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ISSUE 14   August 26, 2010

SULFUR AND WHITE BUTTERFLIES COMMON

There has been some interest in the yellow and white butterflies flying around in field crops and ditches and whether they are an insect pest. These butterflies belong to the insect family Pieridae and to the group called Sulphurs and Whites, which are usually white or yellow in color. Most of their caterpillars are green, usually with one or more pale lateral stripes. Their body surface is covered with minute hairs, which gives them a velvety appearance. Larvae of resident species overwinter as chrysalids.

At least 14 species of this group occur in North Dakota. Common examples include the checkered white (Fig. 1), cabbage butterfly or imported cabbageworm (Fig. 2) and alfalfa butterfly (Fig. 3).


Figure 1.
Checkered butterfly, female on left and male on right (G. Fauske, NDSU)


Figure 2.
Cabbage butterfly female on left and male on right  (G. Fauske, NDSU) 


Figure 3.
Alfalfa butterfly, female on left and male on right  (G. Fauske, NDSU) 

The cabbage butterfly or imported cabbageworm is attracted to plants in the mustard family (cabbage, broccoli, cauliflower, canola) and can be an occasional garden pest. It is typically not an insect pest of canola. The alfalfa butterfly is rarely an insect pest of alfalfa in North Dakota. If large numbers of yellow or white butterflies are observed flying above alfalfa early in season, this is a good indication of possible problems later in the season. Scout fields by sweeping for larvae (caterpillars). An economic threshold level would be 10 larvae in one 180 degree sweep.

 

SAP BEETLES DAMAGING CORN EARS

Sap beetles (or picnic beetles) have been observed feeding and damaging corn ears near Jamestown (Fig. 4).


Figure 4.
Corn damaged by sap beetles
(L. Brower, Stutsman County Extension, NDSU)

One of the most common sap beetles is Glischrochilus quadrisignatus, which is ¼ inch long, black with four orange-red spots on the wing covers and has “knobbed” antennae (Fig. 5).  


Figure 5.
Sap beetle, Glischrochilus
quadripunctatus (J. Hulcr, MSU, Bugwood.org)

Adult sap beetles feed on decaying, ripening plant material. They are commonly observed feeding on overripe fruits (raspberries, strawberries) and vegetables (tomatoes). In corn, they typically invade the ear near injury sites from birds or other insects. Sap beetles also are a nuisance and congregate in large numbers on screen doors of homes, around garbage cans, or picnic areas, or anywhere fermenting plant juices occur. Some sap beetles carry organisms that cause rots in fruits. There is no insecticide that provides good control of sap beetles in corn.

  

PHEROMONE TRAP CATCHES OF BANDED SUNFLOWER MOTH AND SUNFLOWER MOTH DECREASING 

Trap catches for adult banded sunflower moth and sunflower moth have decreased to low levels (Figs. 6 & 7). Larvae can now be observed feeding on the sunflower heads until mid-September. When mature, larvae drop to the soil to overwinter. However, sunflower moth larvae do not survive the cold winters in North Dakota.


Figure 6.
Banded sunflower moth
pheromone trapping map (T. Mittelsteadt, NSA)


Figure 7.
Sunflower moth pheromone
trapping map (T. Mittelsteadt, NSA)

 

LATE-SEASON GRASSHOPPERS INCREASING - SCOUTING IMPORTANT

There have been reports of increasing grasshopper populations, especially in western North Dakota. Adult grasshoppers are very mobile and can fly around to find green crops. So, it is important to continue to scout for grasshoppers in late-season row crops, such as sunflower, corn, flax, etc. When 20 or more adults per square yard are found in field margins or 8 to 14 adults per square yard are occurring in the crop, treatment would be justified. In some cases, only field edges need to be sprayed to protect fields from grasshopper infestations. Be sure to check preharvest intervals before application. For insecticide recommendations, please consult the 2010 North Dakota Field Crop Insect Management Guide:  http://www.ag.ndsu.edu/pubs/plantsci/pests/e1143w1.htm

  

HORNETS/YELLOWJACKETS

The Extension Entomology office has started getting calls on annoying hornets swarming or hornet nests in homes or in trees nearby houses. Hornets (or yellowjackets) (Fig. 8) belong to the family Vespidae.


Figure 8.
Hornet (J. Payne, USDA ARS, Bugwood.org)

All yellowjackets sting and their stinging behavior is considered a defensive reaction when the colony is threatened. They can sting more than once because their stinger stays with the insect. Yellowjackets are more aggressive during August into September and more likely to sting people. Although yellowjackets are actually a beneficial insect feeding on other insects, they often become a pest problem when nests are located near homes, schools, picnic areas, or playgrounds. Pest control is often warranted.

Biology:  These wasps are social insects and build nests of paper-like material. Nests generally resemble a teardrop-shaped soccer ball and often are seen hanging in trees. Sometimes nests are located underground in mammal burrows, cavities or in between house siding. In the northern temperate climates, only the mated queen wasp overwinters from the previous year’s colony.  Queens are inactive during the winter, hiding in protected places like under tree barks or attics. In early spring, the overwintering queen builds a new nest and lays an egg in each cell. Larvae hatch from the eggs and are dependent on the queen for food. The queen forages outside the nest and brings food (caterpillars and other insects) back to the larvae until pupation. Sterile female workers emerge from pupae and take over nest building and brood rearing, while the queen stays in the nest. During late summer into early fall, adult males and newly produced queens leave their parent colony. The colony dies off, and only newly mated queens will find a protected place to overwinter.

Control: Vespid wasps are active outside the nest during the daylight hours. Nearly the entire colony is in the nest during the evening and night-time hours, so control measures should be applied to the nest then. There are many insecticides labeled for control of hornets and yellowjackets. The difficulty is making the treatment without being stung. Usually an aerosol spray of one of the many fast-acting wasp killer will quickly kill all workers present in nest. Examples are permethrin, synergized pyrethrins or pyrethroid insecticides. A slower-acting insecticidal approach is to apply carbaryl (Sevin) dust directly onto the exposed nest and entrance hole. After treatment, check the nest for any activity the following day and re-treat if necessary. Nests should be removed to avoid attracting dermestid beetles at some later time and to keep wasp pupae from possibly reestablishing the nest. If dealing with yellowjacket nests in structures like homes, the nest entrance should never be plugged from the outside. If constrained yellowjacket workers cannot escape to the outside, they may locate a way to escape toward the inside of the home or structure, creating a possible stinging threat for people inside. Yellowjacket nests become an important source of carpet and other dermestid beetle infestations in the home, so the nest should be removed whenever possible. When outside enjoying your picnic, avoid wearing bright colors and perfumes which are attractive to hornets and yellowjackets. 

 

INSECTICIDE UPDATE:  BAYER AGREES TO TERMINATE ALL USES OF ALDICARB

WASHINGTON - The U.S. Environmental Protection Agency and Bayer CropScience, the manufacturer, have reached an agreement to end use of the pesticide aldicarb in the United States. A new risk assessment conducted by EPA based on recently submitted toxicity data indicates that aldicarb, an N-methyl carbamate insecticide, no longer meets the agency's rigorous food safety standards and may pose unacceptable dietary risks, especially to infants and young children. To address the most significant risks, Bayer has agreed first to end aldicarb use on citrus and potatoes and will adopt risk mitigation measures for other uses to protect groundwater resources. New measures to protect shallow drinking water wells in vulnerable areas of the southeastern U.S. coastal plain and lower application rates will be immediately added to product labels for use on cotton, soybeans, and peanuts.

The company will voluntarily phase out production of aldicarb by December 31, 2014. All remaining aldicarb uses will end no later than August 2018. Additionally, EPA plans to revoke the tolerances (legal pesticide residues allowed in food) associated with these commodities. EPA did this to ensure we have the safest food supply possible.

Based upon current toxicological studies, aldicarb at levels higher than those typically found in food has the potential to cause various effects such as sweating, nausea, dizziness and blurred vision, abdominal pain, vomiting, and diarrhea.

Aldicarb is registered for use as a systemic insecticide and nematicide on agricultural crops, and is formulated and marketed solely as a granular pesticide under the trade name Temik. During the phase-out, the pesticide will continue to be registered for use on cotton, dry beans, peanuts, soybeans, sugar beets, and sweet potatoes. Aldicarb products are not intended for sale to homeowners or for use in residential settings. A restricted use pesticide, aldicarb may be applied only by trained, certified pesticide applicators.

The memorandum of agreement and the agency's updated dietary risk assessment and supporting materials will be available in the aldicarb reregistration docket, EPA-HQ-OPP-2005-0163, and in the aldicarb Special Review docket, EPA-HQ-OPP-2006-0197, at regulations.gov.

The U.S. has a safe and abundant food supply, and children and others should continue to eat a variety of foods, as recommended by the federal government and nutritional experts.  

More information:  www.epa.gov/oppsrrd1/REDs/factsheets/aldicarb_fs.html
To view the dockets: http://www.regulations.gov

(News Release from EPA Pesticide Program Updates - 8/17/2010)

Janet Knodel
Extension Entomologist
janet.knodel@ndsu.edu


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