Watch for Alfalfa Weevil and Clover Leaf Weevil Activity:

Alfalfa weevil damage in the northern half of the state is usually noticeable when 375 Growing Degree Days (base 48) have occurred. While we are yet short of this accumulation, it wouldn't be a bad idea to begin to plan to scout for this important pest. On average, northeast Nebraska will hit 300 growing degree-days sometime around April 20-25. Now is the time to begin monitoring for this pest.

While we have been spared alfalfa weevil damage in much of Nebraska over the past few years (with the exceptions of areas of the Panhandle and Boyd and Holt counties, which were hard hit in 1998 and has had some problems since), the potential for damage always exists. While things will be getting very busy in the next few weeks as row crops are to be planted, those of you who are growing high quality alfalfa hay should take the time to monitor fields for weevils over the next month.

Clover leaf weevil (CLW) is occasionally a problem but are very vulnerable to fungus disease and so haven't been pests since the late 80's early 90's when spring rains were rare. Clover leaf weevil larvae will be in the debris around the crowns during day. Scratching in the soil around the crowns and counting the number of larvae found per crown will help give a better idea of clover leaf weevil infestation. Their brown heads will help distinguish them from the black headed alfalfa weevil. Table 1 will compare the alfalfa weevil and the clover leaf weevil.

Both and alfalfa weevil and clover leaf weevils feed on first cutting alfalfa as larvae, and regrowth of the first cutting as adults. While research conducted in northeast Nebraska has shown that clover leaf weevil larvae feeding does not cause yield reduction to first cutting alfalfa, alfalfa weevil feeding can cause severe losses to yield and quality of the first cutting.

Table 1. Comparison of Alfalfa Weevil to Clover Leaf Weevil.

Alfalfa Weevil	Clover Leaf Weevil
Overwinter primarily as adults	Over winter primarily as larvae
Adults brown with dark brown stripe halfway down back, 3/16 inch long	Adults dark brown, pitted light brown underneath, over 1/4 inch long
Larvae prefer to feed on tips	Larvae feed anywhere on plant
Larvae remain on plant most of the time	Many larvae in soil or debris during daytime hours
Larvae have black heads	Larvae have brown heads
Adults leave fields in June	Adults may remain in fields

It is essential that fields be monitored for alfalfa weevil feeding now. Damage consists of small holes and interveinal feeding on the newest leaflets near the stem tips. The larvae are a small (1/16 to 3/8 inch in length), pale yellowish green, becoming a darker green when larger. These legless worms have black heads and a white stripe the length of the back. The alfalfa weevil larvae spend nearly all their time on the plant. They curl into a C-shape when disturbed.

Once the alfalfa is about 4-6 inches or so in height, take a bucket, carefully cut some stems at ground level (30 to 50 per field, from various spots in the field) and shake the stems against the side of the bucket. Average the number of weevil larvae per stem. Use the following charts to aid you in making a decision on whether to control alfalfa weevils. Each chart has been developed for a different alfalfa value. To treat or re-sample depends on the average number of weevils per stem, the stem length, and the value of the alfalfa. When alfalfa reaches a certain height, it may be more profitable to cut the alfalfa early rather than to treat. Insecticides registered to control alfalfa weevil larvae include Ambush, Baythroid, Cythion, Furadan, Guthion, Imidan, Lannate, Lorsban, Mustang Max, Penncap M, Pounce, Sevin, and Warrior. See the Entomology Website at http://entomology.unl.edu/instabls/instabls.htm or use the label to check for use rates.

Wireworm Fields Wanted

With early season insect concerns becoming more common, we are looking for fields that have a history of wireworm problems to put out some insecticide screening trials. Preferably, these fields have a population confirmed this spring by the use of wireworm traps. Please contact Keith at 402-370-4016 or email him at kjarvi1@unl.edu if you are interested in helping us out. Thanks! (KJ)

New Insecticide Label for Mustang Max

Mustang Max will replace Mustang with new lower labeled rates. The use rate in alfalfa for alfalfa weevil is 2.24 to 4.0 oz per acre. Check the label for rates and insects labeled for other crops.

New Herbicides

Several new herbicides recently received registration for use in Nebraska.

Expert from Syngenta contains s-metalachlor, atrazine, and glyphosate and is for use preplant and preemergence in corn plus early postemergence in Roundup Ready corn.

Rosen's Inc has acquired a new business position with several existing active ingredients. Their three new products, which are currently being marketed in Nebraska and the Midwest, include: Volley, Priority and Blanket. "Volley" products contain the active ingredient acetochlor with or without atrazine. They are labeled for preplant, pre-emergence in corn.

Volley contains 6.4 lbs of acetochlor per gallon.
Volley ATZ contains 3 lbs of acetochlor and 2.25 lbs of atrazine per gallon.
Volley ATZ lite contains 4 lbs of acetochlor and 1.5 lbs of atrazine per gallon.
Priority (carfentrazone + halosulfuron) is labeled for post-emergence for all types of corn. It contains 12.5% carfentrazone and 50% halosulfuron per gallon.
Blanket (sulfentrazone) is labeled for preplant and preemergence in soybeans. Blanket contains 75% sulfentrazone per pound.
Landmark MP and Landmark II MP from DuPont contain sulfo-meturon methyland chlorsulfuron. These herbicides control many annuals and broadleaf weeds in non-cropland.

Brady Kappler, Extension Educator - Weed Science

Management Tips

"Do you Chemigate? If so, don't forget to renew your chemigation permit by June 1. Also, check your chemical injection pump soon to ensure that it is ready for the season"

"Do you irrigate corn on coarse soils? If so, Extension Specialists recommend split applying the nitrogen. The last nitrogen application should be on by blister stage." (RD, BK, CS)