Soybean Growth Slowed With Cool Temps – OMAF

Soybean Growth Slowed With Cool Temps – OMAF

on August 12 | in Tek Talk | by | with No Comments

From the OMAF Field Crop Report

Soybeans: Horst Bohner

Soybean plant growth and flowering has been moderate over the last two weeks due to cooler temperatures. Many varieties are at the R4 (full pod) stage of development. Spider mites have been a problem in a few areas where conditions were dry. Stippling causes yellowing, curling and bronzing of leaves, is evident along field edges and pockets within fields. Damage is most severe under hot dry conditions. There can be up to seven generations in a given year but a good rain along with cooler weather will reduce numbers in fields naturally. Dimethoate is the only registered product that will control spider mites in soybeans. Fields should be sprayed if they are above threshold (one damaged leaf per plant) up to the R6 growth stage. (seeds within one pod on the top four nodes fills the pod cavity) Soybean aphid populations are building slowly and continued monitoring will be necessary until the R6 growth stage. Considerable acreage has been sprayed in Eastern Ontario. Most regions in western Ontario have low aphid numbers or no aphid pressure.

Soybean cyst nematode (SCN) and root rot symptoms have increased over the past week. White mould, downy mildew and frog-eye leaf spot are present but have not progressed to significant levels to date. Growers should continue to scout for these diseases over the next few weeks. If SCN is present in the field consider taking soil samples to monitor populations.

 

Forages/Pastures: Joel Bagg/Jack Kyle

Forages: Summer seeding alfalfa and alfalfa-grass mixtures can be a good way to establish new fields so that full season yields can be harvested next year. It is typically done after winter wheat or spring cereals are harvested. Alfalfa needs at least 6 weeks of growth after germination to develop a crown before killing frost to survive the winter. Recommended summer seeding dates are:

• > 2900 CHU areas – August 10th – 20th

• 2500 – 2900 CHU areas – August 1st – 10th

• < 2500 CHU areas- July 20th – 30th.

Lack of moisture for timely germination and growth can be a risk. If soil