Sawflies are yet another common garden insect that we see nearly every day on the farm. Closely related to ants, bees, and wasps, the name “sawfly” refers to the shape of the female flies’ “ovipositor”, which she uses to saw into plants, in order to create a place in which to deposit her eggs. The sawfly has been in existence since the Triassic period of the Mesozoic era. That’s over 250 million years ago! Currently, there are roughly eight thousand species of sawflies on Earth.
Dealing with a Sawfly Problem
Sawflies are easy to tell apart from other, similar insects – like the wasp – because of their broad waist, and lack of a narrowing connection between the thorax and abdomen. In addition, when in the larval phase, the sawfly closely resembles a caterpillar.
There are very few male sawflies, as they are one of the few types of insects that do not require a mate to reproduce, so over time, the vast majority of the bugs have evolved as “parthenogenetic”, or independently-reproductive, females. Despite their similarity to wasps, sawflies will not sting humans or other animals, though they will feed on the nectar and pollen of flowers and other plants.
Adult sawflies rarely live longer than a week – usually just long enough to lay their eggs. Sawflies are also not a highly active species, preferring to only fly short distances in sunny weather. Eggs are laid either singly or in groups called pods. Morever, you will find them either along leaf veins or edges, or scattered across the surface of the leaf or stem. They may be partially injected under the surface and may grow in size so that they partially project out of the leaf or stem as time elapses.
Within two to eight weeks, the eggs will hatch producing sawfly larvae. These closely resemble a caterpillar, except that sawfly larvae have additional “prolegs”, or fleshy projections on the abdomen. Additionally, unlike caterpillars, sawflies only possess a single pair of eyes. Sawfly larvae develop through six instars or stages before they reach adulthood, and the entire process takes approximately two to four months.
Depending upon the specific species of the sawfly, behavior after larval development can be mixed. Some species will leave the plant to pupate in the soil. Yet, others will spin a cocoon on the host plant. Adults emerge in a few months, generally producing only a single generation each year. Although, sometimes they require two years to produce one generation of sawfly.
One detail that sets the sawfly apart from many other insects is that they stick together once reaching maturation. Most species of bug disperse, but not the sawfly. Sawflies feed in groups. This leaves them with the ability to do a great deal of damage in quite a short period of time. Additionally, sawflies are a defensive species. They release a foul liquid when threatened by predators like ants. Many species are also considered “leaf miners”, meaning they feed on the leaf tissue from the inside, out.
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Getting Rid of Sawflies
Sawflies have several natural predators, including many birds, lizards, frogs, ants, predatory wasps, and some other insects. Carnivorous animals such as shrews, certain mice, and some beetles can prove helpful in controlling the sawfly population, as well.
Larger trees are not normally very susceptible to serious or lasting damage from sawflies. Typically, a healthy tree will be able to replace any leaves lost with new growth. However, younger trees and smaller bushes and crops may not be able to come back from a sawfly infestation so easily. Unfortunately, it is common to lose an entire plant to sawflies if they are left uncontrolled.
Removal by Hand
Removing the bugs by hand and dropping them into a bucket of soapy water is always recommended. However, this method can be limited in its efficiency. Many chemicals are on the market that will kill sawflies. But as we know, using commercial chemicals on your organic garden is one thing we will never advise for a whole host of reasons. Some of which include the health of your beneficial pests, as well as your own safety, and the quality of the soil you work so hard to maintain.
Spray Your Plants
A far better and equally effective option is to treat your affected plants with insecticidal soap, which is safe in the garden and will not harm your beneficial insects or other crops. If you find that treating with insecticidal soap is not having the desired level of effectiveness, we recommend trying neem oil next. Finally, if both of these methods still haven’t provided total relief, you may treat the affected plants with a Spinosad-based treatment, using caution around other crops and making sure to never use spinosad during the flowering phase of your plants.
If you are battling the sawflies in your garden or on the farm, keep your head up! We know how difficult these little guys can become and how frustrating it can be to lose a beloved plant. Remember to keep trying different methods, maybe add a few natural predators to your garden, and stay positive. These bugs may be tough, but we won’t let them bring us down!