Leaftier and Leaf Roller Caterpillars

by Andrea Laine, EMGV

I recently learned about leaftiers and leaf rollers. These plant pests may be confused with one another as at first glance the damage they do to leaves looks similar.

This was a scene on my Hydrangea paniculata ‘Limelight’ in early May (see photo below). A tiny creature was cocooned on the leaves where a flower would hopefully form later this summer. Surrounding the creature the leaves were crinkly and curled in a deformed way as were leaves at the tips of other flower stems. I instinctively snipped the stem tip to minimize damage to the plant and get a closer look.

Photo by Andrea Laine

I had a hunch that the creature was the pupa of an insect. But what insect and how much damage could it potentially wreak to my, otherwise healthy, hydrangea? I was curious enough to research further; and it was a good time to re-educate myself about insect lifecycle.

Insects look different in each stage of their development. Typically, there are four stages: egg, larva, pupa, adult. The process by which insects move from stage to stage is called metamorphosis.  Most of us know that the butterflies (adult stage) we admire in our garden were once caterpillars (larva stage). We are probably less familiar with recognizing insect eggs and pupa. I know I am.

“My” pupa is likely a developing moth (insect order Lepidoptera). I believe this because of the way in which it wrapped itself in the leaves at the branch tip of the hydrangea. For protection while they morph from pupa into adults, moth larvae, i.e. moth caterpillars, spin cocoons or silky webs (behavior indicative of leaftier caterpillars), while others roll a leaf around their bodies (leaf rollers). The caterpillar feeds on the developing flower bud and leaf surfaces within their reach. The damage may be unattractive and limit bloom, but it will not kill the host plant.

Hydrangea leaftier caterpillar (Olethreutes ferriferana ) has a distinctive appearance: long green body and brown head. There are as many types of leaftiers and leafrollers as there are plants to pester. Photo credit: University of Illinois Extension.

By the time I took note of the distorted leaves on my hydrangea the moth had advanced to the pupa stage and ceased feeding. According to Durham County Agriculture Agent Ashley Troth, leaftier caterpillars drop to the ground to pupate and leaf rollers largely pupate where they have been eating. No activity on the outside belies much activity internally. During pupation many tissues and structures are completely broken down and structures of the adult are formed.2 The following spring the adult moth will emerge.

Since becoming an Extension Master Gardener Volunteer in 2015, I have become hesitant to destroy an insect lest it be one of the beneficial ones. (Prior to my EMGV education I didn’t acknowledge that many are beneficial.) Given that there are 11,000 species of moth3 in the U.S., I may never learn to distinguish between a good one and a bad one. But, so long as the nibbling of their larvae stays within reason and lets my plant produce most of its blooms, perhaps we can co-exist.

Leaftiers and leafrollers are found on a wide range of plants, including many fruit trees. Prune out the effected foliage, webbing and remove caterpillars from plants. Bacillus thuringiensis (BT) is an effective control for recurring problems, particularly if applied as soon as larvae hatch.4  Trees infested with leafrollers can furthermore be sprayed with horticultural oil.5

Footnotes,  Sources & Further Reading

1, 4, 5 http://www.missouribotanicalgarden.org/gardens-gardening/your-garden/help-for-the-home-gardener/advice-tips-resources/pests-and-problems/insects/caterpillars/caterpillars-leaf-tiers-bagworms-and-web-former.aspx

2 https://content.ces.ncsu.edu/extension-gardener-handbook/4-insects#section_heading_5108

3 https://www.si.edu/spotlight/buginfo/moths

http://hyg.ipm.illinois.edu/article.php?id=359

When you are stumped about something gone wrong in your garden, remember Durham County Cooperative Extension’s  Ask an Expert resource. Send photos and an explanation of what you are seeing to:  mastergardeners@dconc.gov.  

Solitary Bees of Springtime

by Andrea Laine, EMGV

Say ‘bee’ and many of us think bumble or honey. But at this time of year we are apt to see ground-nesting bees out and about our landscapes, visiting the same early spring flowering plants that a honey bee might pollinate.

Ground-nesting bees are native solitary bees that nest individually in polyester-lined tunnels or burrows at least six inches deep in warm, dry ground. Reflective of this behavior, they are also called mining bees or digging bees. They are more likely to nest in areas with exposed soil and sparse vegetation, not dense turf or mulched beds.

MiningBee_M.Bertone
There are many species of bees that nest in the ground and they range in size and color. Pictured here is an adult mining bee. Photo by M. Bertone. 

 

TBilleisen ground bee damage
Evidence of ground nests can resemble tiny ant hills. Photo by T. Billeisen.

A hospitable patch of ground is likely to house a number of solitary tunnels, thus giving the impression at times of a small swarm of low-flying bees. But these bees are not aggressive as they are not defending a hive (as honeybees and bumblebees would be). And, as is the case with all bees, males cannot sting.

For two to four weeks in mid to late spring, females collect pollen and nectar to bring back to the nest. With it they form a ball in the side of the tunnel. They lay a single egg on the ball and when it hatches, the larva feeds on the pollen and continues to develop until the following spring when it emerges from the ground as an adult bee and goes forth to build a new nest.

Solitary bees are beneficial insects: They pollinate plants and their burrowing behavior is hardly noticeable and does no damage. On the contrary, it helps aerate the soil.

 

Sources & Further Reading

Matthew Bertone, Plants, Pests and Pathogens, Feb 26, 2019

https://www.turffiles.ncsu.edu/insects/bees-in-turf/

https://caldwell.ces.ncsu.edu/2014/06/ground-digging-bees/

http://www.gardening-for-wildlife.com/ground-bees.html

 

 

Spooky Garden Creature

by Andrea Laine, EMGV

In September, a fellow master gardener found a strange-looking worm crawling across her porch. At 8 to 12 inches long it was hard to miss.

Platydemus_manokwari_in_Florida_PeerJ2015_fig-1-full

A few weeks later there was another one under a container in her ornamental garden. Since it looks a lot like an earthworm and earthworms are beneficial to a garden, she let it be. And then she learned it’s true nature. The worm, commonly referred to as a land planarian or hammerhead flatworm (Bipalium kewense and Dolichoplana striata are two species), is an invasive species from Southeast Asia and its favorite food source is the gardeners’ beloved earthworms.

Hammerhead flatworms thrive in high temperatures and humidity. They are typically found in dark, moist areas such as under rocks or logs, beneath shrubs, and in leaf litter or garden debris. They may appear on the soil surface after a heavy rain. The worms can endure freezing temperatures by hiding under objects or in commercial greenhouses where they arrive in container plants. Though this was my friend’s first sighting of one, they have been present in the U.S. for more than a century. Like Count Dracula, they shun daylight, feeding and moving about under the cover of darkness.

Unfortunately, the worms mucus membrane repels would-be predators. And don’t even think about squishing one – they can reproduce via fragmentation. But when food resources are low, the land planarian resorts to cannibalism. So, they may be their own worst enemy, afterall.

Resources and Further Reading:

From the Texas Invasive Species Institute: http://www.tsusinvasives.org/home/database/bipalium-kewense

From the University of Florida Entomology and Nematology Department: http://entnemdept.ufl.edu/creatures/misc/land_planarians.htm

A master gardener in Galveston, Texas chooses a more positive outlook on the land planarium: https://aggie-horticulture.tamu.edu/galveston/beneficials/beneficial-57(partial)_land_planarian.htm

Photo credit:
https://commons.wikimedia.org/wiki/File:Platydemus_manokwari_in_Florida_PeerJ2015_fig-1-full.pmg

 

Holy Moley

by Andrea Laine, EMGV

A mole has taken up residence in my yard and, seemingly overnight, disrupted a couple of landscaped ornamental beds and killed two biennials. Well, it’s time to send that critter an eviction notice!

I immediately installed a spike as I’ve experienced good results with them in the past. These low-tech devices periodically emit a sonic vibration that supposedly moles find irritating. It worked, somewhat; The critter vacated the one bed, waddled (I imagine) across the walkway leading to my front door and dove into the next nearest bed to begin again. Aargh.

So, I poked another spike into the soil thinking, “can’t hurt, might help.”  True enough–no moles were hurt. Extension resources say my go-to solution has not been scientifically proven effective.

Know thy enemy
Solving a problem is more difficult when you know next to nothing about its cause. It was time for me to do some reading and uncover a few facts about moles:

  • Moles are solitary animals and, since they live underground, have few predators (snakes and foxes are two). Three to five moles per acre are considered a high population for most areas.
  • Moles are carnivores; they prefer to eat insects and grubs. They eat 70% or more of their body weight each day. With an appetite like that it is no wonder they cover so much (under)ground.
  • Moles are very efficient at tunneling. Observe their front feet in the accompanying photo and you can see why. The feet are broad and flat with long, protruding claws to help toss soil aside. They “swim” through the soil. They can tunnel forwards or backwards. Their deep (10 to 18 inches) and wide tunnels can destroy plant roots in their path, which is likely what happened to my biennials. get-rid-of-moles
  • Moles do not eat plants. If you notice plants or their roots suddenly vanishing, that is the work of white-footed mice or voles who are opportunistic herbivores – they make use of a mole tunnel to reach their food source.
  • In addition to grubs and insects, moles eat earthworms, spiders and other beneficial soil microorganisms. Moles like shaded, moist, cool loamy soil. No one warned me that a reward for improving my clayey soil would be moles. They also enjoy mulched areas and compost piles.
  • North Carolina is home to two species of mole: the Eastern mole and the star-nosed mole. The latter is a rare species and thus, moles are a protected species in this state.


Actions that may solve a mole problem
A 24-inch square piece of hardware cloth, bent in half and buried in the soil may work to protect a small area or a treasured plant. This option is hardly practical for my larger landscape and besides, I treasure all my plants.

Chemical repellents, toxicants and fumigants are not recommended as their effectiveness is limited at best and potentially dangerous to humans, pets and other wildlife. Extension also recommends not planting Euphorbia latharis (mole plant) nor Ricinus communis (castor bean plant) for similar reasons.

The most effective way to control moles is to trap them. Since moles are a protected species in N.C., you need a depredation permit to trap them. Depredation refers to wildlife causing property damage.

Benefits moles bring to nature
I am highly unlikely to experiment with trapping a mole, permit or not. And the problem would have to get pretty bad before I paid someone to trap a mole for me. So, it is time to consider what benefits moles bring to nature. Maybe we can coexist.

  • For starters, moles eat white grubs and the larvae of pest insects. Grubs become Japanese beetles so hooray for moles.
  • Tunneling loosens and aerates the soil. It also mixes the soil near the ground surface with deeper subsoil.
  • Borders of marigolds may repel moles from gardens. This method has not been scientifically tested but who would object to planting marigolds? Thus, I am counting it as a benefit.

Alas, there are just too few benefits of moles in the landscape. Sigh.

640px-Marigold_Flower

Drawing a conclusion
I might have won the battle, after all. One source noted that spring floods are probably the greatest danger to adult moles and their young. I know it’s not spring, but Hurricane Flo just dropped several inches of rain on Durham. Maybe the two inches of water that seeped from the over-saturated soil into my basement was also enough to wash away the smorgasbord that my resident mole was enjoying and he will soon pack up for new digs. Wishful thinking? Can’t hurt, might help me feel better.

Further Reading:

Find lots more detail about moles and trapping them at this resource from Penn State Extension:  https://extension.psu.edu/moles

https://wayne.ces.ncsu.edu/2015/12/moles-or-voles/

https://extension2.missouri.edu/G9440

https://www.ncwildlife.org/Licensing/Regulations/Nongame-and-Other-Regulations/Wildlife-Depredation

http://www.metromastergardeners.org/faq/index.php?action=artikel&cat=9&id=20&artlang=en

Photo credits:
Mole: https://www.almanac.com/pest/moles
Marigold:  Sarbast.T.Hameed [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC BY-SA 4.0  (https://creativecommons.org/licenses/by-sa/4.0)%5D, from Wikimedia Commons