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Eastern New York Field Crops Pest Report, 2002

For 7/19/02:


General: Alfalfa was 3 to 6 inches tall this week at the SUNY Cobleskill Farm. Alfalfa re-growth is looking very good (July 16).

Potato Leafhopper: Potato leafhopper infestation levels are increasing in Eastern New York with the dry hot weather. Watch fields closely after 2nd and 3rd cutting because alfalfa is more susceptible to potato leafhopper damage when it is short. Protect new seedings --should drought conditions become severe consider cutting the PLH thresholds in half.

At the SUNY Cobleskill Farm this week, potato leafhopper infestations were coming very close to threshold in new seedings (July 16).

Check out our on-line publication, Potato Leafhopper Management in Alfalfa

Syrphid Flies: I saw several syrphid flies (also known as hover flies) in my sweep net while scouting for potato leafhopper this week (July 16). Adult syrphid flies like to feed on nectar and pollen of several kinds of flowers. Many species of adult syrphid flies look like bees. After the adults feed they lay 100‚s of white 1mm long eggs in the mist of aphid colonies. Syrphid fly larvae are good predators of aphids and other soft-bodied insects. Larvae are legless maggots that are green, yellow or gray with a yellow or white stripe down their back.

The webpage Syrphid Flies has good pictures of what an adult and larvae look like.

Birdsfoot Trefoil

Potato Leafhopper: Many have noticed high populations of potato leafhopper in birdsfoot trefoil this week (July 18).

Field Corn

General: Field corn is between the V5 and V9 stage of development this week at SUNY Cobleskill. No-till corn is still behind conventional corn in development. The edge of the fields are starting to show early signs of drought stress (July 16).

Raymond Kennett (Dutchess and Columbia Counties) reports that many fields of corn are very drought stressed (July 17).

Corn Rootworm: I have not seen Northern or Western Corn Rootworm adults yet this season. But they will be greeting your pollinating cornfields soon. Most likely you will see the male Western Corn Rootworm adult first and the rest will follow.

What are some of the differences between Northern and Western Corn Rootworm?

Northern Corn Rootworm

  • Northern corn rootworm is a Generalist which means they have several hosts

  • Eggs are laid in corn, other crops, and borders

  • Relatively fewer eggs per female than compared to Western Corn Rootworm

  • Adults tend to stay in or around same field

  • Emerge later than Western Corn Rootworm

  • Shorter adult time in field than compared to Western Corn Rootworm

  • Larvae less competitive than Western Corn Rootworm

  • Threshold: 2 beetles / plant

Western Corn Rootworm

  • Western corn rootworm is a Specialist which means they prefer corn

  • Corn is preferred for egg laying

  • Relatively more eggs per female than compared to Northern Corn Rootworm

  • Adults more prone to migrate to new fields in search of corn pollen.

  • Emerge earlier than Northern Corn Rootworm

  • Longer adult time in field than compared to Northern Corn Rootworm

  • Larvae are more competitive than Northern Corn Rootworm

  • Threshold: 1 beetle / plant

For more information on How to Monitor for Corn Rootworm check out our on-line publication, Corn Rootworm Management in Field Corn.

European Corn Borer

Is European corn borer generally a serious pest in New York State for field corn?

No. European corn borer is generally not a pest to be concerned about in field corn in New York. Like with all insect pests there can be exceptions and certain fields may get infestation levels that can cause yield losses. 

Snails: I found several snails in a no-till field of corn this week (July 16). They seemed to be feeding on the leaves close to the soil surface.

Weeds: There is a nice blanket of Yellow Nutsedge in a few of the cornfields at SUNY Cobleskill this week. Bringing up the rear in a race to see which weed is dominant, Velvetleaf is running a close second (July 16).

Ladybeetles: I saw several species of lady beetles in field corn this week (July 16), including:

Multicolored Asian Lady Beetle (Harmonia axyridis), native to Asia.
Spotted Lady Beetle  (Coleomegilla maculata), native to North America.
Russian Wheat-aphid Lady Beetle (Hippodamia variagata), introduced from Europe.
Seven-spotted Lady Beetle (Coccinella septempunctata), introduced from Europe.
Cream Spotted Lady Beetle (Propylea quatuorodecimpunctata), introduced from Europe

For more information on lady beetles check out Coccinellidae, The Lady Beetles


Soybean Aphids: Raymond Kennett (Dutchess and Columbia Counties) reports that a few soybean aphids were found in a soybean field this week (July 17).

Keith Waldron and his soybean aphid (SBA) crew are finding SBA‚s in soybean variety trials in central and western NY at locations in or near Waterloo, Interlaken, Aurora (Musgrave Farm), and Sonyea/Mt. Morris. Typical numbers are zero to less than 10 per plant. Soybean varieties are generally at prebloom or about R1 stage. Beneficial populations of aphid feeding lacewings, nabids, thrips, minute pirate bugs and various species of lady bugs are in fields. PLH are also on the soybeans but not at significant numbers. Weed control is excellent to good. Very little occurrence of foliar diseases (July 17)

Do a good rain-dance over the weekend. We need it!