Baute Bug Blog

It was a great summer.  Even though some fields didn’t see a lot of moisture, many had just enough to keep slugs going for most of the season.  I often found slugs on soybean or dry bean plants even during the middle of summer.  And now with all of the corn scouting we have been doing this month,  I am frequently finding slug’s slime trails on the corn ears!  This tells me that the slug population has thrived this summer and that slug prone fields should be scouting this fall to know what to expect for fall wheat planting or next spring’s planting season.

Slugs that are present this fall will also be the same ones that overwinter and start up again in the spring in that same field.  So knowing what the slug population is like in each field in the fall will indicate what will be present in the spring.  Higher-risk fields include fields with considerable crop residue including no-till corn, soybeans and canola, wheat fields underseeded with red clover, newly
seeded alfalfa and fields following forages, especially grasses.

Fall scouting for slugs is not that labor intensive.  If scouting during the day, look for shiney silver trails left on the soil or plant surface as a result of their mucous trails.  To determine population levels take small pieces of plywood (approximately 2-3 feet long) or roofing shingles and position them on the soil surface in fields that have been harvested. 10 to 15 boards randomly scattered across the field will provide a good indication of population levels. These boards will act as shelters for the slugs. Visit the boards every 5 days for about a month, counting the number of slugs present under the boards. Morning is the best time to look since slugs will still be hanging out in their shelters.

If slugs are commonly found under monitored boards described above, that field should be considered at high risk for slug injury.  In these high risk fields, planting into conditions that help the crop grow quickly can avoid heavy slug damage.  Any form of tillage that helps remove the crop residue that slugs hide and live in can help. Even moving trash away from the seed bed can help to reduce feeding damage.  If this fall continues to be cool and moist, expect more feeding than usual.

Gaps in the stand are starting to show this week.  Aside from the typical culprits, moist soils can promote the less often accused.

Millipedes are typically a beneficial arthropod that breaks down crop debris and decaying plant material.  However, in the last few years, we’ve been seeing more direct feeding by them.  What is happening?  We have been planting earlier and earlier.  If the weather turns cool and wet, seeds that have sat in the ground for a bit, swell up but are slow to emerge, making for tasty treats for millipedes.  Corn is usually the target crop since it is the first to be planted but reports of soybean seed being fed on by millipedes have also come in this year.  Unfortunately insecticide seed treatments do not control them.  Warmer weather that helps get the crop up and out of the ground is really the only way to avoid this.

Slug feeding is evident this week.  This moist weather has brought them out of hiding.  Fields with decent amounts of crop debris harbour these pests, giving them a moist home to live in.  No till soybeans and spring canola are most at risk.  Though corn is also a host, it can usually grow out of the injury, as long as slug populations are not extreme. No insecticides are effective on slugs so this pest requires cultural control. Tillage is best, but for dedicated no tillers, using any device that can help to remove residue directly around the seed bed may reduce slug damage.  In some cases, it may be too late to take action this spring but make note of fields with slug problems and plan to take action this fall once the crop is off.

One additional note, bean leaf beetles have started to enter soybean fields.  In the fields I’ve been scouting, some plants were actually clipped off right at the base while trying to emerge.  Others had the classic round holes in the leaves.  Fields planted without Cruiser seed treatment should be scouted to ensure threshold is not reached.  16 beetles per foot of row during VC to V2 requires control or if clipping is found.

I’m getting quite a few calls about slugs taking out soybean plantings not once but sometimes twice in the same field.  It has been an ideal spring for slugs with all of this wet cool weather.   And last fall was wet too, which helped all those slugs lay eggs and survive in these problem fields. 

Unfortunately there is not a lot that can be done (affordably anyway) as a rescue treatment.  Only 1 in 4 growers who try the UAN 28% solution, sprayed 3 nights in a row, find it to work.   Especially in a season when it continues to rain or experience heavy dews in the early mornings that can wash off the salt on the slugs.  And Sluggo bait is too expensive to apply on field crops, unless used in very small problem areas and must be applied around May 24 to knock the population down when they first start up.

The only effective and affordable method of control is tillage.  Removing the crop residue will get rid of the habitat that the slugs are hiding out in, being protected from the sun and heat.  Till these problem fields in the fall since the slugs that are present in the fall are the same ones that will be a problem again next spring in that same field.  Go back into these fall tilled fields in the spring and place shingles or small blocks of wood down on the soil surface.  Check under the boards in the early mornings to see if slugs are hanging out.  If slugs are easily found, then more tillage may be needed and potentially the use of the Sluggo bait in the problem areas of the field.

The good news is that once the weather does turn a bit more dry and warm, the crop should be able to grow faster than the slugs can feed and the problem will be behind you shortly.  At least until next spring

Have a fantastic Canada Day Everyone!

Since there is not much crop up yet to spot feeding injury on, there really is not much happening yet on the insect front.  However, anyone that did push planting and planted into too wet or cool soils, or deep planted may start seeing some issues when the crops starts to emerge.  Millipedes and slugs in particular could be a problem this year given how wet it was and neither are controlled by the insecticide seed treatments that everyone is using and expecting to control all things with.  It is really important to get the message out to stop planting too early when the soil is not fit and/or too deep as it is just giving the seed to these pests.  And these insecticide seed treatments do not control everything out there.

Bean leaf beetles adults are out now.  Not sure what kind of populations we are going to see this year.  But with overall planting being on the later side, this could put us at risk for an extended pod feeding period into mid September, as these critters like to feed on late planted soys since the pods would still be green and succulent then.  But we will see.

And as for soybean aphids..well I didn’t find any on the buckthorn I scout every year.  And there have been very few reports anywhere in the states either.   It could just be that we are not looking in the right places, as it doesn’t take much of a colony to give us a decent population on soybeans each year.  But it is really strange that we haven’t found something yet, given the record aphid catches we experienced in the fall in the suction traps.  I’m not willing to say that aphids won’t be a problem this year though.  They’ve taught me to never write them off or claim a “No Aphid Year”.

As always, if you are seeing anything out there..let me know!