PestFacts 8 June 2023

Slaters spotted feeding on crops

Slaters have been reported feeding on bean seeds near Frances in large numbers, often with 5 to 6 slaters per seed. Photographs indicate they are likely pill bugs (Armadillidium vulgare).

West of Cummins and near Kapinnie on the Eyre Peninsula, very large numbers of pill bugs have been observed in canola crops sown into bean stubbles on heavier soil types. The seedlings are being ringbarked.

Slaters are detritivores and mostly feed on decaying vegetable matter. Although the reported incidence of slater damage to crops has grown in recent years, feeding damage on emerging crop seedlings is still relatively rare.

When it does occur, feeding symptoms can look like uneven rasping (similar to slug and snail damage) and they can chew the tops of emerging cotyledons of seedlings, often leaving only the seedling stumps. Other damage includes ringbarking of stems and young branches. The presence of slaters in a paddock, even in high numbers, does not always mean crop damage will occur. It is not known what makes slaters suddenly shift from eating organic matter to seedlings.

Identification

There are three known species of slaters found in broadacre situations, although they vary in their distribution:

• common rough woodlouse (Porcellio scaber)
• pill bug (Armadilidium vulgare)
• flood bug (Australiodillo bifrons).

The common rough woodlouse is originally from Europe and is the most widespread species in Australia. This species is usually pale grey, although brown, yellow, or orange variations are not uncommon, and can reach 20 mm in length. This species does not roll into a ball.

The pill bug is also a European species and occurs commonly across Australia. It is characterised by its ability to roll into a ball when disturbed. It can grow to 18 mm and is dark brown to black in colour, but colour variations can occur.

The flood bug is a native slater that forms large swarms of tens of thousands of individuals. The flood bug is about 7 to 8 mm long and 4 mm wide with an oval-shaped and flattened body, light brown colour with darker irregular spots, and has a dark brown stripe down the middle of its back. It is a species adapted to low-land swampy soil or marshy environments.

To better understand the geographic distribution of slater species that feed on crops, we’re asking growers and agronomists to send in slater specimens for identification.

See instructions for sending specimens below. Email Rebecca Hamdorf at rebecca.hamdorf@sa.gov.au to get a pack of specimen vials sent to you.

Monitoring and control

Slaters are mostly active at night or during moist conditions as they need this moisture to breathe. During the day, it is best to search under stubble residue, rocks, or wood, or dig up the soil with a spade. Night observations are most effective, as it will confirm if the slaters are feeding on crops or not.

Management options are limited after crop emergence, so prevention is a key part of control. Keep note of paddocks with slater problems to help inform decisions in the future. Managing stubble is likely to be the most effective strategy to reduce slater numbers. Some growers have had success managing slaters ahead of canola rotations through burning crop residues.

There are very few products registered for use against slaters. See the APVMA PubCRIS database for up-to-date information.

Source of reports: Nick Hillier, Chris Pearce (Cummins Ag)

Regional overview of pest observations

Over the past few weeks, we have received only a few reports of pest activity.

Slugs

Slug damage in canola and vetch has been reported in the Mid North. Areas of emerging vetch had to be resown, but the slugs aren't feeding on beans. Black keeled slugs (Milax gagates) have been reported as very active after 20 mm of rain in the Upper North. Large numbers of slugs have been reported at Bordertown and Hyman, and have been baited in several areas.

Mites and lucerne flea

Redlegged earth mites (Halotydeus destructor), Balaustium mite and lucerne flea (Sminthurus viridis) were observed in cereal stubble with medic pasture near Hardwicke Bay on Yorke Peninsula. Several predatory mite species were also observed.

Greybanded leaf weevil

Greybanded leaf weevil (Ethemaia sellata) larvae and adults have been reported feeding on marshmallow weed near Hardwicke Bay. It's unknown if adults were feeding directly, but they were present in large numbers. A variety of different-sized larvae were seen actively feeding, mostly under the leaves and eating small holes in leaves.

Nail the snails

A new resource on best practice snail management is available for growers and advisers. The publication, Nail the snails: A practical guide to integrated snail control for Australian grain growers, produced by the South Australian Research and Development Institute with Grains Research and Development Corporation investment, is the second edition of the Bash 'Em Burn 'Em Bait 'Em snail management manual.

The comprehensively revised manual incorporates the newest available research and describes the key recommended actions and timing of controls for four pest snails throughout the crop management cycle.

Check emerging crops for insects

Frequently checking crops during emergence (the first 3 to 5 weeks) is key to detecting pest issues and ensuring crops get a healthy start. It is important to remember that seasonal variations and differences in pest biology mean no single tactic or approach will effectively control pest issues in all situations every season.

When checking crops, sometimes pest damage is obvious but finding and identifying what insect pest, or combination of pests, is causing the damage may not always be so simple.

Tips for identifying damaging insect pests in emerging crops

• Look up and down the seeding rows for missing plants that may have been chewed off at the base or plants with visible chewing damage.
• Look for insects around and under chewed or missing plants. Don't forget to check under the stubble in the inter-rows.
• Check what type of damage the plant has sustained. Understanding the preferred feeding methods and mouth parts of insects can help narrow the lists of culprit insects. To help identify groups of pests by feeding damage, use the I Spy - Identification manual and education resource.

Still can't find a pest? Try:

• Night-time observations to catch the culprits feeding.
• Placing a pitfall trap near the damage. This is just a plastic cup dug into the ground so the top is flush with the soil surface. Put about 10 millilitres of water into it and come back after 24 hours. This has been especially useful in detecting the presence of weevils, slaters, and European earwigs.

Reporting observations

Have you found an insect in the paddock that you have not seen before? It could be a native, an incidental or it could be a new pest species. Get it identified through our free identification service or report it using the PestFacts map. It is hard to identify an insect from a verbal description so take a sample of the insect/s to post or take photographs.

If you do find insects in the paddock, make sure they are correctly identified. Not all insects are crop pests. The presence of a pest doesn't necessarily require intervention, and control methods vary depending on the species due to biology, chemical sensitivities, and resistance.

More information

• Monitoring insects and other crop pests
• How to monitor for early season pests
• Tips on monitoring for insects in early season canola

Original article by Cindy Webster (DPIRD Narrogin) and Dustin Severtson (DPIRD Northam) from PestFacts WA.  Modified by Rebecca Hamdorf (SARDI) for SA.

Identify that pest for free

PestFacts SA offers free identification of broadacre invertebrate pests to all subscribers. Have a pest identified by either:

• sending in specimens
• sending in photos.

Sending specimens

Sending live specimens for identification is the most reliable way to get a correct identification, however what happens between sending and receiving the parcel can be unpredictable. From long times in the postal system to insects eating one another, things can go wrong, but there are a few ways you can make sure the insects arrive in the best possible condition.

• Send as many individuals as you can
  • The more insects you send, the more likely we will receive them in a useful state. For some species it is necessary to check multiple individuals to confirm, and in some cases, there might be many species causing damage at the same time. We recommend at least 20 individuals, but if you only have a few, it’s still worth sending them in.
• Use a sturdy, non-crushable container
  • Takeaway plastic containers in post bags are often crushed in transit, ruining the specimens. Use a sturdier plastic, such as specimen vials or hard plastic containers, or send in a post box with padding.
  • Contact Rebecca Hamdorf at rebecca.hamdorf@sa.gov.au to get a pack of specimen vials sent to you.
• Provide a food source
  • Some insects will cannibalise each other if no other food is available. Provide some of the host plant to keep insects fed. To stop plants from going mouldy, include some tissue or paper towel in the bottom.
• Don’t punch air holes in the container
  • Air holes are not necessary and provide a spot for insects to escape.
• Provide details
  • The more detail about the specimens, the better. Always provide us with an indication of locality and host plant (if not otherwise obvious from the food source) and your information so we can get back to you.
• Send by express post on Monday, Tuesday or Wednesday
  • To ensure the parcel isn’t delayed any longer than necessary, always send at the start of the week. Express post is preferred, to ensure it will arrive as soon as possible.

Send your specimens to:

PestFacts SA / Rebecca Hamdorf
Room E115b, Waite Main Building
Waite Road
Urrbrae SA 5064

Taking photographs

Sending photos for identification is much faster than sending in specimens, but often makes species harder to identify due to the difficult nature of photographing insects. They are small, often very mobile and the photos can end up blurry or don’t show all the identifying features. However, there are several tips and tricks that can yield better results.

• Smartphone photos
  • Usually, we receive photos taken on smartphones. These can be OK as long as you are able to focus at short distances. Photos taken too close often end up blurry. Since most smartphones have a high resolution, it is better to not try and move too close, because zooming in on a sharp image afterwards works better. Also, a photo taken from a bit further away will show more of the environment.
• Use an attachable macro phone lens
  • There are a wide range of attachable lenses available for smartphones, and they are an easy way to take macro photos of insects and mites with your phone.
  • In previous seasons, we have been able to distinguish between redlegged earth mites and blue oat mites from a phone photo alone thanks to the GoMicro clip on phone lens.
• Provide details
  • In a photo, it is always good to have some indication of scale. Get your lucky coin, pen, or pocket- knife out – anything that can give us some idea about the actual size of the insect.
  • Always provide us with an indication of locality and host plant. For pest species this always allows us to narrow down the options quickly.
• Take photos of different angles
  • Important identifying features can be anywhere on the insect, so by taking photos of different parts you ensure you get as many identifying features as possible. Plus, if any photos are blurry, you’ve still got plenty that can be used for identification.

You can send us your insect photos for identification by:

• tagging or messaging our Twitter account @PestFactsSARDI
• contacting Rebecca Hamdorf – phone 0429 547 413 or email rebecca.hamdorf@sa.gov.au
• contacting Maarten Van Helden – email maarten.vanhelden@sa.gov.au.