By Helene Doughty and Tom Kuhar

Everyone is gearing up and planning for potato planting to begin soon! With two primary insect pests of great economic importance: Colorado potato beetles and wireworms, growers are sometimes perplexed on what the best option may be or looking for that new product that will solve all their insect problems.

COLORADO POTATO BEETLES:
No new products have been registered for Colorado potato beetle control for 2023. However, at-planting neonicotinoid insecticides are still working well in our area (thankfully!). Field trials at the ESAREC in 2021 comparing labeled at-planting insecticides yielded great results for Colorado potato beetle control, up to 56 DAP (Figure 1 and 2). Similar residual efficacy has been shown on commercial farms on the Shore as well based on previous assays from 2021.

And for those pesky beetles infesting fields later in the season (likely from neighboring potato fields from the previous year) once the at-planting insecticide has worn off, there are still numerous options for foliar control (being mindful to rotate to a foliar insecticide in a different IRAC group) (Figure 3). A couple new insecticides with new mode of actions should be available later in 2023 or 2024, which have performed very well in our CPB efficacy trials; these include plinazolin a new Group 30 mode of action, and Calantha (a new RNAi insecticide that is highly specific to CPB and not toxic to any other organisms).

WIREWORMS:

Questions about wireworm control come back every year. With recurring problematic fields, growers are always in search of new options. Based on 15 years of research at the ESAREC, the combination of Regent (fipronil) with a neonicotinoid (thiamethoxam or imidacloprid) at planting still offers the best control for seedpiece protection. A new option is available in 2023 with a group 30 insecticide, broflanilide, currently marketed under the trade name Nurizma. We are looking forward to testing it as an at-planting insecticide in our potato field trials in the upcoming season.  We are also interested in assessing the wireworm suppression ability of this same insecticide applied as a seed treatment to wheat cover crops.  Research has shown that this can significantly reduce wireworm populations in a field for subsequent crops like potato. 

More research work in the upcoming years will continue to focus on understanding the biology of this pest in its larval and adult stage as well as reduction of wireworm population in fields for potato production through seed treatments in rotational crops.

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. 

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.

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.

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.

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.

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.

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.

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.

By: Kyle Bekelja, Kelly McIntyre, and Thomas Kuhar

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.

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.

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.