Husker Hort

A Nebraska View of Horticulture


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Sneaky Squash

Early frost in my area meant that the winter squash vines died before the fruits were completely ripe. Winter squash is ripe when the skin can not be punctured with your thumbnail. The squash are perfectly fine to eat, they just wouldn’t have as long as a shelf life as I would liked.

Last night I roasted one of these squashes in the oven. My son was having noodles for supper, so I decided to sneak in some squash. I am not an accomplished chef by any means, but I think the resulting squash bechamel turned out pretty tasty!

It almost looks like Mac and cheese!

That got me wondering about the many uses of this versatile ingredient.

How do you like your squash?

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Yellow Needles in Pine

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Yellow inner needles

Cooler nights and falling leaves signal that fall is here. Pines in the area are starting to change colors too. Knowing the cause of the discolored needles will help to know if it is nature taking its course or if it is a disease infecting your trees.

Across the area, yellow inner needles in pine and spruce have just started to appear. Evergreen needles change color in the fall too, just like deciduous trees. It is a normal occurrence called natural needle drop. The older interior needles of pine and spruce are turning yellow and drop from the tree. The older needles that are lost are usually located closer to the inside of the tree or trunk. Factors that increase the stress on an evergreen can intensify the autumn needle drop. These stress factors can include drought, herbicide injury, root damage, or insect or disease damage.

White pine with natural needle drop

White pine with natural needle drop

Like many living things, evergreen needles also have a lifespan. Pine trees hold their needles for 2-3 or more years. Spruce trees hold their needles longer than pines, usually around 5-7 years. After the needles have lived their lifespan, they fall from the tree. Some trees, like the white pine, make it easy to see the needle drop.

The location of the discolored needles can determine if it is natural needle drop or if something else has infected the tree. If the tip of the branch was the only part affected this spring, fungus could be to blame. Cool, wet springs are ideal conditions for fungus, this spring was no exception. The Sphaeropsis tip blight fungus will infect the new growth as it emerges causing it to turn brown and hang on. If fungicides are applied, the best time to spray preventative treatments for Sphaeropsis tip blight fungus is April.

Sphaeropsis tip blight

Sphaeropsis tip blight

One of the most common pine diseases is also caused by a fungus and can also cause brown needles. Dothistroma needle blight causes reddish lesions found on individual needles. It causes the needle to appear to be half green and half brown on last years’ growth and mainly affects the lower half of the tree. Preventative fungicide applications can be made in mid-May and again in mid to late-June.

Pine wilt can also cause needles to change color. If the entire branch, or tree, turns brown and the needles hang on, it could be pine wilt. The cause of pine wilt is smaller than we can see with the naked eye. The pinewood nematode is a very small worm-like organism that attacks the tissues that move water and nutrients throughout the tree. The nematode doesn’t travel very far by itself, so it uses a ‘friend’ to help it move around. Nematodes hitch a ride on pine sawyer beetles and fall off when they reach a new tree to infest. The first symptom is the tree or a major branch will have a grayish green tint to it. As the nematodes progress and multiply the tree turns tan and then eventually brown. One important thing to remember is that the dead brown needles will remain on the tree for a year or more

Pine Wilt in Scotch Pine

Pine Wilt in Scotch Pine

One way to prevent needles from changing color next spring is through irrigating now. Moisture helps to promote root growth and reduces winter desiccation injury. Supplemental fall irrigation should be continued, when there isn’t precipitation, until close to soil freeze. When air temperatures in winter are above 40 degrees Fahrenheit apply water early enough in the day so it can soak into the ground before temperatures drop below freezing. This will help to avoid the water from freezing on the surface at night when the temperatures drop down. Apply enough water to moisten the soil eight inches deep under the drip line of the tree. Be sure to check the soil moisture before irrigating to avoid irrigating a saturated soil.

Proper identification of the culprit behind the color changing needles can help you determine if this is nature taking its course or if you have some action to take in the future.

For more information contact Elizabeth Killinger at elizabeth.killinger@unl.edu, 308-385-5088, on Facebook, Twitter, her blog at https://huskerhort.wordpress.com/, or visit the University of Nebraska-Lincoln Extension website: hall.unl.edu.


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Is that a Webworm or a Bagworm?

Webworms, bagworms, are they the same thing? If not, why does it make a difference whether you have a bagworm or webworms? It can make a big difference which insect you have to control and the damage that they cause. Correct identification is key to know how to control these pests.

Fall webworms or tent caterpillars are an occasional pest. They are sometimes called ‘bagworms,’ but using the correct common name will help clear up confusion. They appear as white webbed nests on the ends of branches in cottonwood, crabapple, walnut, and other trees. The caterpillars hide in the webbed nest during the day and feed on the trees at night. The caterpillars cause little harm to otherwise healthy trees. Tree health is not usually affected until more than 50 percent of the foliage is eaten. If there are enough nests, about one on every branch, the tree could be completely eaten. If you can safely reach the nest, use a broom to break up the bag of webworms. Follow up by spraying with a strong stream of water or an insecticide like permethrin (Eight) or Spinosad (Conserve). The nests can also be pruned out when possible. Trees that have heavy infestations this year won’t necessarily have a similar outbreak next year.

Bagworms on a juniper.

 

Bagworms are a whole different story from webworms. Bagworms will feed on a wide variety of trees and shrubs, but they mainly prefer evergreens, especially junipers, cedars, and spruce. The reason that they are called bagworms is because they spin their own individual cases or bags around them for protection. As the bagworm grows, so does the bag that contains them. They will add leaf fragments to the outside of the bag for camouflage. The bags look like baseball bat-shaped ornaments hanging from the trees. There is one way to know if your cedar tree has bagworms. If you see little cone shaped things on your cedar tree, more than likely you have bagworms, because cedar trees don’t produce cones.

The earliest sign of bagworm injury on junipers is brown stressed needles at the tips of the branches. If the infestation is severe enough, the tree they are feeding on will have a brown tint to it. Heavy infestations of older bagworms are capable of completely defoliating a tree or shrub. This can cause stress to the plant or even kill it if damage is great enough. This is especially true if they have infested an evergreen which is unable to re-grow new foliage until next year. If you have bagworms on any deciduous plant, ones that lose their leaves every year, they are able to re-grow foliage if needed. Just be sure to pick up the leaves this fall and dispose of them.

There are several options for controlling bagworms. Insecticidal sprays require thorough coverage to penetrate the canopy and contact the feeding bagworms. It is generally preferable to use ground equipment with higher spray volumes and pressures. Aerial applications may fail to provide thorough enough coverage resulting in less than satisfactory bagworm control. The spray has to completely cover the plant, almost to the point the product is dripping off of it. If the bagworms have made their home on a windbreak, the applicator has to be sure to have enough pressure to get product between the two rows of the windbreak. If this area is missed the bagworms that were hiding out there will move and re-infest the rest of the plant. Hand removal is another option for controlling bagworms. After removing the bags, place them in a bucket of soapy water.

There are several options available for insecticidal control of bagworms. Some of the reduced-risk options include Bacillus thuringiensis (Bt), spinosad, or azadirachtin (neem oil) are effective on young larvae and may be needed to be applied repeatedly. Additional insecticidal options include permethrin (Eight), bifenthrin (Talstar), cyfluthrin (Tempo), chlorantraniliprole, carbaryl (Sevin), dimethoate, esfenvalerate, fluvalinate (Mavrik), lambda-cyhalothrin, acephate (Isotox IV), and tebufenozide (Confirm). Depending on the product and size of the insect, secondary applications may be needed.

Be on the lookout now for webworms and bagworms and control them before they make a meal out of your plants.

For more information contact Elizabeth Killinger at elizabeth.killinger@unl.edu, 308-385-5088, on Facebook, Twitter, her blog at https://huskerhort.wordpress.com/, or visit the University of Nebraska-Lincoln Extension website: hall.unl.edu.