CUTWORMS IN CORN

If corn has emerged in good shape, cutworms are the next insect pest to look out for. Cutworms can cause serious damage to corn in the first couple of weeks after emergence, so it is important to scout early- emerging fields for damage. Some damage to field corn from cutworms occurs every year in Nebraska. Several different species of cutworms can attack corn. The severity and the area affected will vary greatly, and is dependent on species involved, previous crop history, and weather conditions.

Cutworms that attack corn can be divided into two general categories based on seasonal life cycles. Black cutworms do not overwinter in Nebraska. Dingy, claybacked, darksided, sandhills, pale western, and other species overwinter as partially grown larvae in the soil.

Since black cutworms do not overwinter in Nebraska, they are dependent on spring weather conditions, primarily prevailing southerly winds, to bring them into our state. Nebraska is on the western edge of the black cutworm's area of influence, and they are rarely found west of the 100th meridian. Because of their cutting habits and the possibility that large numbers can be transported to Nebraska if favorable weather conditions occur, they have the most potential to cause a widespread problem. Light traps and pheromone traps have been used to monitor the flight patterns and populations of black cutworms. Remember, the presence of moths in a trap only indicates potential problems and is no guarantee that extensive damage will occur. Trap counts are more useful in alerting growers and consultants as to when to begin scouting efforts.

The last few weeks have been dominated by low pressure systems bringing up moisture on southerly winds from the Gulf of Mexico. This is favorable for black cutworm establishment. Some pheromone traps in eastern Nebraska have caught significant numbers of black cutworm moths. Corn planted into heavy residue, or fields with winter annuals, or fields planted into spring-killed alfalfa (that may attract egg laying moths) have a slightly higher potential for cutworms. When weeds are destroyed mechanically or by herbicides, cutworms will feed on the newly emerging corn. Because most damage from cutworms occurs roughly in the first week or two after emergence, growers should begin to scout fields as soon as possible after emergence.

Cutworms that overwinter as larvae generally prefer to lay eggs in the fall in green
vegetation such as small grain stubble, legumes, rye, and pasture. The eggs hatch and the larvae feed on the vegetation present before overwintering. In the spring, after the previous crop is removed and the corn emerges, the cutworms will transfer their feeding activity to the corn. Recent experience has been that corn planted into alfalfa that has been killed in the spring has a greater potential for cutworm problems.

Tillage has minimal effect on cutworm populations. If fields are tilled before black cutworm migration, it may limit egg laying in those fields. Cutworms already in the field may suffer some mortality by mechanical action, but there is no guarantee that tillage by itself will eliminate cutworm problems. Many cutworm problems have occurred in fields that have been tilled.

It is extremely rare to experience cutworm problems in continuous corn. Corn stubble is not a preferred egg-laying site. Potential problems in continuous corn may be the result of a previous year's late season flush of weeds, an interseeding of a fall cover crop such as rye, or a flush of winter annuals this spring, which possibly attract egg-laying moths.

Managing Cutworms in Corn

Several options exist for the grower who wants to manage cutworms in corn. Since a vast majority of corn acreage is not affected by cutworms, the most economically sound practice is to scout for cutworm damage as soon as the corn emerges and apply a rescue treatment if necessary. Early detection of a problem is essential because most of the cutting occurs within 7 days of plant emergence. Generally, a rescue treatment should be considered if 5% or more (an average of 1 plant or more in a set of 20) cutting is observed and the worms are one inch or less in length.

As we are moving toward more reliance on pre and post emergence herbicides, it is becoming more common to apply a liquid insecticide in with the herbicide as an "insurance" treatment. Competition is driving the price of some insecticides down, and some treatments can be applied for as little as $3.00 an acre. While on the surface this may appear to be an attractive option, in fact this will be a money loser in the vast majority of cases. Three dollars an acre to control something that isn't there is still $3.00 an acre lost. Another unfortunate occurrence of price competition is the overstating of insecticide properties in regards to efficacy or residual activity. In some areas of the state certain insecticides are being touted as giving a 30-day residual. Since most cutworm treatments are surface applied and not incorporated, sunlight, heat and water will begin to break down these chemicals immediately after they are applied. Expect no more than 5 to 10 days of killing activity even under the best of conditions.

Rescue treatments are effective in controlling soil cutworms. Ambush 2E, Asana XL, Baythroid 2, Capture 2E, Lorsban 4E, Mustang Max, Warrior and Pounce 3.2EC will all give satisfactory control as postemergence sprays. If the soil is dry or crusted, rotary hoeing immediately before or after Lorsban application may enhance control. The other insecticides are pyrethroids and should not be incorporated. See a full list of products and rates at our website http://entomology.unl.edu/instabls/cutworms.htm. For more information on cutworm biology and control see NebGuide G93-1153-A, Corn Cutworms. (KJ)

INTEGRATED MANAGEMENT OF EASTERN RED CEDAR IN PASTURE

Eastern redcedar (Juniperus virginiana L.) is one of 13 juniper species native to the United States. It is the most widespread tree sized conifer and is native to every state east of the 100th meridian. Throughout this vast range, eastern redcedar grows on many soils and under varying climatic conditions.

Eastern redcedar can be a serious problem on grasslands where it competes very effectively with pasture species for light and nutrients reducing forage production. Heavy tree infestation interferes with livestock handling too. These adverse effects often lower rental rates or sale prices of infested grassland. On many sites complete coverage by eastern redcedar can be expected, resulting in total loss of production.

Control measures should be initiated as soon as possible, both to improve effectiveness and reduce total costs. In most cases, a single control measure can't provide long-term management of this species. However, if the control practices are integrated in a systematic manner, significant advances can be achieved. Methods of control must be based on an integrated management approach, which includes a combination of manual, mechanical, cultural, biological and chemical control methods.

Manual control involves pulling or digging trees. It can be very effective for small areas and is most efficient on trees up to 2 feet tall. Mechanical control methods such as cutting or mowing involve use of various hand held or motor-powered tools. Mowing of short trees can be also utilized as part of the regular cutting and haying process. The overall key to success in cutting or mowing is to cut the tree at the soil surface or below the lowest branches. Red cedar trees that are cut low should not regrow. In addition, if the goal is to just reduce overall number of trees and reduce further spreading (eg. management of wildlife habitat), it is recommended to cut only female trees (the trees that produce berry-like fruits).

Biological weed control or bio-control is the use of natural enemies to reduce weed populations to economically acceptable levels. In the case of red cedar control, goats can be utilized as an effective bio-control agent for trees that are up to 3ft tall. Goats are known browsers, whose diet consists 75% of non-grassy species, which means they will not compete with your cattle for grass. They are also alternative tool for control of many noxious weeds, especially for leafy spurge. Keeping several goats at your pasture can help control many non-grassy species including red cedar trees.

Prescribed fire can be also used. This method is inexpensive and effective against smaller trees. However, its effectiveness declines as tree size increases. Adequate fine fuel (usually, last year's dead grass) is necessary for satisfactory results. Safety also is a concern since many managers lack experience with fire and the equipment required to conduct fires.

Chemical control should be also considered. Herbicides should be viewed as just another tool in the integrated approach tool box. Herbicides can be used for both 'individual-tree' spraying and broadcast application.
Individual tree treatments:

Currently there are several herbicides suggested for individual tree treatments in spring or fall. Examples include Tordon 22K, Velpar-L and Spike 20P. Tordon 22K can be used as a spot gun application of soil around the tree before rainfall. Rainfall will help uptake the chemical. The recommended rate is about 1 cc's (ml) per foot of tree height. Cost of Tordon 22K is about $85 per gallon. It would costs about $65 per acre plus labor ($15 /hour) to spray 1500 trees that are about 2 feet tall. Velpar-L can be also used through a spot gun in spring at the rate of 4 cc's (ml) per every inch of tree diameter. Cost of Velpar is about $65 per gallon. Spike 20P is another alternative but only in non-crop areas as a total vegetation control at the rate of 0.5 oz per every inch of stem diameter. Cost of Spike 20P is about $9 per pound of product.

We have also conducted a preliminary study of individual tree treatments at two locations (Center and St. James) in northeastern Nebraska. Excellent tree control (>90%) was achieved with Plenum at 1.5 % volume per volume (v/v), Grazon P+D at 2.0% (v/v) and Tordon 22K at 1.0% v/v (Table 1). All other treatments provided poor control (<50%). Grass injury in the form of temporary yellowing and burning of top growth was evident among all treatments especially for Tordon 22K (Table1). Cost of Grazon P+D and Tordon 22 K ranged from $11-$16 per acre (Table 1). Plenum and Garlon are experimental products; therefore they are not available for purchase.

Here are a few practical hints: (1) To help you determine volume per volume basis, for example the 1% v/v equals 1 gall of product per 100 gallon of water (eg in large tanks). For smaller back pack sprayers use an equivalent of 1.3 oz of product per every gallon of water. (2) Apply about 1.5 oz of the above prepared spray solution per every foot of tree height. Walk around the tree and just spray enough to get a glisten (shine) on the leaf surface. Solution dripping off the tree indicates a rate that is too high and a waste of time and money. (3) As an example, we calculated that 1 gallon of spray solution should cover 15 individual trees that are 6 feet tall at 20 PSI and nozzles XR8002.

Table 1: Percent red cedar control and grass injury at 100 days after treatment in individual-tree study at two locations (Center and St. James).

			Center	St. James	Center	St. James
aProduct name	Dose (%v/v)	b$$/acre	Cedar Control (%)	Grass injury (%)
1. Plenum	0.5	-	30	3	22	15
2  Plenum	1.0	-	84	69	37	42
3. Plenum	1.5	-	96	89	66	45
4. Garlon EV	1.0	-	25	14	13	7
5. Grazon P+D	2.0	11	90	90	44	52
6. Tordon 22K	1.0	16	94	92	74	64
7. Untreated check			0	0	0	0

a Treatments 1-4 are experimental premixes
b Cost per acre not available for treatments 1-4 because they are not marketed products yet.

Broadcast treatments:

In general the taller the trees the poorer the control. Excellent control (>90%) of up to 1 foot tall trees was achieved with Plenum (5pts), Grazon P+D (6pt & 8pt) and Tordon 22K (2pts) at both locations (Table 2). Same treatments, however, provided poor control (<50%) of taller trees (>2 feet). Plenum at 4 and 5 pts/acre provided good to excellent control of up to 2 ft tall trees. All other treatments provided poor control (<50%) regardless of the tree height (Table 2). Physical removal treatment (#10), provided best control (100%), however it was the most expensive method.
Cost of Grazon P+D and Tordon 22 K ranged from $21-$26 per acre. Plenum and Garlon are experimental products and can not be purchased. Cost of physical removal treatment was about $120 per acre. It was based on a calculation assuming that $8 hours of work was needed to cut 1500 trees, 2 feet tall, per one acre and an hourly labor cost of $15. For illustration purposes, 1500 trees per acre are equivalent of 1 tree per 3 square yard. Grass injury in the form of temporary yellowing and burning of top growth was evident among all treatments.

Table 2: Percent control of eastern red cedar at two locations (Center and St. James) as influenced by the tree height in broadcast study at 100 DAT.
Tree height at Center Tree height at St.James

			Tree height at Center			Tree height at St.James
aTreatments	Dose/acre	b$$/acre	0-1ft	1-2	2-4ft	0-1ft	1-2ft	2-4ft	>4ft
1. Plenum	3 pt	-	40	33	13	40	33	26	12
2. Plenum	4 pt	-	-	96	60	73	59	27	15
3. Plenum	5 pt	-	95	85	43	87	70	23	5
4. Garlon GS	4 pt	-	15	8	37	33	19	7	4
5. Garlon EV	4 pt	-	15	12	10	30	20	11	7
6. Garlon EV	6 pt	-	12	20	10	30	16	8	4
7. Grazon P+D	6 pt	21	95	47	18	93	53	40	16
8. Grazon P+D	8 pt	26	96	76	33	88	86	40	18
9. Tordon 22k	2 pt	22	95	50	16	79	63	42	25
10. cPhysical removal		120	100	100	100	100	100	100	100
11.  Untreated check			0	0	0	0	0	0	0

a Treatments 1-6 are experimental premixes
b Cost per acre not available for treatments 1-6 because they are not marketed products yet.
c Physical removal was done by hand held saw and assuming labor cost of 15/hour

What to do with "standing dead-trees":

Commonly asked question is: What to do with the trees that died as the result of herbicide application. This is especially true for taller trees (> 4ft). Of course they can be removed within the same season. However, if that was the original intension, the chemicals should have not been used. Do yourself a favor, save some money. Just cut the trees at the ground level. They will not re-grow, however watch for stumps, they can puncture vehicle tires.
Standing dead trees will reduce the aesthetic value of the land, however there are several benefits of leaving dead trees stand for several years: (a) they will protect the grass to regrow and re-establish on those individual spots, (b) help against soil erosion and (c) protect against wind or snow. Trees that are 4-8 feet do not have much of the red heartwood tissue so they will naturally deteriorate within 3-6 years.