NDSU Crop and Pest Report

Entomology


ISSUE 9  June 26, 2003

GRASSHOPPER CONTROL IN NON-CROP AREAS

There have been questions regarding insecticides labeled for grasshopper control in roadside rights of way. Below is a list of insecticides labeled for such use that allow for use of the forage and also a list of insecticides that do not. The haying/grazing issue is very important., particularly if a community coordinated grasshopper control program is being implemented.

Insecticide

 

Labeled Sites

Restrictions

Insecticides that allow grazing or cutting for Hay

carbaryl (various formulations)

 

Non-cropland - CRP, Set-Aside, Wasteland, Rights-of-Way, Hedgerows, Ditchbanks, Roadsides

Do not apply within 14 days of grazing or harvest for forage or hay

Dimilin

RUP

Non-crop areas (field border, fence rows, roadsides, farmsteads, ditchbanks, wasteland, CRP)

No time limitation on grazing or cutting.

Malathion

 

Non-agricultural lands (Wasteland, Roadside, Soil Bank (Not Grazed)

Some formulations DO have grazing restrictions.

Malathion ULV

 

Uncultivated non-agricultural land (wasteland, roadsides)

No time limitation on grazing or cutting.

Insecticides that DO NOT allow grazing or cutting for hay

Acephate 75%

 

Non-crop areas (field borders, fencerows, roadsides, ditchbanks, borrow pits)

Do not graze or feed vegetation cut from treated areas.

Asana XL

RUP

Non-Cropland (excluding public land such as forests, parks, or recreational). For use on non-cropland adjacent to tilled areas to control migrating grasshoppers.

Do not feed treated crop to livestock.

Warrior (SLN)

RUP/SLN

Non-Cropland: Agricultural areas that include right-of-ways, barrier strips and fence rows that are adjacent to crop outlets registered for the use of Warrior T.

Feeding hay or grazing livestock in treated areas is prohibited.

RUP - Restricted Use Product
SLN - Special Local Need Label

The 2003 ND Insect Management Guide incorrectly lists Penncap-M as being labeled for rangeland and non-crop. This use is no longer permitted and will be removed from the guide.

There have been some thoughts about using insecticides approved for use in alfalfa to treat road-sides where alfalfa is interspersed with grasses and other vegetation. This is not a proper use. In fact, some of these labels specifically state that the products are not even to be used in mixed stands with intentionally-grown forage grasses. So be careful with stretching label interpretations.

 

SUMMARY OF LAWS IMPACTING GRASSHOPPER CONTROL ALONG ROADSIDES

There are multiple statutes that regulate right-of-way grasshopper control programs. The following summary was prepared by Dave Nelson, State Entomologist, ND Department of Agriculture, highlighting key codes regulating control programs. A more complete summary with individual statutes can be found at the following web site, follow the grasshopper links:

http://www.ag.ndsu.nodak.edu/aginfo/entomology/entupdates

Townships and counties authorized to control grasshoppers infesting road rights of way under their authority (1991 law)

Requirements

State Highway Rights of Way

Financing Summary

Counties

Governing body may use county emergency fund (57_15_28) to pay for control costs in county road system rights of way and for cost share with townships.

Maximum balance

Tax limitation for emergency purposes (57-15-06.7)
Tax for emergency purposes not to exceed 2 mills.

Townships

Electors may appropriate funds (57-15-19) for controlling grasshoppers in township rights of way. Total annual tax levy (for all purposes) in a civil township may not exceed 18 mills.

 

POTATO LEAFHOPPER PRESENT IN REGION

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 and dry beans. Potato is another crop of concern.

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. Adults have been the primary stage seen so far. 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 or less

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, and Warrior*.

In dry beans, the threshold for basing spray decisions is when an average of one leafhopper per trifoliate leaf is found. Insecticides approved for use to control leafhoppers in dry beans include: Asana XL*, Capture*, Dimethoate EC (Cygon, De-Fend), endosulfan (Thiodan, Phaser), Lannate*, Malathion 57 EC, Mustang*, 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*, Baythroid*, carbaryl, Dimethoate EC, endosulfan, Furadan 4F*, Guthion, Imidan, Vydate*, and Penncap-M*, and thiamethoxam (Actara).

 

WHEAT MIDGE EMERGENCE UNDERWAY

Wheat midge have begun to emerge in the southeast areas of ND. Some adult midge were observed in the Fargo area earlier this week. There have been others who have reported observing midge in central counties, including Wells and Burleigh. Based on degree day accumulations, these observations may have been male midges, which emerge earlier than the females.

Female Wheat Midge emergence should be underway by the weekend throughout the central part of the state. Though populations were low in the surveyed areas, if wheat is heading and midge are emerging, scouting is advised for determining if treatable levels are present.

The midge degree day map is available at:

http://www.ext.nodak.edu/weather/idd/idd40.gif

Other midge information can be found under wheat topics at the ND Insect Updates web site:

http://www.ag.ndsu.nodak.edu/aginfo/entomology/entupdates/index.htm

Midge Treatment Thresholds for Wheat:

Examine wheat heads at dusk (9 pm and later when temperatures are above 60EF and wind speed less than 6 mph). The orange-colored adult midge can be seen laying eggs on the wheat heads. Plants are susceptible as the head emerges from the boot. In general, Hard Red Spring Wheat treatment is warranted when 1 or more midge are observed for every 4 or 5 heads. Durum Wheat treatment is warranted when 1 or more midge are observed for every 7 or 8 wheat heads. Treatments after 50% of the first heads have flowered are not recommended due to reduced levels of efficacy and for the protection of a parasitic wasp that attacks the midge eggs.

Phillip Glogoza, Extension Entomologist
pglogoza@ndsuext.nodak.edu

 

DIMILIN 2l (Diflubenzuron) Ė Overview of An Insect Growth Regulator labeled for Grasshopper Management - Manufacturer: Crompton Uniroyal Chemical

An insect growth regulator performs differently than conventional insecticides used by many of you. The following information provides an overview of this product so you understand the use patterns and expectations of the product.

Grasshopper susceptible stage: Best results will occur when grasshoppers are in the 2nd to 3rd instar stages. The growth stage between each molt is called an "instar." On average, grasshoppers will molt every six to nine days.

Mode of Action: Dimilin disrupts the formation and deposition of chitin in an insectís exoskeleton, interrupting the immature insectís ability to molt normally. Other affects include coordination and feeding behaviors.

How long before seeing control effects? A grasshopper must ingest Dimilin, then molt before it is affected, and ultimately populations are reduced. Effects of treatment typically begin to appear within 5 to 7 days after treatment, as the grasshopper nymph dies after failing to molt properly. In addition, Dimilin causes grasshoppers to become malformed, and to exhibit impaired coordination and feeding habits. This makes them easy prey for natural predators like ground beetles.

Any control with adults? Dimilin does not control the adults because they will not molt again. However, the consumption of Dimilin by adults can reduce their feeding rates, escape and mating behaviors, as well as egg viability.

What is the application rate? Dimilin is registered in rangeland, pastures and non_crop areas at the rate of 0.5_1 fl oz per acre. If vegetation is dense in non_crops areas or pastures, a 2 fl oz per acre is also recommended. Annual application can not exceed 2 fl. oz. per acre for a year.

Volume and adding a crop oil to solution? By air, use 1 to 5 gallons of water/acre. Add 1 to 8 pints of crop oil per acre to the solution when conditions favor water evaporation (high temperature, low relative humidity). Dimilin may be aerially applied in an Ultra Low Volume (ULV) solution containing at least 4 fl oz of crop oil for a total spray volume of 12 to 32 fl oz of solution per acre. Do not exceed 1 part crop oil to 2 part water. By ground, use 5 to 30 gallons of water per acre for non-crop areas and 5 to 20 gallons per acres for rangeland/pastureland. In ground applications, do not exceed 2 quarts of crop oil per acre.

What is the control effect? Studies conducted by the South Dakota Department of Agriculture and USDA-APHIS have shown that just 1.0 fl oz of Dimilin per acre resulted in 61_86 percent grasshopper mortality, seven days after treatment. Control increased to 98-99 percent mortality after 14 days of treatment and reached as high as 100 percent control 21 days after treatment.

How long is the residual? Dimilin remains active on the plant tissue for at least one full month. That means it's still present to control delayed hatching nymphs, later hatching grasshopper species, and secondary infestations that may occur during this 30 day period.

Rainfast? Dimilin is rainfast and it will continue to control grasshoppers well after rains have occurred.

Safety? Dimilin is safe to livestock, birds, fish, honey bees, and beneficial insects. It also has low mammalian toxicity and is low risk for the pesticide applicator. Dimilin can be applied while bees are actively foraging. Dimilin is toxic to aquatic invertebrate animals. It should NOT be applied by ground within 25 feet, or by air within 150 feet of bodies of water including lakes, reservoirs, natural ponds, marshes, rivers, or streams.

Preharvest interval? There is no haying or grazing restriction except on alfalfa forage. Observe a one_day preharvest interval when cutting alfalfa forage. There is no need to relocate cattle or other livestock when Dimilin is applied.

High pH problems? Dimilin is NOT affected by water pH.

What is the cost? Dimilin costs about $235 per gallon. So, an 1 fl oz per acre rate would cost about $1.84 and 2 fl oz per acre about $3.67 per acre.

Janet Knodel
Area Crop Protection Specialist
North Central Research/Extension Center


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