Spring and eastern tent caterpillars are a month early

Eastern tent caterpillars in the second week of March 2017. Photo: SDF

Last week I went looking for small new nests in hopes I could find eastern tent caterpillars just as they hatched. What I found were large nests with large caterpillars. March is pretty early for eastern tent caterpillars in Raleigh. This is a result of the warmer than ‘normal’ spring we have had. Based on State Climate Office Growing degree day calculator Raleigh (RDU airport) has accumulated 346 GDD (base 50F) so far in 2017. This is not so different than the 316 GDD accumulated by March 27 in 2016. However, it is almost threes times as many as in 2015 (150 GDD), 2014 (92 GDD), and 2013 (108 GDD).


In 2013 and 2014 we did not reach similar GDD until the third week in April putting us almost a month ahead this year. Interestingly, this matches when Google indicates that most people are looking for information about eastern tent caterpillars. According to Google Trends, ‘eastern tent caterpillar’ as a topic in the Raleigh area has peaked in mid-April (e.g. April 6-12, 2014; April 19-May 9, 2015) each year since 2012. This year we already see a peak March 19-25.

Eastern tent caterpillar

Such large changes in insect phenology is important for many reasons. In some cases phenology of mutualists like pollinators may become unsynchronized. In other cases, predators and prey or parasitoid and host phenology may become unsynchronized leading to loss of biological control. Not many people probably care about eastern tent worm prosperity or that of other pests like cankerworms. However, if these critters hatch before their host plants develop leaves they starve. This means migrating birds and other animals people do care about, and that rely on spring caterpillars for food, also suffer.

Of course monitoring and predicting pest activity is an important part of IPM for caterpillars and other pests. The more pest development varies from year to year, or even from warm to cool spots in a city, the harder IPM becomes. Your state probably has a State Climate Office with a growing degree day calculator. As phenology gets more variable, using these tools rather than relying on previous years to implement IPM tactics will be essential.

March 29th, 2017|Categories: Feature, Landscape IPM|Tags: |

Maple Shoot Borers Damaging Maples in Nurseries

This is a guest post by our PhD student Larry Long.

MSB Flagging (Long)

Flagging of apical shoot and frass expelled from larvae developing inside the stem and beneath the lateral leaves. Photo Credit: Larry Long, NCSU

Maple shoot borers (Proteoteras aesculana) are common pests of red maples in nurseries. This caterpillar causes flagging and dieback of the apical shoots of maples (Acer spp.). It is too late this season to manage this pest or damage with insecticides but recognizing the damage could inform your management next spring. Maple shoot borer adults are small nondescript moths that lay eggs on maple stems near expanding buds in early spring. After hatching the caterpillar burrows into the growing shoot where it feeds on the vascular cambium. As the larvae develops it expels frass and silk from the hole through which it entered the stem. Young stems and leaves above the point where the larvae entered eventually die.

Mature larvae exit the shoot then pupating on the ground. There is no evidence of summer season egg laying so it is thought that upon emergence from their pupae the new moths seek overwintering sites.

Monitoring for damage by this pest is not very useful because by the time damage occurs management is impractical. However, if a high proportion of plants are infested this year it could warrant preventive insecticide applications next spring. To confirm that damage is from maple shoot borers and not another pest like potato leafhoppers, cut open flagging stems to see if they are hollow and if larvae are present. The larvae are a tan to cream-colored with a dark head capsule.

Dissected maple stem showing larvae living inside. Photo Credit: Matt Bertone, NCSU

Dissected maple stem showing larvae living inside. Photo Credit: Matt Bertone, NCSU

Preventive management entails applying pyrethroid insecticide from just before bud break until shoots have flushed their first two pairs of lateral leaves. Since this is in early spring you may be making these applications anyway for ambrosia beetle management so there is no need to spray extra just for maple shoot borer. Preventive applications are important because once symptoms appear it is too late for treatment. Damaged shoots should be pruned and a new leader trained to correct tree form.

Dieback or ‘flagging’ caused by maple shoot borer. Photo Credit: Larry Long, NCSU

Dieback or ‘flagging’ caused by maple shoot borer. Photo Credit: Larry Long, NCSU

See our guides for IPM of of trees and shrubs in nurseries on our extension resources page.

May 13th, 2016|Categories: Nursery IPM|Tags: , , |

Happy moths, very sad squash

This is a guest post by Annemarie Nagle

I planted yellow crookneck squash this year as an afterthought, after coming across a half-full packet of seeds and pushing last year’s disappointing crop out of mind in a hopeful bout of springtime enthusiasm.

wilty_squash_smallBy June those babies had grown big, lush and beautiful, and friends stopping by remarked on how great the garden was looking. A couple of weeks later and now those giant squash plants are looking more like an embodiment of how I feel after working in the NC heat for a few hours: pretty wilty.

The nemesis at work in my garden is an insect that will be familiar to aspiring squash (and zucchini and pumpkin) growers from Canada to Argentina. Melittia cucurbitae, the squash vine borer, and its host plants in the genus Cucurbita are native to North and South America. In fact, along with maize and beans, squash were cultivated by the Native Americans as one of the ‘Three Sisters’ that provided the agricultural staples for many tribes.

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Wet, brownish frass volcanoes coming out of your squash vines are a sure sign there are borers inside. Photo: A.M. Nagle

M. cucurbitae adults are beautiful orange and black clearwing moths. They fly during the day (most moths are active at night) and are often mistaken for wasps when encountered in the garden. They lay their eggs along the base, stems, and leaves of squash plants, and the larvae burrow into the stem immediately upon hatching. They set up shop and feed for several weeks through the center of the stem, eventually cutting off water flow to the rest of the plant: thus, the wilting.

The fact that I grew yellow squash in my garden last year (and lost them to borers) didn’t do this year’s plants any favors either. The mature caterpillars, which at this point in the year look like chunky, inch-long grubs with amber heads, chew their way out of the stem and drop into the soil, where they will bury themselves a few inches deep and pupate. There are two generations per year in NC, so the first generation will re-emerge as adults in a few weeks to polish off whatever plants they didn’t get the first time (or any new ones you’ve been hopeful enough to plant). The second generation will overwinter in the soil as larvae or pupae encased in cocoons and will emerge come spring.

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Part of the vine removed to reveal the nearly full-grown caterpillar within. Photo: A.M. Nagle

If you are a more dedicated gardener than I am (I’m a plant pathologist, and better at killing plants than keeping them alive…), there are several measures you can take to protect your squash plants from borers. Lightly tilling the soil in late winter can expose the overwintering pupae to the elements. Also, be sure to destroy squash plants when they are done producing to prevent any borers inside from developing, and rotate locations or years for growing squash. For vining varieties such as pumpkins, which can grow new roots at each node, burying portions of the stem encourages the growth of extra roots that can help portions of the plant survive, even when other portions are eventually attacked.

Keep an eye on your squash for the first signs of borer attack: the presence of eggs, then pin holes and brownish, wet frass accumulating at the base. You can ‘deworm’ your vines by making lengthwise slits in the vine near these holes and killing the larvae inside with a knife or pin. Pile an inch or so of soil or compost around the cut to prevent the vine from drying out and encourage rooting.

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M. cucurbitae adult hanging around my cucumber vines. Photo: A.M. Nagle

Insecticide treatments can prevent hatching caterpillars from burrowing into the stem, but are ineffective if you miss this window, so careful monitoring of adult moth activity is important. Adults are attracted to yellow (think squash flowers) and you can monitor when they become active in your garden by placing out a yellow bowl filled with soapy water in late May. Also bear in mind that squash depend on beneficial insects—bees—for pollination, so insecticides should not be applied to flowering plants.

There are some Cucurbita varieties that seem to be less preferred by the borers, particularly those derived from C. moschata, including butternut squash and some types of pumpkin. I’m thinking perhaps a packet of butternut seeds should be waiting for me next year when planting fever hits.

August 12th, 2015|Categories: Landscape IPM, Natural History and Scientific Adventures|Tags: , , |

Mimosa webworms are building new webs

Mimosa webworms are active in Raleigh. I saw initial webbing this week. These are annual pests of mimosa trees which many people consider pests in their own right. However, if you are you of the many folks who love mimosa trees sans messy caterpillar webbing then it is time for action. The best way to prevent heavy infestations and extensive webbing is to prune out the nest when they are small. Moths overwinter as pupae attached to tree trunks, buildings, or other sheltered locations. The adults emerge in June or so to lay eggs on mimosa and honey locust trees. Caterpillars feed within the webbing for several weeks before pupating. There are multiple generations per year.

New mimosa webworm nest. Photo: SD Frank

New mimosa webworm nest. Photo: SD Frank

Several fact sheets from Penn State, Purdue, Ohio State, and can provide detailed life history information. BugGuide has some great pictures of the adults which are rarely seen. Most insecticides available for caterpillar control will also control mimosa webworm but remember that contact is difficult since they live in waterproof webs. In most cases mimosa webworms will not reduce the health or growth of their rapidly growing hosts. They also don’t seem to eat all the seedlings that pop up all over my yard from the tree next door.

Mimosa webworm. Photo: SD Frank

Mimosa webworm. Photo: SD Frank

June 30th, 2015|Categories: Landscape IPM, Urban Ecology|Tags: , , |

Exotic caterpillar is a greenhouse pest in Canada – keep your eyes open

Golden twin-spot moth. Perry Hampson, Bugwood.org

Golden twin-spot moth. Perry Hampson, Bugwood.org

An exotic caterpillar called the golden twin-spot moth, Chrysodeixis chalcites, is present in some Canadian greenhouses. It is a tropical species but can of course overwinter in greenhouses throughout the world. It feeds on many plant species including tomatoes, cucumbers, and peppers. It is not confirmed in the US so don’t panic just read up on the biology and identification and keep alert.

Golden twin-spot moth larva. Steve Hatch, Bugwood.org

Golden twin-spot moth larva. Steve Hatch, Bugwood.org

May 8th, 2015|Categories: Greenhouse IPM|Tags: , , |

Eastern tent caterpillars setting up camp

Young eastern tent caterpillar on a cherry branch. Photo: SD Frank

Young eastern tent caterpillar on a cherry branch. Photo: SD Frank

Yesterday I found young eastern tent caterpillars building a tent. They seem a little late this year but we’ve had a cool spring. Last year by April 10 I saw large tents full of caterpillars. The young caterpillar above does not have the characteristic colors and pattern of more mature caterpillars.

You have probably noticed eastern tent caterpillars infest the same trees year after year. This is probably because the caterpillars pupate in protected areas, like wood piles or under bark, near the tree where they hatched. They prefer cherry and apple trees so when the female moths emerge in early summer they find the same trees.

The moths lay a couple hundred eggs in early summer on thin branches.

Eastern tent caterpillar (Malacosoma americanum ) egg mass. Photo: Robert L. Anderson, USDA Forest Service

Eastern tent caterpillar (Malacosoma americanum ) egg mass. Photo: Robert L. Anderson, USDA Forest Service

The egg masses look like dried foam. When trees don’t have leaves you can often look up and see them on the branches. If you prune off the egg masses in fall or winter you won’t have caterpillars the next spring.

Eastern tent caterpillars can defoliate large areas of a tree canopy. However, this usually does not cause long term harm. In some cases the crotch of trees, where nests were, can become darkened or slightly rough or disfigured. Prune or poke the nests to remove or disrupt them. More management information is here. Some relatively new insecticides for caterpillars include XXpire, Provaunt, and Acelepryn.

April 6th, 2015|Categories: Landscape IPM|Tags: , , |

Orange-striped oakworms make yearly appearance

This is a quick field note by PhD student Emily Meineke.

For the last few weeks, orange striped oakworms have been raining on my head as I work in the trees. They also drop a lot of poop (entomologists call it frass) which is one of the major complaints by homeowners.

Large oakworms eat entire leaves except for the mid vein. Photo: EK Meineke

Large oakworms eat entire leaves except for the mid vein. Photo: EK Meineke

Orange-striped oakworms congregate on branches to feed every year in late summer but usually do not cause enough damage to warrant treatment.

Young oak worms cause damage called 'window panning' in which they eat the surface of leaves and feed between tiny veins. Photo: EK Meineke.

Young oak worms cause damage called ‘window panning’ in which they eat the surface of leaves and feed between tiny veins. Photo: EK Meineke.

Young orangestriped oakworms are often light in color and darken as they get older. I have found some parasitized individuals, which means natural enemies are doing their part to reduce oakworm outbreaks. Caterpillars also make great food for birds. We have posted previously about orange-striped oak worm biology and management if you want more information.

Large caterpillar poops around the base of a tree. Photo: SD Frank

Large caterpillar poops around the base of a tree. Photo: SD Frank

August 26th, 2014|Categories: Landscape IPM, Natural History and Scientific Adventures, Nursery IPM, Urban Ecology|Tags: , |

Azalea caterpillars hatching

Newly hatched azalea caterpillars. Notice white eggs on the leaves in the background. Photo: SD Frank

Newly hatched azalea caterpillars. Notice white eggs on the leaves in the background. Photo: SD Frank

Yesterday I found the first azalea caterpillars of the year. These tiny caterpillars had just hatched from the white eggs you see in the background. You can scout for these bright eggs in August before the caterpillars hatch and remove them. I think these caterpillars are worth having though since they are very beautiful. Actually the caterpillars are prettier than azaleas tend to be this time of year and they will eat all the leaves stippled by lace bugs! You can read more about these caterpillars that feed on azaleas and blueberries in a post from last August.

August 26th, 2014|Categories: Landscape IPM, Nursery IPM|Tags: , , , |

SAVE THE DATE: LARVAE EXPECTED

This guest blog post is from four of our amazing undergraduate (or just-graduated!) Frank Lab Summer Employees: Nicole Bissonette (Zoology ‘15), Laura Daly (Horticulture ‘14), Karly Dugan (Animal Science ‘15) and Danielle Schmidt (Zoology ‘15). This blog is proof that even non-entomology majors can fall madly in love with bugs.

The expectant MOTHers in the Frank Lab.

The expectant MOTHers in the Frank Lab.

Rescued imperial moth

Rescued imperial moth

Once upon a lunch break, the four of us discovered a moth frantically flapping its wings beneath a Southern Magnolia, unable to fly. We were concerned as she struggled to crawl up the tree and decided to bring her back to the Frank lab. Since our fellow coworkers were out in the field conducting research, we had to put on our entomology caps. After some intense googling, we discovered our lovely, large friend was an Imperial Moth.

Going off our immensely extravagant base of insect knowledge (#sarcasm, #non-entomology majors), our observations lead us to believe that she was pregnant, not relieving herself as we had originally thought. Once brought into the lab, we noticed she stopped laying eggs, since she was probably getting cold due to the air conditioning. So, we relocated her to the balcony outside in the sun. Once warm, her ovipositor picked up speed, and was dropping eggs like ‘dey were hawt.’ We decided to let her lay eggs all night in this plastic container as per suggestions on several other blogs.

Imperial moth eggs.

Imperial moth eggs.

When we came into the lab the next morning, she had laid over 50 eggs! We have decided we are going to raise them as our own and document our experience. Save the date, cross your fingers, and check back for updates on our “MOTHerhood” duties!

August 12th, 2014|Categories: Lab Happenings, Natural History and Scientific Adventures|Tags: , |

Mimosa webworm

Small web in a mimosa tree. Photo: SD Frank

Small web in a mimosa tree. Photo: SD Frank

Mimosa webworms are active in Raleigh. I saw initial webbing just a week or so ago but now they are in full swing. These are annual pests of mimosa trees which many people consider pests in their own right. However, if you are you of the many folks who love mimosa trees sans messy caterpillar webbing then it is time for action. The best way to prevent heavy infestations and extensive webbing is to prune out the nest when they are small. Moths overwinter as pupae attached to tree trunks, buildings, or other sheltered locations. The adults emerge in June or so to lay eggs on mimosa and honey locust trees. Caterpillars feed within the webbing for several weeks before pupating. There are multiple generations per year. Most insecticides available for caterpillar control will also control mimosa webworm but remember that contact is difficult since they live in waterproof webs. In most cases mimosa webworms will not reduce the health or growth of their rapidly growing hosts. They also don’t seem to eat all the seedlings that pop up all over my yard from the tree next door. http://www.ces.ncsu.edu/depts/ent/notes/O&T/shrubs/note07/note07.html

Mimosa webworm. Photo: SD Frank

Mimosa webworm. Photo: SD Frank

July 8th, 2014|Categories: Landscape IPM, Urban Ecology|Tags: , , |