It is no secret that most of the crop (especially cotton and peanuts) are behind thus far due to the excessive rain and unseasonably cool temperatures we experienced as we started the summer. I estimate that crop progression is roughly 10-14 days behind schedule. However, the last two weeks have definitely felt more like home as the heat and humidity finally made it to central GA. Things have been pretty quiet so far in terms of pest pressure, with the exception of a few isolated incidents. As we all know, that will change soon enough.
The biggest surprise to date has been the tarnished plant bug. Every year we will spray some fields, but we have already sprayed a lot of acres. There have even been a few select fields that we have sprayed twice. I have talked with Dr. Roberts, UGA Extension Cotton Entomologist, and he says growers around the state have been treating for plant bugs, especially in the west central and southwest parts of the state. We typically see populations decline as we go deeper in the season, but every cotton field should be scouted for tarnished plant bug. Sweep nets are more effective in monitoring adult plant bugs, but drop cloths are better for immatures. As a reminder, economic thresholds are as follows:
- Less than 80% square retention and plant bugs present
- First 2 weeks of squaring:
- Sweep net: 8 plant bugs/100 sweeps
- Drop Cloth: 1 plant bug/6 row feet
- Third week of squaring through bloom:
- Sweep net: 15 plant bugs/100 sweeps
- Drop Cloth: 3 plant bugs/6 row feet
The cotton aphid is an occasional pest of cotton here in GA, but I always notice them and get questions. Rarely are they at a level where treatment is needed. Severely affected plants can be stunted, and if there are enough plants in a field being affected, then treatment may be necessary. On a positive note, most of the insecticides we use for plant bugs are pretty effective on aphids as well.
Our oldest cotton is now starting to bloom, and much of our top dress nitrogen and potassium applications have already went out. I have already talked with some farmers and consultants about stemphylium. Stemphylium is a foliar disease we observe in cotton every year that is associated with low potassium levels. Normally we do not observe this until the later weeks of blooms, but due to all the rain we have received, it is showing up early this year. We know that both nitrogen and potassium are not stable in the soil, and therefore can “wash” away. I would like to see all potassium go out no later than first bloom. It is hard to catch back up once we get behind. I have been conducting studies with foliar potassium sprays, and I am not ready to make a recommendation concerning them yet.
Most of our peanut crop is blooming, and the oldest is pegging. There are some fields that are beginning to lap. I have received a few calls this week regarding growth regulators. There are two products that are available, Kudos and Apogee. These products act in a similar way to pix in cotton. As of now, I only recommend growth regulators in peanuts on irrigated ground that has a history of producing a lot of vine. Also, if you are planting irrigated GA 12-Y’s, I would definitely apply one of these products. I am in my second year of research with these products, but we saw excellent results last year. If you are considering using these products, there are a few critical details to follow:
- Runner peanuts: two applications of 3.63-5.44 ounces/acre. We are recommending 5 ounces/acre each time.
- The application timing is critical!
- First application: Apply when 50% of lateral vines are touching in row middles. Not when 50% of the middles have lapped. Typically 70-80 days after planting on GA 06-G.
- Second application: 14-21 days after first application.
- Include a COC (1 quart/acre) and AMS or UAN (1 pint/acre) to help with plant uptake.
- Based on the manufacturers comments, the products have been shown to be compatible with a lot of the most commonly used fungicides and insecticides. I have had success mixing Kudos with fungicides, but I cannot speak for all the possible tank mixes out there so please use caution.
- If you do have a fungicide in the tank mix, you can leave out the crop oil.
- Rainfast time is 6-8 hours.
Soybeans in the county range from just planted to almost mature. But the majority of the crop is approaching bloom (R1 growth stage), if not already there. Asian soybean rust is a major concern for soybean growers. To date the only report we have of this disease was found on kudzu in Lowndes County. However, as fields reach R3 (early pod set), the use of a fungicide to protect against rust and other foliar diseases is not a bad play. Most growers will apply boron and an insecticide at this time, and this serves as a great opportunity to add in a fungicide.
Speaking of insecticides, I have been sweeping soybean fields, and insect pressure has been low. The majority of what I am finding are green cloverworms. I have not seen any fields with high enough numbers to treat, but insect pressure will continue to increase as we go through the summer. Make sure your fields are being scouted.
We do not talk about nematodes much in soybeans, but they do exist! I was riding by a soybean field a couple weeks ago and noticed a few yellow areas in the field. I parked and walked out and noticed the plants were dying in these areas. I grabbed my shovel and dug up a few plants and immediately noticed the damage done to the root system by root-knot nematode. A lot of the varieties we plant are root-knot nematode resistant, but this variety obviously was not. If you have areas in your field that are struggling, and there are no obvious reasons, go out and pull some plants. If it is root-knot nematode, you will likely see the galls on the roots. However, there are other species of plant-parasitic nematodes whose damage is not easily seen on the roots. Take note of those areas, and pull nematode assays (similar to soil test) toward the end of the growing season that will tell the number and specie of nematodes in your field.
As most of our corn crop is silking (R1) or beyond, we now are focused on finishing the crop off and protecting it from diseases and insects. The most impactful disease in corn is southern rust. We see it every year, but fortunately for us, we typically have a crop made before it reaches us. I am hopeful that is the case this year. As of today (July 6), the closest report of southern rust has been in Appling County. Now that is not to say that it is not in Bleckley County, but we have not found it. If your corn has reached late R4 (hard dough) stage or beyond, you are safe and do not need to treat. If your crop is not there yet, I would say that is your judgement call. We may not see rust here for another few weeks, or we might find it today. If you are more than a few weeks from dough stage, you will likely have to treat. Other than southern rust, the only other disease I have seen is northern corn leaf blight (NCLB). This disease can be a problem in susceptible varieties and/or in fields with consecutive plantings of corn. The majority of fungicides used to treat southern rust will also help control NCLB.
I recently received a picture from a grower with a question on some symptomology showing up on his crop. I recognized it as sunscald. Sunscald is not extremely common, but we will see it in a field somewhere each year. Sunscald presents itself as bleaching and eventual necrosis of the youngest, uppermost leaves of the plant. Sometimes the husk itself will even show some necrosis. It occurs when the evapotranspiration rate outpaces the plant’s ability to move water throughout the plant. With heat indexes near 110 degrees and sunny days, it is bound to happen. There is not much that can be done about it, but try and meet water demands as best as possible with irrigation.