By entering a number of variables, including temperature, aphid pressure and the presence of natural enemies, the tool will determine whether or not there’s a need to spray. First, the app will ask you to assess a field. You’ll notice that when you click on the “Assess a Field” function, a growth stage alert will appear.
“This app is only useful between the R1 and R5 growth stages,” says Tom Cowan, an entomologist with OMAFRA. “After the R5 stage, the number of aphids doesn’t seem to affect yields all that much.” Cowan introduced the app to farmers at this year’s Farm Smart Expo at the Elora Research Station in July.
Using the GPS function on your phone, you’ll then be asked to enter your location, followed by the average maximum and minimum temperature for the week. This information will help predict what aphid populations will do in the next seven days. If you choose to skip this part, the app will put in default numbers. Cowan cautions that the more accurate you are, the more accurate your numbers will be.
“Insect numbers can increase or decrease depending on temperature. So if it’s going to be a hotter than average week coming up, you may find that that’ll drive insect numbers up a little faster,” says Cowan. “The computer can then put that into the mix of variables to determine what the aphid populations will do.”
Next, you’ll be asked to determine aphid pressure. You can do this by counting the number of aphids on 10 plants that are located at least five metres apart. Be sure to move around when you’re scouting; it will help determine the average aphid pressure of the entire field. The app makes determinations for the entire field; if you come across high-pressure areas, you’ll have to decide whether or not to spot-spray on your own.
When assessing a field, Cowan says, you need to get as close to accurate counts as possible. While it is impossible to count every single aphid on a plant, there is a way to train yourself to get a good estimation of what’s in your field. First, do a proper count to get an idea of what that number looks like, and then move forward using that estimation.
“The Aphid Advisor is a tool,” says Cowan. “Good data in equals good data out. If you give it poor data, you’ll get a poor answer.”
Be sure to do a self-check halfway through to make sure that you’re on target. For those who prefer a visual tool, aphid scouting cards are available in PDF format online: http://www.ontariosoilcrop.org/docs/V4Soy7.pdf. Images are provided for 20, 50 and 250 aphids.
It’s important to do a follow-up assessment after seven days, says Cowan. “Aphid numbers could change, especially in the middle of the season when things start to heat up,” he says. “The more you scout your field, the more information you’ll have on it.”
Finally, the app will ask you to enter the number of natural enemies present in the field. You should, if possible, count the natural enemies at the same time as the aphids, from the same location, and then input the data. Consult the Soybean Aphid Scouting Card for images of common natural enemies. Keep in mind that there are also images available in the app itself.
After all of the data has been entered, one of three results will appear:
- Spray – Based on the data you’ve entered, there are not enough natural enemies to control the aphid population. Scout again in seven days.
- Wait – Based on the data provided, the app has determined that you are on the cusp and may not need to spray. Scout again in seven days.
- Don’t spray – There are enough natural enemies in the right amount, of the proper type. Based on the data provided, you do not need to spray. Scout again in seven days.
Once you’ve completed testing and received a recommendation, you can upload your data to a central database. The database can both store and track information, which can be used to make broader determinations in the future. Due to privacy protection, exact locations cannot be provided, but the information is available by county.
Cowan is careful to reiterate that the Aphid Advisor is a tool created to help growers make management decisions, and the success of the tool depends heavily on the accuracy of the data entered. The Aphid Advisor app is free and available for both iPhone and BlackBerry.
“When soybean aphid populations are not actively increasing above 250 aphids per plant, this is an indication that natural enemies are keeping up with the aphid population,” according to the Soybean Aphid Scouting Card. “Do not use an insecticide in this case as it will kill the natural enemies and enable the aphid population to increase above threshold.”
Common natural enemies of soybean aphids
The natural enemies of soybean aphids include lady beetles, or ladybugs (various species are listed below); parasitic wasps; minute pirate bugs, adult and nymph; and syrphid larvae.
Lady beetle larvae vary in colour. They can be black or greyish-purple with orange or yellow markings. They look somewhat like small alligators.
Both the larvae and the adults feed on aphids. Species include:
• multi-coloured Asian
• Coleomegilla maculata
• lady beetle larvae
Minute pirate bugs, adult and nymph
Just two to five millimetres long, adult minute pirate bugs are quite small. They are oval in shape with a triangular head, and they are black to purple with white markings. The nymphs, on the other hand, are yellowish and reddish brown. They are pear-shaped and have red eyes. Minute pirate bugs, both adult and nymph, are common in soybean crops. They feed on insect eggs and small insects such as aphids and mites.
Syrphid fly larvae are blind, legless and maggot-shaped. They vary in colour and markings, but most syrphid larvae have a long yellow stripe running down their backs. Unlike caterpillar larvae, syrphid larvae have tapered heads. Depending on their stage of development, they can range in size from one to 13 millimetres.
The larvae can be found anywhere there are aphids. Larvae crawl on soybean leaves and feed heartily on aphids. Holding them aloft and quickly draining them, Syrphid larvae can devour up to one aphid per minute.