Nematodes in Atlantic Soybean Production Webinar

Nematodes consistently rank as a top yield robber of soybeans. Please plan to join us virtually on December 5 from 1:00-3:00 PM for the Nematode in Atlantic Soybean Production Webinar. This webinar will include results from Soybean Cyst Nematode seed treatment trials, Root-Knot Nematode on-farm trials, emerging management strategies, and feature a panel discussion on needs to improve nematode management in the region. The webinar is free, but registration is needed for access to the zoom link. Registration information can be found athttps://www.pcsreg.com/2022-nematodes-in-atlantic-soybean-production-webinar.  Please email Alyssa Koehler akoehler@udel.edu with any questions. 

Monitoring Pickleworm – Sep 29, 2022

By Lorena Lopez, Alejandro Del Pozo, and Tom Kuhar.

We continue to see severe pickleworm infestations in squash and pumpkins grown in the Hampton Roads area (Table 1). Summer squash season is gone but beware of your pumpkins. Systemic insecticides are recommended to mitigate pickleworm infestations since contact insecticide cannot reach the larvae that burrow into fruits and flower buds (see the link below for insecticide recommendations). Pickleworm larvae can burrow into pumpkins after harvest as well when they are beautifully displayed in your porches or gardens.

CropRowFruits_with_holesUndamaged_fruitPercent_damaged
Zucchini25550
Zucchini44640
Pumpkin111473
Pumpkin212380
Table 1. Percentage of zucchini infested with pickleworms in the Hampton Roads AREC on Sep. 27, 2022

Monitoring Pickleworm – Week of Sep 22, 2022

By Lorena Lopez, Alejandro Del Pozo, Helene Doughty, and Tom Kuhar

After pickleworms and melonworms showed up late in the summer season, we detected severe infestations (Table 1) in the Hampton Roads area and found both pests in the Eastern Shore AREC (Painter, VA) infesting summer squash and pumpkins. Beware of your pumpkins and examine your plants weekly for these pests which can be severely damaging and affect significantly your yield. In the links below you can find details on how to ID these pests and recommendations on what insecticides to use in case of infestation.

CropRowFruits_with_holesUndamaged_fruitPercent_damaged
Zucchini16460
Zucchini25550
Zucchini35550
Zucchini49190
Pumpkin111473
Table 1. Percentage of zucchini infested with pickleworms in the Hampton Roads AREC on Sep. 19, 2022

Monitoring Fall armyworm – 22 September 2022

By: Kelly McIntyre and Tom Kuhar

This week FAW adults were observed at 3 of 12 monitoring locations throughout the state. The West Central region (Montgomery county) had sites with up to 4 individuals per trap while more eastern regions of the state (Hampton Roads) observed up to 14 individuals per trap in Virginia Beach and Glen Allen, VA. See table for all locations and counts.

Soybean Seed Development & Late-Season Decisions

The soybean crop is rapidly moving along. Normally the R6 or late-seed filling stage will last about 3 weeks, although that time will shorten with late planting. Most of this year’s crop has reached that stage with the exception of late-maturing varieties planted double-crop after wheat harvest.

The crop has made only 50% of it’s yield at the beginning of this stage and about 75% of its yield 8 to 12 days into the stage. Only after the crop reaches physiological maturity is 95 to 100% of the yield been made. If stress such as we are having now occurs during this time, seed size will be small and some seed will abort in the pods.

The dry weather that we’ve recently experienced is speeding up development, aborting seed, and small seed size will likely occur. Areas that have received recent rainfall may not experience this. Unfortunately, yield may not be as good as they appear – the pod load will be deceiving in dry areas.

Aborted seed due to drought

There are still some late-season decisions that need to be made in some parts, such aa harvest aid timing or late-season insecticide application.

So when can you apply a harvest aid to control weeds or possibly speed up development? First you need to follow the label. Different harvest aids have different requirements. Many are not allowed/legal until R7. If you however select a harvest aid that can be applied in the late-R6 stage, I suggest waiting until at least half of the leaves on the plant have dropped and half of those remaining are turning yellow. This is only within a few days until R7; about 15 days after beginning R6. Most of the yield should have been made by this time. Any application before this time could affect yield.

What if you are experiencing insect defoliation? Both Mexican bean beetle and soybean looper are causing some problems in different parts of Virginia. First, is it worth treating for defoliating pests at this late stage? If you have not entered the R6 stage and are still at R5, then severe defoliation (>15%; >10% for late-planted, poor growth) could greatly impact yield. But what if you are in the R6 stage? This will depend on 1) presence of the pest and how much defoliation you have experienced; 2) how long before you are at a “safe” stage, where you’ve reached most of your yield potential; and 3) the amount of leaf area – the more the better.

Our Pest Management Guide thresholds indicate that we can tolerate up to 35% defoliation for soybean that contains fully-developed seeds (with good growth/high leaf area; less for late-planted, poor growth). But we also need to consider how long before we reach R7. If you are half-way through R6, then you are probably “safe” and don’t need to spray, depending on how fast the defoliation is occurring and the number of pests present.

However, if your are only a few days into R6, the decision is much harder. As you can see from the above diagram, we’ve only made 50 to 75% of our yield by this time. With excess leaf area (we have this in many parts of Virginia this year), you can tolerate a good bit of defoliation, even at this stage. The real questions are how long before I reach the “safe” stage and how fast is the insect pest defoliating the crop. As I stated earlier, the dry weather is speeding up maturity; so, time to maturity could be reduced by several days. The crop could be getting less valuable with time. If this is the case, I would not expect a benefit of an insecticide application. But what if the crop is not under stress? As an agronomist, I lean towards protecting crop yield. But, these questions can only be answered on a field by field basis. And you’ll need all the information that you can get, from various sources.

Monitoring Fall armyworm – 15 September 2022

By: Kelly McIntyre and Tom Kuhar

This week FAW adults were observed at 3 of 5 monitoring locations throughout the state. The West Central region (Montgomery county) had sites with 2-4 individuals while and more eastern regions of the state (Hampton Roads) experienced increased numbers with 22 individuals at Virginia Beach. See table for all locations and counts.

Thoughts about late season peanut disease this year…

I have received a lot of questions regarding leaf spot fungicide treatments in the past two weeks. A lot of this is driven by either: 1) fungicide failures in fields with high disease pressure; or 2) fields under heavy drought stress. In both cases I have advised growers and consultants to look at low cost options. I’ll cover both situations below.

Fields with high late leaf spot pressure Late leaf spot outbreaks have shown up in fields that have been sprayed with Miravis that has traditionally performed well in past years. In each case the fields were in a 4 year or less rotation, most of these fields were irrigated, and growers were using the 4 week extended spray interval to take advantage of the residual activity provided by Miravis. What growers and consultants are interested in now is what to do to hold the leaves on until digging. I try to reduce fungicide costs this close to digging while providing late leaf spot management that reduces excessive defoliation. My “go to” has been Microthiol Disperss (dry sulfur formulation) mixed with a Group 3, DMI fungicide. University researchers, including myself, have observed favorable results with this combination in field trials. The hesitancy in using this program is the added complexity of using a dry formulation and sourcing Microthiol Disperss. Some grower opt for liquid formulations of sulfur because of the two reasons just mentioned, but most of the positive results reported have been with Microthiol Disperss and the amount of sulfur provided by liquid formulations is variable depending on each product, and often the amount of sulfur used with liquid formulations is less than what is provided with Microthiol Disperss. I prefer Microthiol Disperss because it has proven effective in managing high levels of late-season late leaf spot and because it is inexpensive (about $1 per pound which is $5/acre at the recommended 5 lb rate). The sulfur provides instant reduction in leaf spot inoculum but little to no residual activity. That’s why I recommend mixing it with a DMI fungicide like Provost Silver or less expensive Alto. DMI’s provide some curative activity, but most importantly residual activity. Group 7 (SDHIs) and Group 11 (strobilurins) don’t provide curative activity and are most active when applied preventively when little-to-no leaf spot is present.

Fungicide decisions on drought stressed peanuts In many areas peanuts are under severe drought stress with many fields exhibiting wilting 24 hours a day with growers being reluctant to apply leaf spot fungicides due to dry conditions. In many cases these fields are 10-14 days away from digging. This is really a situation where I tend to favor no fungicide applications or at least one application of a very inexpensive fungicide. During dry conditions we often avoid using chlorothalonil (Bravo) due to it’s propensity for flaring spider mites. In my opinion the fungus that parasitizes spider mites to keep them in check is already absent due to the severe drought which is why many growers are seeing outbreaks of spider mites in certain areas. Since the fungus that keeps spider mites at bay (and that chlorothalonil reduces) is already absent, if chlorothalonil is chosen I see that as a low-risk application. Another less expensive option would be Alto which shouldn’t flare spider mites. My personal favorite is to not apply a fungicide at all because: 1) there is little to no leaf spot in these wilted peanuts; and 2) leaf spot outbreaks take a good bit of time to get going and by the time you see any leaf spot in these fields it will be too late for the disease to cause yield damage by the time they are dug. In Suffolk, VA the extended forecast shows no rain chances over 20% for 9 days, at least with the weather app I use. So leaf spot pressure will be low until digging in most cases which further decreases the chance of outbreaks occurring. Deciding not to spray a fungicide is a low risk option in my opinion.

Aflatoxin potential It’s been many years since growers have had to think about dry conditions leading to aflatoxin-contaminated peanuts, which is a good thing. This year is different due to the drought stress near harvest. I recommend keeping peanut field harvests separate between fields with low and high risks of aflatoxin contamination. In other words, avoid mixing peanuts from severely drought-stressed and fields that have not had as much drought stress (possibly irrigated). If peanuts that have had drought stress are to be used for seed, they should receive a quality seed treatment to reduce poor stand due to the aflatoxin fungus in peanuts planted next spring.

“Pickleworm” spotted in Blacksburg, VA

By: Kyle Bekelja, Kelly McIntyre, and Thomas Kuhar

Figure 1. Pickleworm (Diaphania spp.) caterpillar infesting a summer squash fruit. Fruit has been cut to make insect visible.

We have spotted pickleworm in Blacksburg, VA! It’s not hard to see how this pest can be economically severe. An infestation of just one caterpillar on a fruit is enough to render it entirely unmarketable. Who wants to cut into a squash to find a big juicy caterpillar living inside? I don’t…actually, as an entomologist I might find this exciting, but we aren’t growing veggies just for entomology enthusiasts. Notice the circular, tunnel-like feeding hole caused by the caterpillar (in Figure 1 and Figure 2), which burrows its way inside the fruit where it will live and feed, evading all efforts to kill it with insecticides.

Figure 2. Pickleworm injury on yellow squash

Management
To manage this pest, scout fields and look for caterpillars in flowers, before fruit set. If one is spotted, this means your crop is infested and caterpillars need to be killed before they enter fruit. Once they enter the fruit, insecticides are useless since damage is already done, and caterpillars are protected by the fruit. See the current Mid-Atlantic Commercial Vegetable Production Recommendations (VCE Publication 456-420) for management of pickleworm on crops other than those provided here. If you’re interested in getting involved in our pickleworm monitoring network, send an email to any of the authors of this post and we will be sure to send you trapping supplies.

Table 1. Insecticide recommendations for melonworm and pickleworm in pumpkins and winter squash (Table: 2022-2023 Mid-Atlantic Commercial Vegetable Production Recommendations)

Biology
This insect is a member of the genus Diaphania, which contains both “pickleworm” and “melonworm.” We will need to rear these caterpillars to adults to determine which species they are, but management recommendations remain the same, regardless. This insect cannot overwinter in Virginia; it is a migratory pest that moves northward, hence arrival is usually late-summer. Adult moths will lay eggs on flowers of cucurbits. Larvae hatch and begin feeding on fruit and may eventually tunnel inside. Once inside, insecticides are useless to kill caterpillars. Caterpillars will emerge into adults after spending 8 or 9 days as pupae.

Monitoring Pickleworm – Week of Sep 8, 2022

By Lorena Lopez and Tom Kuhar 

This week, pickleworm larvae have been detected in the Virginia Beach area, Chesapeake, and Portsmouth. If you have late plantings of squash beware of the presence of this pest in the area. Also, pumpkins could be infested by pickleworms borrowing into the fruit or feeding on the surface of the fruit. Here is a brief description of pickleworm larvae and adults, as well as options for management.

Pickleworms feed on wild and cultivated cucurbit species. Adults are not active during the day, only at night when females lay their eggs close to flowers or flower buds. The larvae burrow into the fruit where it feeds and develops. Larva color varies from light green to translucent with multiple dark spots and varies in size from 0.05 to 0.6 inches long.

Management: Pyrethroid insecticides can be effective at controlling this pest if sprayed in a timely manner (i.e., lambda-cyhalothrin, permethrin, bifenthrin, Baythroid XL, Mustang Max, etc.), but they are not IPM compatible and can result in outbreaks of secondary pests such as aphids.  Usually two or more sprays of pyrethroids in late summer can cause severe aphid problems. Other insecticides that control pickleworms include Radiant and Entrust (spinosyns), the diamide insecticides like Coragen and Harvanta, the insect growth regulator Intrepid, and the lepidopteran-targeting insecticide Avaunt eVo (Indoxacarb).  These products will have less non-target impacts than pyrethroids and also control pickleworm. 

Pickleworm larva inside a zucchini in Virginia Beach.
Adult pickleworm moth.

Monitoring Fall armyworm – 8 September 2022

By: Kelly McIntyre and Tom Kuhar

This week FAW adults were observed at 7 of 14 monitoring locations throughout the state. The West Central region (Carroll and Montgomery counties) maintained FAW presence at some sites (5-6 individuals) and more eastern regions of the state (Hampton Roads and Eastern Virginia) experienced increased instances and counts of FAW (1-49 individuals). See table for all locations and counts.