TPM/IPM Weekly Report

Transcription

1 TPM/IPM Weekly Report for Arborists, Landscape Managers & Nursery Managers Commercial Horticulture June 2, 2017 In This Issue... - Slugs and snails - Japanese maple scale - Fire blight - Problem plants - Hail damage - Botrytis (gray mold) - Cedar quince rust - Azalea bark scale - Calico scale - Bagworm hatch - Phlox plant bugs - Biological control program - Periodical cicadas - Black knot disease - Bristly roseslug sawfly - Termites swarming - Emerald ash borer - Lecanium scale Coordinator Weekly IPM Report: Stanton Gill, Extension Specialist, IPM for Nursery, Greenhouse and Managed Landscapes, sgill@umd.edu (office) or (cell) Regular Contributors: Pest and Beneficial Insect Information: Stanton Gill and Paula Shrewsbury (Extension Specialists) and Nancy Harding, Faculty Research Assistant Disease Information: Karen Rane (Plant Pathologist) and David Clement (Extension Specialist) Weed of the Week: Chuck Schuster (Extension Educator, Montgomery County) Cultural Information: Ginny Rosenkranz (Extension Educator, Wicomico/ Worcester/Somerset Counties) Fertility Management: Andrew Ristvey (Extension Specialist, Wye Research & Education Center) Design, Layout and Editing: Suzanne Klick (Technician, CMREC) Slugs and Snails By: Stanton Gill Beneficial of the Week Plant of the Week Phenology Degree Days Announcements Pest Predictive Calendar IPMnet Integrated Pest Management for Commercial Horticulture extension.umd.edu/ipm If you work for a commercial horticultural business in the area, you can report insect, disease, weed or cultural plant problems found in the landscape or nursery to sklick@umd.edu With rain showing up every other day lately the slugs, snails and tree frogs are having a heyday. Yes, I said tree frogs. In the last week I have had three electronic pictures sent in of tree frogs hanging out on landscaper s wheel barrows, on trees and hanging on the foliage of broadleaf perennials. They are loving this wet spring and singing like crazy. They are good since they eat insects and slugs. The best predators of slugs is toads. So, if your customers have a lot of slugs, Frogs, toads, and glow worms are predators of snails and slugs tell them to start encouraging toads in their landscape. One way to do this is by installing aquatic ponds. Toads lay their eggs in still ponds. Keep in mind you will need to control mosquito larvae in the pond with Bti applications (Mosquito dunks). Another good predator of slugs is glow worms which are larval stages of lightening bugs. The larvae live in the mulch areas and will voraciously feed on slugs.

2 Japanese Maple Scale By: Stanton Gill Last week, we reported that Andrew Ristvey, UME, had crawlers of Japanese maple scale on the Eastern Shore in Queenstown just starting activity. I checked populations in Howard County and Carroll County this week and the crawlers had not started as of Monday, but the first crawlers were reported from Frederick County on May 30. The Eastern Shore area is slightly ahead of central Maryland in degree days. Western Maryland is about 7 10 days behind central Maryland. So those of you in Garrett, Washington and Alleghany counties you have a little bit more time before hatch. I also mentioned the new systemic chemical Altus from Bayer Company. We are setting up trials on the Eastern Shore of Maryland with Brian Kunkel, Double-sided tape is one way to monitor for crawler emergence of Japanese maple scale University of Delaware Extension, to compare foliar and drench applications of Altus compared to foliar applications of Talus. We should have results by the end of the season. Fire Blight By: Stanton Gill Dave Clement and I met with Kari Peter, fruit pathologist with Penn State on Tuesday. She is seeing more and more fire blight show up in soft tip growth in several orchards in Pennsylvania and Maryland. The regular rains are perfect for spreading this disease and the soft new growth is highly susceptible to fire blight. Bill Phalan reported: I have had bad fire blight this year in my Gala apple tree, oddly an Empire tree and a Jonagold tree are unaffected. My trees are in Greenbelt, MD. Marie Rojas, IPM Scout, is finding fire blight on Yellow Transparent, Pristine, and Enterprise apples in Laytonsville. Steve Castrogiovanni, Mead Tree Experts, is finding this disease in Potomac this week. Management: If we get a dry period, rare lately, then prune below the damage, infected tissue and remove the blight stems from the area. If it would stop raining, that would also help out. Most Disease and Insect Prone Plants By: Stanton Gill Leaves infected by fire blight look scorched Photo: Steve Castrogiovanni, Mead Tree Experts Thanks to all who sent in their worst plants list and reasons why they feel they are troublesome plants. I am still compiling the information. You can still submit your choice to sgill@umd.edu. What I would like to do now is develop a list of good potential plants that could be used instead. Send me your underused plants with the fewest disease, insect and cultural problems. One good one I found out about is Distylium Blue Cascade. 2

3 Hail Storm Last week, storms passed through the region and on May 25, several areas were hit with hail storms. Suzanne and Jon Cholwek reported hail in Olney on Thursday May 25 evening around 6PM. They noted that there was also torrential rain and thunder, trees and plants were all shredded, and a lot of deck plants destroyed. Look for shredded plants if you are monitoring areas that received hail storms recently Photo: Suzanne Cholwek Gray Mold in the Landscape By: Karen Rane Arguably the most common fungal disease on the rampage right now due to wet weather is Botrytis Blight, also called gray mold, caused by Botrytis cinerea. Flowers on annuals and perennials are particularly hard-hit, as aging petals are easily colonized by this opportunistic and ubiquitous fungus. Spots on petals may initially be white or tan in color, but if wet weather continues these tissues rapidly turn brown. Entire flower heads of susceptible plants like geranium can become a ball of gray fuzz almost overnight. Infected petals that fall onto leaves will initiate leaf lesions. Stems can become girdled, with dieback resulting. One of the most effective management strategies for Botrytis in the landscape is prompt dead-heading of spent flowers before the fungus invades remove and discard the flowers well away from the garden to reduce the amount of spores that will continue to develop even on dead plant tissue. In wet conditions, you may have to sacrifice partially-infected flowers to keep ahead of Botrytis Blight. Figure 1. Botrytis sporulation (gray fuzz in center) on dead florets of a variegated geranium Photo: Karen Rane, UME 3 Figure 2. Blighted verbena stem, covered with gray sporulation of Botrytis Photo: Karen Rane, UME

4 Severe Cedar Quince Rust Steve Sullivan, Brightview, submitted a hawthorn sample that was severely infected with cedar quince rust. The recent extended periods of rain helped to increase the severity of infection. Cedars are the alternate hosts for spreading the spores to hawthorns and quince. The infection period has passed so it is too late to treat hawthorn and quince at this time. Azalea Bark Scale Nicholas Hoxter, SavATree, found azalea bark scale producing egg sacs on an azalea in Bethesda on June 1. This scale can also be found on hawthorn, andromeda, poplar, willow and ornamental cherry trees. Monitoring: Look for plants that appear chlorotic and unthrifty. Infested plants are often covered with sooty mold that grows on the honeydew excreted by the azalea bark scales as they feed. Eventually twigs may die back. Crawlers are active in Maryland in May to early June. There is a second generation that produces crawlers in late June through mid-july. Control: If the population is low and damage is minimal, look for beneficial insects which do a good job controlling this insect. If necessary, apply a dormant spray for overwintering nymphs on twigs. In summer when crawlers are active, you can use a summer rate ( %) of horticultural oil for control. Monitor infestations of azalea bark scale now for crawlers Photo: Nicholas Hoxter, SavATree Cedar quince rust infection is so severe on this hawthorn that is causing the collapse of the leaf petioles Photo: David Clement, UMD-HGIC Calico Scale Jeff Lavrusky, Brightview, found calico scale crawlers on honeylocust in Germantown on June 1. This soft scale can be a pest to all stone fruit and ornamental fruit trees, as well and other hardwood trees such as dogwood, elm, zelkova, honeylocust, sweetgum, magnolia, maple, pyracantha, buckeye, and tuliptree. Adult females are found on twigs and trunks. In the spring/early summer, they can easily be spotted by their mottled dark brownblack and white color. Newly hatched crawlers (1 st instar) are oval-shaped that start off white to pink then turn yellow. They will move from the trunk and twigs to the leaves of the host plant where they will settle and feed near the leaf vein for the summer. In late summer, they move back to woody tissue where they molt and create a hard waxy coating; overwintering as 2 nd instars. There is one generation per year. Monitor: Look for honeydew on leaves and branches produced by the scale feeding on the phloem sap of the host plant and black sooty mold resulting from a fungus that grows on the honeydew. Also look for lots of ant activity as it can be a sign of a scale infestation. Ants are the scale s protective army guarding their arsenal of sweet tasty food. In heavy infestations, dieback and stunted leaves that turn yellow and drop prematurely may occur. Control: One control method would be a basal trunk application of dinotefuran (Safari or Transtect) or 4

5 acetamiprid (TriStar). Another method is to use one of the Insect Growth Regulators (IGR) such as Distance or Talus mixed.05% horticultural oil. Research has shown that this soft scale can be challenging to control; therefore monitor after any control application for its effectiveness. If egghatch has not occurred in your location and infestation is low/moderate, scraping off the adult female scale has shown to provide control without pesticides. Check for signs of natural enemies as they can aid in controlling populations of scale outbreaks, such as ladybird beetles that feed on eggs, crawlers, young nymphs and adults, parasitic wasp species, and even some birds. Calico scale crawlers are now active; there is only one generation per year Photo: Jeff Lavrusky, Brightview Bagworm Hatch Jamey M. Schwartz, Cumberland Valley Tree Service, reported first instar bagworms in Chambersburg, PA on May 31. So far, we have not received any reports of bagworm hatch in Maryland. Phlox Plant Bugs Phlox plant bugs are active now. Plant bugs insert their straw-like mouthparts into plant tissues and suck out the cell contents leaving the yellowed, stippled areas on the foliage. Phlox plant bugs cause distortion of leaves and flowers. Excessive feeding can stunt the plants. There are at least two generations in Maryland. The later feeding activity can be a serious problem when plants are in bloom. They lay eggs in plant tissue so removing plant material in the fall can help reduce populations the following year. Control: For control, you can use a systemic (e.g. acephate). Feeding by phlox plant bug nymphs and adults cause stippling and distorted leaves and flowers 5

6 Biological Control and Upcoming Events By: Stanton Gill Next week, I will be in Canada to participate in the International Biological Control Conference. This conference is a chance to see the latest developments in effective biological control. Hopefully, I will have some new developments to share with you in the IPM Alert for the week of June 17th. Put on your calendar June 29th. The MNLGA will be holding a nursery field day at Ruppert Nurseries, Inc. in Laytonsville, MD. Visit the MNLGA web site to register. There will be Extension educational stations staffed by Rebeccah Waterworth, Paula Shrewsbury, Andrew Ristvey, Karen Rane, Stanton Gill, Mary Kay Malinoski, and Chuck Schuster. Periodical Cicadas Jamey M. Schwartz, Cumberland Valley Tree Service, adds to our report from last week that he received a report of small numbers of periodical cicadas in a red oak tree from a client in Fairfield, PA. Paul Eriksson, City of Cumberland, found a cicada on a Norway maple here in Cumberland on May 26. He noted that they have seen a few individuals scattered around town in different neighborhoods. Adult female periodical cicadas cut slits into branches to lay eggs; monitor plants for damage Photo: Paul Eriksson, City of Cumberland Black Knot Carl Guerci, found black knot cankers on plum caused by the fungal pathogen, Apiosporina morbosa. You can also find cankers on cherries as well. The best way to manage this problem is to prune out the cankers wherever possible. Fungicides can be used if started early in season, but may not be practical in many situations due to the need for regular spray intervals. Black knot can be a problem on cherries and plums Photo: Carl Guerci Close-up of a black knot canker on cherry 6

7 Bristly Roseslug Sawfly, Cladius difformis By: Nancy Harding, UMD In the May 12 IPM Alert we reported activity of the roseslug sawfly, Endelomyia aethiops, on roses in College Park. Now, the bristly roseslug sawfly, Cladius difformis, another of the three species of sawflies that feed on roses, was found on Knockout roses in Bowie on May 27. The larvae of these three sawflies resemble caterpillars, except they have more than five pairs of abdominal prolegs (legs in addition to the 3 pairs of true legs) and the prolegs lack hooks. They are pale green with a light tan head and can range in size from 1/2 to 5/8 making them difficult to see on the underside of the rose leaves where they feed. The bristly roseslug sawfly is usually covered with short hairs where the other two species are smooth. Adults are small, thick-waisted wasps that are mostly black in color. Feeding of the early instar larvae of the bristly roseslug sawfly causes leaf etching on the lower leaf surface, where the later instar larvae feed between the main veins (skeletonization damage) producing holes in the leaves. This sawfly is the most damaging of the three species, as it has multiple generations (reported 5 6) throughout the season. Therefore control may be necessary. Bristly roseslug is one of three species of roseslgu sawflies commonly found damaging roses in Maryland We will continue to monitor roses for curled roseslug sawfly, the 3 rd of the three species of sawflies on roses, activity which begins a little later in the season. Monitor: Look closely on the underside of the leaves with a hand lens for the bristly roseslug sawfly as they are hard to see due to their small size and green color. Also look for signs of etching damage on the foliage. Steve Sullivan, Brightview, found a heavy infesation of sawflies (species not identified) on roses in Prince George County on June 1 Photo: Steve Sulllivan, Brightview Control: Small infestations may be manually removed and destroyed. For higher infestations, use Conserve (spinosad), which is a reduced-risk insecticide and labeled for use against sawfly larvae, or another sawfly labeled product. Termites Swarming Karen Murtagh reported that termite swarmers were out in Darnestown on June 1. Your customers may see these winged adults which are an annoyance, but do not necessarily mean that they have a termite problem. Termites do not have a pinched waist like ants. Their wings are sutured and fall off easily. Termites have beadlike antennae and ants have elbow-shaped antennae. Emerald Ash Borer Craig Greco, Yardbirds, Inc., is reporting that emerald ash borer adults continue to be active. He found emerald ash borer in Falls Church, VA this week. 7

8 Lecanium Scale Rob Meier, Atlantic Maintenance Group, found lecanium scale on honeylocust in Gaithersburg. Now is the time to look for crawlers of this soft scale. Rob noted that there is a lot of honeydew and the scales were big and plump. Control: Since this scale has many predators and parasites, it is best to use an IGR (Insect Growth Regulator) to control this scale, using materials such as Talus or Distance. The crawler stage is the stage most susceptible to chemical treatment, especially when using summer oil sprays. Crawlers emerge for a period of about 6 weeks. Time treatment by monitoring for crawlers and turning over females to note if crawlers are present among the eggs. Beneficial of the Week By: Paula Shrewsbury, University of Maryland MONARCH BUTTERFLIES A biological wonder! Check under the female lecanium scale covers to see if crawlers or eggs are present; this female oak lecanium scale cover from May 2012 only has eggs Monarchs have been sighted!!! About 3 weeks ago a Master Naturalist in St. Mary s County (So. MD) spotted an early instar caterpillar; last week a caterpillar was found at Cylburn Arboretum (Baltimore, MD). Monarch butterflies, Danaus plexippus (family: Nymphalidae) are one of, if not, the most well-known butterflies in North America. There are few children who make it through school without learning the lifecycle of these beautiful and interesting iconic butterflies. There are Citizen Science projects and other programs with the goal of monitoring and conserving monarchs. Everyone loves monarchs and rightly so! They have one of the most fascinating lifecycles and migratory behaviors of all insects. In This Monarch butterfly female was seen foraging on addition, monarch adults provide pollination services nectar from flowering plants in a meadow in Maryland and the caterpillars are food for other organisms. Photo: M.J. Raupp, UMD Given all of this I think they qualify as a beneficial even if the caterpillars make milkweed plants look a little ratty. Monarch butterflies are often thought to occur only in North America. However, their range also includes Central America, northern South America, Australia, New Zealand, Spain, Hawaii and some Oceanic islands. Other species of Danaus butterflies occur in other parts of the world. The Monarch s wingspan is about 8-10 cm and males are slightly larger than females. The upper-side of the wings are orange with black veins and margins and white spots are located in the black margins. In males, the black veins in the hind wings are narrower than those of females with a dark spot, called a stigmata, on a vein in each hind wing. The underside of the Monarch is similar to the upperside in color but paler in color. The Viceroy butterfly looks similar in color and pattern to the monarch. These butterflies are an example of Műllerian mimicry. Both species share similar predators, both 8

9 are toxic and both present similar warning coloration patterns of orange and black. This mimicry is a form of protection from predators. Since both species are toxic, predators learn twice as fast that orange and black butterflies taste bad! Other orange and black butterflies that look like Monarchs, but are not toxic, present Batesian mimicry. Larvae vary in color patterns as they molt from 1 st instar to 5 th instar. In general, they are very bright and striped with transverse bands of yellow, black, and white. They have 2 pairs of black stink horns, one pair on the thorax (segment behind the head) and the other near the end of the abdomen. The chrysalis or pupa looks jewel-like with a jade-green color trimmed in gold and metallic appearance. Adult monarchs are generalists feeding on nectar from a wide range of native and non-native flowering plants. They often feed on the nectar of plants in the Asteraceae family but are often seen feeding on a wide diversity of nectar sources. However, monarch larvae are specialists feeding only on milkweed (Asclepias spp.). There are several species of milkweed that occur in the wild or that are produced commercially for their ornamental value. Some species used by monarch caterpillars include common milkweed (A. syriaca), butterfly weed (A. tuberosa), and swamp milkweed (A. incarnata). Monarchs and their caterpillar host have an interesting relationship. Milkweeds contain cardenolides which are sequestered by the monarch caterpillar when they consume the milkweed. This gives the caterpillars a defense, also retained by the adult butterfly, in the form of a nasty taste that deters many predators from eating them. Over time some predators have evolved mechanisms to overcome these toxins and are able to consume Monarchs. Monarch females place individual eggs on the underside of foliage of milkweed plants Photo: M.J. Raupp, UMD Late instar monarch caterpillars take the J position just prior to pupation Photo: M.J. Raupp, UMD Monarchs have an amazing lifecycle that involves multiple generations and migration across miles. In North America (NA), in general, there are three populations. There is the eastern NA population that overwinters in Mexico, and in the spring begins its seasonal migration to the north toward southern Canada traveling thousands of miles. Monarchs undergo multiple generations during this long journey to Canada. In the late summer fall months monarchs begin their migration back to their overwintering habitat in Mexico. So basically, the adults that return to the overwintering roost in Mexico at the end of the season are several generations later than those that began the journey (ex. their great, great, grand-butterflies). Around mid- Late instar monarch caterpillars often move away March the overwintering butterflies begin their migration from milkweed to other plants or locations to form northward. There is also a western NA population (west of their chrysalis and transform into beautiful adult the Rockies) that similarly migrates between sites in Canada butterflies Photo: M.J. Raupp, UMD and California. They overwinter or roost in coastal regions of 9

10 California. A third more recently founded population which is non-migratory is in Florida and Georgia. A few winters ago I was fortunate enough to visit one of the overwintering roosts of monarch adults in Monterey, CA. A truly AMAZING site that I recommend you all put on your bucket list to experience. Many ask Why do Monarchs migrate? and How do the Monarch butterflies know where to go?. To answer the why In the spring they likely migrate northward tracking the emergence of milkweed plants for their caterpillars, and more floral resources for the adults. They likely migrate south, not for warmth and food, but for optimal overwintering climatic conditions. Monarchs need cool temperatures (they are not freeze-tolerant), moisture, and protected habitat to survive the winter. They find these conditions in the mountainous regions of central Mexico where millions of Monarch butterflies congregate in a few isolated forests in the mountain valleys of Mexico. Interestingly, they congregate on small patches of forest in these areas where they cluster together by the thousands, often covering an entire tree. As for how Monarchs know where to go no one knows for sure. Scientists think they use the position of the sun, along with an innate circadian rhythm, and the earth s magnetic field to determine north and south directions. They also use the wind and thermals to help them glide for long distances, using less energy than flying. There is still much to learn about what regulates the Monarch s migration behaviors and patterns. You have likely heard discussion regarding monarch decline. Anecdotal observations and monitoring data indicate there has been a long term decline in monarch populations since about the mid to late 1990 s. Monarch populations in their overwintering habitat in Mexico are now at their lowest numbers since data started to be collected and recorded about 20 years ago. There has been much effort towards identifying causes of monarch decline. Like most of these situations it does not appear to be just one factor. Factors include destruction of overwintering habitat, the adoption of herbicide (glyphosate) tolerant crops, infection by the disease Ophryocystis elektroscirrha, and parasitism by a tachinid fly, Lespesia archippivora. There is some evidence that suggests the use of tropical milkweed, A. curassavica, may also play a role in monarch decline. There are numerous environmental and conservation groups who implement projects to monitor and conserve monarch populations. A quick search of the internet can direct you towards these groups. You may want to learn more about monarch decline and participate in activities towards the conservation of monarchs. One of the more straight forward practices you can do to conserve monarchs is to plant flowering plants for the adult monarchs and milkweed (Asclepias spp.) for the caterpillars in your landscapes. Monarch larvae prefer some species of Asclepias to others so be sure to do a little research before purchasing and planting milkweed. Planting flowers and milkweed in your garden provides you and your children / grandchildren the opportunity to watch for the first siting for the season of a Monarch butterfly, and to search the milkweed for Monarch eggs, caterpillars, and then pupae. Remember, when you plant milkweed you should plan on it being damaged by caterpillar feeding. Smile when you see the defoliation because it means you are doing your part to conserve these biological wonders! For more information on monarch butterflies and their conservation go to: Phenology PLANT PLANT STAGE (Bud with color, LOCATION First bloom, Full bloom, First leaf) Coreopsis Tequila Sunrise Buds showing color Ellicott City (June 2) Pycnanthemum tenuifolium (narrow Buds showing color Ellicott City (June 2) leaved mountain mint) Stewartia pseudocamellia First bloom Ellicott City (June 2) 10

11 Degree Days (As of May 31) Annapolis Naval Academy (KNAK) 923 Baltimore, MD (KBWI) 833 College Park (KCGS) 827 Dulles Airport (KIAD) 889 Ellicott City (E247) 806 Fairfax, VA (D4092) 974 Frederick (KFDK) 861 Greater Cumberland Reg (KCBE) 821 Gaithersburg (KGAI) 795 Martinsburg, WV (C1672) 748 Natl Arboretum.Reagan Natl (KDCA) 1098 Rockville (C2057) 994 Salisbury/Ocean City (KSBY) 875 St. Mary s City (St. Inigoes, MD-KNUI) 1011 Westminster (KDMW) 884 Important Note: We are now using the Online Phenology and Degree-Day Models site. Use the following information to calculate GDD for your site: Select your location from the map Model Category: All models Select Degree-day calculator Thresholds in: Fahrenheit F Lower: 50 Upper: 95 Calculation type: simple average/growing dds Start: Jan 1 Pesticide Recertification Conference June 9, 2017 Location: Montgomery County Extension Office, Derwood, MD To register MNLGA Nursery Field Day June 29, 2017 Location: Ruppert Nurseries, Laytonsville, MD Commercial Horticulture Conferences MDA Pesticide Container Recycling Program The 25th year of the pesticide container recycling program will run from June through September. There are 24 collection days at 6 different sites. See the brochure for dates and locations in Be sure to properly rinse the pesticide containers before taking them for recycling. The Agricultural Container Recycling Council provides a chipper to grind the plastic containers into flakes, which are then transported to a contractor for recycling. For additional information, or to schedule a chipping date at your site, contact Rob Hofstetter, special programs coordinator, Pesticide Regulation Section, Maryland Department of Agriculture, at

12 CONTRIBUTORS: Stanton Gill Extension Specialist (cell) Paula Shrewsbury Extension Specialist Karen Rane Plant Pathologist Chuck Schuster Extension Educator David Clement Plant Pathologist Andrew Ristvey Extension Specialist Ginny Rosenkranz Extension Educator Nancy Harding Faculty Research Assistant Thank you to the Maryland Arborist Association, the Landscape Contractors Association of MD, D.C. and VA, the Maryland Nursery and Landscape Association, Professional Grounds Management Society, and FALCAN for your financial support in making these weekly reports possible. Photos are by Suzanne Klick or Stanton Gill unless stated otherwise. The information given herein is supplied with the understanding that no discrimination is intended and no endorsement by University of Maryland Extension is implied. University of Maryland Extension programs are open to all citizens without regard to race, color, gender, disability, religion, age, sexual orientation, marital or parental status, or national origin.