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Weekly Field Crops Pest Report 2011

July 29, 2011, Volume 10 Number 13

  1. View from the Field
  2. Weather Outlook
  3. Fly Traps for Biting Flies of Attacking Animals on Pasture
  4. How to scout for corn rootworm
  5. Are soybeans at risk from spider mites?
  6. Western Bean Cutworm Trap Catches Increase
  7. Clipboard Checklist
  8. Contact Information

View from the Field

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Potato leafhopper (PLH) is increasing in infestation levels on alfalfa in central NY. It is important to scout for PLH in alfalfa now. PLH inject toxic saliva as they suck the plant fluids from the alfalfa. This causes a v-shaped yellowing of the leaflets. If the leaflets have turned yellow you have lost ½ ton of forage per acre and a reduction of 5% in crude protein. Hot weather and drought conditions seem to favor increases in PLH populations.

potato leafhopper damage on alfalfa

(PLH damage to alfalfa)

There are reports of adult corn rootworm beetles (CRW) over threshold levels in corn fields. Remember, if a field is over threshold management actions should be taken next year. The action threshold indicates that there will be enough larvae feeding on the corn roots to cause economic yield losses if no management is taken. See article below for information on monitoring CRW.

Soybean aphids continue to remain generally low. Many fields are in flower and early pod fill which are the stages soybeans are most sensitive to soybean aphid. Make sure you continue to scout for soybean aphids on soybeans. The populations can still rise above the economic threshold of an average of 250 aphids per plant.

Western bean cutworm continues to rise. Reports indicate the number of adult moths caught this week were substantially higher than the previous week.

western bean cutworm adult

Adult western bean cutworm moth-Photo taken by Dale Dewing

Gray leaf spot and northern corn leaf spot have appeared in corn. There are some corn producers treating fields for the diseases. Make sure to scout and confirm you have the diseases before applying fungicide. If you apply a fungicide consider leaving a no treat area to help evaluate the impact.

Weather Outlook

July 28, 2011

Jessica Rennells, Northeast Region Climate Center, Cornell University

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Hot temperatures, some record breaking, put last week's average 3 to over 9 degrees above normal. Precipitation ranged from a tenth of an inch to over inch for most of the state. The base 50 growing degree days ranged from 125 to 200.

Today (7.28.11) will be mostly cloudy with a chance for showers and thunderstorms. Temperatures will be in the upper 70's to mid 80's. The chance for showers and thunderstorms will continue overnight with temperatures in the 60's.

Friday will be mostly cloudy and a cold front will bring showers and thunderstorms producing heavy downpours for some areas. Highs will be in the upper 70's and low 80's. Lows will be in the upper 50's and throughout the 60's.

Saturday high pressure will bring back sunny skies with temperatures in the 80's. Lows will be in the mid to upper 60's.

Sunday we'll have continued sunshine with highs ranging throughout the 80's nearing 90. Lows will be in the low to mid 60's.

Monday another cold front will move through bringing showers and thunderstorms, temperatures will be throughout the 80's. Lows will be in the 60's.

Tuesday's highs will be in the 80's nearing 90 and lows will be in the 60's.

Wednesday will continue the trend of daytime temperatures in the 80's and lows in the 60's.

The five day precipitation amounts will range from a quarter of an inch to one and a half inches. The 8-14 day outlook is showing above normal temperatures and precipitation. The US Drought Monitor has placed western NY, the Great Lakes region, and part of Central NY in "Abnormally Dry" conditions. See their site for map.

Fly Traps for Biting Flies of Attacking Animals on Pasture

Keith Waldron
NYS IPM

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Several fly pests can attack cattle while they are out on pasture especially horn, face, stable, horse and deer flies.  Each fly species has distinctive habits, life histories, and management options. Fly traps are one tactic that can be deployed to help reduce the numbers of horse, deer and stable flies, all common biting flies that attack and cause stress to animals on pasture.

Alsynite (Biting Fly) Trap
A cylindrical alsynite fiberglass sheet reflects light in a way that is particularly attractive to stable flies but will attract house flies also. Sticky translucent fly paper is wrapped around the outside and replaced when saturated with flies.  Place out of reach of animals in a sunny location since they attract flies by visual means. The trap is should be set 1 to 2 feet above the ground and placed about 10 feet from building walls or on pastures in those areas where the animals will be concentrating, such as near water troughs.

Horse Pal
This trap is specifically designed to attract and catch horse, deer, and stable flies by mimicking the underside of a cow. Flies land on the surface of a swaying dark sphere, migrate up toward the light in the screened area, and are ultimately trapped in the jar on top. The collection jar is removed periodically and emptied. Begin by placing 1 to 2 traps in the field and increase as necessary. Traps should be placed near, but out of reach of curious animals to prevent damage.

Epps Trap
Biting flies, such as stable, horse, and deer flies, are attracted to the large shape of the Epps Trap made to resemble a cow. Biting flies tend to circle their host before landing for a meal and perceive the clear plastic spaces of the trap as open space under the animal. They fly into the clear plastic and ricochet into trays of liquid where they drown. Maintain the trap by skimming dead insects from the liquid and replacing the liquid when fouled. Mow weeds beneath the trap to preserve the contrast between light areas and dark. Traps work best placed in a sunny part of the pasture near historic fly problem areas. Use one trap per 20 acres of pasture, or place in a sunlit spot outside stables. Placing the trap out of reach from curious livestock is highly recommended.

Information on pasture fly management including pictures of various fly traps can be found in our publication Integrated Pest Management Guide for Organic Dairies. For more information see Pest Flies of Pastured Cattle and Horses.

How to scout for corn rootworm

Ken Wise,
NYS IPM

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You will need to scout all corn fields that will be kept in corn next year from emergence of the tassel until pollination is complete. Pollination occurs for three weeks and monitoring takes about 20 minutes per field. You will need to monitor each field once a week until you reach a threshold or until pollination is over. Look for gravid, (i.e. mature, egg laying) corn rootworm females beetles--the ones that, when you squeeze their bodies, release white eggs from their posteriors.

Here's how you scout:

  • Are female beetles present? Mature and capable of egg laying? Conduct the squeeze test (see above) to determine if they are ready to lay eggs.
  • Approach a corn plant carefully because the beetles will fly off if they disturbed too much.
  • Grasp the silk with one hand.
  • Count the beetles on the entire plant.
  • Start counting at the top working down.
  • Gently pull leaves away from the stalk so you count any beetles that may be hiding in the whorls.
  • For each corn plant monitored, record the total number of beetles observed. See the sequential sampling chart below. Since western corn rootworms are potentially more damaging than their northern cousins, count each western (yellow striped) beetle observed as "one" and each northern (green type) as "1/2".
  • Check several plants at random (not next to each other!) in several parts of the field.
  • Continue sampling at seven-day intervals until the ear silks are brown, approximately 3 weeks after tassels are first visible, pollination is complete or an above threshold number of beetles are found.

Using the Sequential Sampling Card for Corn Rootworm

  • Keep a running total (RT) of the number of corn rootworm beetles you have counted on each plant. Each northern corn rootworm has half the value of each western corn rootworm. The western corn rootworm does twice the damage to corn than does the northern. So if you count 3 westerns and 4 northern (2 western equivalent) on a plant you would have a total of 5 beetles.
  • If the number of corn rootworm beetles observed is smaller than the "N" ("Not at threshold") number stop and scout 7 days later.
  • If the number of corn rootworm beetles observed is larger than the "T" ("At threshold" or "Treat") number then you need to manage rootworms next year.
  • If the number of corn rootworm beetles observed fall between "N" and "T", continue sampling additional plants until you finally go over or under.
  • In a very low or very high rootworm population a sampling decision can be made in sampling as few as 3 to 8 plants. For moderate populations more samples may be necessary to insure accuracy.

Sequential Sampling for Corn Rootworm (download as a 22k pdf file)

Plant
N
T
RT
Plant
N
T
RT
Plant
N
T
RT
Plant
N
T
RT
1
 
 
 
15
7
23
 
29
20
36
 
43
34
50
 
2
 
 
 
16
8
24
 
30
21
37
 
44
35
51
 
3
 
11
 
17
8
25
 
31
22
38
 
45
36
52
 
4
 
12
 
18
9
26
 
32
23
39
 
46
37
53
 
5
 
13
 
19
10
27
 
33
24
40
 
47
38
54
 
6
 
14
 
20
11
28
 
34
25
41
 
48
39
55
 
7
 
15
 
21
12
28
 
35
26
42
 
49
40
55
 
8
0
16
 
22
13
29
 
36
27
43
 
50
41
55
 
9
1
17
 
23
14
30
 
37
28
44
 
51
42
55
 
10
2
18
 
24
15
31
 
38
29
45
 
52
42
55
 
11
3
19
 
25
16
32
 
39
30
46
 
53
43
55
 
12
4
20
 
26
17
33
 
40
31
47
 
54
44
55
 
13
5
21
 
27
18
34
 
41
32
48
 
55
54
55
 
14
6
22
 
28
19
35
 
42
33
49
 
 
 
 
 
N= No Treatment; T = Treatment; RT = Running Total

Are soybeans at risk from spider mites?

Many of the areas of the state have been experiencing dry weather conditions. Hot weather combined with dry - droughty conditions can increase risk of spider mites becoming a problem in soybeans and field corn. We have not heard of this pest being a problem so far this season but if your fields have been showing drought stress, it would be useful to include monitoring for spider mites in your next field visit.
Two-spotted spider mites are tiny, oval, 8-legged, pale-bodied arachnids.  The feeding of spider mites causes a stippling of leaves.  Severe feeding by many mites causes a bronzing of the leaf.  The injury from spider mite feeding can resemble a foliar fungal disease infection.  Another identifying factor of spider mites is the silk-like webbing they produce.  The webbing can be seen on leaflets and petioles in a heavily infested field.  The mites are able to use the silk to transport by wind to un-infested areas of a field.  When scouting, to help to confirm the presence of spider mites, hold a white piece of paper under a plant.  Tap on the plant, and some of the mites should fall to the paper.  They appear as yellow or yellow brown moving specs. 

Spider mites on soybean:

spider mites on soybean

Early symptoms of spider mite injury on the upper leaf surface:

early symptoms of spider mite injury

Spider mite populations can increase extremely rapidly - they can develop from egg to adult in 5 days with high temperatures.  Cool, damp weather often leads to steep declines in spider mite populations by encouraging fungal pathogens to take control.
Spider mites are regular residents of weedy areas at field edges.  During dry weather, if these weed hosts become stressed, spider mites may begin to move into the nearby crop. Thus, an infestation usually begins at field edges and radiates into the field.  While a spot-treatment with an insecticide may be helpful to combat the start of a severe infestation, it is critical to scout the whole field.  Low numbers of spider mites can be present before the injury can be seen from a distance.  When chemical control is chosen for spider mite management, it is critical bear in mind that pyrethroid insecticide use earlier in the season can increase the risk of spider mite "flare-ups" issues later in the season.

Western Bean Cutworm Trap Catches Increase

Keith Waldron
NYS IPM

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Total Western Bean Cutworm (WBC) counts have risen substantially in the past week at a few locations across the state indicating that the peak flight could be this week or next week.  Our 2011 WBC network consists of 68 traps across the state. So far this season, total WBC counts for the week of 6/14, 6/21 were 0; 6/28, 7/5 were 2; 7/12 were 13; 7/19 were 76; 7/26 were 315. Our running total for the season to date for all traps is 408 moths caught. WBC moths were also collected in Vermont and Maine for the first time this week. Peak WBC moth flights last year occurred the end of July and the first week in August.

Western bean cutworm females are most attracted to late whorl/pre-tassel stage corn. They lay masses of 50-200 eggs on the top surface of a leaf near the tassel. Eggs are round, cantaloupe shaped – white when first laid and turn purple before hatching. See the factsheets listed below for photos. While our current numbers do not indicate any significant concern, continued monitoring over the next few weeks will be important for detecting potential infestations and identifying any fields at risk.

Monitoring in field and sweet corn: search tassel-emergence and silk stage fields for western bean cutworm eggs and larvae.  The threshold for WBC being used in Michigan and Ontario is 5% of plants with WBC egg masses. As with other boring insects such as ECB, it's important to control western bean cutworm before it enters the ear and is protected from an insecticide application.  In her recent blog, Tracey Baute (OMAFRA) suggests focusing scouting efforts to corn fields that have plants with at least a tassel developing in the whorl of the plant to those fields with the tassel fully emerged but not fully shedding yet. These are the fields that seem to be the most attractive for the moths.  And if fields have variable plant heights, they have noticed that there tends to be a higher concentration of eggs on shorter corn in a field first before moving deep in.

WBC scouting in dry beans can be difficult. Egg masses are laid on the underside of leaves and larvae can be very difficult to find – the larvae feed at night and hide in the soil during the day. Ontario and Michigan researchers have found that you should expect pod feeding 10-20 days after peak moth flight. If you don't have WBC traps directly in your own field, at least get an idea of when traps in your area have reached peak moth flight.

WBC Factsheets:

WBC monitoring information is available at:

Western Bean Cutworm - Corn scouting videos:

Clipboard Checklist

Keith Waldron
NYS IPM

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General
* Emergency contact information ("911", local hospital, Chem. Spill emergency contact, other?) posted in central posting area
* Maintain crop records by field, including variety, planting date, pesticides used, nutrient inputs including manure, etc.
* Watch for any patches of herbicide resistant weeds, weed escapes
* Storage areas cleaned and ready to accept hay, wheat harvest
 
Corn:
* Monitor fields for plant vigor, growth stage, reproductive stage pest issues (corn rootworm, European corn borer, armyworm, western bean cutworm, foliar diseases, nutritional deficiencies)
* Monitor tasseling corn fields for presence of corn rootworm beetles, foliar diseases (Gray leaf spot, northern corn leaf spot, northern corn leaf blight).
 
Small Grains:
* Evaluate crop for plant vigor, lodging, maturity / time till harvest
* Grain bins ready to accept upcoming harvest?
 
Alfalfa & Hay:
* Monitor alfalfa seedings for weeds, potato leafhopper & diseases.
* Check regrowth of established alfalfa stands for potato leafhopper, weed and disease problems.
* Storage areas cleaned and ready to accept incoming harvest
 
Soybeans:
* Evaluate stand growth, development and condition
* Monitor fields for soybean aphid, foliar diseases, white mold, natural enemies, weed escapes
 
Dairy Livestock Barn Fly Management:
* Sanitation, sanitation, sanitation - clean animal resting areas, feed troughs, minimize source of moist organic matter i.e. fly breeding areas in barn and in adjacent animal loafing yard
* Check water sources, drainage, roof gutters for leaks and potential overspill
* Continue fly monitoring: install "3X5" index card fly speck monitoring cards through out barn
* Install/refresh/replenish as needed: fly tapes, insecticide baits, natural enemies (parasitoids)
 
Dairy Livestock Pasture Fly Management:
* Monitor animals for presence of pasture fly pests. Treatment guidelines: Horn flies (50 per dairy animal side, 100 per side for beef cattle), face flies (10 per animal face), stable flies (10 per 4 legs). See: http://nysipm.cornell.edu/livestock/default.asp)
* Consider installing biting fly traps to reduce horse, deer and stable fly populations.
 
Storage:
* Keep areas around storage bins and silos clean and mowed
* Monitor temperature and moisture of stored grain
* Check areas around storage bins and silos for vertebrate tunneling
* Check temperature of recently binned grains and baled hay in hay mow
 
Equipment:
* Note any repairs needed for recently used equipment: tractors, tillage implements, sprayers, etc. as they are cleaned and serviced.
* Service hay and grain harvesting equipment as needed.
* Calibrate manure spreaders - maintain records on amount spread per field

PESTICIDE EMERGENCY NUMBERS

Emergency responder information on pesticide spills and accidents CHEMTREC:  800-424-9300

For pesticide information:

National Pesticide Information Center: 800-858-7378

To Report Oil and Hazardous Material Spills in New York State: NYS Department of Environmental Conservation Spill Response: 800-457-7362 (in NYS); 518-457-7362 (outside NYS)

Poison Control Centers: Poison Control Centers nationwide: 800-222-1222

If you are unable to reach a Poison Control Center or obtain the information your doctor needs, the office of the NYS Pesticide Coordinator at Cornell University, 607-255-1866, may be able to assist you in obtaining such information.

Contact Information


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Keith Waldron: NYS Livestock and Field Crops IPM Coordinator
Phone: (315) 787 - 2432
Fax: (315) 787-2360
Email: jkw5@cornell.edu

Ken Wise: Eastern NYS IPM Area Educator: Field Crops and Livestock
Phone: (518) 434-1690
Fax: (518) 426-3316
Email: klw24@cornell.edu