Scouting Report 7.3.24
Alliums: Leek moth was detected in Clinton County traps this week, marking the start of the second flight (first generation) of the season. Pest scouts from Vermont are reporting high numbers of moths in traps, with peak flight for the Champlain Valley estimated to occur later this week. This generation is most problematic for onions. Entrust is the most effective spray option for organic growers, applied ~7-10 days after peak trap catch, targeting caterpillars before they have mined into the leaf. Biocontrol using Tricogramma brassicae wasps released during moth flight have also significantly reduced leek moth damage in crops on farms, but timing can be difficult. Lannate, Radiant, and Warrior II are also labeled products for leek moth in NYS, with 2(ee) recommendation. University of Vermont researchers have found that topping onions to remove infested leaf material prior to curing can be effective in reducing leek moth caterpillar damage to bulbs, with no impact on storage quality.
The foliar fungal disease stemphylium leaf blight (SLB) is becoming a more common sight on early maturing transplanted onions in Orange County. The causal pathogen, Stemphylium vesicarium, has developed resistance to multiple fungicide groups. Statewide onion specialist Christy Hoepting recently updated her fungicide cheat sheet for managing SLB and botrytis leaf blight (BLB) in onions; that document can be accessed here.
Brassicas: Swede midge damage (twisted leaves, blind plants) to early/mid season brassicas is now visible from the overwintered generation. Plants exhibiting damage symptoms cannot be “rescued” with insecticide application. Once damage is visible, larvae have moved from the plant to the soil to pupate. Growers with swede midge on their farm should move fall plantings away from known infested fields and treat seedlings with systemic insecticides (conventional) prior to planting. Insect exclusion netting is also highly effective if installed over ground that has not had infested brassicas for 2-3 years. No OMRI-listed insecticides are effective for swede midge.
Chenopods (Beets, Chard, Spinach): Spinach leaf miner is being reported sporadically throughout the region.
Corn: As European corn borer flights decline, Western Bean Cutworm moths are starting to increase in the region with the first western bean cutworm (WBC) moths captured in Essex, Columbia and Albany Counties this week. We typically see very large numbers of WBC moths in traps that do not correlate to large numbers of eggs, caterpillars, and subsequent economic damage in the field. A spray threshold of 1 egg mass per 100 plants is recommended for fresh market sweet corn. This pest looks similar to ECB, but usually comes in at the tail end or the ECB flight or even a little bit later. With lots of corn out there in silk and some harvest underway, Corn Earworm control needs to be of high importance. CEW moths directly lay their eggs on fresh silks where the larvae hatches and essentially starts to feed on the silk, eventually burrowing into the tip of the ear. The best opportunity to kill the larvae is before it gets into the silk channel. Chlorantraniliprole containing products (Besiege, Coragen), Lannate LV (methomyl) and Radiant are good options for CEW control. Trap catches in our region vary widely from 0 to over 30. Below is the table to help you determine your spray schedule based on the number of moths caught in pheromone traps.
As the heat continues, be on the lookout for Corn Leaf aphids. Continued use of pyrethroid containing insecticides can help flair an aphid problem so make sure to scout and include another insecticide that does not contain a pyrethroid. Those include Assail and Lannate. Also be on the lookout for Sap Beetles as it’s about time for them to make an appearance as well.
Cucurbits: Cucurbit downy mildew in cucumbers has now been found and confirmed in New Jersy, Ohio and western NY. At this time, all cucumbers and melons should be protected. The list of fungicides can be found by clicking here. Look for yellow angular spots on the younger leaves and if damp and cool, a grayish mass of spores might be seen on the undersides of the spots. ALL STAGES of plants are susceptible to the disease so make sure you are protecting all of your plantings and when you are finished harvesting a planting for the season, continue to spray with fungicides, mow or burn off with a non-selective herbicide so it does not become a site for either infection or disease spreader. It is also advantageous to sign up to receive CDM alerts from the Cucurbit Downy Mildew Forecasting site at https://cdm.ipmpipe.org/ If you have signed up in the past, you should still be registered – if not, please do so that disease alerts can be sent to your phone or email within a certain radius of your farm that you choose. This is a great place to also find a great library of diagnostic pictures.
We continue to see bacterial diseases ramp up in cucurbits. Bacterial wilt continues to increase in severity in plants that were fed on by cucumber beetles early in their lives. We are also seeing more of the damage called “Anasa wilt”, which is the term for the blackening of leaves and wilting caused by squash bug feeding. This is particularly pronounced on zucchini and summer squash currently.
The first reports of angular leaf spot have come out of Massachusetts, so growers in ENY should all be on the lookout for this disease. As with all bacterial diseases, controls are limited. In making a spray program be sure to alternate copper products with other protectants for efficacy against bacterial diseases. Conventional growers may also consider ManKocide, which is mancozeb plus copper hydroxide.
Powdery mildew is showing up in tunnel plantings of zucchini, but has not been reported in the field yet.
Nightshades: The hot dry conditions along with hay and straw cutting has really spiked the potato leafhopper pressure in potatoes, beans and even eggplant with “hopperburn” symptoms showing up in these crops. Even eggplant can be injured (marginal burning) by PLH so be sure to scout them often as well.
Be sure to monitor your soil moisture, especially in your tomato crops – a lot of early plantings are beginning to set and size fruit and now is the time to be vigilant in order to reduce blossom end rot. Blossom end rot is caused by a lack of calcium being delivered to the fruit. In many cases, calcium is in abundance in the soil, but because it needs to be dissolved and taking up in the soil solution, dry soils or saturated soils can also be the cause and this week with the heat, plants may shutdown during the middle of the day which can also induce BER as plants are not taking water up. It’s not easy trying to manage all of these factors, so control the ones you can!
This week’s heat may also coincide with aphid arrival as they reproduce rapidly in this weather. Products like Beleaf, Assail and Fulfill are all good insecticide choices. Fulfill is most effective when aphid populations are low and needs to be followed up with a second application about a week after the first. M-pede, Azadirachtin containing products or Pyganic are labeled for organic production.
We did see flower bud abortion due to the heat in many high tunnels this week. The temperatures were simply too high for ventilation and irrigation to prevent this particular event, but hopefully as temperatures drop again plants will quickly generate their next flower cluster.
Colorado Potato Beetle control is essential as populations increase and are driven to feed by the heat. CPB can be difficult to control in larger instars and nearly impossible in adults, so your best chance is when larvae are small. Rimon, Radiant and the chlorantraniliprole containing products (Coragen, Minecto Pro etc.) are still our best choices for conventional growers. If using Rimon, apply 2 times, 7-days apart, at a rate of 12 oz/A at each application, starting at 50% egg hatch or when small larvae are first observed. For organic producers, Entrust or azadirachtin products (Azatin, AzaGuard, Azera, Molt-X, Aza-Direct, Ecozin Plus, Neemix) can be effective but need to be applied again when larvae are small. Apply these 2 times, 7-days apart, and apply at the highest labeled rate starting when small larvae are first observed. Products with the active ingredient Bacillius thuringiensis var tenebrionis are becoming available again and are excellent options for small larvae. The one currently available in NY is Novodor.
The earliest planted potatoes are close to harvest. Until you can get the vines killed to set the skins, handle these tubers with the utmost care to preserve what tender skin they have. If digging with a machine, carry as much dirt up the chain as you can to prevent them from rolling around and drop them as little as possible. If you are washing and packing, be sure that the pulp temperature of the potatoes and the wash water is no more than 10 degrees different. Warm potatoes put into cold water is a recipe for disaster as soft rot bacteria and other pathogens can get pulled into the tubers because of the temperature difference. And if you are packaging them, make sure they are dry before putting them in plastic bags or containers.
Beans: Leafhopper numbers have exploded and snap beans in particular. When plants are small they can quickly become injured which can lead to major yield loss. Thresholds for LH are very low – 1 per sweep. In fields scouted Tuesday numbers were between 5-7 per plant! Pyrethroids such as Warrior II, Mustang can be used, but multiple applications will probably be required. Another labeled material such as Assail (acetamiprid) will give you a week or more of protection and might be a good choice for younger plantings.
Miscellaneous: From Cornell University Assistant Professor of Weed Ecology and Management in Specialty Crops in the School of Integrative Plant Science’s Horticulture Section Lynn Sosnoskie: Just a reminder that herbicide performance, as well as crop safety, can be affected by temperature.
The optimal air temperature for applying most post-emergence herbicides is between 65°F and 85°F. When the air temperature drops lower, plant growth, including that of weeds, slows down. This reduced growth leads to slower uptake and translocation of herbicides (i.e., slower symptom development/herbicide activity). At higher temperatures, weeds may be stressed, which can also reduce herbicide activity. Crop injury may be enhanced under hot weather conditions (injury may be exacerbated by adjuvant selection). Also, over 85 F, some herbicide may be more volatile and off-target movement (and unintended injury) may occur.
Blogs about herbicide use under dry conditions (which does mention temperature):
The Effects of Dry Conditions on Weed Management | Cornell Fruit Resources: Berries
Effects of dry conditions on weed management | CALS (cornell.edu)
Temperature and Herbicide Application Questions | NDSU Agriculture
Basil: Basil Downy Mildew was confirmed in New Jersey this week so if you are growing basil, make sure you are scouting. Initial symptoms include leaf yellowing followed by leaf browning. Affected leaves also curl and wilt, and on the undersides of the leaves, a gray-purple fuzzy material will develop. Andy Wyenandt from Rutgers Cooperative Extension has a great article detailing the controls in both greenhouses and field basil production. The link for this article can be found by clicking here. Please note that Segovis can only be used on basil that is being sold as transplants and is not labeled for field use: “Vegetable transplants can be treated with Segovis prior to retail sale only to residential consumers.” As with any pesticide, please read the label to make sure you are using the correct rates and including any adjuvants that are required.