Reduced risk insecticides & chilli thrips

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Chilli thrips, Scirtothrips dorsalis. Photo credit: Lance Osborne, UF/IFAS

Insecticides are often the most effective and rapid method for reducing damaging insect pests. This is particularly true for many invasive pests who have escaped their natural predators and parasitoids. Several of the most commonly used insecticides, like pyrethroids, provide broad-spectrum control of insects within a relatively short period of time. This means that homeowners can rapidly reduce pests to protect their favorite rose cultivars or pest control professionals can provide speedy relief of pests for their clientele. Unfortunately, these broad-spectrum insecticides are frequently associated with non-target effects like killing off predatory or parasitic insects, which leads to additional pest problems and plant damage.

Other more selective insecticides, like neonicotinoids, can provide longer-term control of insect pests by penetrating plant vascular tissue and persisting within plant content for several weeks. These products are safer for non-target organisms like the predatory mites or parasitoid wasps because they become concentrated within plant tissue where these biological control organisms are rarely feeding. However, they also have limitations because of known threats to non-target organisms like pollinators or predatory insects.

Fortunately, increasingly more synthetic insecticides classified as reduced risk pesticides are becoming commercially available. The U.S. Environmental Protection Agency (EPA) classifies pesticides as reduced risk based on five primary criteria:
1. Low non-target toxicity to people and wildlife
2. Low potential for groundwater contamination
3. Low use rates
4. Low likelihood of pests developing resistance
5. General compatibility with IPM programs

A recent study led by UF/IFAS Entomology & Nematology MS graduate student and Doctor of Plant Medicine student, Matt Borden, investigated the potential of new reduced risk insecticides for their control of an important exotic pest of ornamental plants. Specifically, he tested a relatively new chemistry available to the turf and ornamental industry, cyantraniliprole (trade name: Mainspring), for its control of Chilli thrips (Scirtothrips dorsalis), which is a damaging and difficult to control insect pest of over 100 plant species (most commonly Indian hawthorn and roses in Florida landscapes). These insects feed on newly expanding leaves and cause severe scarring, leaf distortion, and defoliation (see below).

Matt tested two reduced risk insecticides, spinosad (trade name: Conserve) and cyantraniliprole (trade name: Mainspring), against a product containing pyrethroids and a neonicotinoid to measure their effect on chilli thrips and one of their primary predators, Orius insidiosus.

In line with our expectations of reduced risk insecticides, Matt found that both spinosad and cyantraniliprole had minimal effects on the predatory insect. Importantly, Matt also found that both reduced risk products have benefits in terms of chilli thrips control. Spinosad provides rapid control of active chilli thrips populations, but not long term plant protection. Cyantraniliprole provided six weeks of plant protection from chilli thrips damage to Indian hawthorn shrubs, but did not cause rapid toxicity to chilli thrips in laboratory experiments.

Therefore, these results suggest that spinosad provides a safe, rapid reduction in chilli thrips, which can be followed up with a cyantraniliprole application to protect plants from chilli thrips that try to re-establish and cause damage.

To learn more, read the full article here: http://www.bioone.org/doi/pdf/10.1653/024.101.0213

Tunneling in your turf? Watch for mole crickets!

This is a blog post by Doctor of Plant Medicine student, Matt Borden.

Picture 1 - Three invasive mole crickets

The three introduced species of mole crickets. Left: shortwinged mole cricket. Center: tawny mole cricket. Right: southern mole cricket. Credit: W. C. Adlerz, University of Florida.

It’s that time of year! Mole crickets are adults again. During the summer months, juvenile mole crickets are busy feeding and growing larger. During the autumn, many of these insects will develop into hungry adults, which can cause substantial injury to turf.

At night, adult mole crickets fly from site to site in search of mates, while adults and nymphs also burrow through the soil, feeding on roots and tubers. This disturbance and activity is typically most apparent and severe after warm and rainy weather. Narrow, raised tunnels just below the surface are a sure sign that southern or tawny mole crickets are present. These exotic insects will feed on any turfgrass, but bahiagrass and bermudagrass are most susceptible, followed by St. Augustinegrass. During the late fall and throughout spring, moist soils and lights attract adults. You can make your lawn less appealing by keeping the yard dark and not irrigating in the evening.
To learn more about the life cycle, damage, and management of mole crickets in Florida, visit the Featured Creatures page (link to https://entnemdept.ifas.ufl.edu/creatures/orn/turf/pest_mole_crickets.htm), or view and download the factsheet as EDIS Publication #EENY-235 (link to http://edis.ifas.ufl.edu/in391).

Natural enemies of mole crickets

Picture 2 - Larra bicolor male on Spermacoce-Buss

Larra bicolor is an important natural enemy of introduced mole crickets. By planting more wildflowers, such as this shrubby false buttonwood, you can help support these wasps and attract more of these valuable insects to your property. Credit: Lyle Buss, University of Florida

After midsummer, using insecticide is generally not an effective or economic management approach. Luckily, there are a couple of natural enemies that can help reduce mole cricket numbers. The larra wasp, Larra bicolor, is an attractive insect with dark wings and a red abdomen. Attracting more of them to your property will aid in long-term mole cricket control because the eggs they lay on mole crickets hatch into larvae that consume the mole cricket. Plant shrubby false buttonweed (Spermacoce verticillata) to provide Larra wasps with an excellent nectar source throughout the autumn. A beautiful native wildflower species that is also attractive to this beneficial insect is blue mistflower (Conoclinium coelestinum).These wasps are solitary (without a large nest to protect) and do not sting humans. If you would like to learn more about Larra wasps, visit the Featured Creatures page.

Larra wasps aren’t the only natural enemy that was introduced to Florida to control these invasive pests. The insect-parasitic nematode, Steinernema scapterisci, was commercially produced and applied to pastures, golf courses, and sod farms for several years. However, this ceased around 2012 and the current status of these biological control organisms and their impact on exotic mole crickets is unknown. Our post-doctoral researcher, Pablo Allen, is currently conducting research to determine if these nematodes are widely established in Florida and what effect they have had on invasive mole cricket populations.

Time-lapse video of insect-parasitic nematodes emerging from a southern mole cricket. Credit: Adam Dale

Urban warming and drought stress – good news for scale insect pests

Have you ever seen tiny, bark-colored bumps all over the trunk or branches of a tree? In a forest? What about in a parking lot or along a roadside? Maybe you haven’t looked, but if you do, the latter of the two locations is where you’ll strike gold.

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Gloomy scale-infested red maple branch. Photo: A.G. Dale

These tiny bumps are scale insects, sap-feeding pests that drain plants of their nutrient reserves. Scale insects are rarely abundant or damaging in rural or natural landscapes, but are drastically more abundant in cities, which reduces the condition and services provided by our most common urban trees.

The scale insect we are particularly interested in is the gloomy scale, Melanaspis tenebricosa. This insect is drastically more abundant on urban red maple (Acer rubrum) trees than those in natural forests. Maples are the most common urban landscape tree in the eastern U.S.

Recent research from my lab and my colleague’s lab at NC State University demonstrates that scale insect phenomenon is due to a combination of factors. Cities are warmer – called urban heat islands – because they are covered in paved surfaces like roads, parking lots, and buildings. Not only does that make them warmer, but it also reduces the amount of water that gets to tree roots. Heat + less water = drought stress.

Previous research has found that drought stress benefits plant-feeding insects by helping them reproduce more and develop more quickly. Separate research from my lab has demonstrated that urban heat directly benefits scale insect pests in a similar fashion. However, until now no study has investigated how drought and heat interact to affect insect pests feeding on established urban trees.

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Irrigation bag on red maple. Photo: A.G. Dale

We tested this interaction over two years by loading up a 300-gallon water tank and driving it all over the city of Raleigh, NC to water established red maple street trees that were infested with gloomy scale. We did this twice a week for two years, and at the end, collected dozens of adult female gloomy scales from each tree. We dissected these females from irrigated and non-irrigated trees and counted the number of embryos that were developing inside of them.

It turns out that gloomy scales produce significantly more offspring as temperatures warm (as previous evidence suggested), but more importantly, that gloomy scales on drought stressed trees produce significantly more offspring than those on watered trees. Not only do heat and drought stress matter individually, but they combine to additively benefit these urban tree pests!

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Gloomy scale egg cells and embryos. Photo: A.G. Dale

Managing scale insects typically relies on insecticides, which is difficult, expensive, and often unsuccessful. Therefore, effective cultural practices that prevent scale insect infestations and damage are the best approach. We have begun to chip away at this by developing impervious surface thresholds that can guide urban tree planting decisions. However, we can’t remove and replant tens of thousands of red maples already in our urban landscapes. This most recent study suggests that irrigating already-planted red maple trees can mitigate the negative effects of heat and drought by reducing the number of offspring these scale insects produce.

As cities continue to grow and the climate continues to warm, factors like heat and drought will become more prevalent and severe for urban trees. Therefore, addressing these issues by making more informed urban tree management decisions is critical to developing more economically and environmentally sustainable urban landscapes.

This article is published in the journal PLoS One. Find the entire article here: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0173844

Also, a UF press release can be found here: http://news.ifas.ufl.edu/2017/03/gloom-and-doom-when-these-insects-are-on-hot-dry-red-maple-trees/

UF/IFAS blog post on golf course wildflower project

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We recently planted wildflower seeds on multiple golf courses in the area. UF/IFAS communications picked up the story and wrote a press release and blog post about the project. Check them out below:

http://blogs.ifas.ufl.edu/global/2016/11/02/ufifas-researcher-hopes-bolster-pollinators-reduce-water-use-inputs-golf-courses/

UF/IFAS researcher hopes to bolster pollinators, reduce water use, other inputs on golf courses

UF/IFAS Blog Post on Cicada Killers

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Cicada killer female. Photo: Lyle Buss, UF

Research Assistant, Lauren Webb, recently published a blog post on the UF/IFAS blog about cicada killer wasps. These wasps are both a pest and a beneficial insect, and are pretty amazing hunters. To learn more about them, read the post here: http://blogs.ifas.ufl.edu/entnemdept/2016/08/26/giant-wasp/.

Check out a video of a female in action here: https://twitter.com/adamGdale/status/762048360207544320

Impervious surfaces are hard on urban trees, but how much is too much?

cropped-cropped-dsc_0416.jpgImpervious surfaces in the form of roads, parking lots, and buildings can make things warmer, drier, and all-around more stressful for trees planted in them. It can also increase insect pest abundance.

My colleagues and I recently published a paper about how to mitigate the effects of these stressful urban conditions on trees. Below is a link to a blog post written by my collaborator, Steve Frank, at NC State University.

http://ecoipm.org/2016/05/17/impervious-surface-cover-is-bad-for-trees-how-much-is-too-much/

To learn more, read the paper here or visit the extension page to find short documents that summarize our results.

Neonicotinoid update

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Honey bee visiting flowers on an Indian hawthorn shrub. Photo: AG Dale

Ortho, an over-the-counter insecticide brand that many of us know well, has announced that they will be taking all outdoor neonicotinoid products out of their production line. Neonicotinoid active ingredients include: Dinotefuran, imidicloprid, acetamiprid, thiamethoxam, and clothianidin.

51puPpwWg6L._AC_UL320_SR208,320_Ortho Tree & Shrub Insect Control contains dinotefuran.

This is one of the most recent developments in the issues surrounding pollinators and neonicotinoids. Ortho has already begun the process and plans to phase out all outdoor neonic products by 2021. For a more complete story, visit the link below: http://www.npr.org/sections/thesalt/2016/04/12/473953151/home-and-garden-giant-ditches-class-of-pesticides-that-may-harm-bees

Also this week, Michigan State University, in collaboration with the University of Maryland and Ohio State University, published an extension document outlining many of the challenges associated with pesticides and pollinators. It contains information specific to the North Central United States, but has useful pesticide information relevant to Florida pest managers. Check it out here: http://msue.anr.msu.edu/resources/how_to_protect_and_increase_pollinators_in_your_landscape

Tuliptree scale enjoying this weather

I was outside of Orlando today at the UF/IFAS Mid Florida Research and Education Center. As I was walking through a landscape, I noticed several ants actively crawling over the branches and leaves of a southern magnolia tree. This caught my attention and upon closer inspection, I found a pretty large population of tuliptree scale, Toumeyella liriodendri.

The tuliptree scale was first documented in the late 1700s on yellow poplar but didn’t garner attention until the the early-to-mid 1900s, as a significant pest of yellow poplar timber production. This insect is native to eastern North America throughout the range of yellow poplar, but is also found in California on ornamental plantings. Tuliptree scale has been reported to feed on a variety of plants in Florida, including magnolia, buttonbush, cape jasmine, and loblolly-bay.

These insects have one generation per year throughout most of their range, but have been found in all life stages during the winter in Florida. The population I stumbled upon today overwintered as nymphs, which have begun actively feeding and will become adults in early summer. Once adults, the females will move to the bark and begin to produce up to 3600 eggs per individual. As you might imagine, populations can build up quickly.

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Tuliptree scale adult females     Photo: J.S. Castner UF/IFAS

As the weather warms, nymphs begin to feed more actively. This pest is a soft scale insect, which means it extracts sap from the tree and excretes honeydew as waste (unlike armored scales). Over time, this honeydew accumulates on surfaces beneath the infestation, which makes it sticky and facilitates growth of black sooty mold. Sooty mold is both unsightly and reduces the plant’s ability to grow. In addition to sooty mold, severe scale infestations can cause branch dieback, sparse foliage, and potentially death.

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Sootymold from tuliptree scale infestation     Photo: J.S. Castner UF/IFAS

Tuliptree scale has several natural enemies including: Lady beetles, parasitoid wasps, a predaceous moth larva, and a syrphid fly larva. In nature, this team of natural enemies usually keeps this scale below damaging levels. However, most urban landscapes are far from natural, which mixes things up, although it doesn’t mean they are out of the picture.

Another factor that mixes things up are ants. The honeydew that these scales excrete is a tasty treat rich in sugars for many ant species. In fact, over 10 species of ants have been found tending to tuliptree scales for their honeydew. In turn, the ants protect the scales from predators like lady beetles, lacewings, and flies. This symbiosis is great for the scales and ants but can be a pain for landscape managers.

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Ants tending to tuliptree scale nymphs on the underside of magnolia leaves     Photo: A.G. Dale

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Several magnolia leaves heavily infested with tuliptree scale being tended to by ants     Photo: A.G. Dale

When scouting your landscape plants, keep an eye out for active ant populations and sooty mold growth because it may indicate that scales are hanging out nearby. Managing scale insects is requires monitoring, persistence, and proper timing. Now (the nymphal stage) is a good time to target these scales because they are smaller and more susceptible to control than the adult life stage. Horticultural oils can be effective with repeated treatments and full coverage of the infested plant material. Systemic or translaminar products can also reduce populations and get ingested while the insect is feeding. Keep non-target effects of applying these products in mind as they relate to your IPM program. Are your other management strategies compatible with the product(s) you choose? As always, read the product label and follow it. I hope to have an up-to-date Florida scale insect management guide available in the near future.

Here is a short video I took of the ants tending the tuliptree scales: https://youtu.be/G3AidoVXTFI

 

 

Is your cycad turning yellow? Or white?

I recently moved into a new home in Florida. The first day, I walked outside and noticed that the relatively large cycad in my front yard was covered in scale insects.

I went back to check them out yesterday and it turns out it is in much worse shape than I originally thought. The undersides of the leaves are completely white with scale insects. Upon closer look, I determined they are cycad aulacaspis scale, Aulacaspis yasumatsui.

This armored scale insect, native to Thailand, is a major insect pest of cycads in Florida. These insects were introduced to Florida in 1996 and have since become an established pest of cycads throughout the state. Leaves of cycads with heavy infestations begin to yellow, brown, and eventually die. In the photo below, I lined up branches in order from least to most damaged to illustrate the progression of yellowing to death.

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Progression of scale feeding damage on cycad leaves (left to right) Photo: A.G. Dale

You may also notice some black patches on the surface of the leaves. This is sooty mold, which suggests there is another insect pest getting in on the action. Armored scale insects (like the cycad aulacaspis scale) do not excrete honeydew, which facilitates the growth of sooty mold. Insects like aphids, whiteflies, mealybugs, and soft scale insects do secrete honeydew. Upon closer inspection, I found some soft scale insects and a mealybug feeding amongst the A. yasumatsui. Double the trouble for my cycad.

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A lone mealybug contributing to the sooty mold growth  Photo: A.G. Dale

Managing scale insects can be tricky and requires persistence and patience. Regularly inspect your plants so that infestations don’t get to the level of the cycad in my yard. Check the undersides of leaves for scales, but be careful because the leaves of some cycad species will draw blood.

Keep an eye out for evidence of biological control. In 1998, two natural enemies were introduced to Florida to control this pest, a predacious beetle (Cybocephalus binotatus) and a parasitoid wasp (Coccobius fulvus). These natural enemies provide moderate control but have not prevented the spread of this scale. I did find a lone lady beetle larva snacking on the scales, but it was severely outnumbered. If scale insect populations are low enough, these beneficials may be enough. However, they may need assistance if populations become too extreme.

DSC_0439Comparison of a heavily scale-infested leaf (top) to a relatively clean leaf (bottom)        Photo: A.G. Dale

If you need to treat your plants, horticultural oils have shown good control with little impact on the natural enemy community. However, you’ve got to make applications pretty frequently. Some people have reported good control with high pressure water sprays to wash off the insects. Other systemic products may provide control but results are mixed.  The trick to good control when making foliar applications is good coverage. Make sure you’re spraying underneath the foliage where the insects are hiding. If your plant is as heavily infested as mine, pruning the most heavily-infested leaves off and disposing of them before spraying may be the best remedy. Keep in mind this adds stress to the plant. For more information on the biology and management of cycad aulacaspis scale, see the links below.

http://organiclabs.com/Research/Organocide/Update%20on%20Management%20Methods%20for%20Cycad%20Aulacaspis%20Scale1.pdf

http://entnemdept.ufl.edu/creatures/orn/palms/cycad_scale.htm

http://trec.ifas.ufl.edu/mannion/pdfs/CycadScale.pdf

http://edis.ifas.ufl.edu/in253