Pine sawfly larvae can become a big reason to worry for your beautiful pine trees. Let us understand the lifecycle of this pest and how to get rid of pine sawfly larvae.
From the redheaded pine sawfly to the white pine sawfly, enemies are hidden amidst your pine foliage, ready to destroy your plants!
A beautiful symbolic representation of longevity and virtue, pine shrubs are found all across the Northern Hemisphere. These multipurpose conifers are the source of revenue for many businesses.
However, pine sawfly larvae can leave these beautiful shrubs completely naked without their characteristic pine needles, feeding off them in a matter of days. Let’s learn about how to control these bugs.
What Are Pine Sawfly larvae?
The pine sawfly biologically belongs to the Symphyta sub-order of the Hymenoptera order and is part of the same family as ants, wasps, and bees.
Pine Sawfly larvae, as their name suggests, are known to feed on pine shrubs. They can damage the foliage and ultimately cause the death of the shrub.
The female sawflies lay their eggs strategically along the terminal ends of the shrub. Once the eggs hatch, their larvae emerge.
These larvae are of different colors, like black, green, orange, or striped. Most of them have a black head. They can grow up to one inch in size and look very similar to caterpillars in their larvae stage.
When a large group of larvae hatches together, it can destroy the entire needle of the ending branches by eating them away. Over time the shrub defoliates, and it causes a massive blow to the businesses reliant on pine cultivation.
How To Tell Caterpillars Apart From Pine Sawfly Larvae?
Initially, most people don’t recognize these larvae because they look pretty much exactly like caterpillars. However, by the time you might recognize them, they would have already caused a lot of damage, so here’s what you need to watch out for.
The number of prolegs (these are fleshy, false legs on a larvae’s body) in the abdominal region is the main thing that you can use to identify sawfly larvae.
Caterpillars have three to five pairs of abdominal, unjointed prolegs. Sawfly larvae also have them, but they have six or more pairs.
They feed for 4 to 5 weeks before they begin to spin a cocoon to grow into an adult pine sawfly and repeat their life cycle.
What Damage Does the Pine Sawfly Larvae Do?
The hatched larva begins feeding from one end of the pine needle and only moves to the next after the entire needle has been eaten.
The pine needles where the larvae cluster feeds start to defoliate rapidly. They leave behind a dried-up, shriveled, and yellowish-brown section of the branch completely devoid of foliage.
Though many pine shrubs survive the infestation, European pine sawfly Larvae can cause considerable and permanent damage to the conifers. This includes
- Stunted growth
- Non-Uniform growth with areas of permanent defoliation
- Missing aesthetic appeal
- Repeated infestation at the same spot can weaken the branch.
How To Control Them Organically?
Pine sawflies can be taken care of organically in the larval stage by applying these simple methods.
White pine sawflies and most other species are harmless to humans and animals alike, as they do not have stingers at any stage of development.
Localized areas of infestations on a specific shrub do not spread or transfer to others. Hence they rarely cause a massive issue; if left alone, they generally fall down to pupate or die. The shrub will grow pine needles back over time.
Therefore, if watching your shrub get defoliated is not too much of a problem, you might consider leaving them alone.
Pluck Them Off
The sawfly larvae are often easy to see. As they hatch and stay in clusters, it is easy to handpick them off. Even though the process is slightly time-consuming, it is the most cost-effective and easy solution.
Parasites, rodents, and birds are beneficial insects that can easily get rid of your sawflies and their larvae. Beetles and parasitic wasps are other natural predators that can help kill sawfly larvae.
In particular, the Bacillus Thuringiensis (BT) is a parasite that is known to be effective against them.
However, it has been noted that they are not an aggressively effective solution and only provide temporary resolution until the next cycle begins.
Prune Branches Infested By Them
Pruning branches is a common practice, especially if the infestation of pine sawfly and the other variants are limited and the Pine conifer is not yet in the harvest stage.
However, pruning can result in causing structural weakening of the conifers, which many do not like.
Pesticidal Control of Pine Sawfly larvae
One of the best solutions for eradicating various species of sawflies is to opt for genetically enhanced variants of pine trees immune to these pests.
However, as that is not an option available to everyone, so most opt for Insecticides when organic routes do not work.
These are the most preferred choice as they do not cause much damage to the environment or the nearby insects. Some of the most commonly used natural Insecticides are
- Synthetic Pyrethroids lambda-cyhalothrin
Though these insecticides are not dangerous, it is best not to spray on the adjacent flower and fruit plants.
They can cause harm to the bees and other pollinating insects and birds. You can also try spraying the Piner conifers with soapy water as a quick, cost-effective, and hassle-free solution.
One of the oldest natural insecticides used by gardening experts for centuries is Neem Oil. The natural oil works on any species of sawfly and larvae.
Neem Oil contains Azadirachtin, which is extracted from Neem Seeds. Other potent oils are meliantriol, fatty acids, and salannin.
The oil acts by attacking the entire life cycle of Pine sawflies in various ways, preventing adult Sawflies from laying eggs and larvae from growing further.
Most importantly, natural oils are not harmful to bees or other beneficial insects. Some of the most commonly available Horticultural Oils are
- Bio-Neem, Margosan-O
What is the Best Time To Use Pesticides on Pine Sawfly Larvae?
The insecticides are most potent when sprayed on the larvae when they are small. The larvae are at their weakest when they are about half an inch in size.
By the time the pine sawfly larvae grow up to three-fourths of an inch, they develop resistance to these insecticides and hence are not affected anymore.
Generally, you can spray insecticides late in the evening, preferably at dusk, for the best results. Left undisturbed overnight, they force out even the most conspicuously hidden larvae out into the open by the next morning.
Most of them are dead by then, and you can easily handpick and squish the rest. Despite the measures taken, these natural enemies of the Pine conifers reappear every other year at the same location.
This is because these bugs fall off onto the soil when they pupate and stay there until it is time to emerge as adults and lay eggs again.
If the soil is not cultivated and treated regularly, the sawflies are bound to come back.
Frequently Asked Questions
Will Sevin Kill Sawfly Larvae?
Yes, Sevin can kill sawfly larvae. Sevin is one of the most common choices of insecticides used by horticultural experts to get rid of Sawflies.
You can mix 45 ml of Sevin Concentrate with 1 gallon of water and apply the solution generously all along the surface of the trunk, stems, and leaves.
Ensure to drench the sawfly-infested area completely in the solution. Repeat the process every seven days until all the sawflies, including the larvae, disappear completely.
Does Neem Oil Kill Sawfly Larvae?
Neem Oil is one of the best natural insecticides. When the oil is sprayed on the infected area, it stops the female sawflies from laying eggs.
The larvae also cannot grow any further and die off soon. However, it is best not to use neem oil on flowers because it may adversely affect bees and other pollinating insects.
Where do sawflies lay their eggs?
Female sawflies lay an average of 6 to 12 eggs along the lateral ends of each needle. Each adult Sawfly can lay eggs on 12 to 14 pine needles at one stretch.
Using a saw-like organ known as the ovipositor, the female creates a slit on the nutrient-rich section of the needle and carefully lays her eggs there.
Will Pine sawflies kill trees?
Though pine sawfly does not directly kill the pine conifers, their repeated infestation defoliates, weakens, and stunts the growth of the shrub.
This can cause irreparable damage, thus leading to the death of the entire tree in some cases.
Does insecticidal soap kill sawflies?
A natural mix of water and dish soap can effectively kill young sawfly larvae without causing damage to the natural surrounding.
However, it is not very effective against larger larvae or adult Sawflies.
Nothing Beats Constant Vigil!
Keep an eye out for even the smallest changes in the Pine shrubs. The clues are always hidden in plain sight, from black spots to drying sections.
Don’t get fooled by their caterpillar-like appearance, and use the tips we gave here to keep your plants safe. Thank you for reading!
Pine sawfly larvae can be a real menace to pine and other deciduous trees, and our readers have often discussed their encounters with these bugs in a negative light.
Go through some of the emails from readers to see for yourself the damage these pests can do and what methods they might have adopted to stop them.
Letter 1 – Red Headed Pine Sawfly Larvae
destructive worm/caterpillar…moving fast…help! July 26, 2009 Please help me identify this alien army that has shown up and destroyed my evergreen bush in less than three days….will they move on to my other flowers and trees?? Laurie Southeastern Massachusetts (Plymouth County) Dear Laurie, We identified your Red Headed Pine Sawfly, Neodiprion lecontei, on BugGuide, and now that you know what it is, you should be able to find much information posted online. You do not need to worry about these larvae that are related to wasps moving to other plants in the garden.
Letter 2 – Sawfly Larva: What does more damage? A Sawfly Larva eating Leaves or a Crew Cutting Branches???
Found this larva in gunni euc tree need id? February 23, 2010 While cutting gunni euc one of my workers found this worm. I need it id to know if I it is harmful. It is white had has black spots on the side. The face almost looks like it is smiling. Please help!! Jennifer Watsonville ca Hi Jennifer, This is the larva of a Cimbicid Sawfly, a non-stinging relative of wasps and bees. The Sawfly larva will eat some leaves, and we believe it is doing far less harm to the plant than the workers who were probably cutting branches.
Letter 3 – Pine Sawfly Larva
Subject: Caterpillar ID Location: York Region Forest, Newmarket, Ontario, Canada November 6, 2013 10:36 pm Hello Bugman, I would like to get some info on this caterpillar. It was found in York Region forest, just half hours drive of Toronto, Ontario, Canada. It was searching on old decaying tree trunks in the parking lot when I first spied it, during the middle of October 2013. A few days later, I found a second one (may be same one) in the same location. I took both photos, of which you may use for display purposes. I have been searching many butterfly and moth categories, without any luck in naming it. Maybe (I’m thinking) its a sawfly? Its about 1 1/2 to 2 inches in length. I have just started a website and trying to name the species that I have included on it. Thanks for any info… Brian Dear Brian, Just because it looks like a caterpillar and acts like a caterpillar, does not necessarily mean it is a caterpillar. You are correct that this is a Sawfly Larva. It is an Introduced Pine Sawfly Larva, Diprion similis, and according to BugGuide, it is an adventive species introduced from Europe. BugGuide also notes: “Although a serious pest at times, it normally stunts rather than kills its hosts. It can be a more serious problem with young trees and in cases such as Christmas trees where appearance is important. It has natural enemies and diseases, so large outbreaks are only intermittently seen.” Dear Daniel, Many thanks for your reply -to my request asking for identification, regarding the bug that I had found – most informative. No wonder many of the conifer trees in that area that it was found in, had issues with their foliage etc. Brian
Letter 4 – Sawfly Larvae near Milkweed
Subject: Are these Monarchs? Geographic location of the bug: gilford, nh Date: 08/30/2017 Time: 02:49 PM EDT Hi, Found this hatch a leaf between leaves in a patch of milkweed. They have the coloring of Monarch caterpillars, but I have never seen so many together. Do you know what they are? How you want your letter signed: Curious in NH, Wendy O. Dear Wendy O., These look more like Sawfly Larvae to us. Sawflies are non-stinging relatives of wasps and bees whose larvae resemble caterpillars. Here is a BugGuide image of a Sawfly larva in a similar position, and here is a BugGuide image of a similar grouping of Sawfly Larvae. Finally, here is a BugGuide image of a really similarly colored Sawfly Larva, but alas, it is not identified to the species level. We are posting your image and perhaps one of our readers will be able to assist with a species identification. Were they actually on Milkweed? Hi, No, the leaves were intermingled with the milkweed plants which had sprouted up in our flower garden. Thanks for letting me know. They looked so much like mini monarchs that I was confused. I’m in the garden and outdoors a lot and had never encountered anything like these. Thanks for responding so quickly. Best regards, Wendy O.
Letter 5 – Red Headed Pine Sawfly Larvae
Subject: caterpillar cluster Geographic location of the bug: raleigh, nc Date: 09/04/2017 Time: 12:11 PM EDT what in the world is this? do we leave them, feed them to our chickens, or what? How you want your letter signed: carrie Dear Carrie, Though the insects in your image resemble Caterpillars, they are actually Sawfly larvae. Sawflies are non-stinging relatives of Wasps and Bees that have larvae that frequently resemble Caterpillars. Thankfully your image quality was of a high enough resolution that we were able to crop more closely to help identify these Red Headed Pine Sawfly Larvae,Neodiprion lecontei. There is an excellent page on Featured Creatures devoted to this species where it states: “Neodiprion lecontei is an important defoliator of commercially grown pine, as the preferred feeding conditions for sawfly larvae are enhanced in monocultures of shortleaf, loblolly, and slash pine, all of which are commonly cultivated in the southern United States.” We don’t know if the Red Headed Pine Sawfly larvae are able to retain within their bodies resinous compounds from the pine that might make then unpalatable, but we imagine if they don’t taste good, the chickens won’t want to eat them.
Letter 6 – Introduced Pine Sawfly Larva
Subject: Caterpillar Geographic location of the bug: NW corner Connecticut Date: 08/19/2019 Time: 07:15 PM EDT Your letter to the bugman: Looking for an ID. Consulted the Exec Director of Audubon here in CT and he did not know. How you want your letter signed: Lori Welles Dear Lori, We thought this was going to be an easy identification, but more than an hour later, we can state unequivocally that we were way wrong. Our mistake began by not looking at your image that closely, and thinking we were trying to identify one of the Hooded Owlet Caterpillars in the genus Cuculia, but after ponderously searching BugGuide, we realized we were wrong. Our search next took us to The Moth Photographers Group where the Zebra Caterpillar looks similar, but not the same, and the Scribbled Sallow Moth Caterpillar pictured on The Moth Photographers Group and the Toadflax Brocade Moth Caterpillar, also pictured on The Moth Photographers Group also looked similar but not the same. The solid black head on your individual and the round yellow lateral spots were quite distinctive and not found on any caterpillars we could locate. Something about the head did not seem right, so we decided to count prolegs, and there appear to be seven pairs, which caused us to think this must be a Sawfly larva. According to ThoughtCo: “Caterpillars may have up to five pairs of abdominal prolegs (tiny limbs) but never have more than five pairs. Sawfly larvae will have six or more pairs of abdominal prolegs.” Once we searched for Sawfly larvae, we came to Wildlife Insight where we found images that match your individual that are identified as Diprion similis. Armed with that information, we returned to BugGuide and located matching images of the Introduced Pine Sawfly larva, but the individual in your image does not appear to be eating pine. Upon what plant did you find it? According to BugGuide: “hosts: pines (Pinus); 5-needled pines (Subg. Strobus) are preferred, but others may be infested as well.” This BugGuide image contains the information: “This one was on a poplar plant, and the other was eating oak leaves.” Thank you for submitting this challenging identification request. This was feeding on Cosmos. Glad it was a challenge as many friends including the Exec director of Audubon here in CT. could not ID. LBW Welles, The Ballyhack
Letter 7 – Red-Headed Pine Sawfly Larvae
Subject: Strange caterpillar Geographic location of the bug: Eastern Virginia Date: 06/14/2020 Time: 07:55 PM EDT Your letter to the bugman: Hello! I spotted a strange caterpillar at Weyanoke Bird and Wildlife Sanctuary in Norfolk,and pointed it out to my father. I got my phone out and snapped a few pictures of it. I guess my phone hit one of the branches and about 3 of them put their head back and exposed their chest that I saw was covered in spikes (They may have been sharp legs, but I couldn’t tell). They stayed like that for a bit until I backed away. I tried to find them on google, and I looked on a few bug Identification websites, but I saw none that looked like it. I was wondering if you knew what it was! How you want your letter signed: Lydia Simon,age 13 Dear Lydia, Though they look very much like caterpillars, these are actually Red-Headed Pine Sawfly larvae, Neodiprion lecontei. Here is a BugGuide image for comparison. Sawflies are non-stinging relatives of bees and wasps. When larvae are numerous, they may defoliate trees. According to Featured Creatures: “After mating, female sawflies lay eggs in slits sawed in pine needles. Small larvae feed on outer needle tissues; larger larvae consume entire needles. Most species prefer older foliage, but all foliage is susceptible at end of growing season. Larval colonies may migrate from one tree to another, especially upon complete defoliation of the host tree or high feeding competition.”