Ready, Set, Go - The Time to Control Summer Annual Weeds in NOW!

Spring has appeared more quickly this year than it has in years.  With the arrival of warmer air, we also see the gradual increase of soil temperatures which means it is time for homeowners to apply a preemergence herbicide to control crabgrass on turf areas. The timing of that application is critical for effective control of crabgrass and other summer annual grassy weeds. Since the preemergence herbicides recommended for crabgrass control actually prevent germinating seedlings from emerging, these products must be applied before crabgrass seeds germinate. Researchers report that crabgrass seeds germinate when average daily soil temperatures reach 57 to 64 degrees Fahrenheit at a 1-inch depth. 

Some turf managers have monitored soil temperatures as a method of predicting crabgrass germination and determine the optimum time to apply preemergence herbicides. Likewise, the bloom period for forsythia has been used as an indicator for the best time to apply crabgrass control. Forsythia blooms just prior to crabgrass germination signaling the time to apply preemergence herbicides. 

In recent years, models using growing degree days (GDD) have been developed for predicting crabgrass germination and preemergence herbicide application timing. Homeowners and professional turf managers may find the GDD tracker website to be a useful tool to track crabgrass germination and determine the optimum timing for preemergence herbicide applications. Good control of crabgrass can be observed when preemergence herbicides are applied when the points on the GDD Tracker map reach the “under”, “early”, “optimum”  or "late" categories. As of March 30, 2016, central Indiana is heading into the “late” category, and northern Indiana is in the “optimum” category. The “bottom-line” is that applying preemergence herbicides now in central Indiana for effective preemergent control of crabgrass in turf areas.

The following tips are also important for minimizing crabgrass pressure and increasing the effectiveness of pre-emergent herbicide applications:

• Mow cool-season turfgrasses at a mowing height of 3 inches or higher
• Irrigate turf areas deeply and infrequently
• Apply 2 to 4 lbs. of nitrogen per year with the majority applied September through November each year
• Ensure an even distribution of preemergence herbicides, avoiding skips or misses on turf areas
• Always read the label for all pesticide products to determine the appropriate rate of application and spreader setting
• Pre-emergent herbicides must be watered in thoroughly to be effective, time application before rainfall or use irrigation to accomplish this important step.

Taken from Crabgrass Control: Timing is Critical
John Orick Purdue Master Gardener State Coordinator Department of Horticulture and Landscape Architecture, Purdue University

Purdue University Offers Four Plant Doctor Apps for Plant Problem Diagnosis

I would like to encourage you to take a look at the Purdue Plant Doctor suite of smart phone apps. These handy tools will help you diagnose and find recommendations to manage the most common insect, disease and environmental problems on the most common trees, annuals, perennials, and tomatoes in home gardens. The apps are a pocket encyclopedia that uses over 2,000 photos to identify and fix more than 200 problems on over 200 kinds of plants. 

Screenshots from Tree Doctor App

Imagine you are in your home garden and you notice a problem on the leaves of with your favorite shade tree. These apps will help you diagnose plant problems with an app in three easy steps. First identify the kind of plant that has the problem. So, for example, if you are using the Purdue Tree Doctor, choose the kind of tree (eg. oak, maple, or pine) to narrow your search. Second, you choose the part of the plant that looks bad (leaves, flowers, branches, trunk or roots) to narrow your search even further. Third, you match the problem on the plant with our photos by swiping through our collection of high resolution photos. To save you time, the app arranges the photos for each of the plants so that the most common problems show up first! You can confirm your diagnosis by reading details linked to the photo.

If you already know the problem you have, just skip the diagnostic process and look it up from a list. Then you can get detailed information about the damage the problem can cause, its life cycle and how to control it with some combination of cultural practices and, if needed, a pesticide or fungicide.

You may purchase all of the above mentioned apps by clicking on this link to buy from the iTunes or Android store.

Excerpts taken from Turftips Article by Cliff Sadof, Department of Entomology and Janna Beckerman, Department of Plant Pathology Purdue University