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
