Reports here are that black aphids are out but numbers are not necessarily high yet.
UGA Extension Entomologist Dr. Will Hudson has this INSECT update for us:
Black Aphid damage
Growers across the state are seeing an increase in black aphids. For growers with old Schley trees this has been going on for a while, but the other susceptible varieties like Sumner and Gloria Grande are experiencing a build-up now. Remember, if you see nymph clusters you need to take steps to protect your foliage and avoid the kind of damage that can affect your crop next year. Imidacloprid still controls black aphids pretty well, but requires the higher rate on the label (several formulations are available; the 2 lb materials need 5.6 oz/acre). Other neonicotinyls like Belay and Assail are also effective. If you also have yellow aphids then Carbine, or Fulfill would control both. Closer is one of the most effective options at the moment.
Mite damage on pecan leaf
We are also seeing some mite flare-ups in scattered orchards. Mites can be controlled with abamectin products (Agri-Mek, Abba Plus, etc.), Portal, Acramite, or Nexter. The Nexter will get both aphids and mites, and may be a good choice where those pests are present and a weevil spray is needed or likely. Check labels for rates and surfactant requirements.
Dodging showers can be a challenge if you need to treat lots of acres with few sprayers, and sometimes the rain catches you or pops up right after application. If it starts to rain while you are spraying, stop the sprayer. It will do little good to apply an insecticide (or fungicide) that will be washed off immediately. If the rain comes after you finish, you may be okay if the spray has dried on the leaves. A good rule of thumb is that if you get a rain within 1 hour or less of spraying and you will need to retreat.”
We’ve been treating for worms in peanuts now. I’m seeing some loopers mostly. But there are reports of tobacco budworm, and I do see some TBW moths flying. We need to be scouting when we are in the field. The biggest question is our threshold.
Egg mass from armyworms (left); and ‘windowpane’ feeding (right)
For foliage feeding caterpillars, our threshold is 4 – 8 per row foot. Remember, peanuts can tolerate a significant amount of defoliation with no impact on yield, but when we start to see ragged leaves, it becomes difficult to hold back. Our peanuts look really good thanks to timely rainfall. When peanuts are not stressed, we can go closer to 8 on the threshold.
Caterpillars feeding on blooms?
This was in issue a few years ago where UGA Extension Entomologist Dr. Mark Abney had this to say:
Bloom feeding has been observed in peanut for a number of years, and current thresholds do not take this type of damage into account. Peanut produces a lot of blooms, and not all of them will result in harvestable pods even in perfect conditions. The impact of caterpillar feeding on blooms is not known. I think it is reasonable to be more aggressive in making treatment decisions when significant bloom feeding is observed. What is “significant bloom feeding”? That is a question that will have to be answered on a case by case basis taking into account the condition of the field, number of caterpillars, maturity of the crop, and personal experience
For the first time in many years, we have many new products on the market. Here is an update from UGA Extension Entomologist Dr. Mike Toews and Auburn Entomologist Dr. Kathy Flanders:
Products for Empty Bins
- Centynal EC – This is a good product for treating empty bins and elevator boots. Note that the active ingredient in Centynal EC, Defense SC and Suspend SC are identical so these are not good rotation partners.
- Defense SC (labeled for empty bin use only) – This is a good product for treating empty bins and elevator boots, but is not labeled for application directly to grain. Note that the active ingredient in Centynal EC, Defense SC and Suspend SC are identical so these are not good rotation partners.
- Suspend SC – This is a good product for treating empty bins and elevator boots. Note that the active ingredient in Centynal EC, Defense SC and Suspend SC are identical so these are not good rotation partners.
- Tempo SC (labeled for empty bin use only) – Tempo is a good product for treating empty bins and elevator boots, but is not labeled for application directly to grain.
Products for Application to Grain
- Actellic 5E (labeled for corn only) – This product has been the standard for many years, but it is expensive. A full rate will provide protection from weevils for 9-12 months. Reducing the rate will decrease the longevity of the protection. Our data suggest that Actellic is susceptible to heat degradation in the drier when grain temperatures exceed 120 F.
- Centynal EC (labeled for corn and wheat) – Centynal EC is a new formulation that will provide 3 to 6 months of protection from weevils at the 0.5 ppm rate or 6 to 12 months of protection at the 1.0 ppm rate. This material is heat stable in the drier (tested up to 150 F).
- Diacon (labeled for corn and wheat) – Diacon is an insect growth regulator that is effective for killing nearly all immature grain moths and beetles, except weevils. The 4 oz per 1000 bu rate is sufficient for tank mixing.
- Diacon IGR PLUS (labeled for corn and wheat) – This product is a premix of Centynal EC and Diacon. See comments above for rates and activity.
- Malathion (labeled for wheat and corn) – Although widely used in the past, this product is no longer recommended due to well documented resistance in many stored grain insect populations.
- Sensat (labeled for corn and wheat) – This product is new to the market, but has been in our evaluation program for several years. Test results show excellent weevil control for up to 12 months. No dryer stability data at this time.
- Storcide II (labeled for wheat only) – Storcide II is an industry standard for stored wheat, but is not labeled for use on corn. Protection will degrade with heat and time.
- Suspend SC (labeled for corn and wheat) – This product is an older formulation that must be completely suspended before measuring and requires frequent agitation. It provides 3 to 6 months of protection from weevils.
- Three-way tankmix (only tested on corn) – UGA tests from 2014-2016 showed that a threeway tank mix of Centynal (8.5 oz) plus Diacon IGR (4 oz) plus PBO-8 Synergist (13.5 oz) will provide 6-9 months of protection from weevils. This is a moderately priced option for growers in markets where other products are unavailable or cost is a limiting factor.
Regardless of the product used, be mindful that grain protectants are not a silver bullet. Shelled corn should be dried to a maximum of 15% moisture content before dropping it in the bin.
Chemical applications should only be made to clean grain that will be stored for more than 3 months. Apply protectants at the bottom of the auger in a course spray to maximize coverage as the kernels are moving up to the top of the bin. Long-term grain storage requires appropriate moisture content, proper housekeeping, use of a spreader when filling bins, and managed aeration.
UGA Entomologists Dr. Phillip Roberts and Dr. Mike Toews put this information together on corn earworms in cotton.
During the past week we have received a few reports of escaped corn earworm CEW) larvae in Bt cottons which exceed recommended thresholds. Bt cottons are not immune to CEW and never have been. All Bt cottons should be scouted for CEW and growers should be prepared to react in a timely manner if thresholds are exceeded. We have planted Bt cottons for over 20 years. The technology has moved from a single Bt gene to two gene and now three Bt genes. The addition of Bt genes was for two reasons primarily; 1) to improve efficacy and increase the spectrum of activity and 2) for resistance management. The slide below is a general rating for Bt cottons for various caterpillar pests.
Activity on CEW varies by technology, however all technologies should be scouted. Entomologists in Georgia and other areas of the cotton belt believe we are seeing changes in the susceptibility of CEW to some Bt genes. We have been fortunate in Georgia in that only a small percentage of Bt cottons have required treatment for escaped CEW in recent years. However we have observed changes in performance of Bt corn in recent years, i.e. seeing more damage to corn ears. We are also seeing more feeding on squares in Bt cotton which was very rare 5 years ago. One aspect of Bt cotton that we must not forget is that all Bt cottons continue to provide excellent control of tobacco budworm.
When scouting Bt for CEW cotton scouts should examine the top 12 inches of the plant for eggs and larvae and also examine one bloom, one bloom tagged boll (be sure to look under bloom tag), and an additional boll lower in the canopy. If any damage is observed on the plant the entire plant should be searched. It is important to size larvae as small (< ¼ inch) or large (> ¼ inch). Once larvae reach ¼ inch in length it is likely those larvae will survive on the Bt plant and continue to feed. When we observe escaped CEW larvae they are often associated with fruiting structures near the uppermost white bloom. So make sure you check blooms, bloom tagged bolls, and small bolls closely. The slide below shows various images of CEW in cotton.
The threshold for CEW larvae in Bt cotton is when 8 larvae ¼ inch or greater in length are found per 100 plants. When treating escaped CEW in Bt cotton coverage and penetration of the canopy with sprays will be important. We must get the insecticide to the target as larvae will likely be down in the plant canopy. Control of larvae in bolls and under bloom tags will be difficult.
Pyrethroids have been the standard treatment for CEW for many years. In parts of the cotton belt pyrethroid activity on CEW has deteriorated. For example some states in the Mid-South do not recommend pyrethroids for control of CEW due to pyrethroid resistance and field control failures. We annually monitor CEW susceptibility to pyrethroids in Georgia using adult vial tests. Basically we capture adult CEW moths in pheromone traps and place those in pyrethroid treated vials and monitor survival. During recent years and especially during 2016 we observed increased survival of CEW in these tests which suggests susceptibility is changing. However, we have not observed or been made aware of any field control issues when pyrethroids have been used for CEW control. With that said, we have made few field applications of pyrethroids for control of CEW in any crop during recent years. Bottom line is it will be important for us to check behind pyrethroid applications targeting CEW. There are non-pyrethroid alternatives that will provide very good control of CEW. The slide below illustrates CEW survival in pyrethroid treated vials.
We have had an interesting year so far in our hay crop. Our dry Spring kept us from truly getting started, and the current rain is keeping growers from cutting. We have hundreds of acres that hasn’t been cut yet. If it has been cut, it’s mostly been cut once. There is a very small amount of hay that has been cut twice.
This may be one reason we are seeing stem maggot in some fields. I stopped by this field Wednesday, and a large section appeared frosted. Stem maggot has done lots of damage here. The good news is we have yet to see fall armyworms. This too may be cause the rain.
UGA Extension Forage Specialist Dr. Dennis Hancock has given an update on some other insect issues throughout the state:
Bermudagrass Stem Maggot
Damage from bermudagrass stem maggot
Reports of the bermudagrass stem maggot have been coming in from all over the Coastal Plain and into the southern 2-3 counties in the Piedmont. I suspect with the abundant rainfall in most places, we will see BSM pressures similar to the heavy pressure we saw in 2013. Producers need to employ the standard suppression technique (labeled pyrethroid of their choice 7-10 days after cutting and again 7-10 days later, as needed). Moderate N fertilization rates, and good K fertilization minimizes disease and this seems to minimize BSM activity (but it doesn’t eliminate it). In the past, we have recommended spinosad, as well. Current research indicates this is not as effective as we believed it to be. Pyrethroids are our best option currently. We have a new Extension bulletin on BSM found at Bermudagrass Stem Maggot Research Update.
Reports of fall armyworm are also starting to come in. Producers need to scout and spray if the threshold is reached. The newest bulletin is Caterpillar Pests in Pastures and Hayfields.
Where BSM activity is high and FAW pressure is imminent, consider using Besiege (Lambda-cyhalothrin for the BSM and active FAW; Chlorantraniliprole for residual control of FAW).
With this heat, it gets dry quick. I found a few plants with evidence of spider mites yesterday. This of course is not good since it is early. When we are scouting fields, look for spider mites. Look for the reddening on the “V” part of the leaf. UGA Extension Entomologist Dr. Phillip Roberts says early detection is critical.
**The best management practice is to NOT flare spidermites with unnecessary insect sprays. If our retention is good (plant bugs), stink bug threshold is low, and aphids have crashed, we need to hold back. It’s about to get hotter, and dry weather makes them worse too.
Some of our earliest planted cotton is now blooming. I thought it would be good to go through an insect update.
Aphids / Beneficial Insects
As reported last week, we found the aphid fungus in Thomas County. UGA Extension Entomologist Dr. Phillip Roberts located the fungus in Tift County last week. Once it’s found in a field, it takes about a week to ‘crash’ the aphids. There are still reports of aphids this week, and I’ve had a question or two. Remember, UGA has not found any yield difference in treating aphids. We’ve had more aphid populations this year, but I would hesitate on treating, especially when they are in ‘hot spots.’ We need to watch beneficials.
In one field this week, I saw many, many lady beetles. On one plant, I saw almost all of its life stages, confirming how many beneficials are in our fields now. The lady beetles can’t eat all these aphids, but the aphids are bringing them to the field. I’ve seen some parasitic wasps too.
Lady beetle puapae
Lady beetle larvae – “Baby alligator”
I haven’t talked about plant bugs this year. In fields I go in, retention has been good. 80% retention is our goal. I have seen a plant bug here and there. Dr. Roberts says that in the state, they have been spotty, and only a small acreage has been treated to date.
It is now time to scout for stink bugs in blooming fields. Scouts need to crack bolls and look for warts and calloused walls. Treatment decision is based on % of bolls damaged.
Dr. Roberts says whiteflies are a month early. This is usually an indication of a rough year. We need to look for adults. The precense of adult whiteflies influence deicisions of other pests. Treatment for whiteflies must be timely as well. For more on thresholds and insecticides, visit this previous post on Silverleaf Whitefly Management.