The entomology program at the Tidewater AREC has spent this week scouting cotton fields across Virginia growing regions. First, I want to thank our technicians, graduate students, ANR Agents, Johnny Parker, and especially, our cooperating farmers. Cotton surveys are made possible through funding by Cotton Inc. and the Virginia Cotton Board.
I want to emphasize that overall plant bug numbers are very low, square retention very high, and the majority of fields will not be blooming by next week. Fields above threshold at this time are rare and sporadic. Use restraint when making pesticide applications without scouting first because we have many weeks left to manage insect pests. The most important time to manage plant bugs is during the first two weeks of bloom (see below graph from Seth Dorman’s work) and late-planted cotton is at higher risk of yield loss. Spraying at threshold (pre-bloom = 8/100 sweeps and <80% square retention) is as good as spraying every week (which is a pretty bad idea for secondary pest infestations, logistics, and costs).
Until the 2nd week of bloom, scout fields using a sweep net. Pay attention to areas of the field where cotton is rank and or borders other crops, but do not make decisions based on hot-spots alone.
Several insecticides are effective for plant bugs in cotton pre-bloom including neonicotinoids (imidacloprid, thiamethoxam), acephate with or without novaluron (Diamond), flonicamid (Carbine), and sulfoxaflor (Transform). Rotating insecticides, opposed to spraying a broad-spectrum like acephate season-long, will save you trips across the field. See the below table from our 2020 experiments demonstrating that using sulfoxaflor (Transform) alone, flonicamid (Carbine) alone, rotating a neonicotinoid (Centric) with sulfoxaflor (Transform), and using acephate with novaluron (Diamond) resulted in fewer trips across the field when compared to acephate alone. Also note that acephate with novaluron (Diamond) resulted in a second spray only at the end of August when it is debatable whether we have time to make a harvestable boll (i.e., it is likely that yield protection was based on a single spray). ALL INSECTICIDE APPLICATIONS YIELDED THE SAME. I do not recommend pyrethroids because of documented resistance in Virginia. They may or may not work on your farm. Pyrethroid resistance increases as the season progresses. Please make the decision that is right for your farm based on your experience and knowledge.
Please let me know if you have questions and or concerns. Email, call, or text. I hope everyone has a safe and happy 4th!
that Velum Total now has a name and label change. The new product is simply Velum. The insecticide imidacloprid has been dropped
from the product meaning that it no longer contains material to control thrips.
If you purchase the relabeled Velum product, you will need to apply an additional insecticide. I recommend Admire Pro or generic products that include the active ingredient imidacloprid. Granular alternatives in peanut include Thimet 20G (phorate) and AgLogic 15G or 15GG (aldicarb). Refer to label rates.
Thrips are capable of causing yield loss and plant death in certain scenarios. I recommend that you use an in-furrow product in peanut. Foliar sprays are generally insufficient on their own, but may be warranted as an additional input in very high-pressure years. Cotton has the option of having insecticidal seed coating applied in addition or instead of using an in-furrow product (imidacloprid and aldicarb are labeled for both crops). Seed treatments alone require scouting and foliar sprays if warranted.
quantities of Velum Total as you ordinarily would.
We have high numbers of fire ant mounds in our crop fields and around our farms this year. There have been some unfortunate encounters and this message is to make you aware of what these mounds look like and the potential for injury. Mounds look like large piles of loose dirt (keep in mind they have to start small at some point). They are often found around fence posts and mailboxes, but many are located in fields, pastures, and lawns. Field borders and paths are frequently infested. Fire ants sting, just like wasps and bees, and some people will be allergic and require medical interventions. People that are not allergic will have itchy, painful welts that often fill with fluid and may take days or a week or more to heal. Usually, you will have dozens or even hundreds of stings. This is because the swarm very fast and wait to sting all at once. Keep in mind that I have lived around them most of my adult life in North Carolina and we have come to accept them as part of our environment and have learned caution and awareness. I have been stung multiple times, usually once every few years, and usually when I am scouting crops. Be aware of where your feet are standing. Walk quickly when crossing a field because you can disturb them and get away without injury. Treatment options are below for mounds located near homes and barns. You do not want children or young animals near these things.
I would not attempt to clear your crop fields. A single acre can contain hundreds of mounds and millions of fire ants. Fire ants are predators and will eat caterpillars and other insect pests. They will not eat seeds and plants. Large mounds can damage equipment in rare cases. Products exist that can be applied to turf and lawns with year-long residuals (e.g., TopChoice). These products require a pesticide applicator license to purchase. Baits (e.g., Advion) are an alternative if you are not licensed to apply insecticides. These can be purchased online, many local retailers do not carry them yet. Surface treatments do not work because the colony can live very deep underground. Do not attempt to treat once the weather turns cold because it will not work. Wait until spring. Pray for a cold winter.
Be safe y’all and stay healthy. As always, reach out to me if you have questions or concerns. Keep in mind that I am NOT an urban or ornamental entomologist and I am NOT trying to sell you any specific product. FOLLOW THE LABEL WITH ANY INSECTICIDE.
Observations from the field this week indicate that
there are spider mite infestations at some level in most, if not all, peanut, cotton,
and soybean fields in the drought-stressed Virginia regions. Drying of corn and
weeds is contributing to this problem. Let’s all hope we get the rain we need
to make a good crop this season. Rainy, humid weather will favor fugus that
kills mites, but its effect may be mitigated by extremely hot conditions. Just
in case, and since our last bad mite year was 2011, see below for a refresh
about spider mites and how to treat them in each crop…
Concentrate on the field borders and look for the
early signs of white stippling at the bases of the leaves. Do not confuse mite
damage with dry weather injury, mineral deficiencies, and herbicide injury.
Mite infestations will have some pattern, usually originating from field
margins. Consider applying a miticide if more than 50 percent of the plants
show stippling, yellowing, or defoliation over more than one-third of the
leaves. Recommended products include Zeal and Agri-mek (other abamectin
products are available, but not labeled for soybean). Lorsban and dimethoate are
labeled and may require a second application. Bifenthrin will offer some
suppression, but mite infestations will come back stronger.
Heavy infestations usually occur first around the
borders of peanut fields; then they spread inward throughout the fields. Avoid
harvesting spider mite infested cornfields or mowing weedy areas next to peanut
fields until peanuts are harvested. Spider mites will readily move into peanuts
when corn dries down or is harvested. Be prepared to treat peanuts if adjacent
corn is infested. Use adequate pressure and GPA to ensure penetration of the canopy.
Comite is our only registered product that works. See graph below from Dr. Mark
Abney at UGA.
Mite damage first appears as a slight yellowing of the
leaves, which later changes to a purplish or bronze color and is usually
associated with webbing. Damage occurs especially in spots or on field edges
but widespread defoliation is not uncommon if favorable conditions persist. I
recommend abamectin (10 oz/A rate is usually sufficient) or Zeal for control.
Bifenthrin, other pyrethoids, and especially acephate, will flair mites. If
you are treating for plant bugs, I recommend Transform at 2-2.25 oz/A until
wetter conditions prevail. Be mindful of the bollworm flight next week and do
not make automatic sprays for worms until you confirm a problem in your field.
Worm specific products (Prevathon, Intrepid Edge, Blackhawk) are better options
than broad-spectrum insecticides (pyrethroids).
Our annual post-bloom survey starts next week. If you
need help learning how to scout insect pests, call or text me on my mobile
Our first confirmed identification of white sugarcane aphid occurred this week. A BIG thanks to Laura Siegle in Amelia County for her vigilance and sharp eye. What does this mean for sorghum growers? It is time to scout. At least once per week until aphids are spotted in the field. Following that and until threshold is met – scout twice per week. Numbers can increase quickly. Start scouting on the borders of fields. Aphids will infest borders first. Check the underside of leaves. Not every aphid you find is a sugarcane aphid. You can bring samples to me or your local agent.
Corn earworm are likely found in sorghum this time of year. The same products will not kill both sugarcane aphids and corn earworm. Only Transform and Sivanto Prime are labeled for white sugarcane aphids in Virginia. Scout for earworms by beating sorghum heads into a 10-gallon bucket. A rough threshold is 2-4 worms per head. A threshold that includes costs of application and sorghum prices can be found here.
I made an error this week in my Southeast Ag Fax post and referred to the last spray date in cotton as “cutout.” What I should have said is, cotton should be sprayed for an above threshold plant bug population until the bolls that you anticipate harvesting are past susceptibility (~250dd). This may or may not coincide with cut-out (4 nodes above white flower). Keep in mind that, as the season progresses, sprays will offer less of a yield benefit. In Virginia, our critical window of protection is early to mid-bloom. There is a small and real yield benefit in spraying until week 5 or 6, but the lint gain may not offset the cost of applications. Late planted cotton is at high-risk because it overlaps longest with large bug populations and the plants have less time to compensate.
This season, there has been very poor performance of pyrethroids against plant bugs. Bifenthrin (Brigade and generics) performs better than other active ingredients including lambda-cyhalothrin (Karate, Besiege, Warrior II, Lambda-Cy) and beta-cyfluthrin (Baythroid). Acephate (Orthene 97) and sulfoxaflor (Transform) are better products. Diamond, an insect growth regulator that targets nymphs, should be tank mixed with either acephate at 8 oz. or bifenthrin at 6.4 oz. Currently, I do not recommend Diamond with other products without consulting your Amana representative. Diamond is added to prevent infestation and kill nymphs. It may not have quick knock-down. We have tested Diamond’s residual until two weeks post spray. Acephate alone works well at 8 oz. and is not rain fast. I have concerns with acephate and aphid populations that I will discuss this in another post. Both Bidrin and acephate are effective against plant bugs and stink bugs. For bollworms, I recommend Prevathon or Besiege. A well-timed pyrethroid spray may work and it will need to target small worms before they move inside of squares and bolls. Overall, stink bug pressure is moderate and bollworm pressure is light to moderate. Eggs and small worms have been spotted in low numbers in two-gene cotton. Please keep in mind that I am rarely called when insecticides work well. Keep me posted if your specific combination looks terrific!
Our cotton field day is on August 16th at the Tidewater Research Station. Seth Dorman and I will cover insect sprays, scouting techniques, and other topics. Josh Holland, ANR Southampton, and I will provide portable summary tables of product performance (as we have measured in 2019 on-farm trials).
Thanks to Stan Winslow from Tidewater Ag for his advice and video evidence that big-eyed bugs eat plant bugs. Thanks to Josh, Seth, and the TAREC team for their continued scouting efforts.
The much needed rain earlier this week also heralded the start of the moth flight in southeastern VA. Both eggs and adult moths are being picked up by scouting teams. So far, only a handful of fields are over recommended thresholds. I recommend scouting 2-gene cotton (Bollgard II, Widestrike, Twinlink) for eggs and applying Prevathon or Besiege when you find 25 or more per 100 terminals and/or leaves. If you planted 3-gene cotton, you are likely protected. We have measured very little benefit to spraying Widestrike 3, Bollgard III, and Twinlink Plus varieties for bollworm. In these varieties, finding 3 or more live second-stage larvae in one trip (or two worms in two consecutive trips, or one worm in three consecutive trips) triggers an application.
Other insecticides can control bollworm in cotton, but timing is critical. If you are using a pyrethroid, for example, target small worms. No product will clean up a problem field once worms are inside bolls.
Our team, lead by PhD student Seth Dorman, ANR Agent Josh Holland, and Dr. Sean Malone are scouting fields this week for lygus. Few problems fields were detected in southern counties today. However, fields were observed over recommended thresholds. At this point, many people have sprayed. Some may need to spray again and some may not. The only way to know is to scout.
Northern counties will be scouted this Friday and I will update the blog with our findings.
As always, you can reach out to me with your questions and concerns.
Virginia cotton fields are a mixed bag when it comes to plant bug infestations this week – some fields will require sprays and most will not. The only way to know what is in your field is to look in your field. It is time to scout when cotton starts squaring.
Spray cotton for plant bugs when square retention drops below 80% and you capture 8 or more plant bugs per 100 sweeps. Inevitably, there will be fields where bug numbers exceed threshold and square retention is >80%. In this case, I favor spraying to prevent bugs from reproducing in the field, but only if numbers exceed threshold.
As far as I’m concerned, all Virginia cotton fields are at risk for plant bugs. This animal has over 200 known hosts and you will find one in any field if you look hard enough. There are fields that are predisposed to higher populations. These field, in general, are:
In Eastern cotton growing counties. Plant bugs populations benefit from warmer low temperatures. Abundant water in the landscape contributes to warmer lows and cooler highs.
Near corn or double crop wheat/soybeans.
In areas with high deforestation and new growth forests.
Results from our 2018 survey are below. Note that infestations cluster in the eastern region. However, fields in all regions are at risk.
I recommend a neonicotinoid insecticide pre-bloom. This class includes Belay, Centric, and Admire Pro. There is a lot of debate on using Admire Pro. In field tests, sometimes it is as good as Centric/Belay and sometimes it is not. This is why I recommend Centric or Belay. However, spraying Admire Pro will be better than not treating if you are over threshold. If you are not over threshold, do not spray any product. You will put yourself at high risk for infestations. This cannot be overstated.
As always, call me with your questions and concerns. If you do not know how to sample for plant bugs, I will show you. My program has beat sheets for you – free of charge. We will be distributing them at scouting clinics and field days this summer. If you need one before then, please stop by the Tidewater AREC. Please thank your sales reps from Corteva, BASF, FMC, Amana, and Bayer for funding this program. Cotton Inc. and the Virginia Cotton Board also generously provided support. Please thank Seth Dorman and his awesome plant bug scouting crew for generating data specific to our region.
Virginia cotton growers can now use Transform to control tarnished plant bug in cotton in 2019 (June 1 – Oct 1). This product will allow us to rotate modes of action and reduce our dependence on acephate and pyrethroids to manage this potentially destructive pest. Transform is softer on beneficials too, but you must notify beekeepers within 1 mile of cotton fields and, if there are known hives, apply before 7am or after 7pm when cotton is flowering. Transform is applied at 1.5-2.25 oz/A. Follow all label directions and keep a copy of the label with you when applying.
Based on early sampling numbers, we will have another high pressure year. Spray test results from the Tidewater AREC (shown below) can help you chose insecticides. Neonicotinoids (Admire, Belay, Centric, Endigo) should not be used after first bloom and are less effective during this time. Diamond is a growth regulator and is more effective against nymphs. There is evidence that it suppresses adult reproduction.
The single most important thing you can do to protect cotton from plant bugs is to spray at extension recommended thresholds (8 per 100 sweeps or 2-3 per drop cloth sample). As always, the only way to know what is in your field is to scout.
Virginia cotton requires a thrips control product at planting to preserve yield and avoid maturity delays. This is especially true since the arrival of tarnished plant bugs. Any maturity delay early-season will likely magnify plant bug injury. Cotton planted at the end of April and first week of May has put on 1-2 true leaves. It is time to scout for thrips injury and make foliar applications when necessary.
Levels of injury to cotton seedlings rated from ‘0’ (no damage) to ‘5’ (dead terminal
or plant) from thrips. Injury at ‘2-3’ or above approximates a threshold for intervention with an
insecticide application. (Photo and caption from Kerns et al., 2018)
Using a seed treatment alone will likely require a foliar spray based on research from the Tidewater AREC. In-furrow aldicarb and in-furrow imidacloprid with a seed treatment should not need a foliar spray. Scout cotton planted with in-furrow imidacloprid alone and determine if a foliar application is necessary (often it is not – saving you time and money).
Tips for foliar applications: Consider plant-date and growing conditions. Cotton planted late-May into warm soil may not need a foliar spray. Do not apply foliar acephate if plants are growing fast with no to minimal thrips injury. Thrips injury is likely for all cotton planted in Virginia and risk will be high until plants are no longer susceptible. The three diagrams below from the NCSU model show when seedling susceptibility declines based on planting date (May 1, May 8, May 15). The blue line on these diagrams shows you when risk for thrips injury is highest.
Spraying is most effective when the first leaf is the size of a pencil tip to a mouse ear. I recommend a 6-8 oz. rate of acephate. Several scenarios may be responsible for reduced efficacy of sprays:
1. Rain. Acephate is not a rain fast product. Consider reapplying if necessary.
2. Resistance. Acephate at 3 oz. per acre has become less effective in spray tests. Rotate to Radiant if another spray is required or use a higher rate.
3. Species composition. Tobacco thrips are most common in VA, but western flower thrips can co-infest. Acephate is less effective on this species. Rotate to Radiant if another spray is required.
As always, call/text/email me with any questions. Good luck and happy planting!