How to Get Rid of Crusader Bugs on Alfalfa Plants: A Comprehensive Guide

As an alfalfa farmer, I know how frustrating and damaging crusader bug infestations can be. These tiny sap-sucking insects, also known as alfalfa plant bugs, can quickly get out of control and decimate an entire alfalfa crop if left unchecked. Over the years, through trial and error, I’ve learned effective strategies for controlling crusader bugs without resorting to harmful pesticides. In this comprehensive guide, I’ll share everything I know about identifying, preventing, and managing crusader bug infestations in alfalfa fields.

What Are Crusader Bugs?

Crusader bugs (scientific name: Adelphocoris lineolatus) are a species of plant bug belonging to the family Miridae. About 1/4 inch long, these bugs have an oval, flattened shield-shaped body that can be green, yellow, or brown. They have distinctive black markings on their wings and long antennae. As sap feeders, crusader bugs use their straw-like mouthparts to pierce alfalfa leaves and stems and suck out the juices inside. This damages the plant tissues and stunts growth. Large infestations can cause yellowing, wilting, and even plant death.

Crusader bugs thrive in hot dry conditions. In Texas they are most active from May through September. These bugs tend to congregate on the undersides of leaves or in protected spots near stems. When monitoring your alfalfa fields, make sure to inspect these hidden areas. Shake alfalfa plants over a white sheet of paper to dislodge the bugs and get an accurate count.

Monitor Fields Regularly

The best defense is a good offense when dealing with alfalfa pests. Make it a habit to scout your fields at least once a week, especially during summer months when crusader bugs are most prolific. Walk through the field in a zig-zag pattern and examine plants in several random locations. Check under leaves, as this is where the bugs tend to hide and feed.

Monitoring allows you to detect infestations early before they get out of hand. You can then take quick action to control bugs before major crop losses occur. Depending on the size of your fields, divide them into sections and inspect 5-10 plants per section. Compare counts across sections to identify hot spots.

Encourage Natural Predators

Boosting populations of natural crusader bug predators is an environmentally friendly way to keep infestations under control. Lady beetles, lacewings, spiders, and small insect-eating birds all feed on plant bugs. Avoid using broad-spectrum insecticides that may inadvertently kill these beneficials.

Provide habitat to attract predators by planting a cover crop like buckwheat or allowing weeds to grow around field edges. Leaving fallen leaves and brush piles also gives insects places to shelter and breed. Consider installing bird houses or perches to invite more insect-eating birds. With a thriving community of natural enemies, your alfalfa will be more resilient against crusader bugs.

Apply Targeted Insecticides

Sometimes natural control is not enough, especially when dealing with severe crusader bug infestations. In these cases, applying insecticides may be necessary to reduce populations quickly before extensive damage occurs. Always follow label directions carefully. Two products I’ve had success with are:

• Neem oil – Derived from the neem tree, this natural insecticide disrupts bugs’ feeding behavior and ability to reproduce. Mix neem oil with water and spray on infested plants.

• Insecticidal soap – Potassium salts in this soap dehydrate and kill soft-bodied insects like crusader bugs on contact. Spray plants, especially the undersides of leaves where bugs hide.

Avoid broad-spectrum chemicals that may also kill off beneficial insects. Spot treat only infested areas of the field to limit environmental impact. Insecticides can provide rapid relief but should be just one part of an integrated pest management plan.

Focus on Plant Health

A healthy, vigorous alfalfa crop is more resilient against pest damage. Make sure your plants get adequate water and nutrients. Test soil periodically and amend with compost or organic fertilizers as needed. Cut alfalfa on schedule – this encourages lush regrowth that can outpace crusader bug feeding.

Proper planting density, weed control, and crop rotation also promote good plant health. Choosing disease-resistant alfalfa varieties further strengthens your plants. Taking good general care of your crop gives it the best chance against challenges like crusader bug infestations.

Timely Cutting and Harvesting

When dealing with alfalfa weevils, one cultural practice that can help is to cut and harvest the hay crop early, as soon as plants reach the 10% bloom stage. This removes many larvae from the field before they can cause extensive damage. After cutting, keep a close eye on regrowth for any weevil activity.

During harvest, be sure to check bales for the presence of blister beetles. These pests contain a toxin called cantharidin that is dangerous if consumed by livestock. Avoid picking up live or dead beetles with hay harvesting equipment.