Vegetable Notes 2026 Vol. 38:7

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Crop Conditions

A little rain and heat go a long way! The warm weather has pushed things along and given us a reminder of what summer may bring. Potatoes are popping around the Pioneer Valley, tomatoes are going in the ground, and transplanting and seeding are in full tilt. Asparagus and plant sales are strong, and strawberries are just around the corner! Our team is hitting the road scouting. As always, please reach out if you’d like help identifying a pest (insect, disease, or weed!), interpreting a soil test, figuring out a crop issue, complying with food safety or other regulations, or any problem you are struggling to solve on your own! You can reach us by email at umassveg[at]umass[dot]edu (umassveg[at]umass[dot]edu) or by phone at 413-577-3976.

Pest Alerts

Alliums

Onion maggot: We are past peak flight (Table 1) for the first generation of onion maggot in most of the state. The adult flies will continue to lay eggs over the next few weeks, but in decreasing numbers. Keep untreated allium crops covered until the flight is over.

Table 1. GDD for peak flight of key maggot fly pests (Base T = 40°F)

Peak Flight	Seedcorn Maggot	Onion Maggot	Cabbage Root Maggot
1st gen	360	735	452
2nd gen	1080	1752	1261
3rd gen	1800	2975	2176
4th gen	-	-	3014

Brassicas

Imported cabbageworm: No sign of eggs yet on the farms that we’ve scouted, but egg-laying should be starting any day now so keep scouting. Cover brassica plantings with row cover to prevent egg-laying, or be prepared to treat with insecticides once caterpillars are present. See the appropriate crop insect control section of the New England Vegetable Management Guide for labeled products.

Chenopods

Spinach leafminer larvae are mining in spinach, beets, and Swiss chard now, both in the field and in high tunnels. Eggs are also continuing to be laid. Scout for <1 mm long, elongate eggs laid on their sides in neat rows on the undersides of leaves, and slender, winding “mines” that expand into larger blotches. Cover new crops with row cover immediately after planting to exclude adult flies, as long as you’re not planting into a field that had leafminer-infested crops last fall. See the appropriate crop insect control section of the New England Vegetable Management Guide, or last week’s Pest Alerts, for pesticide recommendations. 

Incipio is a newly registered foliar insecticide that offers a novel mode of action for control of a broad range of insect pests in many vegetable crops, including leafminer in spinach and Swiss chard (but not beet!). It primarily works on contact but has some residual and translaminar activity. Because it is a brand-new mode of action, there is no known resistance to this insecticide. For more information on Incipio, see the Striped Cucumber Beetle article in this issue.

Cucurbits

Striped cucumber beetle adults have appeared on cucumbers in Bristol and Hampshire Counties, and likely many other parts of MA. These beetles overwinter in field edges and emerge as temperatures increase, seeking out cucurbit flowers and foliage to chew on. For more information on striped cucumber beetle and the newly registered insecticide Incipio that can be used to control it, see the article in this issue.  

Sweet corn

Growers who report sweet corn trap counts to us are getting their traps set up now, and we will start to gather numbers next week. Some parts of the Pioneer Valley are nearing the start of the first European corn borer flight, which occurs at approximately 374 GDDs base 50°F (Table 2), but the Berkshires and central and eastern MA are further away. 

Corn earworm (CEW): As part of a project to determine whether CEW is overwintering in MA despite historically having been understood not to, some growers have set up pheromone traps for CEW ahead of when they are usually expected. We have received this year's first reports of corn earworm from Bristol Co., with 6 adult moths having been captured this week. This is earlier than last year's first reports which came in during the first week of June. While we don't expect CEW populations to be widespread across the state, these results are further evidence for overwintering populations that may continue to become more commonplace, potentially impacting early corn plantings in some areas. We hope to have more results to share from this project by the end of this year, including findings from hydrogen isotope analyses of these early CEW aimed at more reliably determining where they originated—stay tuned for more information. 

Table 2. Growing degree day (GDD) accumulation, Jan. 1- May 20, 2026

Weather Station Locations	GDDs base 40°F (Cabbage, onion, & seedcorn maggots)	GDDs base 50°F (European corn borer)
Western MA
Deerfield	728	297
South Deerfield	785	327
Easthampton	761	303
Chicopee Falls	848	356
Westfield Arpt	793	327
Central MA
Leominster	739	272
Northbridge	763	285
Worcester	695	260
Eastern MA
Bolton	738	270
Stow	731	268
Lawrence	705	239
Ipswich	671	221
East Bridgewater	744	257
Boston	785	286
New Bedford Arpt	665	203

Multiple crops

Garden springtails are out now and have been observed feeding on Swiss chard, brassica greens, and other early crops. Springtails primarily feed on organic matter but will feed on the foliage of a wide variety of vegetable crops and are most active in the spring or in cool, moist conditions. These small, dark insects are often confused for flea beetles but their bodies are more teardrop-shaped—rounder and coming to a point at the rear. Similar to flea beetles, they will spring away when disturbed. Their feeding damage results in small, round holes in leaves (similar to flea beetle damage) but does not usually warrant an intervention. 

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Berry Blast

The heat earlier this week pushed crops along quickly, but cooler weather and rain later in the week could change the way we operate. The dramatic shift from hot to cooler, cloudy, wet conditions means growers should be thinking about bloom, pollination, and disease pressure all at the same time. Across all berry crops, now is the time to get your insect monitoring traps out, if you haven’t already done so. This is also a good time to make sure spring fertility is on track; but avoid pushing too much nitrogen going into wet disease-favorable weather.

Blueberries are in full bloom across much of the state, with early varieties moving into petal fall and later varieties still coming through bloom. So far this season, frost damage is still being sorted out, and growers will get a better idea of the real crop impact once fruit set becomes easier to see. For this week, keep an eye on pollination, mummy berry, Botrytis, and any blossom/twig blight symptoms following wet weather. For fertility, blueberries should be in the May/June nitrogen window. If fertilizer has not gone out yet, growers can apply the first split now and follow with the second split in June. Ammonium sulfate or urea are the common nitrogen sources, with ammonium sulfate being a good fit where soil pH is still too high for blueberries. Avoid using aluminum sulfate as a fertilizer source.

Strawberries are in bloom in many locations. We had some frost concern, but cultivated varieties generally look good. With the rain and cooler weather coming in, the big concern now is bloom protection. Gray mold/Botrytis is the main disease to keep in mind during bloom, especially when rainfall occurs between early bloom and green fruit. This is the time to protect flowers, maintain good air movement, and remove old leaves and plant debris from the canopy. Growers should also scout for tarnished plant bug and spider mites as bloom continues and fruit begins to size. 

Grapes. Earlier varieties are at the 4– to 8-inch shoot stage, with flower clusters exposed, while later varieties are in full bud burst. This is an important early-season disease window. According to NEWA recommendations, the most important time to protect shoots and fruit from Phomopsis is when shoots are at 3-inches and clusters first become exposed. For conventional growers, at least one fungicide application during this period should be applied. Canes are also most susceptible to powdery mildew during the 3– to 5-inch shoot stage. For black rot, sanitation still matters; berries become most susceptible from cap fall to several weeks after bloom, so bury or mulch old mummies where possible. We are not at peak susceptibility yet in most vineyards, but now is the time to get ready. 

Brambles are showing strong new shoot growth on overwintered canes and new primocane growth is starting to move. So far, crops are responding well to the warmer weather, but the cooler wet pattern later this week could favor cane and leaf diseases. Growers should scout for anthracnose, spur blight, cane blight, and orange rust. This is a good time to remove dead canes and thin crowded growth to keep rows open so that foliage dries quickly after rain. Tie back selected canes to your trellis system before the canopy becomes too dense to manage. Proper pruning and sanitation are still some of the best tools we have for keeping bramble pest and disease pressure down. For fertility, brambles are also in the May/June nitrogen window. Summer-bearing raspberries and blackberries can receive nitrogen split between May and June, using ammonium nitrate or urea. Adjust your rates based on cane growth and plant vigor. Do not overdo nitrogen in dense plantings, because too much growth can make cane disease problems worse.

Final thoughts: Drink water! Hydrate and get some salts in your body. Be safe out there.

-- J. Galvan

Additional Resources: 

• Current bud stages - May 18, 2026 

• New England Small Fruit Management Guide 

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Carrot Weed Management Research Report: Speeding Up Canopy Closure

When I first started at UMass as our weed management specialist, I tried to figure out what some of your biggest challenges were. Many expressed that carrot weed management was hard, so if this is your experience, you’re not alone. Weed control in carrots is notoriously difficult around the world, whether you grow carrots conventionally or organically. Ultimately, this is due to carrots’ narrow canopy, and slow and inconsistent emergence. These traits result in a long Critical Weed-Free Period¹, during which you need to control carrot weeds to maintain yield. I wrote about this in an earlier Veg Notes article here if you’d like to learn more.

This Critical Weed-Free Period is especially long when the soil is too cool or too hot for ideal carrot seed germination, which occurs between 50°F and 86°F. Last summer we received a grant from the New England Vegetable and Berry Growers Association to explore strategies to overcome slow germination and canopy closure in soils above that temperature range. We tested 3 strategies that have been useful to some degree elsewhere in the world:

• Increasing planting density^2,3
• Planting varieties that may have better germination and growth in hot conditions^4,5
• Priming seeds before planting^6,7

This work was done primarily at the UMass South Deerfield research farm, where we planted carrot seeds in the hottest part of the summer. Data loggers placed within the field showed that soil temperatures placed 1 inch in the soil profile – about where carrot seeds are germinating – were above the 86°F maximum ideal temperature every day (Fig. 1). These temperature were even warmer than we expected, and in fact, often the soil temperature at that depth was above the ambient air temperature. This research definitely confirmed that carrot seeds are often stressed when being planted in the summer for fall harvest and storage.

We compared the germination and growth of 7 different carrot varieties, generously donated from Johnny’s Selected Seeds and Harris Seeds, including a mix of favorites as well as newer varieties that may germinate better in hot conditions. We planted all varieties at two different densities, a 3-row bed with 16 inches between rows, compared to a 4-row bed with 10 inches between rows. All within-row spacing was 1.5 inches. Plantings were watered as necessary with overhead wobbler sprinklers. We measured the time it took to weed each plot, canopy cover, carrot harvest (number and weight), and Brix levels (sugar content).

Additionally, we did a laboratory study comparing the gemination of primed and unprimed seeds. 50 seeds of each variety were counted into petri plates that were either stored at room temperature (68°F) or in an incubator set to 95°F. Seeds had either been primed in aerated polyethylene glycol for 3 days or not primed. Polyethylene glycol serves to hydrate the seed (interestingly, it is the same active ingredient you would find in MiraLAX if you’ve ever had the unfortunate need to take that—in both cases, it is hydrating something!) Hydrating the seed speeds up the germination process. Germination was counted after being incubated for 10 days after priming. All data were analyzed in R, version 4.3.2, using general linear mixed models. 

In the field trials, we did observe measurable differences in carrot growth. The varieties White Satin and Shin Kuroda had the highest yields, and Bolero, Caravel, and Mokum had the lowest yields (Fig. 2). There was a similar trend for canopy cover: Shin Kuroda, White Satin, and Purple Star had the densest canopy cover and Mokum and Caravel had the thinnest (Fig. 3). From this small amount of data it looks like larger canopies are correlated with more carrots. Unfortunately, larger didn’t correlate with sweeter, and the trend was almost opposite for the sugar content of the carrots. Shin Kuroda (high-yield and dense canopy) was the least-sweet carrot, and Mokum and Bolero (low yields and thinner canopies) were sweetest (Fig. 4). 

Despite these clear differences in carrot yield and canopy, there wasn’t any difference in the amount of time it took us to weed each plot. We had thought that if the canopy was thicker, there would be fewer weeds germinating, and weeding would be quicker, but that’s not what happened. We’re not sure if our assumption—that it would be faster to weed plots with fewer emerged weeds—was incorrect, or if there weren’t any differences in weed emergence, or if there was something else going on. These are some questions we hope to answer going forward.

On average, we did observe an increase in yield and canopy cover at higher-density plantings compared to lower-density plantings, although there was no significant difference when only comparing one variety at a time. Again, we’re not sure if poor overall carrot germination may be interacting with this observation. What we can say is, if you’re anticipating poor germination at a particular planting time, and you’re likely to have stressed seed and potentially poor germination during summer plantings, increasing the seeding density is a relatively easy way to improve your stand and yield^2,3.

We plan to continue this work for another year. The treatment we are most excited to try again next year is seed priming. We only used this treatment in the lab this past year, but we saw striking and consistent results between primed and unprimed seeds. When seeds were unprimed, they had consistently poor germination when incubated at 95°F. However, when seeds were primed, there was no longer a significant difference between germination at 68°F and 95°F (Fig. 6). If it’s possible to prime seeds before planting, this may be an effective strategy to improve germination despite inhospitable conditions^6,7. Polyethylene glycol is not approved for use in organic production systems, but it may be an excellent option for conventional carrot producers.

Conclusions from year 1:

• Summer-planted carrots are often seeded into soil that is hotter than the ambient air and therefore well outside their ideal germination temperature.
• If you’re anticipating poor germination mid-summer, increasing the seeding density is a relatively easy way to improve your stand and yield.
• Priming carrot seed with polyethylene glycol significantly improved germination at high temperatures in the lab and is an interesting potential for conventional carrot producers.
• Of the varieties trialed last year, White Satin, Shin Kuroda, and Purple Star developed the densest canopy cover in our field trial; White Satin and Shin Kuroda also produced the highest yields. Bolero, Caravel, and Mokum had the lowest yields; Mokum and Caravel also had the thinnest canopies. Shin Kuroda was the least sweet and Mokum and Bolero were the sweetest.

References

1. Swanton, C. J., O’Sullivan, J. & Robinson, D. E. The Critical Weed-Free Period in Carrot. Weed Sci. 58, 229–233 (2010).
2. Colquhoun, J. B., Rittmeyer, R. A. & Heider, D. J. A holistic carrot production system for season-long weed management. Weed Technol. 34, 876–881 (2020).
3. Freitas, F. C. L. et al. Periods of Weed Interference in Carrot in Function of Spacing Between Rows. Planta Daninha 27, 473–480 (2009).
4. Colquhoun, J. B., Rittmeyer, R. A. & Heider, D. J. Tolerance and Suppression of Weeds Varies among Carrot Varieties. Weed Technol. 31, 897–902 (2017).
5. Nascimento, W. M., Vieira, J. V., Silva, G. O., Reitsma, K. R. & Cantliffe, D. J. Carrot Seed Germination at High Temperature: Effect of Genotype and Association with Ethylene Production. HortScience 43, 1538–1543 (2008).
6. Szafirowska, A., Khan, A. A. & Peck, N. H. Osmoconditioning of Carrot Seeds to Improve Seedling Establishment and Yield in Cold Soil. Agron. J. 73, 845–848 (1981).
7. Nascimento, W. M., Huber, D. J. & Cantliffe, D. J. Carrot seed germination and respiration at high temperature in response to seed maturity and priming. Seed Sci. Technol. 41, 164–169 (2013).

--Maria Gannet, UMass Extension Weeds Specialist

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Striped Cucumber Beetle

Including information on the newly registered foliar insecticide, Incipio

As we head into June, we are beginning to see the first striped cucumber beetles (SCB) become active and begin feeding on cucurbit foliage. Adult beetles overwinter in plant debris at field edges and move rapidly into cucurbit crops with the onset of warm weather. High tunnel and greenhouse cucumbers draw beetles first, followed by early field crops. Densities can be very high, especially in non-rotated fields or fields close to last year’s cucurbit crops. Adult beetles feed on cotyledons and young leaves, which can kill young plants and cause stand reduction, delay plant growth, and reduce yield. They lay eggs in the soil near plant stems, and larvae feed on plant roots. This hidden damage reduces plant vigor and yield. Striped cucumber beetles also vector the bacterium Erwinia tracheiphila, the causal agent of bacterial wilt; this disease can be more damaging than direct feeding injury. It is important to focus on early, effective control to avoid yield impacts and protect pollinators.

Cultural controls

Crop rotation can reduce the impact of cucumber beetles, as can using transplants and protecting young cucurbits with row covers. In addition to insect protection, spunbonded row covers also provide extra early-season heat, though it is important to remove them during times of excessive heat and at flowering to allow for pollination. Insect netting prevents beetle damage and does not trap in heat.

Scouting and thresholds: Cucurbit plants at the cotyledon and 1-to 2-leaf stages are more susceptible to infection with bacterial wilt than older plants. Thus, it is especially important to keep beetle numbers low before crops reach the 5-leaf stage. If you plan to control SCB with foliar insecticides, scout at least twice per week up until SCB emergence and for two weeks after, and treat after beetles colonize the field. Scout at least 25 plants to monitor the number of beetles and damage. The economic threshold depends on the crop. To prevent bacterial wilt in highly susceptible crops such as cucumber, muskmelons, summer squash, and zucchini, we recommend that beetles should not be allowed to exceed 1 beetle for every 2 plants. Less wilt-susceptible crops (butternut, watermelon, most pumpkins) will tolerate 1 or 2 beetles per plant without yield losses. Spray within 24 hours after the threshold is reached. Proper timing is key.

Perimeter trap cropping is another cultural control that has been shown to reduce or eliminate the need for insecticide sprays to the cash crop while providing effective beetle control. Trap cropping exploits the fact that SCB are more attracted to Cucurbita maxima crops (e.g. buttercup and hubbard squashes and giant pumpkins) than C. pepo or C. moschata crops (e.g. pumpkins, summer squash, butternut squash, other winter squash). Note that some specialty pumpkin varieties are C. maxima types and very attractive to beetles. Plant 1 or 2 rows of a C. maxima variety in an unbroken perimeter around the field, using 2 rows near woods or last year’s fields, and space plants no wider than the between-row spacing that is used in the main crop. Trap crops planted in rows within the main field also work as trap crops that attract beetles as they move within the field. Do not use a crop that is highly susceptible to bacterial wilt (see scouting and thresholds section) in the border. Beetles must be killed in the border, either by applying foliar insecticide when beetles first arrive or using a systemic insecticide at planting. Regularly scout both borders and the main crop to assess beetle numbers. Repeat perimeter sprays if needed to prevent influx into the main crop, and spray the main field if thresholds are exceeded.

Insect netting in high tunnels: SCB can be especially damaging in high tunnels where the plant number is lower and the cost of seed is high. Some growers are experimenting with covering high tunnel sides and doorways with insect netting to exclude SCB. We’ve heard some success stories with this tactic, and some frustrations about ripping expensive netting, reduced airflow in netted tunnels, and incomplete exclusion that leads to resident high tunnel SCB populations. Tunnel netting is best combined with crop rotation out of cucurbits so that the beetles that do make it into your tunnel one year will be unable to find food the following year. Consider using shade cloth to reduce heat which builds up in the tunnel when netting is used and ventilation is reduced.

Beneficial nematodes: Some growers have expressed interest in applying entomopathogenic nematodes to the soil to control SCB. These nematodes would target the soil-dwelling larval and pupal stages of SCB. Significant research has not been done on this topic, but theoretically it would be difficult to entirely control SCB using nematodes because of the high populations of SCB in the environments surrounding a field. Although SCB strongly prefer cucurbits, they are able to subsist on the pollen, petals, and leaves of other plants beyond the edges of a field. Even if the SCB larvae and pupae in the soil in a field were successfully killed, more adults could continue coming in from field edges throughout the season.

Chemical Control

Foliar Insecticides

There are a number of broad-spectrum conventional insecticides which can be used for foliar control of adult beetles, including carbamates (e.g. Lannate), pyrethroids (e.g. Warrior II), neonicotinoids (e.g. Admire Pro), and diamides (e.g. Harvanta)). All are highly toxic to bees and should only be used before bloom. Avoid using foliar neonicotinoid sprays if the same class was used as a seed or soil treatment (see below). See the cucurbit insect management section of the New England Vegetable Management Guide for more details.

Incipio is a newly registered foliar insecticide that offers a novel mode of action for control of a broad range of insect pests in cucurbits, brassicas, fruiting vegetables, and more. It utilizes Syngenta’s new Plinazolin technology, which falls under the new IRAC Group 30. Incipio was recently approved by the EPA along with other formulations for use on onions (Vertento), potatoes and tree fruit (Zivalgo), and pea and bean seed treatments (Equento). These products all contain the active ingredient isocycloseram which acts by binding to vital neurotransmitter receptors in insects, disrupting signals important for nervous system regulation and resulting in death. It primarily acts upon contact with insects, which means that thorough foliar coverage is essential for maximizing control. It does have some residual and translaminar activity that allows it to affect insects exposed to or feeding on treated surfaces for some time after treatment. Because this is a brand-new mode of action, there is no known resistance to this insecticide. To prevent resistance from developing among insect pests and maintain the long-term efficacy of these products, follow instructions on labels and rotate use with products from different IRAC groups within and across seasons. 

Protecting Endangered Species: Because of its broad spectrum of efficacy, isocycloseram is also highly toxic to pollinators that are exposed to direct sprays or treated surfaces, as well as fish and aquatic invertebrates that are exposed through runoff into bodies of water. To mitigate risks to pollinators, Incipio should be used prior to blooming and at dawn or dusk when bees are less active. See the final paragraph below for more information on protecting pollinators. These products’ labels are also among the first to carry additional use restrictions to comply with the Endangered Species Act’s risk mitigation requirements. Although products purchased with pre-update labels are not subject to the new restrictions, this is part of a long-term EPA approach in which similar measures will gradually be included in updates to all pesticide labels. Pay close attention to the listed restrictions on labels, which may include mandatory mitigation measures to reduce pesticide drift and runoff, as well as possible additional use restrictions depending on what, when, and where you will be spraying. To determine whether your application will take place in a “Pesticide Use Limitation Area” (PULA) and the additional mitigation measures that requires, you will need to access the EPA’s website, “Bulletins Live! Two” no more than 6 months prior to your planned application. For instance, to protect the critically endangered rusty patched bumble bee, there is a PULA near Harwich, MA which restricts any application of Incipio and other isocycloseram products on cucurbits in bloom from two hours after sunrise until two hours before sunset. While the number of PULAs in MA are so far limited and largely isolated to areas surrounding major bodies of water, more may be added as new products receive label updates. Ensure that you are following all labeled instructions and restrictions to protect vulnerable wildlife and comply with federal law. For more information about Endangered Species Act label updates, visit our article on the topic from earlier this year. 

Systemic Insecticides

Systemic insecticides, including neonicotinoids and diamides can be applied to seed (e.g. thiamethoxam or Farmore treated seed) or as an in-furrow, banded, drench, or drip irrigation application to the seed/seedling root zone during or after planting/transplanting operations (e.g. Verimark). These offer about 21 days of protection right at the critical establishment period and before flowering. Note specific application methods and rates on labels. Take care to reduce risk to pollinators when using systemic insecticides—see the section below for details. 

Organic Insecticides

Kaolin clay (Surround WP), pyrethrin (Pyganic Crop Spray 5.0 EC), and azadirachtin (many products) are labeled for SCB. Surround does not kill the beetles but instead acts as a physical deterrent. With direct-seeded crops, apply Surround as soon as seedlings emerge if beetles are active. Transplants can be sprayed or dunked before setting out in the field—consult with your organic certifier about dunking beforehand to ensure they will allow this use pattern. As with other non-systemic insecticides, Surround must be re-applied after heavy rain and on new growth. Pyganic is a contact insecticide that provides a short-term knock-down of adult beetles with no residual effect. Azadirachtin is an insect growth regulator that works by contact and ingestion against immature insect stages, and it can be applied to the soil to target SCB larvae; it also acts as a repellant and antifeedant, interfering with adult sensory organs and hindering their ability to find food and reproduce. Spinosad (Entrust) is not labeled for and is not effective against SCB.

Reducing risk to pollinators

The New England Vegetable Management Guide describes many steps that growers can take to protect honey bees and native pollinators when using insecticides. The issue of neonicotinoids in particular has received a great deal of attention in recent years. This is a group of insecticides that have a chemical structure very similar to nicotine. They have been widely used in agriculture because they are effective against a wide range of insects, have lower mammalian toxicity compared to older classes of insecticides, and because they can be absorbed by roots and moved through the entire plant, reducing the need for foliar sprays. This trait allows for applications to be made to soil or on seeds, with less exposure to humans and to non-target insects. Neonicotinoids are highly toxic to bees, and label requirements prohibit use on blooming crops or where there are blooming weeds or borders. Additional concern about impact on bees arises because research has shown that detectable, low concentrations of neonicotinoids can move into pollen or nectar. These are present at sublethal concentrations but may affect the foraging behavior of bees or suppress their immune system. The long-term or colony effects of sublethal concentrations of neonicotinoids are difficult to assess in the field because bees from each colony travel long distances and forage in many different habitats and types of plants. In cucurbits, both native bees (e.g., squash bees and bumble bees) and honey bees visit flowers to gather both pollen and nectar and are essential to crop pollination. Research in cucurbits has shown that higher levels of neonicotinoids were found after foliar and chemigated insecticides were applied during flowering. Lower levels were detected in treatment regimens that involved a single application at planting via seed treatment, a drench application to transplant trays, or transplant water treatment. Thus, growers should avoid high rates and multiple applications, especially as the crop approaches flowering.

--UMass Extension Vegetable Program. Updated for 2026 by Ali Shokoohi