Time to Scout your Fields for Grasshoppers

By Jim Forbes, BC Ministry of Agriculture

Last year we had quite a number of calls regarding grasshoppers. With the open fall we had and a relatively dry spring so far, 2015 is shaping up to be even worse than last year for grasshoppers.  I was in a field on Monday evening and came across a significant infestation of the little blighters at just the right stage for treatment.  For those of you with long memories, the Grasshopper Control Act was repealed in 1998 so you have been on your own with regards to controlling them for 17 years now.

The biggest key to successful treatment is to catch them early and at the right stage for the products to act before they have consumed much crop, and before you really have to saturate them with the product to kill them.  Catching them at the early stages means monitoring your fields now, when the grasshoppers are usually small enough that they are hard to notice.  By the time the grasshoppers are big enough that you can’t miss them, then you have already lost significant crop, have fewer options and those options may be less effective.  Here are some other points to consider:

Identify – Identification of species, abundance, and stage of development are all important factors in successfully controlling grasshoppers.  Of the approximately 60 species of grasshoppers in BC, only 4 cause appreciable damage (see the links below for species and pictures) and warrant control treatment, so it pays to know which ones you have.

Is Control worth it? – Usually the economic threshold for controlling grasshoppers is about 7-12 grasshoppers per square meter in the crop, 13 or over is considered severe and control is generally recommended.  You will find that the numbers tend to be almost twice as high by the roadside so it is important to walk out in the crop and do the survey (walk a W pattern in the field and count at a minimum of 4 points along each leg of the W).  For range it is best to  use the values from the roadside as in the table in this link: http://www.al.gov.bc.ca/cropprot/grasshopper.htm .

Option 1, Baits – There are two types.

Carbaryl bait can work well at the right stage (younger stages, 3rd instar) for short-term killing of the hoppers.

Nolobait {a biological control that is a microsporidial pathogen} takes more time to kill (3 to 6 weeks so does not reduce the damage as quickly) but can infect more of the population and can decrease populations in subsequent years without affecting other species.  It is available through Purity Feeds but must be ordered from the manufacturer as required as it has a relatively short shelf life, so you have to plan ahead: http://wci.colostate.edu/Assets/pdf/Grasshopper/NoloBait.pdf

Option 2, Spray – If you are going to spray (see options below), it is best when the majority are in the third or 4th stages (about 6-10 mm or less than ½ inch long), before they can use their wings.  Insecticides are generally require more care and attention to details than a lot of herbicides as they can have more acute toxicity issues for humans & livestock so it is advisable to hire a certified pesticide applicator.  Use with Cautionthere are also issues for non-target species to consider, particularly if there are beehives within a few miles. Get to know your local bee keepers and discuss your situation with them.

Option 3, Ride it out and encourage natural predators – Depending on which species of grasshoppers you  have you might not actually be experiencing damage; on the other hand, if you do have some of the 4 damaging species it is likely there will be some more around in years to come.  Some producers have had some success with putting up bluebird houses in areas that see chronic infestations – it doesn’t kill them all but it can help prevent some of the large build ups that can occur when the grasshoppers go unchecked. From my experience Blue grouse, wild turkeys and chickens also tend to favour grasshoppers as a food source.

More information about grasshoppers is available in these links:

http://www.al.gov.bc.ca/cropprot/grasshopper.htm

http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex6463?opendocument

http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/faq6750

http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex3497

Last year Robson at Purity provided the following information regarding grasshopper control options available at Purity Feeds

PLEASE NOTE that while the relative differences may be similar, prices will likely have changed significantly with the change in the US/CDN $ exchange rate.

1. Lagon 480 E (Dimethoate)

  • Registered for grasshoppers on pastures/range
  • Water volume is 80L/acre (21 gal/acre) for good coverage.
  • Chemical rate is : 220ml-400ml/acre. Use the 400 ml/acre rate when the grasshoppers are larger or heavy infestation.
  • Remove cattle when spraying.
  • 28 day pre-harvest and pre-grazing interval for the 400 lm/acre rate.
  • Cost/acre=$15.40/acre

2.  Sevin XLR (Carbaryl)

  • Registered for grasshoppers on pastures/range
  • Water volume is 80L/acre (21 gal/acre) for good coverage.
  • Chemical rate is : 1.0-1.4 L/acre. Use the 1.4L/acre rate when the grasshoppers are larger or heavy infestation..
  • Remove cattle when spraying.
  • 0 day pre-harvest and pre-grazing interval for Sevin XLR.
  • cost/acre=$29.72/acre

3. Malathion 85E (Malathion)

  • Registered for grasshoppers on pastures/range
  • Water volume is 80L/acre (21 gal/acre) for good coverage.
  • Chemical rate is : 0.40-1.1 L/acre. Use the 1.1L/acre rate when the grasshoppers are larger or heavy infestation..
  • Remove cattle when spraying.
  • 0 day pre-harvest and pre-grazing interval for Sevin XLR.
  • cost/acre=$32.70/acre

4. NoLo Bait (Nosema locustae spores)

Hopefully anyone who experienced issues with grasshoppers last year is already checking their fields. Even if you were OK last year, it pays to be vigilant.

Sincerely,

Jim Forbes,
Regional Agrologist

Ministry of Agriculture
441 Columbia St.
Kamloops, BC, V2C 2T3
Ph: 250-828-4513”