April's Ag Advice By April Borders Musk thistle is a noxious weed common to our area. It is usually found in pastures, range lands, trees, along creeks and dugouts. It is a biennial plant that can grow between 4 to 6 feet tall, with coarsely toothed, dark green leaves with white midrib and spine-tipped lobes. The flowers are large � up to 2 inches and are powder-puff shaped. They can be a deep rose or lavender color which are borne singularly and are nodding on curved stems.
The key to good control of musk thistle is to treat the plants with herbicide when they are young and still in the rosette stage. Treatment after bolting is less effective because seeds may still develop. These plants are prolific seed producers and uncontrolled plants can produce up to 20,000 seeds.
Musk thistle is not poisonous to livestock but if it is in pastures, livestock will not graze near it and may refuse to enter heavily infested areas. Musk thistle is also a highly competitive plant and will compete with desirable forage species for sunlight, moisture and nutrients. Grasslands grazed too closely are prime candidates for musk thistle infestations.
Good grazing management will retard infestations in grazing land. Also good management in cultivated crops usually retards musk thistle. Fields with heavy infestations can be cropped for a few years so tillage and herbicides can reduce infestations.
There are several methods of control for musk thistle. One way is through suppression by mowing or shredding. This results in reduced seed production. In most stands mowing at early bloom stage is best because plants will not resprout. Cutting plants at the base will kill individual plants since they don't resprout from the roots. Seed may be produced by plants cut in full bloom so heads should be removed. Younger plants may require additional control measures.
A second option is the musk thistle seed weevil, a natural predator to the musk thistle. The weevil larvae feed at the base of the flowers and interfere with seed production. This can be a slow process since it can take six to eight years before an appreciable reduction is noticed.
The third option is chemical control. There are several herbicides that offer good control of musk thistle. Apply the herbicide when plants are in the rosette stage and prior to bolting. Control declines with herbicide application after the rosette stage.
There are grazing restrictions that apply to these treatments so use caution. The restrictions are listed for lactating animals and hay harvest interval for lactating dairy animals so follow precautions to prevent contamination of livestock and/or hay.
Let's turn and look at some pests that we should be on the watch for in our newly planted crops. As corn begins to emerge, it is important to be out scouting frequently as there are a variety of insect pests waiting to cause havoc. We need to be on the look out for cutworms. Cutworms can cause serious damage to corn in the first couple of weeks after emergence, so it is important to be out scouting. There are several species of cutworms that attack corn. Weather conditions and previous crop history will influence the severity of the problem.
Early detection is essential since most of the cutting occurs within seven days of plant emergence. Generally, a rescue treatment should be considered if 5 percent or more (an average of at least 1 plant in 20) cutting is observed and the worms are one inch or less in length. You need to scout for cutworms regardless of whether you used an insecticide treatment at planting or whether it is a Bt corn hybrid.
Producers should also be looking at their alfalfa fields and watching for the alfalfa weevil larva. With our cool temperatures, feeding has been delayed and spotty but as we start to warm back up they will be on the move in force. Frost has nipped out first cutting of alfalfa and set us back, so we don't want to let these little creatures set us back a second time.
For more information on pest control stop by or call the Clay County Extension Office at 677-7111.