Sugarcane aphid was first seen as a pest of sorghum in Alabama in 2014. It cost sorghum producers a lot of money due to cost of control as well as in yield losses in spite of control. In the past week or so, sugarcane aphid has been found on Johnsongrass in southeastern Arkansas as well as in Johnsongrass and sorghum in Texas.
It is likely that the aphid will be found in Alabama soon. If you plan on growing any kind of sorghum or sorghum hybrid this year, you need to know as soon as sugarcane aphid appears in your area. Start by checking Johnsongrass that is near the fields that have been or will be planted to sorghum IMMEDIATELY. Pay close attention to the undersides of the leaves. Scout Johnsongrass weekly until the sorghum has emerged. At that point you can redirect your scouting efforts to the crop.
This is a new pest, and entomologists and Extension agents and specialists are still trying to come up with the best way to look for the aphids, as well as to determine the most effective action threshold for treating with a foliar insecticide. At the bottom of this blog post you will see links to REQUIRED READING or VIEWING if you plan to grow sorghum successfully this year. DO NOT plant sorghum if you are unable to scout your fields for aphids and apply 1-2 applications of a foliar insecticide.
Sorghum growers can stay ahead of the problem in 2015 by using the following tactics:
1. Use an insecticide seed treatment on your sorghum seed, which will give you at least a few weeks of early season protection from sugarcane aphid. Look for seed treated with clothianidin (Poncho 600 @ 5.1-6.4 fl. oz. per hundred pounds of seed or equivalent), imidacloprid (Gaucho 600 @ 6.4 fl. oz. per hundred pounds of seed or equivalent), or thiamethoxam (Cruiser 5 FS @ 5.1-7.6 fl. oz. per hundred pounds of seed, or equivalent).
2. Scout the sorghum twice weekly starting as soon as the crop emerges if an insecticide seed treatment was not used. Start scouting weekly as soon as the crop emerges if a seed treatment was used. Look all over the plant especially the underside of the leaves. A stick or sweep net handle may come in handy to turn the plants/leaves over to see the undersides of the leaves. Examine the plants in 50 row-ft on each edge of the field and 25 feet into the field. Also check sorghum growing near Johnsongrass.
3. When aphids are found, scout twice a week. Several action thresholds have been proposed (see details in the links below), but they will result in taking action at more or less the same time. As the season progresses, and more is learned about the pest, these thresholds may change. In summary these thresholds are:
- Depending on growth stage, treat when 20 to 30 sorghum plants out of 100 have aphids and you can find areas of the field with numerous aphids and heavy deposits of aphid honeydew (Mississippi).
- Treat when 50 aphids per leaf are colonizing 20 percent of the plants (before or during boot milk stage) (Louisiana).
- Treat when 25% or the plants are infested with 50 or more sugarcane aphids per leaf (Arkansas).
- Treat when there are 50 to 125 aphids per leaf (consider lower side of this range if you are sampling once a week, and the higher side if you are sampling twice weekly and natural enemies are present) (Texas A&M AgriLIfe Research and Extension).
4. In Alabama, three insecticides are available for controlling sugarcane aphid on sorghum in 2015:
- sulfoxaflor (Transform WG at the rate of 0.75-1.5 oz./A). Do not apply within 14 days of harvest or 7 days of grazing or forage, fodder or hay harvest). Do not apply more than 3 oz of Transform WG per acre per year. Cost of this material, not including application costs, is around $5-12 per acre. For grain, forage, and sweet sorghum.
- flupyradifurone (Sivanto 200 SL at the rate of 4-7 fl. oz./A). Do not apply within 21 days of harvest or 7 days of grazing or forage, fodder or hay harvest). Do not apply more than 28 fl. oz. of Sivanto 200 SL acre per year. For grain, forage, and sweet sorghum.
- chlorpyrifos (Lorsban Advanced at the rate of 2 pints per acre, or generic equivalent). This treatment will cost around $12 per acre and has a 60 day harvest and grazing restriction. It should not be used when sugarcane aphids are very high. For grain sorghum only.
5. Sugarcane aphids continue to cause yield losses through the dough stage. At black layer or after, they are a concern if they build up in the heads and interfere with harvest.
6. Other recommendations to minimize problems with sugarcane aphid: plant early, use a high seeding rate to promote a thick stand, do not over fertilize, use enough water per acre (five gallons/A by air or 15-20 gallons/A by ground, do not use a broad spectrum insecticide such as pyrethroid to control caterpillars (see required reading and viewing links below).
7. If you think you have found sugarcane aphid on sorghum or johnsongrass in Alabama, please contact me or your regional Agronomic Crops Extension agent. Consider downloading the Alabamacrops app (for Android or iPhone/iPad), which makes it easy for you to contact your regional agent or submit a photo or question.