2003 Nebraska Weed Tours
On June 23, 10 a.m. there will be a joint tour of weed and soil science program with Dr. Charles Shapiro and Dr. Stevan Knezevic. The site is 1.5 miles west of Brunswick. In town, take 4th street with turns in to Road 863, which is the only black top road going west. The field is just west of a turkey farm that has a large plastic turkey in front of a house.

We will start with the study of "Field Sandbur control in irrigated no-till corn" and then move on to see the "Nebraska Soil Fertility Project."

Sandbur is a major grass weed problem in corn, mostly west of HWY 81 in the state. This study examines 15 herbicide treatments of PRE, or PRE followed by POST, including most major products such as Outlook, Bicept II, Prowl, Harness, Lumax, Axiom, Balance Pro, Cinch-ATZ, Option, Accent, and Steadfast.  So far some products worked well while some did not at all, come and see it yourself. 

The Nebraska Soil Fertility Project is a three-year statewide effort by UNL Soil Scientists and others to refine the fertilizer recommendations in irrigated corn. Started in 2002 at 11 sites the experiments include a range of nitrogen, phosphorus and potassium treatments in combination.  The objective is to determine the native soil fertility contributions under high yield environments. The site near Brunswick, Nebraska is no-till corn following soybeans.

On July 10, 1:00 P.M. there will be a weed tour at the Haskell Ag Lab at Concord.

On July 23^rd there will be a Tour of weed control plots in pasture. Major weed species include: western ragweed, hoary vervain and eastern red cedar.  We will start at 10 A.M. at Terry Gompert’s house (2 miles south of Center, intersection of highways 13 & 84). There will also be a demonstration of specialized equipment for mechanical control of red cedar, and an insect update.

Aug 6^th is a Purple Loosestrife Day at the Niobrara State Park, starting at 10A.M. with a few  speakers, lunch, and then field visits of bio-control release sites, and herbicide plots.  

Any questions, feel free to call me, otherwise please come and join us. (SK)

POTATO LEAFHOPPERS IN ALFALFA

Potato leafhoppers have had ample opportunity the last couple of weeks to ride southerly air masses into Nebraska. Checks of an alfalfa weevil plot near Winside indicate that the leafhoppers are present and should be scouted for.  Southerly winds bring this insect into Nebraska, as is does not overwinter here.

These small (1/8 inch long), bright green, wedge shaped insects (Fig 1) may cause severe damage to alfalfa by injecting a toxin into the plant as they feed.  This feeding results in a distinctive yellow or purple triangle shape at the tip of the leaf.  First year spring planted alfalfa fields are particularly attractive to and vulnerable to potato leafhoppers, as are fields planted last year.  In older fields, these insects are usually a problem on second and third cuttings.  Newly developed resistant varieties will protect from potato leafhoppers fairly well, but alfalfa in the seedling stage may still be damaged.  All fields should still be scouted, as large numbers of leafhoppers may still cause a problem, even in resistant variety fields.

Fig. 1. Adult potato leafhopper
Fig 2. Potato Leafhopper

Treatment decisions are based on numbers captured by sweep net.  A sweep net is the only reliable way to scout for potato leafhoppers. See the following tables for decision-making help. Note that there do not have to be many to cause a problem.  Most insecticides registered for potato leafhopper will give good control.  See Table 4 for a partial list of registered insecticides. (KJ)

Table 1.  Dynamic Treatment Thresholds for Potato Leafhoppers (average number per sweep) on Alfalfa that is 1 to 4 inches tall.

Value of hay (per ton)		Cost of insecticide application (per acre)
	$8	$10	$12	$14	$16	$20
$ 60	0.4	0.5	0.6	0.7	0.8	1.0
$ 80	0.3	0.4	0.5	0.5	0.6	0.75
$100	0.25	0.3	0.4	0.4	0.5	0.6
$120	0.2	0.25	0.3	0.35	0.4	0.5
$140	0.2	0.2	0.25	0.3	0.3	0.4
$160	0.15	0.2	0.3	0.3	0.3	0.4

Table 2.            Dynamic Treatment Thresholds for Potato Leafhoppers (average number per sweep) on Alfalfa that is 4 to 8 inches tall.

Value of hay (per ton)		Cost of insecticide application (per acre)
	$8	$10	$12	$14	$16	$20
$ 60	0.7	0.8	1.0	1.0	1.3	1.7
$ 80	0.6	0.6	0.75	0.9	1.0	1.3
$100	0.4	0.5	0.6	0.7	0.8	1.0
$120	0.3	0.4	0.5	0.6	0.7	0.8
$140	0.3	0.35	0.4	0.5	0.6	0.7
$160	0.25	0.3	0.4	0.4	0.5	0.6

Table 3.      Dynamic Treatment Thresholds for Potato Leafhoppers (average number per sweep) on Alfalfa that is 8 to 12 inches tall.

Value of hay (per ton)		Cost of insecticide application (per acre)
	$8	$10	$12	$14	$16	$20
$ 60	2.0	2.4	2.8	3.0	3.9	5.0
$ 80	1.8