Weekly Field Crops Pest Report 2007
View from the Field
This week soybean aphids were over threshold at the Columbia County soybean sentinel plot field. They ranged from 45 to 600 aphids/plant with an average of 260/plant. There were many lady beetles larvae and pupae in the field. The photo below shows a leaflet with 190 soybean aphids.
I also saw many aphid mummies that had been previously home to parasitoids. The following photo has several soybean aphid mummies.
I saw a few Japanese beetles in the soybeans. Watch for next week’s article on defoliating insect pests of soybeans.
Potato leafhoppers were over threshold this week at the Cornell Research Farm in Valatie this week. The 10 to 12 inch alfalfa is starting to exhibit the characteristic “V-shaped” yellow leaf tip.
Western NY and Finger Lakes
Bruce Tillipaugh, CCE of Wyoming County, reported finding spider mites on soybean fields. See the article below for more details.
have been seen on soybeans. See the article below for more details.
I’ve seen a few potato leafhoppers (PLH) in alfalfa, but most of the PLH I’ve seen are adults. This is typical of other areas of the western part of the state, according to several reports. I’ve been asked several times in the past week about PLH on soybeans. They are not a pest threat at the low numbers we typically see, that is, fewer than 4 PLH per leaf.
Soybean aphids are at or close to the 250 per plant threshold in several locations in Cayuga County. They are being watched carefully to see if populations are increasing. In most cases, ladybugs of all stages, syrphid fly larvae, and aphid mummies are all common. Sarah Woodard, scout for the Cayuga County Soybean TAg saw downy mildew in soybeans this week, too.
Low numbers of soybean aphids were seen at a soybean field during Mike Stanyard’s Livingston/Ontario County Soybean TAg team meeting this week, and numbers of soybean aphid were still low at the Ontario County sentinel plot.
Are soybeans at risk from spider mites?
Many areas of NY are experiencing a lack of rainfall, which are often associated with outbreaks of spider mites in soybeans. We’ve also had short spells of really high temperatures. Together, hot and dry are the ideal conditions for spider mite invasions into soybean fields.
Two-spotted spider mites are tiny, oval, 8-legged, pale-bodied arachnids. The feeding of spider mites causes a stippling of leaves. Severe feeding by many mites causes a bronzing of the leaf. The injury from spider mite feeding can resemble a foliar fungal disease infection. Another identifying factor of spider mites is the silk-like webbing they produce. The webbing can be seen on leaflets and petioles in a heavily infested field. The mites are able to use the silk to transport by wind to un-infested areas of a field. When scouting, to help to confirm the presence of spider mites, hold a white piece of paper under a plant. Tap on the plant, and some of the mites should fall to the paper. They appear as yellow or yellow brown moving specs.
Spider mites on soybean:
Early symptoms of spider mite injury on the upper leaf surface:
Spider mite populations can increase extremely rapidly - they can develop from egg to adult in 5 days with high temperatures. Cool, damp weather often leads to steep declines in spider mite populations by encouraging fungal pathogens to take control.
Spider mites are regular residents of weedy areas at field edges. During dry weather, if these weed hosts become stressed, spider mites may begin to move into the nearby crop. Thus, an infestation usually begins at field edges and radiates into the field. While a spot-treatment with an insecticide may be helpful to combat the start of a severe infestation, it is critical to scout the whole field. Low numbers of spider mites can be present before the injury can be seen from a distance. When chemical control is chosen for spider mite management, it is critical to bear in mind the risks of "flare-ups" from use of pyrethroid insecticides.
Thinking Corn Rootworm? Know Which Fields are at Risk
Corn rootworm populations can build in a cornfield from year to year. Fields that are not rotated and remain in corn for several years are most at risk from corn rootworm damage. A two to three year rotation out of corn or cucurbits such as pumpkins reduces the risk that a corn field will reach an action threshold for this pest. This spurs the question, “Do you scout a 1st year cornfield after sod for corn rootworm?” Yes, because any pollinating cornfield can attract corn rootworm. Even worse, late pollinating corn can attract many hungry corn rootworm beetles from fields where they did not get enough pollen. After the beetles eat their fill on late season pollen they will lay eggs in the soil. So yes, you have to scout all cornfields for corn rootworm that will be planted to corn next year. You do not need to scout fields that will be rotated out of corn next year. For more information on corn rootworm checkout our online publication: Corn Rootworm Management Guide 972 pdf file
European Corn Borer Opens the Door for Anthracnose Stalk Rot
While scouting, I observed signs of European corn borer (ECB) in corn this week at the Cornell Research Farm in Valatie. There were broken leaf midribs, frass in the whorls, and holes in the stalks. European corn borer damage can on occasion cause localized problems for field corn producers. However, while its damage may be conspicuous, it more typically does not cause significant economic losses in NYS. If a field has had a history of ECB problems producers might consider crop rotation or the use of an ECB resistant (Bt) hybrid. In addition to direct feeding damage, the holes bored by ECB larvae can provide a means for the anthracnose fungus to enter the plant. Conditions that favor anthracnose stalk rot are continuous corn, surface corn residue (minimum & no tillage) and wet, humid, warm weather. Anthracnose stalk rot symptoms may appear after tasselling. Look for vertical, tan to reddish brown, water-soaked lesions (streaks) in the rind. Lesions become large, dark brown to shiny black. The best management practices to minimize or avoid anthracnose require action before or at the time of planting, i.e. the use of diseases resistant hybrids and hybrids with a good standability rating. Crop rotation with non-grass crops and plowing under infected residue are also recommended. Fields with high amounts of anthracnose leaf blight should be checked for indications of anthracnose stalk rot. If stalk rot is found you may wish to target that field for early harvest to avoid losses associated with premature lodging. For more information on corn diseases checkout our online publication: Diseases of Corn Management Guide 234k pdf file
NYS Soybean Rust Update
Weekly scouting is being done in twenty New York State sentinel plots located in the following counties: Cayuga, Chautauqua, Chemung, Chenango, Columbia, Cortland, Jefferson, Oneida, Onondaga, Ontario, Orleans, Oswego, Otsego, St. Lawrence, Seneca, Steuben, Suffolk, Wayne, and Wyoming. Plant stages in these plots reported to date range from V-2 to V-5.
NY SBR and soybean aphid (SBA) updates can also be found at the national sbr/sba website.
Dairy Livestock Barn Fly Management:
SEED GROWERS FIELD DAY
NYSIP Foundation Seed Barn
WEED SCIENCE FIELD DAYS
Valatie Research Farm – July 6
Robert B. Musgrave Research Farm- July 11
H.C. Thompson Research Farm- July 12
AURORA FIELD DAY
ROBERT MUSGRAVE RESEARCH FARM
Julie Dennis: Western NYS IPM Area Educator, Livestock and Field Crops