Cabbage Whitefly- A “newish” pest comes to town.
Teresa Rusinek
The cabbage whitefly is a recent arrival to the Hudson Valley and highly attracted to brassica crops. If you grow brassica crops, keep an eye out for this pest and control it while populations are low.
Originally from Europe, the cabbage or brassica whitefly (Aleyrodes proletella) is making its way around the world where it is now reported in Russia, Taiwan, Australia, Brazil and Africa. It established itself in eastern United States in 1993, then moved west where it was detected in California in 2001 and more recently in Oregon in 2014. It been reported on Long Island in organic production.
The adult stage is a small 1.5 mm white-winged insect that rests on the undersides of brassica leaves and flies about when a leaf is disturbed. The adults lay tiny white eggs in a half-moon or circular pattern on the undersides of the leaves. The immature stages are flat, scale- like, and feed on plant sap as do adults. Cabbage whitefly adults are distinguished from greenhouse and sweetpotato whiteflies by two gray blotches on each forewing.
When populations get high, plant vigor and quality are reduced by the mass presence of eggs, nymphs and adults. Furthermore, the adults and nymphs deposit honeydew on foliage, much like aphids, on which sooty mold grows, spoiling the appearance and marketability. In our climate expect several generations per season and under the right conditions, a significant population can establish itself in a short time. It is also likely to successfully overwinter on host plant debris in the environment.
As the name implies cabbage whitefly feeds and reproduces on plants in the brassica family, including some wild relatives like pepperweed; however, it is also known to feed on other crops and weeds like alfalfa, fava bean, sowthistle, dandelion and pansy We don’t yet know the extent to which this complicates control, but the broad range of hosts suggests it will be difficult to control culturally through rotations or plowing under crop debris. Keeping field edges clear may help populations from building up and moving into the field. Some biological controls might be introduced though we don’t yet know how they will perform in the field. In one study looking at two commercially available whitefly biocontrols, Encarsia formosa readily parasitized cabbage whitefly but Eretmocerus eremicus did not. Insecticides organic growers can use include M-Pede Insecticidal Soap, azadirachtin (Aza-Direct, AzaGuard, Azatrol, Azatin O, Molt-X, Neemix, etc.) or a horticultural oil (SuffOil-X, Sunspray Ultra-Fine). These are strictly contact materials, so coverage on the underside of leaves needs to be thorough and several applications may be required. Conventional growers can also use Admire Pro (foliar or soil), some pyrethroids (e.g. Warrior II, Mustang Max, Baythroid XL), Fulfill, Movento, Endigo ZC, Voliam flexi, and Exirel. Growers may already be applying these materials to control other brassica pests such as thrips, aphids, and diamondback moth caterpillars.
Sources:
North American Plant Protection Organization Phytosanitary Alert System. NPAG Data: Aleyrodes proletella Brassica Whitefly. Draft September 24, 2001. Accessed 12/17/2015 at http://www.pestalert.org/storage/AproletellaNAPPO.pdf
Oregon Pest Alert: Cabbage White Fly. Oregon Dept. of Agriculture, May 19 2015. http://www.oregon.gov/ODA/shared/Documents/Publications/IPPM/CabbageWhiteflyAlert.pdf
Linden A. van der & M. van der Staaij. 2001. Banker plants facilitate biological control of whiteflies in cucumber. Proc. Netherlands Ent. Soc. 12: 75-79. Accessed 12/17/15 at http://www.nev.nl/pages/publicaties/proceedings/nummers/12/75-79.pdf
Daniel Gilrein, Extension Entomologist, Cornell Cooperative Extension of Suffolk County, LI Horticultural Research and Education Center , Riverhead
Whitefly adults and nymphs on brassica leaf. Photo by Teresa Rusinek
Scouting Report 6.26.24
All crops: Many scarab beetle pests are active throughout the region, including Japanese, Asiatic garden, rose chafer, and oriental beetles. These beetles have large host ranges and adults cause chewing damage to leaves and fruit this time of year. Check product labels for specific crop-pest spray recommendations. Adults are difficult to control but may be suppressed.
Crops are really moving along now that a lot of the region has received rainfall in addition to the heat. Make sure you are checking the moisture levels in plasticulture crops – even though we’ve been getting rain, it doesn’t always make it under the beds and into the root zone. Reach under the plastic and check to see how the beds feel – rule of thumb: if you can squeeze the soil and have it stay together without it falling apart or squeezing water out, that’s pretty good soil moisture. If it falls apart it is too dry and obviously if it squishes and water runs out it is too wet.
Alliums: Onion thrips populations increased slightly during the heat wave last week. Allium crops near fields that have recently been cut for hay should be scouted carefully as adult thrips often migrate out of hay fields in June. Organic growers above a threshold of 1 onion thrips/leaf can consider applying Entrust SC at 8 fl oz/acre co-applied with a labeled insecticidal soap (M-Pede, for example, at a 1% v/v concentration). Conventional growers who applied two sequential applications of Movento prior to bulb initiation in onions can often skip 1-2 weeks of subsequent insecticide applications. For more information on thrips management in 2024, check out page 63 of Dr. Brian Nault’s presentation here.
In the north, the second flight of leek moth has not yet started in Essex and Clinton Counties where traps are deployed. Onions, leeks, and chives are at risk for damage from the second flight, while garlic bulbs most often escape damage. We anticipate flights to occur anytime now. Netting should be installed over crops now if growers are planning to use this tactic. 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.
Brassicas: Cross-striped cabbage worm (CSCW)and diamondback moth caterpillars (DBM) are both actively defoliating brassicas in the Hudson Valley. CSCW eggs are laid in clusters and, as a result, feed intensely on plants where caterpillars are present. Labeled Bt products (Dipel DF, Javelin, Agree, XenTari, Bt NOW, OLF) are effective on smaller caterpillars, while Entrust SC may be used on larger caterpillars. DBM populations are widely resistant to IRAC 3A pyrethroids; see Dr. Brian Nault and Christy Hoepting’s presentation on management options for DBM here. Conventional insecticides like Proclaim and Radiant are effective options for larger caterpillars of both species.
The spring emergence of overwintering Swede midge continues this week in the north. We are now seeing signs of damage from this generation in brassica plantings, including twisted leaves, swollen petioles, and blind plants. New transplants should be protected with an insecticide application or with insect exclusion netting, or planted in fields far from infested early season crops. No OMRI-listed insecticides are effective, but Assail, Admire Pro, Senstar, Movento, and Warrior II are labeled for swede midge for conventional crops. Broccoli and cauliflower are most sensitive to damage and should be protected until crowns are ~2 inches in diameter. More information on swede midge can be found here, and a guide for organic growers can be found here.
Cabbage whitefly has already appeared in kale plantings in the past two weeks. The cabbage whitefly is a recent arrival to the Hudson Valley and highly attracted to brassica crops. If you grow brassica crops, keep an eye out for this pest and control it while populations are low. For more information on identification and management options see this article on cabbage whitefly.
Lots of heat stress going on in brassicas, especially those planted on black plastic mulch. If these 90 degree days persist, a little overhead irrigation might be a good idea, especially on those plants that were or are just being planted. For summer plantings, you might also want to consider trying some white plastic mulch to reduce some of the heat related issues we run into this time of year with these plantings. For more information about broccoli and heat stress, see this factsheet by UMass Extension.
Chenopods (Beets, Chard, Spinach): Nothing new to report
Corn: European corn borer activity has increased in the north, with some fields experiencing infestation over the action threshold. Corn is rapidly growing with many early plantings tasseling and silking. European Corn Borer can be found in whorls and emerging tassels. Make control applications when 50% of the tassels are just starting to emerge from the whorl and open followed by a second application as the rest of the tassels open. Spraying corn that is in the whorl stage will probably result in poor control as the larvae are very well protected which is why we target tassel sprays because larvae are generally most exposed at that time as they try to burrow into the stalk where they can be protected.
Cucurbits:
The bacterial foliar disease angular leaf spot is severe in some areas of the Hudson Valley on winter squash. Rotate out of cucurbit production in affected fields for 3 years if possible. The causal pathogen is known to be seedborne in cucumber and thought to be seedborne in other cucurbit crops. If you notice symptoms in transplanted cucurbits in the greenhouse, isolate those trays and minimize periods of leaf wetness (bottom water if possible) as the bacteria spreads through splashing. Labeled copper formulations can provide some suppression, but fruit symptoms may be present regardless depending upon environmental conditions near harvest.
Powdery mildew has been found in the region this week. A 2024 spray guide for cucurbit powdery mildew is forthcoming.
Cucurbit downy mildew was detected in Salem County, NJ in the past week. Sentinel plots on Long Island have not yet showed symptoms if downy mildew. Growers in the southern part of the ENY region should be scouting regularly. Please let us know if you see downy mildew symptoms in your field so that we can contribute to the national map.
Squash bugs (adults and eggs) have been reported throughout the Northeast in high tunnels and in the field. Cucumber beetle populations are erratic throughout the region, and should be scouted for to determine control measures. The economic threshold varies by crop but generally speaking, growers should spray if they are seeing 1-2 beetles per plant.
Two spotted spider mites have shown up in melons with the recent hot conditions. Symptoms can include leaf puckering to a bronzing of the young leaves. They can increase in populations very, very quickly if left unchecked. Acramite, Abemectin (Agri-Mek, Reaper etc.), Endigo, Gladiator, Zeal or Portal (only labeled for cucumbers and melons) are labeled for control. Coverage is essential, especially on the undersides of leaves and deep into dense canopies so increasing water volume is generally recommended.
Weed control in vine crops is a timely consideration, especially application of post emergent grass herbicides. We have several post emergent grass herbicides that are very effective, especially when the grasses are small and actively growing. They include Section, Select Max and Poast. More information including rates and more importantly, adjuvants that are required can be found by clicking this link: Post Emergent Grass Herbicides for Vine Crops.
For broadleaves, we have one product that can be broadcast over the field and plants which is halosulfuron or Sandea/Profine/Stadia. However, plants need to minimally have 2 true leaves and it’s better if they have 4-5 with no visible female flowers. Max rate is 1.0 oz so if you used a .5 ounce at planting pre-emergent, you can still use a .5 ounce post emergent along with a non-ionic surfactant (NIS). Sandea/Profine/Stadia will work on yellow nutsedge, pigweed and very small ragweed and velvetleaf. It will NOT work on common Lambsquarter! And DO NOT TANK MIX YOUR POST EMERGENT GRASS HERBICIDES WITH SANDEA/PROFINE/STADIA – They need to be applied as separate applications 4-5 days apart. Also, if you use Sandea/Profine/Stadia, be prepared to see some injury – growing points will turn yellow and the plant will slow down for a week or so but grow out of it.
Nightshades: Pruning and tying activities continue as tomatoes, in particular, have really advanced in the last week. The occurrence of the recent rains will probably also increase bacterial diseases such as Bacterial Canker – look for necrosis on the edges of leaves and what we call “Bird’s eye spot” or a tan ring surrounded by a white ring on developing fruit. Copper plus a mancozeb applications will help, but need to be applied before rains happen. Fruit can be infected pretty much at any time including in the flower stage. And don’t work plants when they are wet as this also helps spread the disease.
Beans: Leafhoppers remain the number one culprit again this week! Beans have a very low tolerance for potato leafhoppers, so scout early and often, especially younger plantings. Pyrethroids generally provide good control, but will require multiple applications.
Miscellaneous:
There have been many reports of four-lined plant bug around the Northeast this season, including in the north part of our ENY region on herbs (spearmint and others). FLPB feeding on herbs appears as brown spots that can be mistaken for foliar disease. Both tarnished plant bug and FLPB are out in large numbers this time of year coinciding with haying, as the insects move from newly mowed hay fields to crops searching for food. Control is challenging when large numbers are migrating from adjacent fields.
