by Elizabeth A. Tomlin
“If you find it, we need to know!” said Kevin Ganoe, Cornell Cooperative Extension’s Field Crop Specialist for Central New York (CCE CNY).
Ganoe was speaking to a room of crop farmers during one of CCE CNY 2019 Field Crop Pest Management meetings that took place in seven counties, where topics spanned a variety of current issues from scouting for herbicide resistant weeds to scouting for the invasive Spotted Lanternfly (SLF).
“We don’t want these things to become established in New York State.”
The Spotted Lanternfly was number one for discussion on the agenda, and Ganoe told attendees that one of the things to be on the lookout for is the “honeydew” excretion that is deposited by the insects as they swarm feed.
“They’re excreting, basically, sugar.” Ganoe said, comparing the excrement to that of soybean aphids.
“They do the same thing. On your pants, by the end of the day, it feels like you walked through cotton candy. It’s the only way I know how to describe it.”
Besides impacting plants, it also becomes a quality of life issue, since the sticky excrement attracts other unwanted pests, such as Yellow Jackets and wasps.
Although the SLF is not an immediate pest to field crop growers, farmers diversifying should be kept abreast of the negative impact these invasive insects would have on other crops, such as grapes, many fruit crops, hops, shrubs and trees — including maple trees. SLF has been spotted in several New York counties. However, no infestations have been reported at this time. Pensylvania is one state that has been impacted by these insects. New York has placed a quarantine on many products coming into the state.
Ganoe reported that the insects are known to be great hitch-hikers, with egg masses laid on any flat surface, and easily transported across state boundaries.
Herbicide resistant weeds should also be on a producer’s radar, with marestail leading the list, as it has been positively identified in several New York counties and has been documented as having the ability to survive applications of glyphosate. (Ganoe emphasized that marestail is sometimes known as horse weed, not horse tail, which is different weed with a fern-like appearance.) Some areas have populations of marestail that show resistance and survive applications of both glyphosate and Group 2 herbicides, such as Classic and FirstRate.
Marestail overwinters, setting seed in the autumn and emerging in the spring. It produces up to 200,000 seeds per plant, with an 80 percent germination rate. The seeds, attached to a feather like structure or pappus similar to a dandelion, are easily dispersed by wind. Research suggests that once the seeds get into the air they can travel over 100 miles.
Grower’s observations are critical in spotting resistant weeds, as they reproduce and quickly spread.
Ganoe said farmers who encounter resistant maretail — or any weed that shows resistance to herbicides — should contact their local CCE office promptly.
Four other previously confirmed herbicide resistant weeds include common lambsquarter, smooth pigweed, common groundsel, and common ragweed. These are all resistant to triazine herbicides.
Charts depicting herbicides and weeds they are best targeted for, were examined and explained.
Ganoe said marestail must be controlled when it is no more than 4 – 6 inches tall and provided suggestions for herbicides to control it, including a spring application containing a residual herbicide. Reading and following label instructions is mandatory.
Some weeds are frequently misidentified, causing confusion as to which herbicide to use, so identification is critical.
Attendees confirmed that annual broad-leaf weeds are a problem.
Richfield crop/ dairy farmer George Weise spoke about problems with bindweed and other attendees agreed that they were having the same problem, with one farmer admitting he has a “whole field of it.”
Bindweed is a perennial and control is a problem because many of the chemical agents used for control can harm crops.
“One way bindweed is spread is through tillage.”
Ganoe said horse nettles are also a problem for many farmers, as it comes in late, after crops are already established.
“Know what weeds you are trying to control and learn some of these chemistries.”
Using the wrong chemistry can build weed resistance.
Using the same weed control for multiple seasons also contributes to resistance.
Crop rotation can assist in avoiding resistant weeds. Corn, soybean and wheat rotations are one suggestion.
Tillage helps to deter maretail and it does not tolerate shade.
Soybean producers who get their crop in earlier to get a canopy closure as soon as possible, will benefit.
Ganoe reported earlier soil warming dates that can result in earlier planting and harvest.
Tall waterhemp is another resistant weed becoming established in NYS, although it has been reported in fewer cases than resistant marestail.
Tall waterhemp has rapid, early season growth, growing at more than 1 inch per day, quickly reaching over 6 feet, while germinating throughout the growing season. It has been found on farms in Central and Western New York.
Strong evidence suggests that some glyphosate resistant populations of marestail and tall waterhemp in New York are also resistant to Group 2 ALS inhibitors.
Generally, by the time a resistant weed population is discovered in a field, it is estimated that 30 percent is already resistant. This is why it is so important for producers to be vigilant with scouting.
The first discovery of Palmer amaranth on a New York farm in October, 2018, is alarming. The Weed Science Society of America ranks Palmer amaranth to be the most difficult to control weed in the United States.
It not only has a devastating impact on crop yields, it is extremely prolific — with a single Palmer amaranth plant possibly producing a million seeds per season — and has stems tough enough to damage farm equipment.
Ganoe said some of these resistant seeds may be coming into New York through farm machinery that has not been cleaned well before transporting.
Soybean growers that are planting dicamba resistant soybean varieties are cautioned that revisions to the herbicide labels are necessary for review. Stewardship guidelines associated with these new crops are strict.
Off target movement (drift) of dicamba herbicides cause damage to conventional soybeans and other crops, such as grapes and some vegetables. Avoid sprayer equipment contamination by cleaning equipment immediately after use and follow recommended procedures specifically, as directed on the herbicide label. Dicamba specific training is now required for all applicators. Maximum wind speed during application has been lowered from 15 mph to 10 mph. Hours of application are now limited to be made only between sunrise and sunset.
Information on dicamba changes can be found at the EPA dicamba website http://bit.ly/2fEk1sh.
For more information on field crop pest management contact Kevin Ganoe at firstname.lastname@example.org.