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May 30, 2020

Specialty Crops Injury Caused by Dicamba Herbicide Drift

Figure 1. Non-tolerant soybean foliage when exposed to a sublethal rate of dicamba 2 weeks after treatment. Leaves are cupped with the bottom edges curved towards the top surface of the leaves.

By Maggie Wasacz1 and Thierry Besancon2

1 Rutgers Weed Science Graduate Student; 2 Rutgers Weed Science Extension Specialist for Specialty Crops

Glyphosate-tolerant soybeans were first commercialized in 1996 in the United States. By 2006, almost 9 out of every 10 soybean acres were planted with glyphosate-tolerant cultivars. However, reliance on glyphosate alone for soybean weed control stimulates the selection of weed biotypes naturally resistant to glyphosate. By 2019, there were 43 weed species known to be resistant to glyphosate, including species such as Palmer amaranth or waterhemp that can easily out-compete soybean and reduce yield by more than 50% if left uncontrolled.

What is Dicamba Herbicide?

One way to control glyphosate-resistant weeds is to treat them with herbicides other than glyphosate, such as dicamba. Dicamba is a synthetic auxin herbicide that has been used to control broadleaf weeds for over 50 years. Chemical and seed companies have recently developed new soybean varieties that are tolerant to dicamba and that started to be commercialized in 2016. With the development of genetically modified dicamba-tolerant soybeans, dicamba may be sprayed more frequently during the growing season. Additionally, dicamba is regularly applied in corn, for right-of-way applications, and in the early fall for perennial weeds control.

Dicamba can injure sensitive broadleaf plants through tank incorrectly rinsed after spraying dicamba, particle drift during the dicamba application, and vaporization after dicamba has been applied . Particle drift refers to the herbicide being carried off-target by the wind during the application. Wind speed, particle droplet size, nozzle type, carrier volume, application method, and application speed will affect the extent of particle drift. Vaporization, on the other hand, occurs when the herbicide evaporates from the target plant and these vapors travel off-target.  For more information on herbicide drift, please refer to the following PPA post 10-best-management-practices-to-avoid-herbicide-drift.

If some of the dicamba sprayed onto a soybean field moves off-target and lands on a nearby field planted with a sensitive crop, the results can be very harmful. This injury could potentially cause aesthetic damage as well as reduce yield reduction.  Potential for yield loss is influenced by amount of dicamba as well as when the injury occurs. Small volumes of dicamba products can cause leaf cupping and deformation, plant twisting, and in extreme cases, plant death of sensitive crops.

Screening Vegetables for Dicamba Sensitivity

Greenhouse studies conducted at Rutgers University in 2019-2020 screened economically important vegetable crops from the mid-Atlantic region for sensitivity to sublethal doses of dicamba. These micro-rates of dicamba simulated varying levels of drift conditions in the field. To put the rates into perspective, the highest dose in this study was equivalent to about one drop of product per quart of water. The goals of this study are to develop recommendations that can help growers design their planting strategies around dicamba-treated fields as well as to use this data to help refine recommendations to maximize protection of sensitive crops.

Crop-Specific Reactions to Simulated Dicamba Drift

The most sensitive crops in this study were the leguminous crops, including non-tolerant soybean, lima bean, and snap bean, as well as solanaceous crops, such as tomato, eggplant and pepper. These crops demonstrated severe injury.

Soybean injury is characterized by the underside edges of the leaves curling upward toward the top surface of the leaves (Figure 1). Lima bean and snap bean have similar injury symptoms, both exhibiting injury in several ways. Higher rates caused some leaves to not emerge at all, while lower rates caused leaf cupping injury that caused the top edges of the leaves to curve downward towards the ground. Other symptoms included a bubble-like texture on the top sides of the leaves, as well as leaf crinkling.

Figure 2. Eggplant 2 weeks after treatment. The undersides of affected leaves are curled upward toward the top surfaces of the leaves.

Figure 3. Bell pepper 2 weeks after treatment. The leaves are cupped with a bubble-like texture on the top surface.

 

 

 

 

 

 

Figure 4. Tomato 2 weeks after treatment. Leaflets are curled, reduced in size, and deformed.

For eggplant and bell pepper, injury was expressed as the undersides of the leaves curling upward toward the top surface (Figures 2 and 3). Additionally, leaf crinkling is seen in bell pepper foliage (Figure 3). Finally, tomato plants express dicamba injury with leaf twisting, cupping, stunting, and crinkling. At higher rates, these leaflets will be extremely stunted and deformed (Figure 4). Lower rates will show slight cupping, leaf crinkling and a change in leaf surface texture. Among the most tolerant crops from this study were basil, pumpkin, lettuce, and kale. These plants incurred the lowest amount of damage. The moderately sensitive crops included watermelon, cucumber, and summer squash. Watermelon foliage exhibits injury differently than many of the other crops tested in the study. Rather than leaf cupping, watermelon leaf texture appears shriveled and more deeply lobed with small bubbles on the top leaf surface (Figure 5).

 

 

Figure 5. Watermelon 2 weeks after treatment. Leaves are deeply lobed with a puckering, bubble-like texture.

Figure 6. Summer squash 2 weeks after treatment. Leaf edges are curved downward toward the ground.

Figure 7. Cucumber 2 weeks after treatment. Leaf is cupped and the bottom edges of the leaf are curved upward towards the top leaf surface.

 

Summer squash and cucumber, however, show leaf cupping when injured. In summer squash, the top edges of the leaf curve downward towards the ground (Figure 6).  The foliage of cucumber tends to curve the bottom edges upward toward the top surface of the leaf, although both directions of cupping were observed. (Figure 7).

On-Going Research at Rutgers

This summer, Rutgers researchers will select a few of these crops to take yield in a field-based dicamba drift study that tests different drift rates and application timings. Although this study gives some preliminary information, more detailed studies are necessary to confirm these findings. However, in the meantime, this greenhouse work gives us a brief snapshot of which species to be most concerned with when working near dicamba treated fields and provides help with field identification of these injury symptoms.

If you suspect that dicamba drift may have injured your crops, please contact you local county extension agent or Rutgers weed science specialist (Dr. Thierry Besançon) as soon as possible, and take detailed pictures of the observed damages.

 

 

Filed Under: Blueberry, Commercial Ag Updates, Fruit, Organic Production, Tree Fruit, Vegetable Crops, Wine Grape Tagged With: , , , , , ,
May 29, 2020

Help, Spotted Lanternfly Nymphs are in my Vineyard!

Management of Spotted Lanternfly Nymphs in New Jersey Vineyards

Megan Muehlbauer and Anne L. Nielsen

Vineyards in Salem and Hunterdon Counties in New Jersey are beginning to report spotted lanternfly (SLF) nymph sightings (Figure 1). These small black nymphs have white dots on their abdomens and will hop if disturbed. Although it is concerning to find them in large numbers in vineyards, we are not recommending that grape growers spray insecticides at the nymph stage.

Vineyard

Spotted Lanternfly Nymphs

(Photo Credit: https://www.pottsmerc.com)

Why? Thus far, there has been no definitive research showing that young SLF nymphs cause damage to grapes.  If SLF is feeding on grapes during the 1st and 2nd instar (nymph) stages, they are likely feeding on the fleshly new growth, not on the canes or cordon as the adults do.

However, these nymphs are also likely representing a very low number of the total population of SLF in and around the vineyard they are being seen at, because research has also shown that nymphs feed on multiple host plants.  To further elucidate details of SLF life cycle, and feeding habits, we are surveying to determine which life stages are found in commercial vineyards throughout the growing season.

As you make a decision on whether to spray the nymphs in your vineyard, It is important to keep these two points in mind.

1) Do not overuse pyrethroids in a vineyard as they can flare mealybug populations which vector leaf roll virus.

2) Save highly effective insecticides with good residual (Brigade, Actara, Scorpion, Carbaryl, and Mustang Maxx) for use against the adults in late summer through harvest.

If you want a material to apply now while the nymphs are just becoming active in the vineyard, the biological pesticides, BoteGHA (1-2 qt/acre) or BotaniGard 22 WP (0.5- 2 lbs/acre), are effective against the nymphs and will minimally impact other pests. These products have Beauvaria bassiana, a beneficial fungus that attacks insects and has good efficacy against SLF nymphs and a 4 hour REI.  Keep in mind when using B. bassiana materials, they take a few days to kill SLF and the fungal growth will turn the nymphs into fuzzy white cotton balls (Fig 2). As a biological material they work best under humid conditions. Recommendations tank mix compatibility for BoteGHA can be found here

Bug under a microscope

There are two other pests in NJ vineyards, grape berry moth and Japanese beetles, that commonly require management in the early summer. While there is no action threshold for SLF nymphs in the vineyard, management can be combined with existing pest management programs. Grape berry moth timing is approaching and we recommend using an insecticide that is effective against both SLF nymphs and grape berry moth if you have SLF nymphs in your vineyard (Table 1).

Just remember that the degree-day timing for grape berry moth is based on using growth regulators or diamide chemistries and application of a broad-spectrum material would be applied 1-2 days after the predicted timing. Japanese beetles typically occur in late June/July and again, there are insecticide materials that are effective against both SLF nymphs and Japanese beetle (Table 1).

Table 1. Insecticide efficacy against SLF nymphs and key grape pests

Rating of Insecticide Efficacy*
Insecticide SLF Nymph ** Grape Berry Moth Japanese Beetle
Avaunt 30SG E G G
Brigade 10WSB E E –
Entrust 2SC F G –
Imidan 70WP E G –
Carbaryl E G G
Actara 25 WG E – G

 

*E – Excellent; G – Good; F – Fair; ‘-‘ not rated

**H Leach, DJ Biddinger, G Krawczyk, E Smyers, JM Urban 2019 “Evaluation of insecticides for control of the spotted lanternfly, Lycorma delicatula, (Hemiptera: Fulgoridae), a new pest of fruit in the Northeastern U.S.” Crop Protection 124:104833

 

The recommendations for spotted lanternfly control are centered around the adult stage which are considered the primary damaging stage.  If adults are found in your vineyard they likely warrant management. In 2019 we saw SLF move into Northern NJ vineyards in large numbers at the end of September. It is important to note that they do not discriminate between vines that have been harvested or not. The only available threshold for SLF in grapes is 10 adults/vine, however this is quickly exceeded in some vineyards. We are recommending that growers apply a border spray targeting the vines on the borders or the first few panels if rows are perpendicular around your vineyard, with a focus on areas near hedgerows as it has been shown that those are the areas that SLF if most likely to congregate in at higher densities.  Further information on adult SLF control, recommended insecticides and rates will be in a forthcoming Plant and Pest Advisory Post.

Filed Under: Fruit, Tree Fruit, Wine Grape Tagged With: , , , , ,
May 26, 2020

Fruit IPM For 5/26/20

Peach:

Plum Curculio (PC): PC oviposition continues in all areas of the state. We have accumulated about 253 DD since petal fall (apple) in southern counties. The Cornell model calls for insecticides applied up to the 340 DD50 mark. The current prediction is for southern counties to hit 340 on or about 5/30. This allows for the last of the PC activity to be covered by the residual from the last insecticide application. Therefore applications made this week in southern counties should control this generation of PC. In northern counties PC is still a primary target and needs to be controlled during the next couple of applications. [Read more…]

Filed Under: Blueberry, Fruit, Tree Fruit
May 26, 2020

Last “Ask the Ag Agent” Webinar Tonight at 7:00PM

The last springtime Rutgers Cooperative Extension, “Ask the Ag Agent” weekly 1-hour sessions for farmers will take place tonight 5/27/20 at 7:00PM. We realize the season is well underway and most farmers are out in the fields. With the regular sessions ending for now, please reach out to your local County Agricultural Agent at anytime for assistance. We are open for business, and as times have changed we have changed with them.

This last online webinar/call in event will begin promptly at 7:00PM with an open forum to discuss ag-related questions about production, marketing, regulations and any other topics farmers wish to discuss.

Thank you to all who joined each week over the past two months and thank you to the Ag Agents and Extension Specialists who have participated. Bill Bamka, Stephen Komar, Meredith Melendez and Michelle Infante-Casella created and hosted this forum one week after the State of NJ went into lockdown and it has been quite the journey. Please join us for one last session for spring. All are welcome.

To access via WebEx on a computer go to https://go.rutgers.edu/rc9n3kxt

Join by phone
+1-650-429-3300 USA Toll
Access code: 799 743 872 # and then # again to join

Filed Under: Blueberry, Commercial Ag Updates, Cranberry, Field, Forage & Livestock, Food Safety, Fruit, Landscape, Nursery, & Turf, Organic Production, Strawberry, Tree Fruit, Uncategorized, Vegetable Crops, Wine Grape Tagged With:
May 26, 2020

Reminder for Tonight’s On-Farm Direct Marketing, Farmer Panel Webinar

Tonight at 7:00PM – Last Session for the On-Farm Direct Marketing May Webinar series.

Covid directionsFarmer Panel: Tracy Duffield-Duffield’s Farm Market, Dave Specca- Specca’s Pick-Your-Own Farm and Jess Niederer – Chickadee Creek Farm and CSA will discuss what they have changed on their farms due to COVID-19.

Please join us online at https://go.rutgers.edu/k0d59m8h

or

On the phone 1-650-429-3300 with Access code: 226 795 368 # and then # again.

Filed Under: Blueberry, Commercial Ag Updates, Fruit, Organic Production, Strawberry, Tree Fruit, Uncategorized, Vegetable Crops, Wine Grape Tagged With: ,
May 22, 2020

10 Best Management Practices to Avoid Herbicide Drift 

The last few weeks have been very windy, and we already received numerous calls from specialty crops growers inquiring about the risk of herbicide drift or investigating if observed crop damages may be the result of herbicide drift.

Blueberry flowers

Fig.1 Paraquat drift on blueberry flowers

Why does it seem like crops are more affected by herbicide drift in the spring? Well, mostly because this is the time when newly planted crops develop new shoots or reproductive structures that may be very sensitive to herbicide drift (Figure 1). This is also the time of the year when most postemergence herbicide are applied to control emerged weeds and subsequent new flushes. When both events coincide and if weather conditions favor herbicide drift, this could lead to disastrous injury on sensitive non target crops!

Drift is defined as physical movement of an herbicide through air, at the time of application or soon thereafter, to any site other than that intended. It can be particle drift from fine herbicide spray droplets that can travel over long distances during period of high wind. High wind speed, low relative humidity, high temperatures, small droplet size, and spray boom maintained high above the ground are factors that increase the risk of particle drift. Depending on the herbicide, application and weather conditions, fine droplets can travel up to several miles! It can also be vapor drift which results from the ability of an herbicide to vaporize and mix freely with air. Volatility of any herbicidal substance is characterized by its vapor pressure. The higher the vapor pressure of a substance, the greater its tendency to volatilize (Table 1). However, other factors such as herbicide formulation and weather conditions will influence volatility. Some herbicides classified as growth regulators (2,4-D, dicamba, triclopyr or clopyralid) are well known for the higher risk of vapor drift associated with their use when herbicide formulation and/or weather conditions increase volatility (Figure 3).

Herbicide Vapor Pressure (mmHg)
Glyphosate IPA 1.58 x 10-8
Glyphosate Ammonium Salt 6.75 x 10-8
2,4-D DMA <1.0 x 10-7
2,4-D Acid 1.4 x 10-7
Atrazine 2.9 x 10-7
2,4-D BEE 2.4 x 10-6
2,4-D EHE 3.6 x 10-6
Trifluralin 1.1 x 10-4
Clomazone 1.4 x 10-4
Table 1 Vapor Pressures for 2,4-D Formulations and Several Commonly Used Herbicides. Abbreviations: IPA, isopropylamine; DMA, dimethylamine; BEE, butoxyethyl ester; EHE, 2-ethylhexyl ester.

So, there are a few things that you need to consider reducing the risk of potentially expansive damages to sensitive crops:

  1. Select nonvolatile or low volatility herbicides to minimize the risk of vapor drift. Growth regulator herbicides such as 2,4-D, MCPA or triclopyr can be formulated as ester or amine salt. The ester formulation is notorious for its volatility; therefore, always use these herbicides formulated as amine salt to reduce the risk of vapor drift. Other herbicides than growth regulators have high vapor pressure that makes them prone to vapor drift (clomazone, trifluralin, EPTC), but either should be soil incorporated or are formulated in a way (micro-encapsulation) that will limit the risk of vapor drift.

    Beet plant

    Fig. 2 New growth chlorosis on beet. A WSSA group 27 herbicide (“bleacher”) was applied preemergence at planting in a neighboring corn field and drifted to the beet field because of high wind.

  2. Carefully read the herbicide label. The product label will provide information regarding when it is not safe to apply the product based on various parameters such as wind speed, temperature, humidity. You may also find information buffer requirement when spraying near sensitive downwind plants or information on the type of nozzle you must use for a specific herbicide.
  3. Select nozzles that produce the large size droplets while providing adequate coverage at the intended application rate and pressure. You can also select specifically designed drift-reduction nozzles (for example, drift-guard or air induction types) operate at lower pressure (15 to 30 psi) and produce large droplets that will have less potential for drift. A good source of information on droplet characteristics and operating pressure for various nozzle types is the TeeJet nozzle catalog (https://www.teejet.com/CMSImages/TEEJET/documents/catalogs/cat51a_us.pdf).
  4. Use low application pressure and drive at low speed when applying herbicides. Herbicide drift will increase with application pressure and speed…
  5. Keep the boom stable and the nozzles close to the soil as this will minimize herbicide drift but also potential injury to the crop on which herbicide is applied. You may want to consider using a shielded boom when spraying herbicide that are prone to drift or may injure your crop. Keep in mind that postemergence herbicide will provide optimal weed control when applied timely with regards to weed development. If the weeds are too tall (see the maximum weed size for each weed species on the label), then it’s too late to spray!

    Damaged crops

    Fig. 3 Damages to pepper (left), cucumber (center), and eggplant (right) caused by dicamba herbicide applied at 1/1000 of the labeled rate on soybean.

  6. Mix spray additives recommended by the label to reduce the production of fine spray droplets. Avoid tank mix ammonium sulfate with volatile herbicides as ammonium sulfate increases volatility. You can also consider the use of drift retardants that reduce drift by increasing the viscosity or surface tension of a spray solution. However, research shows that while some drift retardants may help under some conditions, the prevention of herbicide drift should primarily rely on nozzle selection, boom height, application pressure, and environmental conditions.
  7. Do not apply herbicides when wind is blowing toward sensitive plants or when wind speed exceeds 10 mph. Ideal spray conditions are when wind speed is between 3 and 10 mph. Low winds (< 3 mph) tend to be unpredictable and variable in direction and may indicate conditions that help the development of a temperature inversion. Applying any herbicide when wind speed exceeds 10 mph may result in catastrophic consequences for neighboring sensitive vegetable or horticultural crops (Figure 2).
  8. Do not apply herbicides when temperature inversion occurs. Inversions occur when warm light air rises upward into the atmosphere and heavy cool air settles near the ground, preventing the mixing of air layers. Temperature inversion will cause small-suspended droplets to form a concentrated cloud that can move long distances (up to several miles). Typically, temperature inversions start at dusk and break up with the sunrise because of vertical air mixing. To confirm the presence of an inversion, air temperature should be measured carefully at two heights out of the direct sun: 6 to 12 inches above the ground or the top of a nearly closed-crop canopy, and at a height of 8 to10 feet above the surface to be sprayed. When the temperature at the higher level is greater than the temperature at the lower level, an inversion exists. The greater the temperature difference between the two levels, the more intense the inversion, and the more stable the lower atmosphere. To test for sure, you can use smoke by burning a small amount of dry vegetation to see if the smoke dissipates or hangs low to the ground. If the smoke hangs in the air together then moves off slowly without dissipating, it indicates that a temperature inversion exists and that you do not want to spray as  long as the temperature inversion persists. Usually, temperature inversion will dissipate when temperature rises 3 degrees or more above the morning low, or when the wind speed increases to more than 3 mph.
  9. Spray when temperatures remain below 80°F to minimize vaporization and droplet evaporation. This will minimize vapor drift but also help with weed control by avoiding that spray droplets evaporate before reaching the target…
  10. Leave a buffer zone between treated fields and sensitive plants. Herbicide labels may specify the width of the buffer zone. The buffer zone will allow larger droplets to settle before reaching sensitive plants. The buffer zone may not be effective in settling small droplets.

Remember that all herbicides are capable of drift, no exception.

When spraying a pesticide, you have a moral and legal responsibility to prevent it from drifting and contaminating or damaging neighboring crops and sensitive areas. Always monitor weather conditions and their evolution carefully when spraying an herbicide. Overall, do not spray if all conditions are not suitable, and stop spraying if conditions change and become unsuitable.

Filed Under: Blueberry, Cranberry, Field, Forage & Livestock, Fruit, Landscape, Nursery, & Turf, Nursery, Strawberry, Tree Fruit, Vegetable Crops, Wine Grape Tagged With: ,