How do I get rid of alfalfa weevil?

Two cultural practices can be used to reduce alfalfa weevil damage. Fall removal of alfalfa for hay or by grazing following freeze-down will reduce egg-laying sites. Early harvest in the spring can be used instead of an insecticide application.

What does the weevil do to alfalfa?

As the larvae grow, they chew larger holes, giving the plants a shredded or skeletonized appearance. A heavy infestation of larvae can consume enough foliage that an entire field may take on a grayish appearance. Adult weevil feeding damage is usually minor, taking the form of small, circular cuts along leaf margins.

Where is alfalfa weevil from?

Alfalfa weevil, (Hypera postica), insect pest of the family Curculionidae (order Coleoptera) whose larvae damage crops, most often alfalfa and clover. Though originally from Asia, the alfalfa weevil was introduced from Europe into the United States in the early 20th century and is now present in all 48 mainland states.

Is the alfalfa weevil a beneficial organism?

The alfalfa weevil is the most important insect pest of alfalfa in Colorado. Beneficial insects and diseases can combine with good crop management practices to minimize the need for chemical controls.

What do you spray for alfalfa weevil?


Insecticide Rate per Acre Harvest or Graze (days)
Ambush 2EC (permethrin) 6.4 to 12.8 fl oz more than 6.4 fl oz = 14 days
Dimethoate E267 .75 to 1.5 pt 10
Baythroid 2 (cyfluthrin) 1.6 to 2.8 fl oz 7
Furadan 4F (carbofuran) 1/2 pt 1 pt 2 pt 7 14 28

What does alfalfa weevil damage look like?

Scouting for Alfalfa Weevils Damage consists of small holes and interveinal feeding on the newest leaflets near the stem tips. The larvae are small (1/16 to 3/8 inch long) and pale yellowish green, becoming a darker green when larger. These legless worms have black heads and a white stripe the length of the back.

What eats alfalfa weevils?

Bathyplectes wasps Bathyplectes wasps lay their eggs in the small alfalfa weevil larvae. As the parasite develops, it consumes the weevil larva and forms a cocoon inside that of the weevil.

Which life stage of the alfalfa weevil is the most damaging to alfalfa?

Both adults and larvae feed on alfalfa foliage, but the larvae cause the majority of the damage. Larvae feed initially on the inside of terminal leaves and later move to foliage on the lower portion of the plant. Early season larval damage (first and second instars) shows up as pinholes in leaf terminals.

What is eating my alfalfa?

Four species of aphids feed on alfalfa in Texas: the pea aphid, cowpea aphid, blue alfalfa aphid, and spotted alfalfa aphid. Aphids are soft-bodied, slow-moving insects that live in colonies and suck plant sap from stems, leaves, and terminals. Infested plants turn yellow and wilt, and their growth can be stunted.

Do alfalfa weevils bite?

The alfalfa weevil is a small, 3/16-inch (5 mm) long, brownish-grey weevil with a darker brown band down the back. It normally spends the winter as an adult at the base of clover or alfalfa plants, or under leaves or other debris outdoors. Alfalfa weevils do not bite and certainly are not blood suckers.

How do you identify alfalfa weevil?

The distinguishing characteristics of the alfalfa weevil are its black head capsule and prominent white stripe that is present on its back and runs the length of the body. Alfalfa weevil larvae also have a less distinguished white band on each side of their body.

What do alfalfa leafhoppers look like?

Potato leafhoppers are tiny, yellowish-green, wedge-shaped insects. An early symptom of leafhopper damage is a triangular or V-shaped yellow or purple area at the tip of alfalfa leaves. This discoloration is caused by a toxin the leafhopper injects into the alfalfa plant as it sucks out plant juices.

Do weevils like hay?

Weevils are key pests of alfalfa, causing yield and quality losses mainly to the first alfalfa hay cutting. The alfalfa weevil complex includes the Western, Egyptian, and Eastern strains that are all likely the same species (Hypera postica). Each year, growers throughout the country deal with this devastating pest.

Is alfalfa weevil an invasive species?

Alfalfa weevil is one of the two most-damaging insect pests of alfalfa in Pennsylvania (the other is potato leafhopper). It is an exotic species that likely evolved in Asia, but appears to have been introduced to the United States at least three times.

What are weevil grubs?

Adult black vine weevils (3/4 inch long) are large slate-gray to black insects that cannot fly. They are small (1/2 inch long), white, C-shaped grubs that tunnel through roots as they feed. Leaves will often wilt (even when properly watered) and plants may be stunted or die.

What pesticides are used on alfalfa?

The products used in alfalfa that are most troublesome include the herbicide diuron (Karmex or Direx), Velpar, and the insecticide chlorpyrifos (Lorsban, Lock-On, Cobalt, Stallion). Diuron is used for winter weed control in alfalfa (primarily as a pre-emergence material) while chlorpyrifos is used for weevil control.

Can weevils fly?

Many weevils are considered pests because of their ability to damage and kill crops. Some weevils have the ability to fly, such as the rice weevil. One species of weevil, Austroplatypus incompertus, exhibits eusociality, one of the few insects outside the Hymenoptera and the Isoptera to do so.

Do aphids fly?

Although aphids cannot fly for most of their life cycle, they can escape predators and accidental ingestion by herbivores by dropping off the plant onto the ground. They are often attended by ants, for the honeydew they produce and are carried from plant to plant by the ants through their tunnels.

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