Ornamentals Insect and Mite Update – David J. Shetlar, Ph.D. The “BugDoc” The Ohio State University, OARDC & OSU Extension Columbus, OH © November, 2007, D.J. Shetlar, all rights reserved

Notes: What follows is information provided during the various OSU Pesticide Recertification Seminars that are held across the Ohio during the winter months. In order to gain actual recertification credits, you will need to attend an actual session, in person. There are many opportunities to get commercial and private recertification credits during the year. If you are in one of the Ohio Green Industries (e.g., turf or ornamental plant care, nursery production, greenhouse production, etc.), you can also get most of your recertification credits and various industry conferences and shows. The Ohio Turfgrass Foundation offers its conference and show in December, the Ohio Nursery & Landscape Association holds its CENTS show in conjunction with the OSU Nursery Short Course in late January and the Ohio Florists’ Conference is generally in July. Other opportunities exist and ODA rules state that any recertification program must be open to the public though a fee for services can be charged. Check with the Ohio Department of Agriculture web site to find out about all the opportunities available.

Outline Information Resources Review of Pests Emerald Ash Borer Control Update

Notes: Before we discuss actual insecticide and miticide issues, let me give you a little outline of what is to come. First, you should become familiar with ALL the informational resources that you can use to help in your quest for safe and effective use of pesticides. We’ll cover the sites that are offered by The Ohio State University. We’ll then cover some of the common insects and mites that affected our ornamental plants in This will also include a brief overview of the emerald ash borer that everyone is concerned about and I’ll cover some of the major changes in insecticides and miticides that have occurred in recent years.

Notes: Ohio State University Extension’s primary Internet information resource is the OhioLine. This web site is located at ohioline.osu.edu. On this site, all the current factsheets and bulletins are posted. While it may seem difficult to find what you are looking for, try the search button. When you use this, enter in the name of the pest or problem about which you are looking for information and the search programs usually does a pretty good job of coming up with the most likely informational resources. In 2008, we are expecting a new look to the OhioLine with resources organized in a more user-friendly manner. Also, we will soon be able to take orders for bulletins online by using a credit card.

Notes: Dr. Tim Rhodus in the department of Horticulture and Crop Sciences continues to maintain his WebGarden site. This site is essentially an online encyclopedia of plant information and the various fact sheets and bulletins posted by all the land grant universities across the United States have been surveyed and indexed. If OhioLine doesn’t have information, the WebGarden usually does!

Notes: The Ohio State University, Extension Nursery, Landscape & Turf Team (ENLT-Team) is a group of horticulturalists, entomologists, plant pathologists and related specialists that meet on a regular basis to share information and develop new outreach materials for Ohio’s Green Industries. During the growing season, members of the ENLT-Team meet by a phone conference every Tuesday morning to discuss what they have seen, what has been submitted to offices and our diagnostic clinic, and discuss what we might see in the near future. Notes of this discussion are taken and converted to a web-format newsletter by noon of each Thursday. So, the Buckeye Yard & Garden OnLine site (bygl.osu.edu) is the place to review what we are seeing and recommending.

The P.E.S.T. Newsletter available from: Ohio Nursery & Landscape Association 72 Dorchester Square Westerville, OH

Notes: Many of you subscribed to the P.E.S.T. Newsletter which I produce and distribute through the Ohio Nursery & Landscape Association. This newsletter comes out every other week from mid-March through mid-October and it contains the BugDoc’s “unique” perspectives on pest issues in Ohio’s landscapes. This newsletter is available, by subscription, only through the ONLA office. Be sure to tell the good folks at the ONLA that you are a member of one of Ohio’s associated green industries to get a discount. These would be ONLA, the Ohio Turfgrass Foundation or the Ohio Lawn Care Association. You can receive the traditional printed copy through the mail, a PDF version by and a color version is posted on a private web site.

Come visit the BugDoc at:

Notes: I maintain my own web site for distributing information on insects and mites that attack ornamental plants and turfgrass. It’s located at bugs.osu.edu. This site is where many of our extension entomologists post information, but if you click on my name, Dave Shetlar, my home page will pop up. Notice that I have postings of recent presentations, both as web viewable pages and as downloads which you can use with your computer in training. Also notice that I have my own links to factsheets and I teach a course, Entomology 462, on pests of ornamental plants, turfgrass and greenhouses. This entire course is posted on the internet.

Ohio Weather 2006 wetter than normal, 2007 dryer and hotter than normal! April, 2007 late hard freeze!

Notes: Well, let’s get to what I saw in Ohio in First, however, I believe that the weather was one of the major factors driving the changes in insect and mite problems across Ohio. In short, we seem to be continuing our trend of alternating between wetter than normal and dryer than normal summers. The summer of 2006 saw a cooler and wetter than normal summer, but last year, 2007, most of Ohio experienced a major, prolonged drought. These alternating conditions can be quite stressful to landscape plants and insects and mites often take advantage of these stressed plants. Also, remember that late freeze that we had across Ohio in April? We had warmed up quite a bit and many of our trees and shrubs were beginning to break bud, when WHAM, the cold snap hit and froze back many plants.

Insect and Mite Activity in 2007 Bagworms & Mimosa Webworms! Banner year for calico scale! Emerald Ash Borer – new discoveries, almost weekly! PEOPLE are spreading it! Other borers – white pine weevil continues to spread; bark beetle problems. Warm-season mites – everywhere!

Notes: As you can see, there is quite a list of critters that caused problems across Ohio last season. In fact, I can’t cover them all! I saw continued major problems with the common bagworm and localized outbreaks of the mimosa webworm. In spite of the late cold snap, many honeylocusts and other trees were heavily infested with the calico scale last spring. We had lots of borer problems due to the previously mention plant stresses, but the emerald ash borer is probably borer highest on most peoples’ minds. In spite of this, our other borers have not disappeared! We continue to see problems with the white pine weevil, some clearwing moth borers and bark beetles. While we had lots of problems with spruce spider mites in 2006, the hot and dry summer of 2007 seem to benefit many of the warm-season mites.

Notes: This is a picture of an unfortunately spruce that has been attacked by a major population of bagworms. These caterpillars often escape detection because of their camouflaged cases. And, on conifers, many home owners view the bags as being seed cones! In any case, on conifers, when bagworms completely defoliate branches or a portion of the tree, that part can actually be killed! So, speedy action is essential on conifers to avoid severe damage. Treatments should be made in mid- to late June across most of Ohio.

Notes: Many places in Ohio experienced major browning of honeylocust trees by mid-August. This was due to the mimosa webworm which commonly has two generations and occasionally three in Ohio. Last year, I’m sure we had three generations in most places. The key to control of this pest is to eliminate the first generation of caterpillars whenever possible. The first generation usually occurs in June into early July. Females emerging to lay eggs for the second generation prefer to attach the eggs onto the silk of the nests of the first generation. So, if you eliminate the first generation, the moths will tend to fly to trees that remained infested!

Notes: In parts of southern Ohio, the forest tent caterpillar showed up in plague numbers. This pest doesn’t make the true tent in crochets of trees like its cousin, the eastern tent caterpillar. Also, the eastern tent caterpillar prefers cherry and apple, but the forest tent caterpillar has a broader appetite. They will commonly defoliate oaks, elms, maples and other deciduous trees. Outbreaks of the forest tent caterpillar usually last for one to three years before the natural parasites and predators get them back under control.

The Gypsy Moth – still moving across Ohio!

Notes: I wanted to remind you that our old friend, the gypsy moth, is still with us! It has been slowly spreading across Ohio but tree- defoliating outbreaks have been rare for the last decade. This seems to be due to the wetter and cooler spring conditions which lead to outbreaks of a fungal disease among the caterpillars. However, last year, we got hot and dry in June and many of the gypsy moth caterpillars were unaffected by the fungus. If we have another dryer than normal spring in 2008, we may see some major, defoliating outbreaks in Columbus to Cleveland and in the Springfield area. Be forewarned!

Caterpillar Insecticides Traditional Dursban Sevin Orthene Alternatives Tempo, Talstar, Deltagard, Scimitar, Astro Conserve Merit, Meridian (no!) Arena? (suppression) Bt Soaps or Oils X

Notes: If we look at the insecticides available for caterpillar control, we see that we still have Sevin and Orthene as some of our traditional carbamate and organophosphate chemistry. Most of you have switched to the pyrethroids for caterpillar control, but these still have to be sprayed into the trees as pyrethroids don’t have systemic action. Many of you have asked if there are some systemic insecticides that would be easy to inject into the soil or the trunks of tall trees so as to avoid tall tree spraying that is always at risk of drift problems. In reality, our neonicotinoids, especially imidacloprid or Merit and thiamethoxam or Meridian still don’t seem to be very good at knocking down caterpillars. There are some data to suggest that Arena may have some activity, but more work needs to be done to confirm this. While not listed here, the trunk injectable insecticide bidrin is very active against caterpillars, but I recommend using caution as bidrin is a pretty “hot” insecticide.

European Pine Sawfly larvae eggs adults

Notes: Conifer-infesting sawflies, like the European pine sawfly have continued to be locally abundant, but we are seeing other species attacking deciduous trees and shrubs. The rose-slug sawflies, dusky birch sawfly, and oakslug sawfly have been noticeable. Remember that sawflies, though they look like caterpillars, are not! The larvae have the fleshy leg-like structures, prolegs, on the abdomen, but the adult insect is a wasp-like critter, not a butterfly or moth.

Sawfly Insecticides Traditional Dursban Diazinon Sevin Orthene Still/Now Available Pyrethroids (permethrin, resmethrin, esfenvalerate, bifenthrin, cyfluthrin) Merit, Safari, Arena & Aloft, Meridian Soaps or Oils X X

Notes: In the case of sawfly control, they are very susceptible to the neonicotinoid insecticides! So, Merit, Meridian, Arena or Safari would be good choices for sawfly prevention or control. On the other hand, Sevin and ortherne as well as the pyrethroids are excellent, knock-down insecticides. And, if you can hit the larvae with your spray, insecticidal soaps and horticultural oils can do an excellent job.

Calico scale adults on honeylocust (can be found on many deciduous landscape trees). Calico scale nymphs on leaf undersurface.

Notes: The calico scale was a major pest of urban honeylocusts, especially in the southern half of Ohio. However, this scale can occur on many other deciduous trees, especially maple and elm. It is a good example of a typical soft scale which has crawlers that emerge in late spring. Our other lecanium and cottony scales have similar life cycles. In essence, the crawlers settle on the undersurface of their host’s leaves where they feed and undergo two instars. By late summer, the males are produced and new females move from the leaves back to the stems and branches of their hosts. They remain here until the following spring when the females puff up to produce eggs or young. The take home message is that controls should be directed at the crawlers and nymphs that are settled on the leaves, not the adults that are on the branches in the spring!

Pine needle scale females. Note pinkish eggs at end of scale test (shell) and a settled crawler at upper left. Group of pine needle scale settled crawlers (tan) and a couple of fresh crawlers (pinkish) in color.

Notes: The pine needle scale is a good example of an armored scale and it has a life cycle similar to the oystershell and euonymus scales. All these scales have two, and sometimes three generations in a season. However, the best time to knock out these scales is in the first generation or first emergence of crawlers. This usually happens in late May or early June and the settled crawlers and young nymphs are pretty susceptible to both contact insecticides, especially if mixed with a 2% horticultural oil, or a mobile systemic insecticide is used.

Scale Control (crawlers) Traditional Diazinon Dursban Sevin Orthene Dimethoate (nursery) DiSyston (disulfoton) Alternatives Tempo, Talstar, Deltagard, Scimitar, Astro Merit (soft scales) Meridian (landscapes), Flagship (nursery) Safari (armored & soft scales!) Arena & Aloft? Soaps & Oils X X

Notes: Traditionally, scale control was keyed on crawler sprays, whether you your dealing with a soft or armored scale. You can still use this technique if you are using Sevin, Orthene sprays, or one of the pyrethroids. The traditional systemics, dimethoate (for nurseries only) and disyston (as Bayer advanced rose systemic granules) can still be used, but we are now recommending the less toxic neonicotinoids for scale control. However, as with other insecticide categories, each of the neonicotinoids has its own spectrum of scales that are controlled. In short, imidacloprid (Merit) and thiamethoxam (Meridian and Flagship) have been pretty good at controlling soft scales but they have been relatively ineffective against armored scales. The best neonicotinoid for armored scale controls is Safari (which contains dinetrifuran). Arena and Aloft (a combination of clothianidin plus bifenthrin) also has excellent activity on soft scales, but we don’t have enough field experience to see how these will work on armored scales.

Emerald Ash Borer EAB adult and D-shaped emergence hole. Larvae look a bit like flat tapeworms! More information? –

Notes: I really don’t have time to adequately cover the emerald ash borer issue in Ohio. However, there are several important things that need to be covered. First, the state and federal government no longer have eradication programs in place. Homeowners still believe that if a tree is found to be infested that the “government” will come in and mow down all the ash trees in a half mile radius. This is no longer being done. Second, there are federal and state managed quarantines. The federal quarantines entire states and such quarantines regulate movement of ash logs and products between states. Ohio quarantines counties where EAB has been detected. This regulates movement of firewood or products between infested (quarantined) and non-infested counties. Both State and Federal quarantines have protocols and permit processes that can be followed to move ash logs and materials. Municipalities and property owners are basically on their own to manage EAB. There are plenty of controls that are known to be effective whether used by an individual or a commercial applicator. Most of this information is on our web site: ashalert.osu.edu

Notes: EAB has been found in many counties, mainly those that have major interstate roads that run from Michigan across Ohio. We believe that it is primarily human activities that is moving EAB to locations outside of the primary infestation zone. EAB is not unique among borers that attack trees. Remember that it is in the same genus as the bronze birch borer, the twolined chestnut borer and the honeylocust borer. We know how to control these other borers and the controls are essentially the same!

Borers – Agrilis species (bronze birch, twolined chestnut, honeylocust, hornbeam, emerald ash borers) Bronze birch borer

Notes: Most of the Agrilis borers have very similar life cycles with adults emerging in late May and laying eggs through June. The larvae burrow in the sapwood area during the summer and early fall. These larvae form prepupal and pupal cells under the bark of host trees in late fall but they don’t actually pupate until the next spring to emerge as adults for the next generation. All make D- shaped exit emergence holes as adults and most arborists and landscape care technicians are familiar with the controls used to manage native Agrilis borers. EAB is no different in its life cycle or reaction to these controls!

Borers Continue – White Pine Weevil – white pine & SPRUCE

Notes: Remember that even with all the emphasis on EAB, we still have other important borers that attack Ohio trees! The white pine weevil continues to attack pines and spruces over much of Ohio and this pest can severely damage the tops of infested trees. Systemic insecticides, applied in April into early May or even in the previous October into mid-November have been quite good at keeping the damage from this pest minimized.

Borers Continue – Bark Beetles – mainly conifers

Notes: When you ask the BugDoc what should be done about a bark beetle infestation, my normal response is, “How sharp is your chain saw?” In Ohio, most of the bark beetles that show up in our landscape conifers and deciduous trees are insects of opportunity. They generally don’t attack a tree unless the tree is under extreme stress, dying or DEAD! While the tree may still have some green, it is most likely dead! So, the first thing to do would be remove the infested tree and chip it before another generation of bark beetles can emerge from the trunk. Then check nearby trees of the same species to see if they are showing signs of stress. If they are, try to do things that would lessen the stress and consider preventive borer control techniques.

Borer Insecticides Traditional Dursban Lindane DiSyston (disulfoton) Dimethoate (nursery) Bidrin injection Orthene injection Alternatives Tempo, Talstar (Onyx), Deltagard, Scimitar, Astro Merit injection (beetles only!) Flagship? (nursery) Safari, Arena & Aloft, Meridian??? X X

Notes: We have had considerable changes in the insecticides that can be used for borer control. First, remember that there are two basic strategies for borer control: preventive surface exclusion (or what I call prophylactic) and preventive to early curative systemic control. The prophylactic control means that you spray the trunk and major branches with an insecticide that will form a protective layer on the bark which will kill any small insect that tries to chew through the insecticide barrier to get inside the tree. Systemic insecticides can be injected into the plant or into the soil but some can be simply mixed and poured at the base of the tree. The insecticide is picked up by the roots or vascular system of the plant to be translocated throughout the plant. In the past, we used Dursban and Lindane as prophylactic insecticides, but now we rely on the pyrethroids. Under systemics, we still have disyston, dimethoate (for nurseries only), orthene and bidrin (by trunk injection only). These insecticides knock out most of the borers. The neonicotinoids have all been very good systemics for control of beetle borers but the have been poor against lepidopterous borers, like the banded ash clearwing, peachtree borer and dogwood borer.

Honeylocust spider mites inhabit leaf undersurfaces. Oak mites inhabit the upper leaf surface. Maple spider mites – common on red and silver maples. Warm-season spider mites

Notes: Because of the dryer than normal conditions in 2007, we saw many of the summer, warm-season mites in our landscapes. The maple spider mite was especially noticeable on silver and red maples. We also saw quite a bit of activity from the honeylocust, oak and elm spider mites. The important thing to remember is that most of these host-specific species are easily controlled with most miticides. However, if you get an infestation of the twospotted spider mite which prefers winged euonymus, viburnum and perennials or bedding plants, you should be careful to not keep spraying the same miticide, especially if an earlier application didn’t work!

Miticides Traditional Kelthane Morestan Dimethoate (nursery) Orthene ? (injection, drenches only) Alternatives Avid (all mites!) Hexygon (eggs & larvae only, spider mites only) Floramite (spider mites only) Sanmite (spider mites only) Forbid (all mites!) Conserve Pyrethroids – NO!?? Soaps or Oils X X

Notes: We have a pretty extensive list of new miticides but we need to remember that several of these newer products ONLY kill true spider mites. So if you have hemlock rust mites or some other rust or eriophyid mite, these pesticides won’t help you. Only Avid and Forbid kill spider mites as well as eriophyid mites. These may be better choices where you might be spraying a variety of trees and shrubs for mite control.

Birch leafminer female laying egg. Extensive leafminer damage can leave a tree looking as if it has leaf scorch. Birch leafminer larva in mine.

Notes: We still have quite a variety of leafminers that can attack our urban landscape plants. Remember that most of these are sawflies (like the birch, hawthorn, and elm leafminers) or flies of some sort. This is important because most of the new neonicotinoid insecticides kill both of these kinds of insects. For the birch, hawthorn and elm leafminers, drenches or injections of neonicotinoids in October into mid-November or before leaf expansion in the spring can protect these plants for the entire season.

Holly leafminer damage. Two holly leafminer pupae in mines and old pinholes. Holly leafminer adult.

Notes: The holy leafminer is an example of a dipterous leafminer. This one is best controlled by applying a systemic insecticide when the adults are laying eggs. The target is actually the newly hatched larvae that feed in late May and into early June. Applications made once the mines are over half enlarged usually result in poor control.

Boxwood Leafminer

Notes: Over the last few years, we’ve seen more activity from the boxwood leafminer. This species prefers standard boxwood cultivars and it is a midge or another dipterous leafminer. The key to control this one is to target the young larvae that mine the new leaves. Spring applications should be made just as the new leaves and shoots are beginning to emerge and expand. You won’t kill the previous generation nor stop drop of last year’s damaged leaves, but this application will protect the new leaves.

Leafminer Insecticides Traditional Dursban Lindane Dimethoate (nursery) DiSyston Orthene Neem (azadirachtin) Still/Now Available Pyrethroids (permethrin, resmethrin, esfenvalerate, bifenthrin, cyfluthrin) Merit, Flagship, Arena & Aloft, Safari Conserve ? X X

Notes: As with borers, leafminer control has generally been achieved by using a prophylactic treatment to kill the adults or using a systemic insecticide to kill any larvae that is mining a leaf. Unfortunately, prophylactic treatments are rarely effective because the adults of many of these leafminers are out for a short period of time and this time may vary from year to year depending on the weather conditions. The pyrethroids are used as prophylactic controls. The rest of the listed insecticides are systemic in action but most have a limited number of pests that they control. The neonicotinoids (Merit, Flagship, Meridian, Arena and Aloft) are good at controlling sawfly, dipterous and beetle leafminers. Orthene, neem and conserve also have activity against some of the moth leafminers.