Vegetable Scouting Report for May 29, 2025

Alliums: The first flight of Leek Moth (overwintered generation) is coming to an end in the north, with trap counts declining. The second flight is expected to occur beginning in late June, with subsequent caterpillars causing damage to garlic scapes, onions, leeks, and other alliums. Flight information will be posted here in the upcoming weeks to help time spray schedules and other management tactics. Insecticides are best timed 7-10 days following peak flight.

 Asparagus:  Asparagus Beetles are very active right now and as harvest continues, it is very important to control them as they will cause severe damage to emerged spears such as twisting, bending and scarring.  There are a number of products labeled including Assail/ArVida (acetamiprid, 12 hour REI, 1 day PHI), Entrust, Lannate (1 day PHI but 48 hour REI), permethrin and Sevin.  As harvest also comes to an end, don’t forget about post-harvest herbicides – Callisto (mesotrione), Karmex, Dual Magnum, Metribuzin, Lorox and Sandea/Profine are labeled – but the field must be clean cut at your last harvest before applications can be made to reduce injury concerns.

 Brassicas:  Flea beetle populations continue to increase, especially with this little stretch of dry weather. Young transplants and leafy crops like Arugula, Bok Choy tend to be very susceptible to Flea beetle feeding damage.  Thresholds are low with one beetle per transplant or for direct seeded crops 50% infested during cotyledon stage. Insecticides labeled include pyrethroids (Warrior or other labeled formulations, Asana, Baythroid XL etc.).  Organic products include Entrust (suppression only or other labeled formulations)  Floating rowcovers or exclusion netting can work well as well as long as it is placed before beetles are present and edges are secured tightly to prevent beetles from making their way under the covers.

Cabbage Maggot damage can also be found throughout early broccoli and cabbage plantings.  Look for wilting plants that when pulled up will have small brown tunnels in the stem at the soil line – there may also be white, legless maggots within the stem.  Treatments must be applied at planting in order to be effective.  These wounds may also allow pathogens to attack the plant as well.

 Cucurbits:  Herbicide Options for Pumpkins and Squash:  With the change in weather and the date on the calendar, lots of vine crops will be seeded in the next 2 weeks so it’s time to talk about herbicide options.  Because most of these products are seed germination inhibitors the 3 keys to having a weed free or acceptable weed level are, field preparation, application timing and moisture!  Fit and plant the field as closely together as possible.  Do not fit the field and let it sit for more than 2 or 3 days before planting it as this will allow weed seeds to germinate.   And finally, and probably the most critical, moisture:  All of these materials require either a rain or irrigation after application in order to “activate” them.  If it looks like there is no rain coming for a while and you don’t have irrigation, my suggestion is to go ahead and still get the herbicide on.  It’s better than waiting for a rain and if worse comes to worse you can always irrigate it in!

Tank mixes are more effective instead of just one product alone except for Strategy which already has 2 different active ingredients premixed (clomazone/Command and ethalfluralin/Curbit).  Many of these products have a narrow range of weeds they target so tank mixing a couple of them improves overall weed control.  Tank mixes that we think have potential for pumpkins and winter squash are:

• Sandea (Profine is the generic version) plus Dual Magnum plus Command 3ME – great for pumpkins, winter squash and other fall ornamentals
• Sandea plus Command ME or Strategy plus Sandea – also safe on the above
• Another combination would be Command 3ME, Dual Magnum plus Reflex – however, I would only use this on pumpkins. Do not use on butternut squash or those varieties in the Maxima family (kabocha, Jardale, Big Moose etc.) as too much injury can occur.

More information regarding other labeled materials and rates can be found in Table 1 by clicking 2025 Pumpkin and Winter Squash Herbicide Table  As always, please read the label carefully and if you have questions please do not hesitate to call Chuck Bornt at 518-859-6213.

Striped cucumber beetles have also begun to emerge so be on the lookout, especially in small transplants – if you used treated seed for your transplants, the likelihood that there is still activity is very unlikely so post broadcast treatments maybe required.

Potatoes:  New Insecticide Registered in NY for Colorado Potato Beetle: Calantha™ (ledprona) is now registered in New York State for Colorado potato beetle control on potato (Group 35). Calantha™ is a foliar-applied double strand­ed RNA (dsRNA) based bioinsecticide for the selective control of Colorado Potato Beetle (Leptinotarsa dece­mlineata) on potato plants. Control of Colorado Potato Beetle with Calantha™ requires thorough coverage of the crop foliage since it must be ingested by the insect to be effective. Calantha™ is most effective on small larvae in the first or second instar. For best results applications should be targeted to coincide with about 50% egg hatch and applied to young larvae if possible. Calantha™ can also be effective against the second generation, provided that the first generation was successfully managed using a different mode of action. Calantha™ typically causes the larvae to stop feeding within 2-3 days of application, but it may take up to 7-10 days for treated larvae to die and fall off the plant.

Recommend 2 applications, 7 days apart, at a rate of 16 oz/A. The first application is to be applied at egg hatch so small larvae are targeted. In NY, no more than 2 applications are allowed per growing season. Adjuvants may improve control and latex based adjuvants or par­affin-based mineral oils have shown the most consistent improvement in research trials. 4 hour REI. (Source: Sandy Menasha, Long Island Fruit and Vegetable Update, No. 6, May 8, 2025)

Sweet corn:  Sweet corn is looking a bit yellow from cooler and wetter conditions suffered early this month but is recovering quickly with the sun and warmth the last couple of days.  So far, stands look very good with the exception of wet spots.   This year we need to also be on the lookout for a new sweet corn pest, the Corn Leafhopper (Dalbulus maidis) which was only recently found in NYS last year in field corn.  The Corn Leafhopper itself is not the issue but the bacterial pathogen that it transmits called Corn Stunt (Spiroplasma kunkelii).  This bacterium belongs to a specialized class of bacteria known as mollicutes that includes phytoplasmas.  A great introduction by Cornell Plant Pathologist Dr. Gary C. Bergstrom to this disease, its symptoms and the Corn Leafhopper can be found at Corn Leafhopper and Corn Stunt  and I highly recommend taking a look to familiarize yourself with the symptoms and if you suspect anything, please contact your local CCE ENYCHP vegetable specialist.

Sweet Potatoes: In conversations with some of our southern state colleagues, pay particular attention to your fertility rates.  Phosphorous encourages root length while potassium encourages root bulbing and nitrogen encourages overall canopy growth which is not necessarily what we want!  Recommended rates include 40 – 60 pounds of actual nitrogen, 20-40 lbs phosphorous and 120 – 150 lbs of potassium (phosphorus and potassium should be based on soil test results).

Handling Slips:  Plant your slips as soon as you receive them—do not try to hold them for more than a couple of days.  If you can’t plant them right away:

• Do not put them in a cooler—keep them in a cool, shady area.
• Do not leave them in the boxes in the sun either! If possible, open the boxes and spread your slips out if you can’t get them planted right away.
• Do not “soak” your plants in water! This  only makes them slimy and encourages bacterial breakdowns. If you need to hold your plants for more than 3 or 4 days, place them standing up in shallow trays filled with sand or potting mix and keep the media moist.

Planting: Planting is the most labor consuming issues with this crop.  A wheel fitted with small spikes that can be run on the top of the beds I think works best or using a piece of 3/8 – ½” rebar and poking holes and planting is quicker and doesn’t leave that huge hole in the plastic.  This also lets you get a deeper hole without burying the growing point as each node along the stem we can get into the ground is potential for more yield!  Make sure the beds are moist so the hole doesn’t collapse on itself when you remove the rebar and make sure to give the hole a little pinch after you put the slip in to seal it up.  Make sure beds are moist and maintain good moisture for at least 7—10 days after planting.  Running the drip if you use plastic or operating overhead sprinklers for several days after planting, especially if temperatures are going to be in the upper 80’s -90’s will ensure proper rooting.

Miscellaneous:  From Cornell Weed Specialist Dr. Lynn Sosnoski:  While rainfall is needed to incorporate soil-applied, PRE herbicides, heavy rainfall can have negative impacts:

• Heavy rainfall can lead to the loss of treated soil, reducing herbicide effectiveness.
• Weed seeds can disperse through running water, leading to new infestations.
• Herbicides may concentrate in low-lying areas, increasing the risk of crop injury in those zones.
• Uneven herbicide distribution results in inconsistent weed control.
• Wet conditions can delay crop emergence and/or stress crops, decreasing their vigor and ability to compete with weeds. It may also make the crop less able to metabolize herbicides, leading to increased injury.

POST herbicide use can also be affected:

• Most POST herbicides require 1–8 hours of dry weather after application; rainfall during this period can reduce herbicide performance.
• Weeds that are stressed by wet conditions may be less responsive to herbicide treatments.
• Weeds that survive initial control efforts may re-root, regrow and become harder to manage.

Cultivation is also affected:

• Saturated soils delay cultivation and reduce its effectiveness (i.e., clumps that protect seedlings), while increasing the risk of soil compaction.

Here are a couple of other resources Dr. Sosnoski recommends for the impact of wet wether on herbicides and weeds:  Effects of flooding and wet conditions on weed management | CALS)   See also from Manitoba: Province of Manitoba | agriculture – Weed Control Under Wet Conditions

Contributors:  Cornell Cooperative Extension Specialists Chuck Bornt, Teresa Rusinek, Ethan Grundberg, Elisabeth Hodgdon and Crystal Stewart-Courtens.