Crop Profile for Sorghum in North Carolina

Prepared: January, 1999
Revised: November, 1999

General Production Information

 

Production Regions

Grain sorghum grown in the coastal plain of North Carolina is mostly used as a rotational crop behind potatoes, wheat, or other early season crops. In the piedmont, some sorghum is grown for both grain and silage.

 

Productions Practices

Sorghum is grown in North Carolina much as field corn is done, although it is usually planted later. The vast majority of corn is rain-fed rather than irrigated, though sweet corn is more typically irrigated. Corn is grown on a wide variety of soil types from loamy sands to clays to organic soils. Conventional, strip-tillage, and no-tillage culture are all widely practiced. Recently, there has been a shift to conservation tillage (no-till, strip-till, minimum-till), and this trend continues at present. Typically corn grown in the coastal plain is rotated, whereas the crop is usually not rotated when grown in the piedmont or mountains. Field corn is characterized by early inputs of fertilizer, herbicide, and insecticides, followed by little attention until harvest. Field corn culture, including harvest and postharvest handling, is totally mechanized. Sweet corn culture is similar to field corn culture except for an intensive use of insecticides (during the reproductive period), irrigation, and manual labor.

 

 


Insect Pests

Use of insecticides
and loss of phosphate and carbamate insecticides

Most field corn and sorghum get less than a single application of insecticide yearly. Both crops have a low profit margin, and growers are reluctant to spend money on insecticide except where there is a demonstrated or perceived risk. Many of the insects listed below, with accompanying phosphate or carbamate insecticide information, are very sporadic in distribution, both in time and space. Whereas the pest may not cause much loss of value within a single year, some years the pest can be very important. Likewise, a pest may not occur over much of the production area but may be very important on specific farms.

Pest managers have to deal with the high variation of pest types and abundance. Flexibility is very important in appropriately meeting pest management needs. Having a variety of product selection is critical to appropriately managing pests and allowing sustainability in the agricultural system. Insecticide resistance also places high demand on having insecticidal compounds that serve as alternatives or components in a mix. Losing pesticides through market attrition, pest resistance, and regulatory restriction can leave the pest manager and grower in an inferior position. For example, North Carolina has the second-largest contiguous area of organic soils in the U.S. Much of this acreage is devoted to corn production. Currently, only two insecticides remain viable alternatives for billbug and wireworm control. The two, terbufos and carbofuran, have had their use rates reduced, although one has had former rates reinstated via a special state label. Both are potential candidates for cancellation. The loss of one or both products will seriously affect corn insect management and farm sustainability in the region.

 

Insects

Corn earworm

Crop interactions:
Corn earworm, H. zea, infests the heads and consumes developing grain. The degree of infestation is greatly influenced by the synchrony of egg-laying moths and blooming of the crop. Corn earworm is one of a complex of pests, including sorghum webworm and fall armyworm, that may occur as a mixed population of grain-feeding pests.

Control:
Early planted grain sorghum seldom is economically infested with head-feeding caterpillars. Later-planted sorghum is scouted, and above-threshold infestations are treated with insecticides.

Table 1. Phosphate & carbamate insecticides used to manage corn earworms in sorghum
Chemical Class Avg. Active
Ingredient
Crop Treated
(estimate)
Timing Substrate Soil Types
Methyl parathion phosphate 0.75 lb/acre < 1% seedling plants not applicable
Chlorpyrifos phosphate 1 lb/acre <1% seedling plants not applicable
Carbaryl carbamate 2 lbs/acre <1% seedling plants not applicable

 

Fall armyworm

Crop interactions:
Both whorl and heads are infested by fall armyworm, S. frugiperda. Sorghum is attractive to egg-laying moths in the early-whorl stage and again during flowering. Very high populations may develop on late-planted whorl-stage plants. On heads, fall armyworm is usually a minor partner with other head-feeding caterpillars.

Control:
Early planted grain sorghum is seldom attractive to egg-laying moths. On late-planted sorghum, scouting, thresholds, and insecticides are the primary controls deployed.

Table 2. Phosphate & carbamate insecticides used to manage fall armyworms in sorghum
Chemical Class Avg. Active
Ingredient
Crop Treated
(estimate)
Timing Substrate Soil Types
Methyl parathion phosphate 0.75 lb/acre < 1% whorl & heading plants not applicable
Chlorpyrifos phosphate 1 lb/acre <1% whorl & heading plants not applicable
Carbaryl carbamate 2 lbs/acre <1% whorl & heading plants not applicable

 

Sorghum webworm

Crop interactions:
The sorghum webworm, Nola sorghiella, is a small, common, grain-feeding caterpillar in sorghum that usually occurs in mixed populations with corn earworm and fall armyworm. The small caterpillars eat into the grain and consume the content within.

Control:
Early planted grain sorghum is seldom attractive to egg-laying moths. On late-planted sorghum, scouting, thresholds, and insecticides are the primary controls deployed.

Table 3. Phosphate & carbamate insecticides used to manage sorghum webworms in sorghum
Chemical Class Avg. Active
Ingredient
Crop Treated
(estimate)
Timing Substrate Soil Types
Methyl parathion phosphate 0.75 lb/acre < 1% heading plants not applicable
Chlorpyrifos phosphate 1 lb/acre <1% heading plants not applicable
Carbaryl carbamate 2 lbs/acre <1% heading plants not applicable

 

Sorghum midge

Crop interactions:
Sorghum midge, Contrainia sorghicola, is a sporadic pest in North Carolina, but when it does occur, it can devastate the crop. It is most commonly found in high populations where serial plantings are made and alternate hosts are abundant. The adult fly is very fragile and lives only a short time. Maggots develop within the developing grain, destroying the grain in the process.

Control:
Early planted grain sorghum is seldom attractive to egg-laying flies. On late-planted sorghum, scouting, thresholds, and insecticides are the primary controls deployed.

Table 4. Phosphate & carbamate insecticides used to manage sorghum midges in sorghum
Chemical Class Avg. Active
Ingredient
Crop Treated
(estimate)
Timing Substrate Soil Types
Methyl parathion phosphate 0.75 lb/acre < 1% heading plants not applicable
Chlorpyrifos phosphate 1 lb/acre <1% heading plants not applicable
Carbaryl carbamate 2 lb/acre <1% heading plants not applicable

 

Aphids

Crop interactions:
Several species of aphids attack sorghum, but the main one is the corn leaf aphid, R. maidis. They are minor pests. The aphids infest plants during the whorl stage.

Control:
Biological control organisms keep most aphid infestations in check. When they become very abundant during periods of low biological control activity, insecticides may be applied.

Table 5. Phosphate & carbamate insecticides used to manage aphids in sorghum
Chemical Class Avg. Active
Ingredient
Crop Treated
(estimate)
Timing Substrate Soil Types
Dimethoate Phosphate 1 lb/acre <1% whorl plants not applicable
Malathion phosphate 0.9 lb/acre <1% whorl plants not applicable

 

 

On-Line Resources

North Carolina Integrated Pest Management

North Carolina Pesticide Impact Assessment Program

Insect Pests of Sorghum

Corn Earworm

Fall Armyworm

Sorghum Webworm

Sorghum Midge

Aphids



Contacts

John Van Duyn, Extension specialist, V. G. James Research and Extension Center, North Carolina State University

Ronnie Heiniger, Extension specialist, Department of Crop Science, V. G. James Research and Extension Center, North Carolina State University

 

 

References

  1. Crop protection reference. C&P Press. New York, N.Y.
  2. 1998 North Carolina agricultural chemicals manual. North Carolina State University. Raleigh, N.C.
  3. North Carolina Department of Agriculture and Consumer Services Statistical Service. Raleigh, N.C.


Database and web development by the NSF Center for Integrated Pest Managment located at North Carolina State University. All materials may be used freely with credit to the USDA.