Landscape & Garden Alerts - Pacific Northwest Pest Alert Network

2022 Pruning Deciduous Trees & Shrubs

General Landscape and Garden Treasure Valley

Posted on: January 25, 2022 by Nic Usabel

The dormant season is a great time to prune deciduous trees (landscape & fruit) and shrubs. It is not recommended to prune grapevines at this time. As a general guide remove no more than one-third of the tree when pruning. Below are a few resources on how to prune.

Prune shrub species which grow on the current season’s growth during the dormant period, usually late winter early spring. A few examples of flowering shrubs in this grouping including butterfly bush, heather, heavenly bamboo, hydrangea, shrubby roses and rose of sharon. Reference the third link for more information.

For shrub species which form buds on last season’s growth prune these species within about two months after the flowers fade. On these species, flower buds form in late summer and early fall. Winter pruning decreases the number of flowers the following spring as branches containing flower buds are removed. A few examples of flowering shrubs in this grouping include azaleas, lilac, magnolia, mockorange, serviceberry, and witchhazel. Reference Pruning Ornamental Trees & Shrubs, from Purdue University.

For most areas of Idaho, plants that bloom before June 1 formed the flowers the previous year on old wood. Those that bloom after June 1 form flowers on new growth. Keep in mind that this is rough guideline.

The City of Nampa Parks & Forestry Department will offer tree pruning classes. See the attached file Horticulture Workshops for more details.

If you have additional questions, contact your local UI Extension office. To search by county visit https://www.uidaho.edu/extension/directory/counties

» Horticulture Workshops

2022 Pre-License Training for Ornamental Pesticide Applicators

All Crops All Locations

Posted on: December 20, 2021 by Nic Usabel & Kimberly Tate

The UI Extension Pesticide Safety Education Program will be offering pre-license training during the 2022 Idaho Horticulture Expo in Boise. This training will be in-person with a two-day agenda. Focus will be on the following categories: Ornamental Insecticide (OI), Ornamental Herbicide (OH), General Pest (GP), and Core (CO).

Registration includes access to eLearning modules and study materials housed on the National Extension Foundation website. These materials prepare students for the 2-day class and the statewide exams. ALL materials will be available to each registered student with continued access until three weeks after the training. January 20 – 21, 2022, daily at 9am – 4pm MST (limit 45 students) Boise Centre, 850 W Front St., Boise 83702

This educational training is funded through an ISDA grant. There will be no cost to the student. COVID-19 restrictions will be determined by the instructors. Registered students will be notified of the current guidelines. To register, visit our website https://www.uidaho.edu/extension/ipm

For questions contact:

Ronda Hirnyck | rhirnyck@uidaho.edu | 208-364-4046
Kimberly Tate | ktate@uidaho.edu | 208-364-4581

» 2021-PreLicense_URBAN-Training_POSTER.pdf

2022 Idaho Horticulture Expo

General Landscape and Garden Treasure Valley

Posted on: December 15, 2021 by Nic Usabel

The Idaho Nursery and Landscape Association will host the Idaho Horticulture Expo January 19-20 at the Boise Center.

Here is a peak at just some speakers:

Stepahnie Adams, Morton Arboretum
Amanda Thompsen, author of Kiss My Aster
Tim Prather, University of Idaho
Dr. Brent Bean, BYU Idaho
See the full schedule

Credits available:

11 continuing education credits for Arborists.
11 recertification credits for Pesticide Applicators

Register today at inlagrow.org.

» https://inlagrow.org/event-4572799

2021 Live Evergreen Trees as Indoor Holiday Decoration

General Landscape and Garden Treasure Valley

Posted on: December 10, 2021 by Nic Usabel

If using a live, with roots attached, evergreen tree for your indoor holiday decoration here are some items to consider.

First, consider where in the landscape you will plant your tree. Select an open area which lacks overhanging tree branches or wires. If you don't have such a site, consider a dwarf conifer or evergreen shrub. Choose a tree that will thrive in your soil condition and climatic condition. Proper planning now will save you time and money later.

When you visit a nursery or garden center, you will find a variety of evergreens to choose from. Evergreens are commonly available as containerized trees grown in a pot or balled and burlapped trees.

Before the ground freezes, dig a hole 2-3 times wider than the root ball, but only as deep as the root ball itself. The soil which is removed from the hole will need to be stored where it will not freeze. This soil will be used in planting the tree after the holiday.

Trees have a better chance of survival if they are not displayed in the house for more than a 7 to 10 days. If purchasing the tree early keep the tree in a cool location before moving it indoors and water as necessary. Extended exposure to the indoor temperatures can counteract the winter dormancy in conifers. A short display period and prompt planting is the best way to insure the survival of the tree in the landscape.

When you are ready to plant position and level the tree. If the root ball is wrapped remove any cover or wires. Inspect the tree root ball for circling roots and straighten, cut, or remove them. Identify the trunk flare, where the trunk widens near the root zone, and ensure that the root flare is viable at ground level once planted. With the reserved soil fill the hole and gently but firmly apply pressure. Water thoroughly and apply a woodchip mulch. For more detailed planting instructions of trees visit treesaregood.org.

With appropriate care, planting, and management you will be able to enjoy your tree in the landscape for years to come.

Resources:

Selection and Care of Living Christmas Trees, NC State Extension

2021 Protecting Trees from Sunscald

General Landscape and Garden Treasure Valley

Posted on: November 19, 2021 by Nic Usabel

Sunscald or southwest winter injury happens during the winter. Intense direct and reflected sunlight will activate tissues under the bark. At night, temperatures fall, and cells freeze, causing cell death. This damage is often not noticed for a few years until the bark has split open exposing the damage below. The damaged sites are prone to attack by wood-boring insects and fungal pathogens.

Recently planted trees, young trees, and trees with thin bark are more susceptible to sunscald. Trees species which are susceptible include maple, linden, mountain-ash, honeylocust, birch, walnut, crabapple, flowering cherry, fruit trees, aspen, ash, tuliptree, and willow.

To prevent sunscald damage from occurring keep the lower trunk insulated or shaded in winter. Susceptible trees can be protected by wrapping the trunk with paper tree wrap, overlapping about 33% with each turn. Wrap trunks upward from the base of the tree to a point just above the lowest branch. Wrap should be removed in early spring after the risk of a hard frost has passed. If not removed the wraps can harbor insects and disease. Trunks can also be protected by placing a light-colored board to the south and west of the tree trunk. In large applications white latex paint can be diluted 1:1 with water and applied on the southwest side of the lower trunk. Landscape design and planting susceptible trees to the north and east of buildings or evergreens can help to shade the lower trunk.

References:

» Sunscald on Tree

2021 Fall Control for Coryneum Blight & Peach Leaf Curl

General Landscape and Garden Treasure Valley

Coryneum blight (Thyrostroma carpophilum) & Peach leaf curl (Taphrina deformans)

Posted on: November 1, 2021 by Nic Usabel

Coryneum blight or commonly known as shothole disease which is caused by fungus Thyrostroma carpophilum. Trees which have been affected develop small, round, tan-to-purpleish spots which then dry and fall out of the leaf producing a shothole effect. Most cultivars of peach, nectarine, apricot, and almond are very susceptible while cherry and plum are less susceptible. In addition, ornamental plant species can show damage. Beyond the leaf, symptoms can also be seen on the current season and 1-year old fruiting wood. Infections consist of round, reddish spots which are slightly sunken.

Chemical control will occur after 50% leaf drop in late autumn by spraying with a copper-based fungicide, chlorothalonil, or Bordeaux mixture. Follow the label instructions for rate and application procedure. Prune out affected twigs when practical. Culturally control shothole disease by not allowing irrigation sprinklers to wet the tree foliage, select cultivars which are disease resistant when available, and remove and dispose of affected foliage and twigs.

Peach leaf curl caused by fungus Taphrina deformans and is specific to peaches and nectarines. Trees that are infected will have leaves that are distorted or curl, appear blistered, and develop a yellow or red color.

Control can be achieved by a single fungicide application in the fall after 90% of the leaves have fallen. Chemicals used for control are copper products or chlorothalonil. Follow the label instructions for rate and application procedure. Homeowners should also remove and dispose of infected leaves that have fallen to the ground, to remove as much inoculum as possible. Resistant varieties can be selected for additional cultural control.

References:

» Peach Leaf Curl on Nectarine

» Shot Hole on Peach

2021 Pesticide Fall Recertification Webinar Series

General Landscape and Garden All Locations

Posted on: October 22, 2021 by Nic Usabel

The UI Extension Pesticide Safety Education Program (PSEP) will be conducting 6-webinars on Tuesdays from Nov. 2 - Dec. 14. Completed webinars receive one-pesticide credit*. These webinars are synchronous and held from 10 AM - 11:15 AM (MST). The cost is $10 per applicator/webinar. Enroll now on our UI Marketplace HERE. Check out the details in the attached UIPSEP Fall Recertification Webinars poster. For more information, contact Kimberly Tate at ktate@uidaho.edu.

*For pesticide credit: Pesticide applicators must answer questions throughout the webinar session. This requires individual computer and internet access for each user. Answers will be collected to confirm attendance was maintained for the entire webinar.

2021 Idaho Master Gardener Programs in the Treasure Valley

General Landscape and Garden Treasure Valley

Posted on: October 13, 2021 by Nic Usabel

Interested in becoming an Idaho Master Gardener. See below for program information offered by University of Idaho Extension.

UI Extension, Ada County (Boise, ID): Be added to the interest list by calling 208-287-5900 or email ada@uidaho.edu indicating your interest in the Idaho Master Gardener Program. Additional information can be found at uidaho.edu/ada.

UI Extension, Canyon County (Caldwell, ID): This location serves Canyon and Owyhee counties. Class to meet weekly Wednesday morning from 9am - noon January 12 – May 4. Be added to the interest list by emailing canyon@uidaho.edu or calling 208-459-6003. Registration packet will be released to interest list mid-October. Additional information can be found at uidaho.edu/canyon.

UI Extension, Elmore County (Mountain Home, ID): Be added to the interest list for the 2023 class by calling 208-587-2136 ext. 1250 or email elmore@uidaho.edu. Additional information can be found at uidaho.edu/elmore.

UI Extension, Washington County (Weiser, ID): This location serves the Payette River Valley (Gem, Payette, Washington, Adams counties). Additional information can be found at uidaho.edu/washington or by calling 208-414-0415.

Don’t see your county listed? Use the Idaho Master Gardener webpage to find all program options across Idaho.

» https://www.uidaho.edu/extension/master-gardener

2021 Fall Lawn Fertilization & Care

General Landscape and Garden Treasure Valley

Posted on: September 15, 2021 by Nic Usabel

University of Idaho turf specialists recommended splitting the application of lawn fertilization into three (3) applications; early May, early September, and late October/November. Review the first reference below to identify fertilization application amounts using a soil test result or the second reference for general recommendations for southern Idaho. Apply according to label directions.

If your lawn is suffering from soil compaction or development of a thick thatch layer fall is the optimal time to core aerate. For more information on core aeration review Core Aeration of Lawns.

Fall is a great time to control perennial weeds in the landscape if opting to use herbicides. Perennials will begin storing carbohydrates in the roots promoting herbicides to be drawn deeper into the root system and allowing for better control.

If there are additional questions on lawn care or weed management reach out to a local University of Idaho Extension office.

Canyon County Master Gardeners are holding an online Fall Perennial Plant Sale. View the inventory selection at https://bit.ly/ccmgstore.

References:

2021 Reduce Watering Frequency During Fall

General Landscape and Garden Treasure Valley

Posted on: September 14, 2021 by Nic Usabel

The days are shortening, and evening temperatures are cooling. Now is the time to adjust the frequency between irrigation days for the landscape and garden.

Lawn irrigation systems can be set to increase the number of days between irrigation based on soil texture. Adjusting the frequency of watering versus the run time allows for replenishment of the water holding capacity and usable water in the soil profile. See publication links below for greater explanation. This deep and infrequent method encourages a deeper root growth of plants.

A reminder to deep water trees and shrubs prior to shutoff of irrigation water. See our previous alert, 2021 Deep Water Trees & Shrubs.

Canyon County Master Gardeners are holding an online Fall Perennial Plant Sale. View the store today at https://bit.ly/ccmgstore.

Reference:

2021 Deep Water Trees & Shrubs

General Landscape and Garden Treasure Valley

Posted on: August 31, 2021 by Nic Usabel

Many irrigation districts across the Treasure Valley have indicated that water delivery will end early this season. If your irrigation season will end soon consider deep watering your trees and shrubs before irrigation delivery has stopped.

For established trees irrigate trees starting halfway between the trunk and the dripline and extending well beyond the dripline. See photo linked below for a visual. For large trees this could encompass the entire lawn. For newly planted trees irrigation is best concentrated near the trunk and slightly beyond the root ball to encourage roots to move out into the surrounding soil. Shrubs can be watered in a similar fashion to ensure the roots of the shrub have received water. Evergreen trees and shrubs will continue to lose moisture from their needles or leaves all winter long.

Consider using mulches on the soil surface to conserve moisture. In addition, it will help with weed control and uniform soil temperature. Keep mulch 2 inches away from tree and shrub stems to discourage root and crown disease.

References:

» Tree Dripline Image

2021 Curly Top Virus in Tomatoes

General Landscape and Garden Treasure Valley

Beet Curly Top Virus

Posted on: August 26, 2021 by Nic Usabel

The Canyon County Master Gardener Integrated Pest Management Team recently detected a tomato plant with symptoms of curly top virus. The virus is carried by the beet leafhopper, Circulifer tenellus. The leafhopper takes up the virus when feeding and keeps it in its body the rest of its life. The most frequently cited hosts include Kochia, Lambsquarter, Halogeton, Russian thistle, Greasewood, and Atripex.

The symptoms on tomatoes include the rolling up and twisting sharply of the leaflets to expose the undersurface. Foliage is stiff and leathery, and the entire plant is a peculiar dull yellow. Leaflet veins are purple, and the plant is often stunted. Many roots and rootlets die, as do severely affected plants. Young plants infected with the disease are usually killed.

The sporadic nature of Beet Curly Top Virus makes it very difficult to implement practical management strategies. One of the most promising strategies is to use resistance cultivars of tomatoes. Observations have shown that plants grown in shade do not contract the virus, so shading could be a possible management strategy. Excluding the beet leaf hopper with row cover buried in the ground and placed over the tomatoes until plants can no longer be contained inside can reduce early infection. Pull and dispose of infected plant material.

References:

» Chocolate Cherry Tomatoes showing symptoms

2021 Spotted Wing Drosophila on Blackberries

General Landscape and Garden Treasure Valley

Spotted Wing Drosophila (Drosophila suzukii)

Posted on: August 16, 2021 by Nic Usabel

A Canyon County Master Gardener has detected Spotted Wing Drosophila (SWD) in blackberries. SWD targets a wide variety of fruits including raspberries, blackberries, and strawberries. SWD can damage ripe-to-overripe fruit by depositing eggs directly beneath the surface. Review the Utah State University publication linked in the reference material for monitoring methods.

To recognize SWD damage, look very closely for scarring or spotting on the fruit surface; liquid exuding (when squeezed) out of scar/hole where eggs were laid; softening, collapsing and/or bruising of fruit at damage site; small white larvae and pupae that can be seen with naked eye if fruit is opened; and, under a microscope, two hair-like filaments sticking out of fruit where they are connected to a white egg within the fruit can sometimes be seen. Reach out to your local Extension office if you need help with identification or review the linked reference materials for additional details.

Non-Chemical Control

Pick ripe fruits frequently to minimize potential SWD host material.
Fine-mesh floating row covers can protect low growing fruits.
Use traps around fruit production areas to capture and kill adult flies.
Damaged or fallen fruit should be removed, buried, solarized, crushed or stored in sealed container to exclude flies.

Chemical Control

Should be coupled with monitoring efforts. Rotate chemical families to avoid resistance and follow the label for each crop.
See specific fruit for recommended chemicals. Review links below.
Pesticide families that help control SWD include: spinosyns, pyrethroids, carbamates, and organophosphates. Follow the label to determine appropriate rates, risks, and fruits in which it can be applied.
Do not apply when bees and other pollinators are present, such as when plants are flowering or when pollinators are active.

Reference Materials:

Spotted Wing Drosophila: An Emerging Berry and Stone Fruit Pest, PNW Handbook
Blackberry and Raspberry: Spotted Wing Drosophila , PNW Handbook
Spotted Wing Drosophila, Utah State University

2021 Blossom-End Rot

General Landscape and Garden Treasure Valley

Blossom-End Rot

Posted on: August 12, 2021 by Nic Usabel

Blossom-end rot is showing up on tomato and pepper plants. Eggplant, squash, and watermelon can also be affected.

Blossom-end rot is a physiological disorder due to a shortage of calcium in young fruit. Blossom-end rot often occurs when soil moisture fluctuates as water stress interferes with calcium uptake in the plant. Most Treasure Valley garden soils have enough calcium and additions are not recommended. Some varieties are more prone to blossom-end rot than others.

Cultural Control Practices:

Use infrequent deep irrigation to keep the soil uniformly moist and avoid water stress or fluctuating soil moisture.
Organic mulch can be used to prevent wide fluctuations in soil moisture.
Avoid over fertilizing.
Avoid hoeing or cultivating near the roots.

Reference Materials:

» Tomato with blossom-end rot

2021 Tobacco Budworm, Petunia & Geranium

General Landscape and Garden Treasure Valley

Tobacco Budworm (Chloridea virescens)

Posted on: August 11, 2021 by Nic Usabel

Tobacco budworm damage has been observed by Canyon County Master Gardeners during and Integrated Pest Management walk in Caldwell. Now is the time to monitor your petunia and geranium plants which are commonly affected by this pest.

Tobacco budworm feeds on buds and petals. The adult is a moth which is light green with gray or brown overtones and a few wavy, creamy colored bands. The moth is active in the early evening and lays eggs on buds or leaves. The caterpillar varies in overall color but is common in dark forms, green, or light brown. The caterpillar becomes full grown in about a month at which point it will burrow into the soil and transform to a pupal stage. The adult will emerge and begin the cycle again. Overwintering pupae are generally killed if exposed to temperatures below 20°F. Maintaining potted plants in protected areas (garage) can allow budworm pupae to survive in the soil.

Control
• Monitor and detect early. Check buds and flowers for small holes.
• A small planting could allow for handpicking as a control. Most caterpillars hide around the base of the plant in the day and climb onto plants at dusk or early evening.
• Application of microbial insecticide Bt Bacillus thuringiensis should be made late in the day and applied to provide good coverage.
• Additional insecticide options are available and should be applied when pollinators are not active or present on the plant.

Reference Materials:
• https://extension.colostate.edu/topic-areas/insects/tobacco-geranium-budworm-5-581/
• https://blogs.k-state.edu/kansasbugs/2016/07/15/geraniums-and-petunias-beware-of-the-tobacco-budworm/
• https://ag.umass.edu/greenhouse-floriculture/photos/budworm-petunia-calibrachoa-geranium-0

» Tobacco budworm

2021 Apple Codling Moth, Third Generation

General Landscape and Garden Treasure Valley

Codling Moth Cydia pomonella

Posted on: August 5, 2021 by Nic Usabel

The third generation of codling moth egg hatch is forecasted to begin August 10. Current degree day models indicate 2030 DD as of August 4. Third generation egg hatch begins at 2160-2200 DD.

Continue to keep fruit protected through September 15. Protection of fruit can stop after this time even if fruit has not been harvested. By mid-September there is not enough day length to signal eggs on the fruit to hatch.

Follow label directions for harvest and post-harvest requirements.

Reference Materials:

2021 Peach Twig Borer, Second Generation

General Landscape and Garden Treasure Valley

Peach Twig Borer (Anarsia lineatella)

Posted on: July 15, 2021 by Nic Usabel

The second generation of peach twig borer is beginning egg hatch. Current degree day models indicate 1253 degree days (DD) as of July 14. Second generation cover sprays begin 1200 - 1300 DD. First cover sprays for second generation should be applied now.

To view management control options review the PNW Handbook link below to select an option appropriate for your setting. Apply according to label directions.

Reference Masterials

2021 Apple Codling Moth, Second Generation

General Landscape and Garden Treasure Valley

Codling Moth Cydia pomonella

Posted on: July 2, 2021 by Nic Usabel

The second generation of codling moth will begin egg hatch this weekend. Current trap biofix degree day models indicate 1069 DD as of July 1. Beginning egg hatch begins at 1120 DD, currently forecasted to be met by July 3.

Rotate among insecticide classes between generations to prevent development of insecticide resistance. Reference publication links to view insecticide options for commercial or residential sites. Commercial products with the active ingredients including; spinetoram, acetamiprid, chlorantraniliprole, etc. Residential products with active ingredients including; lambda-cyhalothrin (restricted use pesticide), or esfenvalerate and Spinosad (general-use pesticides). Non-spray option is to bag the fruit.

This pest needs prevention all season long for clean fruit.

Reference Materials:

2021 Squash Bug

General Landscape and Garden Treasure Valley

Squash Bug (Anasa tristis)

Posted on: June 30, 2021 by Nic Usabel

Squash bugs have been reported in Canyon County by an Idaho Master Gardener. It is time to check the underside of cucurbit (pumpkins and squash are the most attractive) leaves for the bronze-colored egg clusters. In addition, monitor plants for nymphs, adults and plants wilting.

Management:

Wooden boards, shingles, or heavy cardboard can be placed on the ground next to the host plant. Squash bugs tend to move under the board/object at night. In the morning, turn the object over and destroy the pest.

Hand-pick and destroy adults, nymphs, or egg clusters. Other options include rolled duct tape around fingers to pull off egg clusters, cutting off the egg part of the leaf or applying petroleum jelly directly to the eggs. Increased success is achieved when started early in the season and done every 2 to 3 days to keep numbers low.

Cultural methods include sanitation, plating squash varieties that are more tolerant of squash bug feeding, crop rotation, and time of planting.

Additional control methods can be found in the linked publications.

Reference Materials:

PNW Management Handbook: Squash Bug

Squash Bug, Utah State University

2021 Peachtree Borer

General Landscape and Garden Treasure Valley

Peachtree Borer (Synanthedon exitiosa)

Posted on: June 23, 2021 by Nic Usabel

The peachtree borer Degree Day (DD) model indicates that now is the time to begin management. This pest is a concern for stone fruits: Peach, nectarine, apricot, cherry, and plum. Key symptoms of peachtree borer infestation include the presence of sawdust and frass mixed with the gummy substance near the base of the trunk. Prevention is the best method of control.

Larvae injure the fruit tree primarily by burrowing into the tree trunks just at or below the soil line but may enter trunk up to 12” above the soil line. Larvae feed in the cambium beneath the bark girdling the tree.

Chemical Control, Home Use:

For orchards less than 1 acre, or for home yard trees, preventative trunk sprays are the primary control. Apply the first application immediately after first trap catch (or based on DD) and repeat application based on product label guidelines. Follow the required pre-harvest interval (time between last application and allowed harvest of fruit) of insecticide product. Apply insecticide as a bark drench at a rate of ½ to 1 gallon of spray mix per tree. Thoroughly cover the lower 12 inches of trunk and soak the ground at the base of tree. Do not allow the sprays to contact fruit. For chemical options review the PNW handbook.

Chemical Control, Commercial:

Reference the PNW handbook to review application recommendations.

Cultural Management Control:

Larvae inside the trunks can be killed by inserting a wire into entry holes. Kill larvae in the late summer and fall before they spend the winter and inflict their most extensive feeding damage the following spring. Keep base of tree free of vegetation – heat and dryness reduce the survival of eggs and larvae.

Reference Materials:

PNW Management Handbook: Peach and Nectarine - Peachtree Borer (previously linked above)
Greater Peachtree Borer, Utah State University
Peachtree Borer, Colorado State

» https://pnwhandbooks.org/insect/tree-fruit/peach-nectarine/peach-nectarine-peachtree-borer

» https://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=1651&context=extension_curall

» https://extension.colostate.edu/topic-areas/insects/peach-tree-borer-5-566/

2021 Turfgrass Mowing Height & Watering

General Landscape and Garden Treasure Valley

Posted on: June 22, 2021 by Nic Usabel

The weather in the Treasure Valley is warming quickly!

MOWING

Now is the time to check the mowing height at which your turfgrass is cut. Increasing the length of grass blade encourages a deeper root growth and provides more shade cover of the soil surface reducing water evaporation.

For summer mowing height Kentucky bluegrass and fine fescue are recommended to be maintained at 3 inches, perennial ryegrass at 2 inches, and tall fescue at 4 inches. Ensure that the mower blade is sharp and follow the one-third rule; remove no more than one-third of the leaf growth each mowing.

Grass clipping which are left on the lawn by mulching decompose quickly, feed soil organisms, recycle plant nutrients, and increase organic matter in the soil.

WATERING

The goal of irrigation is to keep the lawn healthy when rainfall is not dependable. The key is to moisten the top 10 inches to 12 inches of the root zone. Watering deeply (10 to 12 inches) but infrequently produces healthy turf. Practicing deep watering reduces weed populations, benefits landscape trees and shrubs, increases water use efficiency, and forces an exchange of soil atmosphere with each irrigation. Early morning is the best time to water.

Determining how deep irrigation water goes can be done by using a soil probe or shovel to check soil moisture the day after irrigation. At 10 to 12 inches deep the soil should feel slightly damp. If the soil feels dry at the 10- to 12-inch depth increase the duration of water application to fill the root zone. As weather conditions change this fall adjust the frequency of irrigation to maintain plant available water in the root zone. Frequency of irrigation refers to the number of days between each water application.

Identifying or knowing soil type will help to determine the frequency of water application, rate of water infiltration, and the soils water holding capacity. For example, heavy clay soils have a greater water holding capacity, but have a slower infiltration rate (speed at which water enters the soil). These soils can be watered less frequently and may need multiple application of water on day of watering to allow water to move into the soil. Sandy soils have less water holding capacity and a greater infiltration rate. These soils need to be watered more frequently to maintain comparable turf.

For a more calculated approach to water application reference the publication links below.

» https://www.extension.uidaho.edu/publishing/pdf/CIS/CIS1157.pdf

» https://www.extension.uidaho.edu/publishing/pdf/CIS/CIS1098.pdf

» https://www.uidaho.edu/extension/garden/landscapes/lawn

2021 Peach Twig Borer

General Landscape and Garden Treasure Valley

Peach Twig Borer (Anarsia lineatella)

Posted on: June 4, 2021 by Nic Usabel

Management of the peach twig borer, based on degree days and trap catches, will take place June 6 – June 10. This pest is a concern for those growing peach, nectarine, apricot, plum and prune.

ABOUT

Adult moths are 0.3 – 0.5 inches long, with light and dark gray mottled wings. Scales on the front of head cause the head to appear pointed. The larva is a caterpillar, about 0.5 inch long, with a dark brown head and distinctive, alternating light and dark bands on the body.

Larvae injure fruit trees by feeding on the buds and twigs early in the season, then the larvae bore into the shoots, causing a characteristic "flagging" or wilting of the new growth. Later generations of larvae feed within shoots or even on the fruit itself. Flagging of twigs indicates an infestation.

CONTROL

For chemical control management options review the PNW Handbook, link #1 below, to select a control option appropriate for operation. Apply according to label directions.

For cultural controls prune out shoot strikes (dead shoots) in the late spring and early summer as soon as they are detected to prevent these larvae from completing development and contributing to summer generations of the pest. If old shoot strikes are observed during pruning in late winter to early spring, plan to apply early season controls. Old strikes hold onto the dead leaves and appear as “flagged” terminals.

» https://pnwhandbooks.org/insect/tree-fruit/peach-nectarine/peach-nectarine-peach-twig-borer

» https://climate.usu.edu//includes/pestFactSheets/Peach-Twig-Borer.pdf

2021 Fruit Thinning

General Landscape and Garden Treasure Valley

Posted on: June 2, 2021 by Nic Usabel

Fruits which are crowded should be thinned. Apples, pears,
Asian pears, apricots, plums, and peaches all respond positively to thinning.
Cherries and nut trees are usually not thinned. Thinning fruit will 1) increase
fruit size, 2) improve the trees productivity in the year to come, and 3)
reduce limb breakage as fruits begin to size. Too many fruits on a tree
translates into small fruit that is often of poor quality.

General rules for thinning: 1) The earlier the better, 2)
remove smaller fruits and leave the larger ones, 3) remove fruits with disease
spots, hail damage, or other defects, 4) aim for even spacing.

General guidelines by fruit – see links below for additional
detail.

Apples & pears: Almost always need thinning. Should be thinned
to one fruit per spur with a good spacing of one fruit per 6” of branch. Asian pears spaced at one fruit per 6-8” of branch. Be careful not to break off spurs while
thinning – spurs produce flowers and fruit for many years if not broken.
Recommend to thin apples within 40 days of full bloom and pears within 60 days
of full bloom.
Peaches & nectarines: Should be
spaced at one fruit per 6-8” of branch. Fruits that are joined should be
removed. Recommend to thin peaches about 70 days past full bloom.
Plums: Should be thinned to have
spacing at 6” between fruit along the branch.
Apricots: If tree experiences heavy
fruit set thin fruit spaced to 3” along branch.

Trees will exhibit
“June Drop” which is when the tree will naturally drop fruit. Some prefer to
wait until this event happens to thin, however there are great advantages to
thinning early. More details can be found in the links below.

» https://extension.wsu.edu/maritimefruit/fruit-thinning-for-high-quality/

» http://homeorchard.ucdavis.edu/8047.pdf

2021 Western Cherry Fruit Fly

General Landscape and Garden Treasure Valley

Western Cherry Fruit Fly (Rhagoletis indifferens)

Posted on: May 28, 2021 by Nic Usabel

Western cherry fruit fly adults are about 0.2 inch long.
They have brownish to black wings with dark bands. White maggots infest
cherries. The mature maggot makes a hole in the cherry as it exits. Flies
overwinter as pupae in the soil.

Management begins once the cherries start to blush (ripen to a salmon blush
color) when the fruits are susceptible to egg-laying by the adult females. Consider
the maturity of the ripest fruit on the tree/in the orchard when determining
control methods. Spraying a product with the active ingredient kaolin can create
a physical barrier that prevents females from laying eggs into the developing
fruit. For additional control options see the links below.

Current models indicate the degree days, as of May 27, between
1066 DD and 1111 DD depending on location.

» https://pnwhandbooks.org/insect/tree-fruit/cherry/cherry-western-cherry-fruit-fly

» https://climate.usu.edu//includes/pestFactSheets/WC-Fruit-Fly.pdf

» http://treefruit.wsu.edu/crop-protection/opm/western-cherry-fruit-fly/

2021 Aphid Monitoring

General Landscape and Garden Treasure Valley

Aphid (Family Aphididae)

Posted on: May 27, 2021 by Nic Usabel

Many different aphid species feed on ornamental landscape
plants. Aphids feed by inserting thin mouthparts into the plant phloem and
sucking out sap. Aphids are globular and 1 to 6 mm long depending on life stage
and species. They can be black, brown, yellow, red, gray or green. The legs and
antennae are usually long and fragile. Aphids may be wingless or have
functional wings. The offspring are smaller than the adults and are always
wingless.

Aphids excrete a sweet, sticky liquid called honeydew. When
aphids are abundant, honeydew often completely coats leaves and other objects below, giving infested plants a sticky or varnished appearance.

SCOUTING & MONITORING

Scout plants at least twice weekly when plants are young and
growing rapidly.
Check the underside of leaves where aphids congregate.

CONTROL – CULTURAL & MECHANICAL

On Shrubs and garden plants aphids can sometimes be managed
by simply washing aphids off plants with a forceful jet of water.
If natural enemies are present such as lady beetle larvae or
lacewing larvae these voracious predators will help to manage the control of
aphids without chemical application.
Several species of minute stingless wasps
will also parasitize aphids.
Encourage natural enemies by planting yarrow, alyssum, herbs
and other plants with small attractive flowers.
Manage nitrogen levels.
Use row covers

CONTROL – CHEMICAL

Thresholds help to determine whether and when to treat for
aphids.

When plants are young, aphid populations are increasing and
aphids occur on 50-60% of the leaves.
Aphid populations remain at 8 to 10 or more per leaf for two
or more consecutive weeks.

If high numbers of aphids regularly occur and
injure plant or are not sufficiently controlled by beneficial insects an
insecticide could be used for control. See publication links for suggested
control.