When do adult sawflies appear?

Adults usually emerge from wheat stubble from May to June in Montana. Emergence generally coincides with the maturation, or heading out, of smooth brome grass.

Why is sawfly cutting worse on the east (or west) sides of my field?

Adults fly upwind from the overwintering sites, and begin to lay eggs as soon as suitable host plants are encountered.

How far do sawflies fly?

The maximum known dispersion is one mile. Females fly until they find suitable host plants. If they are moving into a spring wheat field that is still in the tillering stage, the sawflies may disperse far into the field. However, in fields where wheat has reached the heading stage, infestations may be concentrated in the edge. Flights occur when the temperature is warm and the winds are calm.

Can I plant barley and get rid of sawflies?

No, sawflies reproduce in barley, although infestations are less visible than in wheat.

Will crop rotation help to reduce infestations?

Yes, if the rotation includes non-hosts such as canola and there are no wheat or barley fields nearby.

Is tillage effective?

Tillage usually has little effect on sawfly populations because adults can dig through the soil. Even moldboard plowing did not reduce numbers of adults in experimental trials. Heavy tillage can kill beneficial parasitoids.

Are there any insecticides registered for sawfly control?

No.

Why aren't insecticides effective?

The adult stage is the only stage that is vulnerable to insecticides because the eggs and larvae are protected within the plants. The adult emergence period may last over a month, and eggs are laid as soon as they fly into fields. Insecticides are effective for only a few days, and repeated applications are not only cost prohibitive but could also contaminate the grain.

Does swathing kill sawflies?

No, most larvae are in the lower stems, or stubs, when the wheat is dry enough to swath. However, swathing may reduce harvest problems caused by lodging.

Are sawflies killed during unusually cold winters?

No, they survive temperatures that are well below freezing.

Many small orange colored wasps are in the fields when I am combining. Are they some type of sawfly?

No, they are parasitoid wasps that attack and kill sawfly larvae.

Where did the parasitoids come from?

They were probably first found in native wild grasses, and have recently become more common in wheat. They attack only sawflies.

Where did the sawflies come from?

This is actually a topic of debate among some entomologists. It has been hypothesized that the wheat stem sawfly originated in China. There are sawflies, similar to the ones in Montana, that infest wheat in China. However, other scientists argue that our species (Cephus cinctus) is native and originally attacked wild grasses before moving into cultivated fields.

Sawflies used to only infest my spring wheat. Why are they infesting my winter wheat?

Sawflies are now emerging nearly a month earlier than previously, so they are present when the winter wheat is susceptible. Late planted spring wheat fields now frequently avoid attack.

Can I plant solid-stemmed wheat for a few years and get rid of sawflies?

No, sawflies can survive and reproduce in solid-stemmed wheat, although not nearly as well as in hollow-stemmed wheat. One female may lay up to 50 eggs, therefore it doesn't take many survivors to infest and damage a more susceptible variety.

Can we bring parasites from China to help control sawflies in Montana?

There is at least one parasite in China that does not occur in Montana. Its effectiveness is uncertain in its native land since the level of sawfly damage in Chinese wheat is similar to that in Montana wheat. We are planning laboratory tests to determine if the Chinese parasite will attack and effectively control Montana sawflies.

What can you tell me about sawfly population dynamics?

Sawflies can reproduce by 10-fold each year. Therefore, control practices must kill over 90% to impact the next year's population. Sawfly damage in many regions is worse now than 30 years ago. This could be due to continued adaptation to wheat, by dispersal of a more virulent strain, or location within a long-term host/parasitoid cycle.