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ISSUE 6  JUNE 10, 1999

 

SUNFLOWER BEETLES ON THE MOVE

    Sunflower beetle adults became very active over the weekend and movement to new sunflower fields is
very noticeable now. Egg laying has gotten underway quickly. The pale yellow to orange eggs on the
leaves and stems should be hatching soon.

    Though we have not had reports of large numbers of adults feeding on seedlings like we have a few
years ago, it is time to intensify scouting to determine population levels in your fields.

    Scouting Method: Sampling should be 75 to 100 feet from the field’s edges. Adults and/or larvae
should be counted on 20 plants at each of 5 sites along an X pattern for a total of 100 plants. The average
number of adults and/or larvae per plant should be determined.

    Economic Threshold: Adult - one to two per seedling. Larvae - 10 to 15 per plant will cause
approximately 25 to 30% defoliation if allowed to continue feeding. Control is advised if average
defoliation reaches the 25 to 30% level.

 

Insecticides Approved for Sunflower Beetle

Trade Name

Product/Acre

Dosage
(lb AI/acre)

Asana XL*

1.45 - 5.8 fl oz**

0.0075 - 0.03

Baythroid*

1.6 - 2.8 fl oz

0.025 - 0.044

Sevin

(varies)

1.5 - 2

Furadan 4F*

0.25 - 0.5 pts

0.125 - 0.25

Lorsban 4E

1 - 1.5 pts

0.5 - 0.75

Scout X-tra*

0.71 - 1.42 fl oz

0.005 - 0.01

Warrior*

1.28 - 2.56 fl oz

0.01 - 0.02

*restricted use insecticide

** reduced rates are for SF beetle larvae

 

POTATO LEAFHOPPER CONCERNS

    The potato leafhopper invades North Dakota fields each year following migration of the leafhoppers
from southern states where they overwinter. An early arrival can mean problems for a number of crops.
Leafhoppers are currently being found in alfalfa, dry beans, potato, soybeans, and others.

    The small (1/8 in.), pale green, wedge-shaped winged adults move rapidly by jumping. Sweep nets
are useful for confirming their presence in a field. The nymphs are paler green, lack wings, and
characteristically walk sideways when disturbed on the leaf surface. The nymphs can be found on the
undersides of the leaves. The nymphs are generally more damaging than the adults since they feed for
several weeks on the leaves where they hatch. Adults move around much more.

    Feeding injury by potato leafhoppers results in a symptom called "hopperburn". The visual symptoms
include leaves changing from green to yellow to brown as they deteriorate. When leaf injury is present,
plant growth is impaired. Control of potentially damaging populations should not be delayed to the
point where damage symptoms are visible.

    In alfalfa, potato leafhoppers that arrive early can cause problems with regrowth after the first
cutting is complete. Because of their early arrival, monitoring regrowth with the use of 15 inch sweep
nets to detect adults is highly recommended.

 

Treatment Thresholds for Potato
Leafhoppers on Alfalfa

Alfalfa Stem Height (inches)

Leafhoppers/net sweep (avg)

3

0.2 adults

6

0.5 adults

8 - 11

1.0 adult or nymph

12 - 14

2.0 adults or nymphs

Insecticides approved for use to control leafhoppers in alfalfa include: permethrin*, Baythroid*, carbaryl,
dimethoate EC (Cygon, De-Fend), Furadan*, Lannate*, Lorsban, Malathion 57 EC, Penncap-M*,
and Warrior*.

    In dry beans, the threshold for basing spray decisions is when an average of one leafhopper per
trifoliate leaf is found. In 1997, early arrival of leafhoppers resulted in adult infestations in seedling dry
beans. Concerns over these populations prompted some individuals to treat infested fields, however,
reduced rates of insecticide were generally used. Reduced rate treatments were effective at reducing
the adult populations on these small plants. On larger plants with nymphal populations at threshold levels,
labeled rates would be recommended. Insecticides approved for use to control leafhoppers in dry beans
include: Asana XL*, Dimethoate EC (Cygon, De-Fend), endosulfan (Thiodan, Phaser), Lannate*,
Malathion 57 EC, Orthene 75S, and Penncap-M*.

    In potatoes, treatments are recommended when leafhoppers can be found at a level of 1 nymph
per 10 leaves. In general, sample 35 leaves from 5 locations in a field. The nymphs are sampled by
selecting leaves, and counting the number present. Sample for the presence of adult leafhoppers by
using a sweep net. Do not let infestations and damage progress to the point that yellowing of foliage
is easily detected. Insecticides approved for use to control leafhoppers in potato include: permethrin*,
Asana XL*, carbaryl, Dimethoate EC, endosulfan, Furadan 4F*, Guthion, Imidan, Vydate*, and
Penncap-M*.

 

SPINTOR LABELED FOR APPLICATION TO POTATO FOR CONTROLLING BEETLES

    Spintor, with the active ingredient spinosad, has received a federal label permitting its use on potatoes
to control the Colorado potato beetle. Spintor is a product of DowAgrosciences. The active ingredient
is a metabolite produced by the actinomycete Saccharopolyspora spinosa. This class of compounds is
referred to as Naturalyte products. The compound has demonstrated activity against caterpillars, flies,
thrips, and some beetles.

    The addition o f this compound to our arsenal of weapons against potato beetles is welcome. It provides
a unique mode of action to aid in insecticide resistance management programs. The compound has a degree
of selectivity, aiding in the conservation of insect predators that help control our pests naturally. It will not
control aphids and leafhoppers.

    This product will likely fit best when used against first generation beetle larvae. Products that affect aphids
and leafhoppers can be reserved for use later in the season when all three pests may require control. Spintor
is active against larvae and adults of the beetle; best results will be achieved when small larvae are targeted
for control.

    Resistance management guidelines on the label state that the product should not be used on consecutive
generations of beetles, and it should not be used more than twice per single generation.

    The recommended rate for Spintor to control Colorado potato beetle is 3 to 6 fl oz per acre. The label
recommends 5 gallons of water by air and 10 gallons by ground. Spintor can be applied by chemigation
through irrigation systems.

    The following insecticide efficacy information for Colorado potato beetle control was provided by R. A.
Suranyi, J. Munyaneza, D. W. Ragsdale, and E. B. Radcliffe, University of Minnesota. The experiment
was conducted at Crookston, Mn. During the 1998 season.

Colorado Potato Beetle Insecticide Trial to control Small
and Large larva, Crookston, MN. 1998.

   

Mean # of SMALL CPB larvae / plant

Insecticide

Product / a

Pre-Treat (2 July)

Post-Treat (7 July)

Percent
control

Admire 2F

18.9 fl oz

0.0 a

0.0 a

100.0

Admire 2F

13.1 fl oz

0.0 a

0.0 a

100.0

Agenda 1.67

3.7 fl oz

29.8 b

0.1 a

99.4

Provado 1.6

3.75 fl oz

23.0 b

0.6 a

95.5

Spintor 2EC

3 fl oz

21.5 b

0.3 a

97.5

Agri-Mek

8 fl oz

29.4 b

0.6 a

95.9

Thiodan 50WP

2 lbs

38.9 b

1.1 a

94.5

Agri-Mek

4 fl oz

24.8 b

2.3 b

82.6

Asana XL

9.6 fl oz

18.4 b

0.4 a

96.1

Imidan 70WP

1.4 lbs

39.6 b

4.8 b

69.8

Furadan

1.0 qt

41.6 b

3.6 b

83.0

Untreated

------

21.5 b

11.4 c

0.0

 

Mean # of LARGE CPB larvae / plant

Insecticide

Product / a

Pre-Treat (2 July)

Post-Treat
(7 July)

Percent control

Admire 2F

18.9 fl oz

0.0 a

0.0 a

100.0

Admire 2F

13.1 fl oz

0.0 a

0.0 a

100.0

Agenda 1.67

3.7 fl oz

13.0 b

0.2 a

98.2

Provado 1.6

3.75 fl oz

14.9 b

0.4 ab

97.7

Spintor 2EC

3 fl oz

14.0 b

0.5 abc

96.2

Agri-Mek

8 fl oz

8.1 ab

0.7 abcd

91.4

Thiodan 50WP

2 lbs

8.9 ab

1.4 bcd

84.5

Agri-Mek

4 fl oz

11.0 ab

1.9 cd

82.5

Asana XL

9.6 fl oz

8.4 ab

1.8 d

78.8

Imidan 70WP

1.4 lbs

11.1 ab

5.3 e

52.1

Furadan

1.0 qt

6.5 ab

10.0 f

0.0

Untreated

------

18.9 b

19.7 g

0.0

Phillip Glogoza
Extension Entomologist

 

HEAVY FLEA BEETLE PRESSURE ON CANOLA!

    Flea beetles are still moving into canola fields regardless of the planting date. Numerous acreage is
being or will be treated in the early crop stage - seedling. Unfortunately, some Gaucho-treated fields
have had to be sprayed. There are several possible reasons why the Gaucho-treated seed isn’t working
as well this year.

    One explanation is the wet, rainy weather has leached some of the insecticide preventing the seed
from absorbing it during germination. In turn, the leaching or chemical degradation has reduced the efficacy
or time span when the insecticide is effective. Remember, flea beetles are actively feeding for a 3-4
week window, and seedlings with low levels of pesticides may not be killing flea beetles. In addition, flea
beetles appear to be concentrating on the reduced acreage of canola planted this year. So, flea beetle
pressure is high on a decreased numbers of fields.

    On early seeded canola fields, late April to early May, seeds did not germinate and emerge until 2-3
weeks due to the cool, wet weather, and Gaucho has little efficacy against flea beetles after 21 days.
Some observations also indicate more flea beetle problems on Gaucho-treated seed for the smaller seeded
(150,000 seeds per pound) and less vigorous varieties of canola like Hudson. Research from Canada
indicates that the larger seeded (70,000 seed per pound) varieties, like Hyola, can endure more flea
beetle damage.

    Field monitoring is very important for fields in the susceptible stage - seedling. The Economic
Threshold (E.T.) for flea beetle on canola is 25% foliar damage (pitting) during the seedling stage.
Remember, scout several areas of the field. If fields are above E.T., a foliar treatment of Warrior is
recommended. After plants reach the two true leaf stage, canola plants can sustain and outgrow most
flea beetle damage.

    Tank Mixing Warriortm with Herbicides. Some questions have arose about tank mixing Warrior
with herbicides. The Zeneca field representative indicates that Warrior is compatible with most canola
herbicides like Assure. It is not recommended for tank mixing with Assert. When tank mixing, Warrior
should always be placed in the tank last. A jar mix is a quick and easy way to see if the chemicals are
compatible.

Jan Knodel
Area Plant Protection Specialist
Minot Research and Extension Center


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