Grain aphids usually are held in check by their natural enemies, which include predators, parasites, and fungal diseases. When looking for aphids, it is important to recognize these natural enemies. Check grain fields each week starting in the fall or early spring if damage symptoms are evident. Infestations of aphids, particularly the greenbug and corn leaf aphid, occasionally build up in the fall. The first noticeable symptoms are often circular yellow to brown spots with dead plants in the center. These spots may increase in size if the infestation is allowed to persist. To determine aphid activity on tillering grain, examine 20 sites throughout the field. Each site should consist of at least 5 linear feet of a row. Look at areas in the field that are showing plant stress symptoms. Aphid damage may be confused with moisture stress or nitrogen deficiency. Count the number of aphids on small plants and, if aphids are numerous, estimate the numbers per linear foot of a row of larger plants. Make a tally of the proportion of each species, particularly if greenbugs are present.
Treatment during the fall for aphid control is normally not necessary, except in the southernmost counties in intensively managed wheat where aphids have a history of transmitting virus diseases in fall. The potential for viral transmission is impossible to predict; however, consider treatment when infestations exceed 10 to 20 winged aphids per linear foot of row, especially if the greenbug aphid is the predominant species and plant damage is observed. Treatment during the early spring before heading is occasionally needed if localized infestations are causing stand reductions and late winter weather is unusually mild. Treatment is suggested if aphid counts exceed 150 per linear foot of row throughout the majority of the field and a low degree of beneficial insect activity is present. If greenbug is the predominate species, lower thresholds to 50 per linear foot of row.
To determine aphid activity after the grain heads form, count the number of aphids on 100 heads throughout the field. Do not bias sampling by checking a few heads along the field margins where infestations usually are higher. Check for natural enemies at the same time that aphids are being counted. Aphids usually are clustered as colonies among bracts of the grain head and may move slightly when disturbed. Anything that actively moves when disturbed is probably a predator. Make a note of the ratio of predators to aphids.
The need for treatment depends primarily on the number of aphids, plant maturity, and the presence of natural enemies. Treatment during the grain head stage is generally considered when aphid numbers exceed more than 25 per head, especially if the crop is late, cool weather is forecasted, and the natural enemy complex is lacking. Control is not advised if the crop is approaching the hard-dough stage where there is good predator/parasite activity. Ratios of one or more predators to every 50 to 100 aphids are sufficient to achieve biological control.
You are viewing records 1 - 5 of 13. Next 5 Records| Insecticide and formulation | Rate of active ingredient per acre | Rate of formulation per acre | Time lmits: Days before harvest | Remarks |
|---|---|---|---|---|
| dimethoate (Dimethoate 4EC) |
0.25-0.38 lb | 0.50-0.75 pt | 35 | Restricted Use: Wheat only. May not give acceptable control when temperatures are below 60 degrees F. |
| disulfoton (Di-Syston 8E) |
0.25-0.75 lb | 4.0-12.0 oz (wheat) | 30 | Restricted Use: When applying as a broadcast spray with water or liquid fertilizer to barley at planting. When applying to barley as a foliar spray in the spring or fall, do not graze treated fields or cut for forage after any application. |
| disulfoton (foliar-fall or spring) |
0.5-1.0 lb | 0.5-1.0 pt (barley) | 30 | Restricted Use: When applying as a broadcast spray with water or liquid fertilizer to barley at planting. When applying to barley as a foliar spray in the spring or fall, do not graze treated fields or cut for forage after any application. |
| imidacloprid (Gaucho 480) |
1.0-3.0 oz per cwt of seed | Wheat, Barley Oats and Rye. Either a commercial seed treater or the producer at or immediately before planting may make applications. The former is recommended to ensure that seed is thoroughly coated to effectively control aphids transmitting barley yellow dwarf virus. Only for use in preventing disease transmission during fall. Gaucho XT contains metalaxyl fungicide (same as Allegiance FL seed treatment fungicide) and tebuconazole fungicide (same as Raxil fungicide). Check label for plant back restrictions. | ||
| imidacloprid (Gaucho XT) |
3.4 oz per cwt of seed | Wheat, Barley Oats and Rye. Either a commercial seed treater or the producer at or immediately before planting may make applications. The former is recommended to ensure that seed is thoroughly coated to effectively control aphids transmitting barley yellow dwarf virus. Only for use in preventing disease transmission during fall. Gaucho XT contains metalaxyl fungicide (same as Allegiance FL seed treatment fungicide) and tebuconazole fungicide (same as Raxil fungicide). Check label for plant back restrictions. |
