July Grasshopper Management
As we enter a period of hotter and drier weather, grasshoppers will begin to move into crops from field edges. In the coming weeks, be sure to scout your fields to ensure defoliation from grasshopper feeding is kept at a minimum.
One of the best ways to scout for grasshoppers is to use the square foot method. Randomly select an area several feet away and visualize a one square-foot area around that spot. Walk toward this spot and count the number of grasshoppers you see in or jumping out of this area. Repeat this procedure 18 times and divide the total number of grasshoppers by two. This will give you the number of grasshoppers per square yard. Economic thresholds for grasshoppers range from eight to 40 grasshoppers per square yard, depending on a variety of factors.
If grasshopper levels have reached threshold, treatment with an insecticide may be feasible as long as pre-harvest intervals are considered. Many insecticides used for other insects in alfalfa and other forages are also labeled for grasshoppers. For current insecticide recommendations for controlling grasshoppers in rangeland, forages, alfalfa, and other crops, please contact your county extension office.
It's also important to remember that our goal isn’t to completely eradicate grasshoppers from our fields, but to reduce their numbers to below threshold levels and give our crops a chance to “win the race” against pests until the first hard freeze of the season.
Rained-On Hay
Summer thunderstorms can quickly turn good hay drying weather into wet windrows. That does not mean the hay is a total loss, but rain on cut forage can reduce both yield and quality.
How much is lost depends on the forage type, how dry the hay was, how much rain fell, and whether the forage was re-wetted multiple times. Losses are usually lower when rain comes soon after cutting and the hay is not repeatedly soaked.
Wisconsin research found that 1 inch of rain on alfalfa after one day of drying caused a 22% dry matter loss, compared to a 6% loss with no rain damage. When alfalfa received 1.6 inches over several days, losses increased to 44%. Grass hay usually has lower losses than alfalfa because it does not lose leaves as easily.
Rain may not reduce protein much unless leaf loss is high, but energy can take a bigger hit as carbohydrates decline. Rained-on hay also has greater risk of mold, heating, and heat damage, especially if baled too wet.
Once hay has been rained on, the priority is to reduce additional losses. Turn windrows only if it will help drying more than it will increase leaf loss. Chopping may be a better salvage option than waiting for dry hay, while severely damaged forage may be better used as mulch.
Finally, keep an eye on rained-on windrows for insect pressure and weed growth. Salvage what you can, store it safely, and let the hay test — not just appearance — guide how that forage gets used.
Water Quality and Blue-Green Algae
Clean water is critical for cattle health, especially during heat events. However, dry conditions can make water quality worse. As water evaporates, salts and minerals become more concentrated. In some locations, this can cause cattle to limit intake, refuse water, or develop health issues.
Nitrates are another concern. They can come from groundwater feeding a pond, but runoff from fertilized fields, manure, or other nitrogen sources is often the bigger risk. Cattle can tolerate nitrate levels in water that would be unsafe for humans, but elevated nitrate water combined with high-nitrate feed or forage can push total intake into dangerous levels.
Blue-green algae, more accurately called cyanobacteria, is common in still water during summer. Warm temperatures, sunlight, low water levels, and excess nutrients can allow blooms to develop quickly. Blooms may look like green paint, pea soup, or surface scum, and wind can concentrate them along shorelines where cattle drink. Not every bloom is toxic, but when toxins are present, livestock losses can occur quickly.
Copper sulfate has traditionally been used to manage algae, but it must be used carefully and according to label directions. Treating an active bloom can release more toxin into the water, and repeated treatments may create environmental concerns. For recurring problems, limiting pond access, pumping water to a tank, reducing nutrient runoff, cleaning tanks, or providing another water source are better long-term options.
Don’t assume water is safe just because cattle have used it before. Dry weather, heat, runoff, and stagnant conditions can change quality quickly. If water quality is in question, remove access and provide clean water until the source can be evaluated or tested.
