Pasture and Forage Minute: Grazing for Interseeding, Controlling Thistles and Fall Armyworms
Grazing for Interseeding
Pastures and hay meadows provide higher quality feed, are more productive and require fewer inputs when they have good forage legumes growing in them.
Outside of moisture, nitrogen is often the limiting nutrient in pasture production. While commercial fertilizer may be a quick and easy option, it’s costly. Instead, let’s grow our own N using legumes.
Do you have a pasture area or hay meadow that is relatively free of weeds and makes up no more than about 15% of your total pasture acres? If so, here is what I want you to do. From now until that grass will grow no more this year, graze that grass hard. Grub it down, then graze it some more. With dry weather this summer, maybe you have already accomplished this on a portion of your ground already.
Now, why would I recommend overgrazing? Surely it will hurt the grass. Well, that's exactly what we want. Next spring, you will interseed legumes like red clover, white clover and alfalfa into that grass to make it more nutritious and productive. We may even consider a winter frost seeding if conditions are right.
The biggest challenge to establishing legumes into a grass sod is competition by that existing grass on new, slow-growing legume seedlings. Anything you do to reduce competition and slow down grass growth will help. Overgrazing this fall prior to next spring’s seeding will weaken the grass and slow its spring growth, thus giving new legume seedlings a better chance to get started. With drought causing unplanned overgrazing this summer, interseeding may be a way to make some lemonade out of that particular lemon. Of course, all this depends on moisture next spring to work.
While you’re at it, also collect some soil samples. Then analyze them and apply any needed fertilizer. Legumes especially need good phosphorus and the proper soil pH.
So, add some legumes to your pasture next spring. Graze your grass this fall until virtually nothing is left. Then, keep grazing a couple weeks more just to make sure. Legumes you add next spring will establish better because of it.
Fall Thistle Control
Did you spray thistles this past spring and summer? If so, it would be a good idea to revisit those areas and even though it has been dry, there are likely some remaining or new growth that has occurred. October and early November is a key time to control thistles in pastures. There are several biennial thistles, but musk, plumeless, Scotch and bull thistles are our most problematic. Biennials require portions of two growing seasons to flower/reproduce. They develop from seed the first season into a flat rosette. When trying to control biennial thistles, destruction of rosettes prior to flowering (bolting) is an effective means of preventing seed formation and subsequent spread.
Another thistle to look out for is Canada thistle. Canada thistle is a creeping perennial that can be controlled with fall spraying, in conjunction with other management options in the spring.
While in the rosette stage, thistles are more effectively controlled using herbicides. It is important to note that fall spraying of thistles is not a silver bullet and effective control often needs repeated applications. It will take several years of timely control before the soil seed bank is reduced. There are many herbicides labeled for thistle control. Take care when purchasing products and always read/follow label directions before use.
GrazonNext® HL, Milestone®, Chaparral®, Graslan® L, Stinger®, Overdrive® and Tordon 22K® are all products that are labeled for use on biennial thistles as well as Canada thistle. 2,4-D mixed with dicamba is also an effective option but should be sprayed when temperatures are warmer for the highest efficacy. When using Tordon 22K® or Graslan® L, both products are restricted use and contain picloram. Use extreme caution around other vegetation — especially trees — as both products will kill woody plants.
Fall Armyworm Awareness
Last year, portions of eastern Nebraska saw an unprecedented number of fall armyworm caterpillars feeding on alfalfa, brome regrowth in pastures and newly seeded small grain crops such as wheat, triticale and rye. While we may not see similar numbers this year, it is a good idea to be “fall armyworm aware” and keep an eye out for this insect.
Fall armyworm caterpillars can be distinguished from other Lepidopterans by markings on the head that resemble an inverted “Y” and four spots on the last abdominal segment that form a square. This insect does not overwinter in Nebraska but rather migrates north from southern states when populations build up in late summer. Once caterpillars are ¾-inch, they can do considerable damage in a few days. Because of this, it is important to scout fields and pastures in the early morning and late afternoon when caterpillars are most active, to spot them when they are small.
Remember, a reasonable treatment threshold is finding three or more caterpillars per square foot within a field or pasture. There are several insecticides labeled to control this insect including Mustang Maxx, Besiege and Sevin. For forage crops, be sure to check the grazing restriction and post-harvest interval. When considering a chemical treatment option, keep in mind caterpillars ¾-inch or longer are close to maturity and can be harder to control with an insecticide.
Fall armyworm feeding declines with cooler temperatures and the adult moths eventually migrate south. In the meantime, be sure to keep an eye on your pastures and newly seeded fields for any sign of infestation.