an SDSU Extension Master Gardener – $250.

To take course at discounted rate, you must provide 50 hours of volunteer service over the next two years as a Master Gardener. The balance of the full course fee will be invoiced if service commitment is not completed. Obtain 6 CEUs.

• Training to Obtain Certificate of Recognition in Horticulture – No volunteerism required – $600.

Participants will receive the same training but will not be required to volunteer and will receive a Certificate of Recognition in horticulture. Obtain 6 CEUs.

Register at If you do not see the actual registration link immediately, please be patient, it will be live in a few days. Having trouble registering? Contact us at or call 605-782-3290. Registration deadline is May 19.

Witches’ broom in Rocky Mountain juniper. iGrow photo
Seedling cacti. iGrow photo
Western gall rust on pine. iGrow photo
Mountain pine beetle feeding damage on pine. iGrow photo
Pine shoot blight affected tree. iGrow photo
Pine with excessive wood pecker feeder. iGrow photo