Keep Banded Moth in your Cross Hairs
Tuesday, April 2, 2002
filed under: Insects
Keep Banded Moth in your Cross Hairs
Your Trigger Finger Should Also Be Ready For Other Potential Bug Problems
Keep the banded sunflower moth in your cross hairs this growing season, and your trigger finger ready for other bugs that may affect sunflower.
Phil Glogoza, North Dakota State University extension entomologist, says there was a high incidence of banded moths last year, and a mild winter may help their overwintering survival rate. “With high winter survival, we could be set up for problems, with populations increasing dramatically this coming year,” he says.
Sunflower field surveys conducted in the Dakotas last September indicated other insects that should be monitored as well. Lygus, head moth, red sunflower seed weevils, and sunflower midge, had a sporadic field presence with damage to a varying degree.
Seed damage within fields from the banded moth averaged about 7% in North Dakota, according to the NSA field surveys, and ranged from a low of 2% in the west central part of the state, to as high as 10% in east central N.D. In South Dakota, seed damage averaged about 3%, with a low of 1% in northwest S.D., and a high of 7% in the north central part of the state.
According to the NSA field surveys, seed damage attributed to the red seed weevil was greater in South Dakota than in North Dakota. Seed damage in S.D. averaged 9%, with the greatest amount of damage in the southwest part of the state, at 18%. N.D. seed damage averaged 4% statewide, with 8% in the southeast part of the state.
Banded Moth Backgrounder
According to NDSU, banded sunflower moths begin to emerge from the soil about mid July and are present in the field until about mid August. Adult populations (east central North Dakota) are usually at their highest levels the latter part of July, with an average life span of seven to 10 days. Moths flutter from plant to plant but do not feed.
Within a week after emergence, the moths begin to lay eggs on the bracts of the sunflower heads in the late bud stage. Females deposit more eggs on pre-bloom to bloom stage sunflower heads (R4-5) than on early bud (R2-3) or post-bloom (R6) sunflower heads. Eggs will be present through early August, hatching in five to eight days after being deposited. Newly emerged larvae are usually found on sunflower bracts. As they get older and larger they move to the disk flowers where they begin feeding on pollen, and then seeds. The maximum density of larvae in the sunflower head occurs in mid August. After feeding to maturity, larvae drop to the ground and spin cocoons in the soil where they pass the winter.
Seed damage done by larvae of the banded sunflower moth resembles damage caused by the red sunflower seed weevil. However, the banded sunflower moth normally consumes the entire kernel, whereas the seed weevil larva consumes only about one-third of the kernel. Also, the exit hole in the seed created by the banded sunflower moth larva is slightly larger than the one made by the seed weevil larva and is usually located on the top, rather than on the side of the seed.
In most cases banded sunflower moth larvae will have exited the seeds by the time the heads are harvested. This is in contrast to red seed weevil larvae, which may still be in the seed at harvest and can cause heating and moisture problems in storage.
Evidence of infestation of sunflower seeds by the red seed weevil can be confirmed through an examination of the seed after harvest. Damage from banded sunflower moth is less likely to be detected by examining harvested seeds. Since the seed kernel is entirely consumed by the larva, the seeds sometimes pass through the combine.
Treatment should be considered when one moth for every two sunflower plants inspected is found. Because moths initially congregate around field margins prior to flowering, treatment of field margins may reduce the adult population below damaging levels. If perimeter treatments are used, field monitoring for banded moth should continue in case of additional moth migration to the field.
Standing Alfalfa Strips May Help Control Lygus
Lygus bugs, also called tarnished plant bugs, were present in many North Dakota sunflower fields last year. The NSA field survey last September indicated an average seed damage of 4%, with lower damage levels found in South Dakota fields.
Research by NDSU at several sites in North Dakota last year found lygus in sunflower at flowering, with populations declining markedly as sunflower bloom declines.
Adult lygus bugs are about a quarter inch long and an eighth inch wide. Older adults will usually have a distinctive mottled coloration with light wing tips and a pale yellow V-shaped mark near the middle of the back. First-stage nymphs are very small, wingless and bright green in color. They may look similar to aphids, but are much more mobile. Adults are able to fly and will migrate from crop to crop.
The insects prefer softer plant tissue and small-seeded broadleaf plants. Canola, alfalfa, soybeans, sugarbeets, mustard, safflower, buckwheat, mustard, and sunflower are all attractive to lygus. Entomologists believe sunflower is probably not a preferred crop, but it moves to sunflower and other green broadleaf plants when other crops such as canola and alfalfa mature or are harvested.
Crop scientists believe lygus feeding activity on immature, developing seed causes brown spot in confection sunflower. The feeding activity is microscopic and can’t be seen with the naked eye. The damage becomes apparent later as brown spots on hulled sunflower kernels, which reduces their market value.
In the South, lygus bugs can damage cotton by feeding on developing flower buds. There, growers are encouraged to leave standing strips of alfalfa next to their cotton fields. Lygus will concentrate in these standing strips, and reduce the numbers migrating in search of greener plants to feed on. “Without research to back it up, it’s possible that if you have confection sunflower with alfalfa near by, consider leaving a patch of the alfalfa standing in the July cutting,” says Glogoza. “The adult lygus may be more attracted to staying in the alfalfa than dispersing, helping to minimize movement of lygus into later-season broadleaf crops such as sunflower or sugarbeets.”
Fortunately lygus bugs can be controlled at the same time confection sunflower is treated for other insects, such as the seed weevil and banded sunflower moth. The only insecticide currently labeled for lygus bugs on sunflower is Lorsban 4E. Other insecticides are labeled for application during flowering but do not currently include lygus on the label.
Entomologists suggest two treatments to sufficiently protect confection sunflower heads from insect feeding: One application at the onset of pollen shed or approximately 10% bloom, followed by a second treatment seven days later. This regimen should adequately control insects on confection sunflower throughout flowering.
Bob Majkrzak, president and CEO of Red River Commodities Inc., Fargo, N.D., says that confection producers who followed the two-spray program last year generally had good insect control results.
Overall insect damage last year was down, and brown spot from lygus declined considerably, he says, due largely to increased producer awareness of controlling insects, and spraying when appropriate.
He says there is a direct correlation between field treatments and percent of seed damage in confection sunflower: Those who sprayed twice generally had excellent control. “We’re hearing guys who may have only sprayed once, and ended up with three to five percent damage, and some who were lucky to get damage under two percent. Anybody who tried to get away with no spray almost all had problems. We saw damage in those cases reach double digits. Then, it just renders the entire crop unusable for human consumption, and even from a bird food perspective, when a buyer will ask, ‘why are all these holes in the seed?’”
Majkrzak says timing is critical for control, and even a few days can make a key difference. “Some growers may have lined up a spray pilot, but then had their treatment moved back because it rained or was too windy. And if you have a hybrid that goes to full bloom in a week, missing a couple of days can really be a huge problem, because these bugs can do a lot of damage in one or two days time.”
Although confection sunflower producers should consider two treatments, oil sunflower growers may be able to get by with one treatment. Entomologists, empathetic to market prices and crop production costs, advise producers to watch their developing sunflower crops and use their best judgement. If lygus bugs, banded sunflower moth, or the red seed weevil are present at economic levels, treat sunflower at 10% bloom (R-5). Applying only one treatment may risk damage if one or more insects re-infest the crop again while it’s still vulnerable to damage. The yield impact of lygus on oil sunflower is not clear.
While sunflower growers need to be vigilant in monitoring common insect pests, there can also be localized “hot spots” of other insect problems. NDSU’s Glogoza says there were grasshopper hot spots in south central N.D. last year. These areas should be watched closely this year for possible treatment, depending on how the weather develops.
Michael Catangui, South Dakota State University extension entomologist, says that the Dectes stem borer (also referred to as the longhorn beetle or soybean stem borer) and pale striped flea beetle have caused high levels of damage in localized areas of South Dakota in recent years. However, the red seed weevil has been a more noticeable problem throughout the state. Seed weevil treatment, recommended when one to two weevils are found per plant, is advised on confection sunflower when three out of 10 plants are beginning to shed pollen.
High Plains Saw Head Moth in ’01
Roger Stockton, extension crops specialist, Kansas State University, Colby, says insect pressure in 2001 was higher than the last few years, particularly the sunflower head moth “There were reports of other insects such as the spotted stem weevil and the longhorn beetle (soybean stem borer) but it was the head moth that seemed to be most prevalent last year, particularly in central Kansas,” says Stockton.
It’s not unusual for insect pest populations to cycle up and down with weather patterns and the population cycle of natural predators. Stockton points out that a growing season with higher moth numbers in 1987 was preceded in 1986 and followed in 1988 with average moth numbers. “We hope that would be the case next year, but there’s no way of guaranteeing that at this point.”
Stockton says pyrethroid insecticides such as Warrior, Asana XL, Baythroid, and Scout X-Tra are not as effective when applied during temperatures above 95 degrees, “and we had quite a few of those type of days at spraying in central Kansas. It didn’t seem to be as much as a problem in western Kansas.”
The heat also accelerated bloom, thus resulting in a narrower window for insecticide applications. “A lot of growers will spray at the onset of bloom, then seven days after the first application if needed. Because of the heat, sunflower finished blooming quicker. So when some went back into the field seven days after the first application, not only did they find insect pressure but sunflower was finished blooming, and they had missed the opportunity in some instances for a timely second application.”
Factored together, higher insect pressure combined with less favorable application conditions resulted in less effective control for some sunflower producers in 2001, says Stockton. The pest pressure and dry conditions combined for variable yields. “For the kind of heat and insect pressure we had, there was still a 1,200 lb/acre yield average in central Kansas. Sunflower can be heat and drought tolerant but when you get enough dry, hot days, it can have an effect on yield. Some guys were an inch or two off of rainfall from having a good crop.”
Stockton says Kansas saw an increase in irrigated sunflower acres in 2001, and yield reports on irrigated circles were good.
“Many of those fields missed the effects of the heat and some insect pressure,” says Stockton. “We may see more irrigated sunflower in western Kansas next year. Well production is low enough for some that they can’t irrigate corn, so they’ll use no-till and go with winter wheat and plant sunflower or sorghum with limited irrigation and get two or three crops in two years.”
For more information on limited irrigation, see articles under Irrigation/Water Use online at www.sunflowernsa.com. Click on “The Sunflower Magazine” link, then “the archives.”
Aster Yellows or Seed Maggot to Blame for “Petal Heads”
During bloom of the 2000 growing season, producers and agronomists alike noticed some odd-looking, misshapen sunflower, some with ray petals growing in the middle of the head, usually in a pie-shaped wedge formation. Sunflower experts believe either aster yellows, seed maggot activity, or both, was to blame for the occasional “petal heads” found in sunflower.
Mycogen/Dow agronomist Bruce Due is even more convinced of that. He and others kept a closer eye on the phenomenon last year. Aster yellows was generally more prevalent north of I-94, and the seed maggot more prevalent south of I-94.
Aster yellows is a minor disease that can be transmitted to flax, canola, sunflower, and other plants, primarily spread by six-spotted leafhoppers that migrate from the south. Aster yellows can result in head sterility, misshapen heads, and misplaced ray petal formation on the head.
Due says the sunflower seed maggot causes more localized seed sterility when newly hatched larvae tunnel into the corolla of young blooms. Bract damage and a crease of scar tissue on the head that is sometimes (but not usually) accompanied by the misplaced ray petals is more characteristic of seed maggot activity, he says.
The aster yellows/seed maggot observations have been mostly cosmetic. Yield losses from both aster yellows and the seed maggot are usually minor, with treatment generally not recommended. Field observations of misshapen sunflower heads were sporadic with little damage in 2000, and the observations were even less last year, says Due.
Insect Info on the Internet
2002 N.D. Field Crop Insect Management Guide
NDSU Crop Insect Publications
North Dakota State University Entomology
South Dakota State University Extension Entomology
Kansas State University Extension Entomology