10. These aphids are usually found deep in the whorl of preboot sorghum, but they also occur on the underside of leaves, on stems, or in grain heads. Moldy ears could also reduce grain quality and make harvest difficult. Bird cherry oat aphid is green with an orange saddle between the cornicles.Photo by David Cappaert, www.ipmimages.org. From my observations this week, I noticed aggregated colonies at the end rows, but some areas have aphids throughout the field. This sorghum aphid problem is new for us so we are having to make some ‘educated guesses’ about what constitutes a threat, and what the best control options might be. To estimate the number of SCA and determine if management is needed in a field, follow the guidelines in our new Scouting Sugarcane Aphid guide. In fields with very uneven development, two applications may be necessary, one when approximately 25-50% of the tassels have emerged, and again after 75-100% of the tassels have emerged, if the field is still over threshold. However, I could find no data to show that corn leaf aphids ever occur in field-wide populations that would justify an insecticide application and as farther indication of this, there is no treatment threshold. What is the corn growth stage? They excrete sugar-rich honeydew that can cover the aboveground portion of plants. The corn leaf aphid can be found on corn, sorghum, wheat and barley in Nebraska. They are closely related and look very similar in size and color. Some years, the blue-green corn leaf aphid can also be found in the upper part of the canopy, but this species seems less common in southwest Minnesota than it once was. The black aphid on the upper left has been parasitized by a wasp. How do I use them? There is very little tolerance for aphid contamination or honeydew in the corn silk of fresh market sweet corn. Larvae feeding in the whorl are protected from insecticide applications and mortality will not be as high as at tassel emergence, when larvae feeding in the emerging tassel are exposed to the spray. All aphids have piercing-sucking mouthparts and feed on the sap from the plant phloem. 5. sugarcane aphid. They have spikes rising from the top rear of their abdomen. Skip Navigation. Is the field under drought stress? ADULT: A small (1/16 to 3/32 … 17). The honeydew can promote a sooty mold that interferes with plant photosynthesis. Resistance of the maize variety Jalal against corn leaf aphid Rhopalosiphum maidis, its impact on pest density and effects on yield and yield components. They show up at the top of the plant, where the tassels emerge. Look down into the tops of the silks for newly hatched larvae, and pull the ear away from the stalk slightly to look for larvae feeding between the stalk and the ear. To monitor aphid populations, examine 100 plants (5 sets of 20) for corn leaf aphids during the whorl stage (3 weeks prior to tassel emergence). When temperatures are in the 70’s during the day and the 50’s at night egg masses will take about a week to hatch. For armyworms look for ragged feeding holes and frass pellets the texture of coarse sawdust. Corn leaf aphids may be found from about four weeks prior to tasseling through tasseling. Corn leaf aphids not only infest cultivated grasses, such as corn, but many grassy-type weeds as well. Corn leaf aphids are found in the whorl of younger plants and later on the tassel and upper leaves. As they eat, corn leaf aphids make a sticky gunk called honeydew. 8. Note the long black cornicles (tail pipes). 7. and Iowa State University Extension and Outreach. Corn leaf aphid, Rhopalosiphum maidis Hosts: The corn leaf aphid shows a preference for barley, sorghum, and corn, in that order. Try to leave a strip that is a fair comparison to the majority of the field - not just along the field edge. Rate infestations on each plant using the following rating scale: 0 - no aphids. Larvae will leave the tassel as it opens up and no longer provides a moist, protected feeding environment, and move down the plant looking for protected places to feed. Spam protection has stopped this request. It can be found on wheat late in the spring, and it moves to corn and sorghum after wheat heading. It also infests many other wild and cultivated grasses. Only on rare occasions do aphids reach damaging populations. Corn leaf aphids, Rhopalosiphum maidis (Fitch), are small, 1.5 to 2.5 millimeters (1/16 to 3/32 inch), bluish-green insects with a purplish patch around the base of the prominent cornicles. The threshold for ECB and armyworms at tassel emergence is 15% infested plants. In large groups, they give the top of the corn stalk a dirty or moldy look. The economic threshold for this aphid is to treat when populations of 100 or more aphids per tiller are present. Currently, there are no treatment thresholds for aphids in corn past tasseling, but regular sampling will help you make educated decisions about a foliar application at this time. The aphid overwinters in Texas and winged migrants fly to the region each spring. Populations include both winged and wingless females. This article was originally published on August 23, 2016. This form is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply. Once a field is silking, the worm threshold drops to 5% infested plants. Soybeans are susceptible to aphid injury till the crop reaches full seed. They use piercing-sucking mouthparts to suck sap from the plant. 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