Current Situation: Happy Friday the 13th!! Dry conditions have set in over the last couple of weeks. According to the UGA Weather Network, the Moultrie location recorded 1.07 inches of rain over the last 31 days. The last drought monitor was released on May 12, 2022 and shows that Colquitt County is experiencing abnormally dry conditions. Hit or miss rain showers occurred across the county on the evening of 5/12/22.
Cotton crop ranges from just planted to 2 leaf stage of development and the peanut crop is in the early stages of the planting window. The corn crop is ranges from V4-V10 stage of development and the irrigation requirements are increasing. The wheat crop is drying down fast. According to Bob Kemeriat, UGA Plant Pathologist, NO soybean rust or southern corn rust or tar spot has been found yet
How can I minimize pre emerge herbicide inury on my cotton? There is no doubt that residual herbicides are the foundation of our control programs. Cotton injury caused by the pre emerge herbicides is an issue that many growers face every year. Below are some tips to hopefully minimize injury from PRE herbicides.
- Plant high vigor seed into moist soil (preplant irrigation often needed if available).
- Shallow planting depth increases herbicide injury potential.
- Apply proper PRE residual herbicides within 24 hr of planting.
- If feasible, irrigate between 30 hr after planting and prior to 24 hr before emergence. Then do not irrigate again until at least 5 days after emergence. Most often, the greatest damage occurs when the first irrigation/rainfall event happens during emergence.
- Irrigate to develop a perfect cotton stand; however, limit irrigation events during the first two weeks after planting to as few as possible after activating residual herbicides.
Grasshoppers: I have been getting a report or two of elevated grasshopper populations in strip till fields.. According to Dr. Phillip Roberts, UGA Cotton Entomologist, control of grasshoppers is recommended when plant damage is occurring, grasshoppers are present, and plant stands are threatened. Nymph (wingless) grasshoppers are relatively easy to control with insecticides. However control of adult (winged) grasshoppers is more difficult. High rates of labeled pyrethroids have performed
fair to good on adults (control of adults or “flyers” is difficult). Dimilin, which is an insect
growth regulator, provides good control of nymphal grasshoppers and has provided good
residual activity in field demos, but it takes a few days to cause mortality. Dimilin will not
control adult grasshoppers. According to Dr Phillip Roberts, acephate applied at higher rates would be an option for control (0.75 lb).
Thrips: Thrip pressure in cotton has been variable in Colquitt County depending on planting date and at plant insecticide that was used. Scout for thrips and injury early. The threshold for thrips is 2-3 thrips per plant with immatures present. The presence of immature thrips suggests the at-plant insecticide is not providing control (i.e. thrips eggs were laid on the plant, eggs hatched, and immature thrips are surviving). Immature thrips are crème colored and lack wings whereas adults will typically be brown with wings.
Cotton seedlings are most sensitive to yield loss from thrips feeding during early stages of
development. Excessive thrips feeding and plant injury on 1-2 leaf cotton has a greater yield
penalty than cotton infested at the 3-4 leaf stage. Once cotton reaches the 4-leaf stage and is
growing rapidly, thrips are rarely an economic pest. According to the UGA Pest Management Handbook, Orthene 97 or Acephate 97 at 3 oz/a would be an option.
Peanuts: Peanut growers will be making the decision to spray or not spray an early-postemergence (cracking) herbicide. According to Dr. Eric Prostko, UGA Weed Sciencist, if the peanut field was clean at planting and a strong residual herbicide program was used (activated with moisture), it is very likely that a cracking spray will not be needed. See below (i.e. no weeds in my standard PRE program at 12 DAP):
My general recommendations for early-postemergence (cracking) treatments in peanut are as follows:
a) Either paraquat (2 lb/gal) @ 12 oz/A or paraquat (3 lb/gal) @ 8 oz/A + either Storm @ 16 oz/A or Basagran @ 8 oz/A + one Group 15 herbicide [either Anthem Flex @ 3 oz/A or Dual Magnum @ 16 oz/A or Outlook @ 12.8 oz/A or Warrant @ 48 oz/A or Zidua @ 2.5 oz/A (liquid)].
Generally, I have no preference between the Group 15’s when my suggested PRE/EPOST/POST peanut weed control programs are followed.
b) Add NIS @ 0.25 v/v when using Anthem Flex, Warrant, or Zidua.
c) If need be, growers can make their own Storm (I call it Georgia Storm), by tank-mixing Ultra Blazer (16 oz/A) + Basagran (8 oz/A). This is a slightly different rate than what is applied with current commercial Storm formulation @ 16 oz/A (equivalent to Ultra Blazer @ 11 oz/A + Basagran @ 11 oz/A).
d) Use at least 15 GPA and pressure/nozzle configurations to produce medium to coarse droplets (236-403 microns).
e) Excessive dust caused by dry weather and tractors driven at Warp Speed 10 will reduce the effectiveness of paraquat.
Aspergillus crown rot in peanut. I ran across a plant or two of Aspergillus crown rot this week. Below is a diagnostic image of a peanut seedling affected by Aspergillus crown rot. Shredding of tissue at crown of plant and presence of dark, sooty sporulation. Aspergillus crown rot is the most important seedling disease of peanut in Georgia. It is most problematic in hot and dry soils as we have experienced as of late. Most field will have a little crown rot; crown rot becomes a serious issue when stand loss is severe as this can affect tomato spotted wilt and yield.
When tank-mixing various pesticides, what is the correct mixing order?
The general formulation science mixing order is as follows:
a) water soluble bags (WSB)
b) water soluble granules (WSG)
c) water dispersible granules (WG, XP, DF)
d) wettable powders (WP)
e) water based suspension concentrates/aqueous flowables (SC, F)
f) water soluble concentrates (SL)
g) suspoemulsions (SE)
h) oil-based suspension concentrates (OD)
i) emulsifiable concentrates (EC)
j) surfactants, oils, adjuvants
k) soluble fertilizers
l) drift retardants
There is an app called Mix-Tank (Precision Laboratories) that you might find useful (https://www.mixtankapp.com/).
If you have any questions please contact your local county Extension agent.
Jeremy M. Kichler
Colquitt County Extension Agent.