Cotton
Lately, the biggest question we are getting is how much longer do I need to spray my cotton? This is not always a cut and dry answer. Research from our colleagues in the mid-south suggests most insecticide applications can be terminated at cutout (NAWF5) + 300-400 DD60’s.
Calculating the number of DD60’s, or heat units, gives us an idea of how mature the crop is. More information on DD60’s and cotton growth and development can be found here.
Typically, 850 DD60’s are required to develop from flower to open boll. Another consideration is the last effective bloom date. This is the last day in which a white flower has a 50% chance to accumulate the necessary heat units to open prior to the historical first frost date.
Depending on your location in the state, 18-24 days are required to receive 300-400 DD60’s, thus our general recommendation is to protect the latest bolls you expect to harvest until they are at least 3 weeks old. Keep in mind that the we have reached the point of the season where fewer harvestable bolls are at risk from most insect pests, so we can relax our thresholds a bit.
This allows us to maximize the return on investment from an insecticide application (i.e., stink bug TH moves to 50% internal injury at the 8th week of bloom). As always, don’t hesitate to give us a call if you have any questions.
Current recommended thresholds, insecticides and rates can be found in the Alabama Cotton IPM Guide. The cotton insect pest portion of the 2020 Cotton and Soybean Scouting School can be found on YouTube.
Soybeans
We are still catching soybean looper (SBL) moths in traps across state. We can expect to see yield loss during the reproductive growth stages around 20% defoliation, so be prepared to intervene if defoliation approaches that mark. Keep scouting for redbanded stink bugs (RBSB).
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Our threshold for RBSB is 4 per 25 sweeps or 1 per 5 row feet. We can relax this threshold to 10 per 25 sweeps from R6.5 to R7, however RBSB can continue damaging soybeans beyond R7 if conditions are not conducive to help seeds dry down. We posted an article about SBL and RBSB on the ACES website.
Current recommended thresholds, insecticides and rates can be found in the Alabama Soybean IPM Guide. The soybean insect pest portion of the 2020 Cotton and Soybean Scouting School can be found on YouTube.
