Number 10 - June 28, 2013

Last Weekly Issue the body, that lets other leafminer adults know that this leaf or part of the leaf is This is the last weekly issue of the Home, already taken. As a result, a leaf commonly Yard, and Garden Pest Newsletter for this contains only a single leafminer, or the year. During the summer, there are fewer leafminers tend to be located at a distance pests and management timing is less critical from each other in the same leaf. than in the spring. Issues will be published every other week during July, August, and The hatching larva tunnels through the leaf September. We will publish a final issue in tissue, feeding on the mesophyll cells. In a mid-October that will include an index to leaf, chlorophyll is contained primarily in articles published during the year. the mesophyll cells, causing leaves to be (Phil Nixon) green. As these cells are eaten by the leafminer larva, whitish or light-colored areas appear because the remaining Leafminers epidermal cells tend to be mostly transparent. With these epidermal cells We have had several reports of columbine being exposed to drying as the mesophyll and other leafminers around the state. They cells are eaten away, they soon turn brown appear to be more numerous this year, and die. Thus, recent mines are whitish and probably due to the heavy and frequent older mines are brownish, making it easy to rains this spring. Most full grown leafminer tell whether the leafminer is still actively larvae burrow out of the leaf and drop to the feeding. soil to pupate. Dropping onto moist soil increases their survival, resulting in the next Holding a mined leaf up to the light makes it generation being more numerous. I don’t easier to see the entire mine, including remember seeing entire leaves covered with smaller areas that were eaten when the columbine leafminer mines previously, as in larva was newly hatched. If the larva is still the accompanying photo. present, one can frequently see the silhouette of the feeding larva. Also obvious Leafminer larvae live inside the leaves of will be the fecal material deposited by the many trees, shrubs, vines, and herbaceous larva. plants. This environment within the leaf provides a moist area that is protected from Fully grown larvae chew their way through at least some predators and parasites. As a the leaf epidermis to the leaf surface and result, many insect species have adapted to typically drop to the soil to pupate, although this lifestyle, including flies, moths, wasps, some moth larvae spin a cocoon and pupate and beetles. on the leaf surface. With the diversity of insects that live as leafminers, the size and The adult fly, wasp, moth, or beetle inserts appearance of emerging, full-grown larvae its eggs into or onto the leaf tissue. Many vary. Those of flies and wasps are typically leafminer adults also lay down a legless and usually 1/16 to 1/8 inch long. pheromone, a hormone produced outside of Many fly larvae are bright yellow, pink, or red when they emerge to pupate. Moth and beetle emerging leafminer larvae are Because leafminers typically have several typically legless as well, but are commonly generations per year, removing and 1/4 to 1/2 inch long. The adult emerges destroying mined leaves while the larvae from the pupa to attack more leaves. are still inside can reduce the number of Leafminers typically have more than one mined leaves later in the season. Leaves that generation per year. Some leafminer flies, still have whitish mines should still contain including columbine leafminer, have several the larvae; the larvae have usually already generations per year. left the mines if the mines are brown. (Phil Nixon) Because newly hatched leafminer larvae are very small, they tend to make small, narrow tunnels through the mesophyll. Some Japanese Beetle leafminer larvae continue to make narrow tunnels that meander through the leaf; they Thanks to a variety of readers that are referred to as serpentine leafminers. responded to the article last week on Their narrow, winding tunnels appear Japanese beetle. I can now report that they somewhat serpentlike, that is, snakelike. have been present in southern and central Columbine and honeysuckle leafminers are Illinois since the third week of June and serpentine leafminers. were seen in LaSalle and Will Counties on June 24. With the warm temperatures of the Other leafminers may form slender, past week, they should have emerged in the snakelike tunnels initially but soon turn to rest of northern Illinois by now. feeding on the mesophyll cells in a broad area, resulting in what is called a blotch Typical emergence pattern for most insects mine. Birch and holly leafminers are blotch is that the males emerge a few days before leafminers. Blotch mines are commonly the females. About a week after the adult bounded by leaf veins, resulting in straight- Japanese beetles become numerous, sided mines. Other blotch mines cross leaf "balling" is likely to occur. When a female veins and become more rounded in shape. Japanese beetle is emerging from the soil, males gather at the location. As she Although leafminer damage is obvious, it emerges, they are attracted to her, crawling usually has little effect on plant health. on top of each other. The result is a ball of Although the mesophyll that is eaten does 25 to 200 Japanese beetles, frequently about not produce sugars for the plant, the the size of a golf ball. They are most undamaged cells in the leaf continue to noticeable on closely mowed turf, so most produce. An exception to that is when the reports come from golf courses. leafmining is so extensive that it causes leaf drop. Birch leafminer is the only one that Beetles mate, and the females tunnel into causes leaf drop in Illinois and only in the the turf to lay eggs. These eggs hatch into northernmost row of counties. Farther white grubs that feed on the turf's roots, south, the damage is noticeable but not resulting in browning and dieback of the severely damaging. Holly leafminer may turf in late summer and fall. Female beetles produce enough aesthetic damage in are strongly attracted to moist, actively southern, particularly southeastern, Illinois growing turf, so stopping or reducing to warrant control but rarely causes leaf irrigation during July results in reduced egg- drop. In states to the east and south, holly laying, with fewer grubs. The beetles go to leafminer damage can be very severe. the neighbors' moister, greener lawns to lay Systemic insecticides are recommended for their eggs. Typically, unwatered lawns do control of both leafminers. not have enough white grubs to warrant Heavily attacked ornamental plants in insecticide application. obvious locations in the landscape can be sprayed with carbaryl (Sevin), cyfluthrin Male and female beetles are similar in (Tempo), or other pyrethroid. An appearance, being stocky, 3/8- to 1/2-inch- application typically controls the beetles for long, metallic green beetles with copper- about 2 weeks. Because the beetles are out colored wing covers. They are present in for about 6 weeks, three applications are high numbers for about 6 weeks. They feed needed. Due to the repeated applications on the foliage and flowers of a wide range of and large plants that are commonly plants, being most common on smartweed, attacked, the use of insecticide can be crabapple, linden, birch, willow, rose, grape, reduced by spraying only plants where the apple, peach, and brambles. They do not damage is very noticeable. Plants in less feed heavily on needled evergreens, ashes, obvious parts of the landscape and large magnolias, oaks, and maples other than trees can go untreated because the damage Japanese maple. They feed during the day at will be less noticeable. The beetles are so the top of the plant on the leaf's upperside-- numerous and mobile that the beetles on they appear to like sunshine. Individuals the untreated plants make little difference typically fly to another food plant every 3 in the number of beetles attacking treated days. These flights tend to be long, from 3/4 plants or the amount of turf injury by the to 1-1/2 miles. subsequent white grubs.

The adults feed through the upper Systemic insecticide application is also epidermis and mesophyll, leaving the lower effective, with imidacloprid (Merit, Xytect, epidermis intact. Initially, damaged leaves Optrol) applied as a soil injection or soil are whitish but soon turn brown as the drench being the most common method of exposed lower epidermis dries and turn application. The insecticide will move into brown. This type of damage is called the foliage within a couple of weeks. window feeding. Heavy feeding results in Imidacloprid does not typically move into holes in the leaves and can progress on the flowers of rosaceous plants such as rose, favored hosts to skeletonization, with only crabapple, and hawthorn, but can be found the major leaf veins remaining. in linden flowers. Imidacloprid has been linked in some studies to colony collapse Beetles are attracted to previously attacked disorder (CCD) in honey bees, so avoid use plants. Homeowners can greatly reduce on trees and shrubs where the insecticide damage by handpicking, particularly for the enters the flowers. As the imidacloprid first week or two after beetle emergence. remains in the plant for almost one year, Use a wide-mouthed jar (such as a peanut one cannot avoid movement into the butter jar) containing rubbing alcohol or a flowers through application timing. detergent and water mixture. Hold the jar (Phil Nixon) under a beetle, poke it, and the beetle will fold its legs and fall into the jar, being killed by the alcohol or drowning in the soapy Bagworm water. Doing this daily or every other day for the first couple of weeks results in plants Bagworms have hatched throughout the with little damage compared to the state and appear to be a little early than neighbors' plants. Throughout the rest of normal. Treatment is recommended in the season, beetles will be more attracted to southern and central Illinois at this time as the plants next door. they have completed their ballooning and are settling down to feed in earnest. They will still be ballooning in northern Illinois, so treatment should be effective after the female bag contains 300 to 1,000 eggs. fourth of July. Because bagworm eggs overwinter in the old bags, an effective control measure on Bagworm overwinters as eggs in the female shrubs and smaller trees is to handpick the bag. They hatch in late spring, exiting the bags from September into spring and bottom of the bag. The tiny caterpillars destroy them. climb to the top of the tree where they each spin out a silk strand 1 to 3 feet long. This Bacillus thuringiensis kurstaki (Dipel, catches in the wind and carries the tiny Thuricide), spinosad (Conserve), cyfluthrin larva wherever the wind blows. This is (Tempo), permethrin (Astro), and other called ballooning. The bagworm population pyrethroids are effective even on older continues this process for about 2 weeks. larvae. Even so, they are more effective on They are most common on spruce, eastern younger larvae, so treatment soon after they red cedar, other junipers, arborvitae, white stop ballooning is recommended. In pine, crabapple, and pin oak but are found addition, controlling younger larvae on many other species of trees and shrubs. prevents the damage that would be caused They are more common on deciduous hosts by the larvae through the season. in southern Illinois than farther north. (Phil Nixon)

Bagworm larvae feed on the edges of broadleaf foliage, sometimes to the midvein. What Does Plant Disease Sanitation Leaves of needled evergreens are eaten Really Mean? back to the base until nothing remains. Defoliated needled evergreen branches or A plant pathologist’s goal is to properly entire trees frequently die. Because identify and manage plant disease to reduce bagworms start at the top of the tree and the economic and aesthetic damage to work their way downward, it is common to plants. Unfortunately, many still think that see the top third of evergreens dead due to our goal is to control plant disease by defoliation. Deciduous trees will refoliate, spraying fungicides. We focus on an with the damage being primarily aesthetic. integrated disease management approach, which includes exclusion, eradication, Bagworms spin individual silk tents and protection, and resistance. But, what do all cover them with host foliage. The bagworms of these really big words mean? When it feed through the summer. As the comes to managing plant disease, utilizing caterpillars grow, they increase the size of prevention and suppression of plant the spindle-shaped bags up to 1-1/2 inches pathogens is recommended. Some ways to long. Pupation ranges from mid-August to suppress a plant disease are rotation, very early September. As long as the resistant varieties, sanitation, leaving land caterpillar is feeding, it places bits of host idle, or weed control. Sanitation is one of foliage around the top of the bag. Once it has the many ways to achieve “eradication”, pupated or died, this practice stops and the when practicing integrated disease top of the bags turn from green to brown. management and is defined as the This is useful in scouting because pupated elimination of plant disease pathogens. bagworms are not susceptible to insecticide How do you think that plant pathogens sprays, and killed bagworms do not fall survive from year to year? They survive on from the tree. plant debris and infected plant parts after each growing season. Here are some After mating with male bagworm moths, the recommended sanitation practices: female bagworms fill their bodies with fertilized eggs and die in the bag. Each Tillage Plant pathogens are less likely to survive if http://www.ag.ndsu.edu/pubs/plantsci/tre organic matter is quickly decomposed. In es/h1036.pdf addition, tillage can help eliminate plant Does covering wounds on trees help? We do roots that linger after harvest in the soil and not recommend that you cover a wound, can harbor plant pathogens. because recent research indicates that this practice is of no value and might even Weed control accelerate wood decay. In some cases, weeds can be a source of plant pathogens and it is suggested that Removing dead plant material weeds be controlled. If you believe weeds In most cases, plant parts should be are diseased, they should be buried, burned, removed as soon as you notice they are or removed, and not composted. In other diseased or dead during the growing season. cases, numerous weeds can increase Raking leaves, removing dead fruit, or humidity, which could make conditions digging up entire plants (including roots) more favorable for plant disease. are all examples of sanitation. The dead plant material could contain bacterial, Insect control fungal, or even viral pathogens. The next Some insects may need to be controlled question is always what do we do with this because they could be vectors of plant diseased plant material? The diseased plant pathogens and transmit plant pathogens material should be buried, burned, or such as viruses or bacteria to plants. Plant properly disposed away from your healthy disease vectors include aphids, leaf hoppers, plants! It is not recommended that you pile and cucumber beetles. this material near the garden. There are conflicting opinions, when it comes to Pruning limbs composting diseased plants. Ultimately, This year, the U of I Plant Clinic will be death of plant pathogens will depend on the recommending more pruning of trees, effectiveness of your composting system. thanks to the development of fungal cankers Generally, composting of diseased plants is after drought stress and the increase of the not recommended because the composting bacterial disease, fire blight. If you notice heat may not entirely (100%) kill all of the branches are dead or have sunken, dark disease organisms. As you use and spread cankers, with foliage that is yellow, brown, compost, you could also be spreading plant wilted or absent, you may need to prune. If pathogens. Most plant pathogens are host you fear further plant pathogen spread specific; therefore, using compost consisting during the growing season, pruning should of leaves, grass clippings, or shrubs in the be done in dry weather. Ideally, pruning vegetable garden can be done, because usually should be done in late winter or these plant pathogens most likely will not early spring, when trees are dormant. The affect the garden plants. However, some key is to prune PROPERLY! Pruning cuts research institutions recommend should be made in healthy bark and wood, destroying diseased leaves and needles. several inches below the diseased or dead area. Pruning tools should be sharp and Avoid movement or destroy soil pathogens used in a manner that promotes a smooth Don’t forget that plant pathogens can be cut to help with wound closure. Remember, present in the soil; therefore be sure not to when pruning an entire branch, wood move contaminated soil to other areas. should be removed before it meets the Remember to disinfect or destroy boots, collar. The branch collar should not be stakes, cages, pots, saucers or anything else removed. that has come into contact with the soil. Soil For additional information on pruning, within pots should not be reused from year please refer to the following fact sheet: to year. It is recommended that dead plants and soil in pots be placed in the trash. Root scott/horticultural%20myths_files/Myths/ rot pathogens such as Pythium, Pruning%20tools.pdf Phytophthora, and Rhizoctonia as well as (Stephanie Porter) wilting plant pathogens such as Verticillium can all affect a wide array of plants, so proper disease identification is needed and Recommendations for sending suspected replanting with the same host plant is not oak wilt samples to the U of I Plant Clinic recommended. I am often asked if there is a way to remove plant pathogens from the Summer has arrived. Along with the new soil. Fumigation can be costly, but is used in season, comes days with extreme commercial situations. Soil removal can be temperatures. High temperatures have the attempted; however, it is difficult to potential to kill plant pathogens and thwart completely remove plant pathogens from diagnostic efforts before the samples arrive the soil. If replanting, in an infested area, at the Plant Clinic. The pathogen responsible we often recommend a cultivar with some for oak wilt is a good example. This fungal resistance or a non-susceptible host plant. pathogen is intolerant of temperatures We also encourage good cultural practices above 90°F. It is also thought to be sensitive (proper planting, proper site, watering/not to drying and other competing fungi. overwatering, pruning, or fertilization), to Exposure to these conditions during keep the plant in good health to avoid future shipping may result in inconclusive text plant disease infection. results. Properly packaging and shipping samples will greatly help reduce the Disinfect machinery, tools, pots, equipment, potential for an inconclusive diagnosis. and even HANDS When sending an oak wilt sample, start by It is very important that you disinfect selecting a branch showing early symptoms machinery or tools after use to prevent of the disease. Oak wilt symptoms will vary plant pathogen spread to other plants. by host. In general, oaks in the red group Disinfecting can be done with steam, hot develop discolored and wilted leaves at the water under pressure, or a 10% (1 part top of the tree or at the tips of the lateral bleach to 9 parts water) or 10% soak for 30 branches in late spring and early summer. minutes). Some research institutions even Leaves curl slightly and turn a dull, pale recommend soap and water or rubbing green, bronze, or tan, starting at the alcohol for disinfection. No matter the margins. The infection progresses rapidly. disinfecting method, whatever you are Usually, an infected tree will drop all its cleaning should be allowed to dry. leaves by late summer. Remember that bleach can discolor metal or clothing. Corrosion of cutting tools due to Infection of hosts within the white oak disinfection via bleach is also a common group, tend to progress slowly, over several complaint. One tip might be to rinse with years. Leaves on infected white oaks water and treat the cutting tool with a light become light brown or straw colored from spray of cooking oil after it has come into the leaf tip, progressing toward the base. contact with a bleach solution. I have The leaves curl and remain attached to the recently come across some new research branches. The disease is often confused with compiled into a fact sheet that discusses general dieback, decline, or anthracnose. other alternative options for the disinfection Infected branches from both oak groups of cutting tools and can be found at the should show symptoms of vascular following link: streaking. Peeling back the bark of an http://puyallup.wsu.edu/~linda%20chalke infected branch will reveal sap wood with r- steaks of brown discoloration. Sample Collection and Submission  “This plant is gorgeous in early to Tips mid-Summer!”  Collect suspected oak wilt samples  “Invasive as they get--one of my from a living branch showing early biggest pests!” symptoms of the disease. The pathogen will  “They are the most pleasing shade of not survive in dead or dry branches. blue in my gardens!”  Try to send branches with  “I finally have a name for this little symptoms of vascular streaking. Our best beastie. I called it Hitler-weed because it chance of isolating the pathogen occurs invaded everything around it. I'll be pulling when culturing tissues with vascular this until the day I die. Once established just streaking. try to get rid of it. I dare you.  Mail samples the same day they are collected, or refrigerate and mail them soon I too have battled Asiatic dayflower for after. admittedly many years now. It always  Send samples early in the week. This returns to the same spot. According to will help to prevent samples from being weed scientists at Iowa State University and held over the weekend in a hot mail truck. University of Nebraska Lincoln1, seed  Higher rates of successful isolation dormancy is an important adaptive occur with samples that’s were kept cool. characteristic of this genus. They and When possible, send samples in an others who have researched this weed inexpensive cooler with a disposable ice report that more than 80% of the seeds can pack. germinate even after four and a half years in  Clinic results for oak wilt testing the soil seed bank. That’s fairly high. often take 7-14 days to complete. The Plant Additionally, seeds can germinate Clinic will send a detailed report with throughout the growing season. This recommendations when the results are creates steady work for weeders. I can available. understand why many have decided to (Travis Cleveland) simply live with this weed.

Recently I found it in a new area – in the Asiatic Dayflower – The Little Beauty that windbreak bordering the south end of my Caused So Much Confliction property – and the thought actually crossed my mind, “Do I really want to fight it here? The jury is out on Asiatic dayflower. Half of The blue flowers are stunning though a little them are out enjoying how their gardens small.” The realist in me says, “no, I’m tired have been graced with this plant’s pretty of fighting” but the stubborn perfectionist in blue flowers. The other half is (and likely me says “hell yes”. I’m conflicted. has been for quite some time) waging war on this invasive weed. How can we be so This windbreak borders a field. I trust my divided when it comes to this escaped farmer neighbor would rather I control it ornamental? before it spreads to his field. Asiatic dayflower is becoming a troublesome weed I stumbled across an interesting discussion for farmers because it is difficult to manage online about Asiatic dayflower (Commelina and can easily survive applications of communis), also known as common glyphosate (Roundup and others). Just to dayflower and blue dayflower. Here are clarify, its survival is NOT a result of the some direct quotes from that discussion. increased use of glyphosate. However, we Naturally, it could leave one a little are seeing more of this plant in agricultural conflicted: production fields because of the increased use of glyphosate. Other competitive weeds are killed while this one is left to survive that gave me a chuckle. “I like the idea of and take over. And it will. dropping the little shoots in butter and watching them wilt….I really do not like this Research by weed scientists in Connecticut2 plant.” found that flumioxazin (BroadStar, SureGuard, Chateau and others) provided 1. Response of Asiatic Dayflower excellent season-long control of Asiatic (Commelina communis) to Glyphosate and dayflower. There are additional reports Alternatives in Soybean. Santiago M. Ulloa that triclopyr (Turflon and others) is and Micheal D.K. Owen. Weed Science, Vol. effective against this weed. Remember to 57, No. 1 (January-February 2009), pp. 74- carefully read and follow all label directions. 80; http://www.jstor.org/stable/40586977 Hand pulling can be effective if the soil is moist. Often however, stems will simply 2. Effective Herbicides for Asiatic Dayflower break off. Stems are capable of rooting at Control in Conifer Beds. Mervosh, T.L. and the nodes. Be sure to discard pulled plants. J.F. Ahrens. Connecticut Agric. Exp. Stn., Prevention of seed development is also Windsor. Proceedings, Northeastern Weed highly recommended. It cannot tolerate Science Society, Vol. 57, p. 38 (2003); mowing, so it is not commonly found in http://www.newss.org/proceedings/proce lawns. It prefers moist, rich soil and shade. edings_2003_vol57.pdf Cultivation may be used. (Michelle Wiesbrook) Many are surprised to learn that this somewhat creeping or ascending plant is an annual monocot – even though its leaves are up to 1.5 inch wide, much wider than that of Modified Growing Degree Days (Base 50⁰ most grasses. The seedlings look grassy F, March 1 through June 27) with parallel veins. It is a member of the spiderwort family. The stems & leaves are Station Actual Historical One-Week Two- thick and fleshy. Stems can reach 1 to 3 feet Location Temp. Average Projection Week (11 year) Projection in length and the nodes are swollen or Freeport 983 961 1138 1293 bumpy. Leaves have smooth margins and St. Charles 985 907 1134 1282 no petiole; they are 2-4 inches long. There DeKalb 1016 1024 1173 1327 is a sheath at the base of each leaf that Monmouth 1131 1087 1290 1149 clasps the stem. The flowers are pretty with Peoria 1152 1143 1321 1492 2 large petals above one smaller white petal. Champaign 1219 1181 1393 1569 Springfield 1304 1274 1487 1673 They are found July through September in Brownstown 1292 1350 1478 1667 small clusters in the leaf axils. Look quick, Belleville 1367 1363 1551 1739 because they only last a day (its name Rend Lake 1470 1475 1663 1857 should have tipped you off) and they aren’t Carbondale 1425 1392 1605 1791 very big. Dixon 1443 1465 1626 1814 Springs

If you are feeling adventurous (and hungry), Insect development is temperature this plant is edible according to my Peterson dependent. We can use degree days to help Field Guide. This 2 minute video predict insect emergence and activity. (http://www.youtube.com/watch?v=4D5M Home, Yard, and Garden readers can use the sCkl1FM ) shows the many uses that one links below with the degree day person has found for it. I think the blue accumulations above to determine what flowers make her dishes quite attractive. insect pests could be active in their area. Eating this weed can aid in revenge seeking. GDD of Landscape Pests I’ll share with you one last comment I read GDD of Conifer Pests Degree day accumulations calculated using the Illinois IPM Degree-Day Calculator (a project by the University Of Illinois Department Of Crop Sciences and the Illinois Water Survey). (Kelly Estes)