The longest day of the year is the Summer Solstice, which occurs around June 21 each year (although I’d contend it always used to be on the last day of school before summer break). After the Summer Solstice, each day gets a few minutes less sunshine than the one before it, and this switch triggers flowering in indeterminate soybeans, which are varieties that can generate both vegetative and reproductive growth at the same time. Typically, indeterminate soybeans are those in maturities earlier than Group 5, and they are grown in Canada and the northern half of the U.S.

Although I mentioned the Summer Solstice is the triggering mechanism for flowering in indeterminate varieties, the reality is early-planted beans often start flowering a few days before June 21, but my point remains – once flowering begins, that means the plant has moved to reproduction. As such, plants are much more sensitive and should be handled with more care.

Here is a brief list on some of the items you should try to complete by the time soybeans flower, as well as some of the things you should consider doing after flowering.

FINISH HERBICIDE SPRAYING

Your goal should be to finish herbicide spraying by the time the beans begin to bloom. Products like Enlist One and Liberty have an R1 (beginning bloom stage) cutoff so you need to be done before the beans are in full bloom (R2). Let’s say you sprayed a harsh product when the beans are in full bloom. Chances are you will cause the plant to abort some flowers, thereby lowering your potential yield. Also, after R1, you lose the very best weed control options, so don’t miss that window!

Here’s the challenge, though. Beans at R1 are often not completely closing the rows yet, especially if you’re in 30-inch rows or wider. That means you don’t have a complete crop canopy and sunlight is still hitting the ground, allowing weeds to continue to emerge and grow. For this reason, the in-season application of residual herbicides is critical. Also, strategies incorporating early planting, higher populations, and narrow rows have an advantage for weed control.

KEY POINT: Watch the herbicide labels for when you can and can’t spray. R1 and R2 are often the cutoffs, but a small number of products go by the pre-harvest interval (PHI), allowing for later applications.

COBRA FOR DISEASE CONTROL?

If you’re targeting sclerotinia white mold with your spray application of Cobra, it needs to be applied early. Getting it done just before flowering begins is smart and can be scheduled in the second week to maybe even the third week of June. If you miss this window, spraying Cobra in full bloom is risky, as described above. If you are concerned about white mold or other diseases and flowering has already begun, use a good fungicide like Endura (the best product for white mold) or one of the multiple-mode-of-action products like Revytek, Delaro Complete, Lucento, or Viatude.

PLANT GROWTH REGULATORS, A.K.A PGRs OR PLANT GROWTH HORMONES

PGRs are often used around flowering to help set and retain more flowers in soybeans. In the past, we used a straight cytokinin product and found it helped increase flowering, but in a drought this actually hurt the plant as it couldn’t feed all the flowers, which lost us yield. Now, we prefer products like Amass during flowering, as it contains several ingredients including kinetin to promote flowering and pollen viability, as well as GABA and Choline Chloride to promote chlorophyll development and drive sugar production to feed all those blooms you’re trying to maintain.

DICAMBA DRIFT

Once soybeans hit the reproductive stages of growth, drift from dicamba applications can really cause some damage. Up until this point, a little bit of drift normally just causes leaf cupping and rarely results in yield loss. When beans are flowering, you need to be careful. If you have dicamba that will still be applied in non-crop areas or in-crop, make sure the wind is blowing away from any soybeans or other sensitive crops in the area for 48 hours after application to avoid volatility concerns. Also, follow the label closely to reduce physical drift and volatility.

INSECT DAMAGE

Bugs can infect soybeans with diseases, defoliate plants, damage roots and stalks, and even clip off soybean pods. Scouting early is important, but late-season (after flowering begins) insects are often more harmful. Fortunately, there are many great, inexpensive insecticides. Just be sure to follow the labels for pre-harvest intervals, and most importantly – scout, scout, scout.