Using Sandea herbicide in pumpkins and squash

Author: Annie Klodd, UMN Extension Educator, Fruit and Vegetable Production

Sandea injury symptoms on a pumpkin leaf. University of Kentucky.

 

A question came in last week about if and how the herbicide Sandea can injure pumpkins. I consulted with Dr. Sushila Chaudhari at Michigan State University, as well as the Sandea label, to answer this question.

Sandea (halosulfuron) is an herbicide registered for pre- and postemergence application in pumpkins and numerous other crops.

Sandea has efficacy on a number of broadleaf weeds including pigweed, ragweed, velvetleaf, mustards, nutsedge, lanbsquarters (preemergent), morning glory/field bindweed (suppression).

It is an important option for pumpkin growers, since few other effective broadleaf herbicides are labeled in pumpkin. However, pumpkins and squash are also broadleaf plant species that can be injured by Sandea under certain conditions. Therefore, care must be taken to apply it successfully. Use research-based university recommendations and the Sandea label to determine when and how to apply Sandea.

Become familiar with the terms "preemergent" and "postemergent" before you continue reading this article. 

Application Recommendations:

For preemergence activity:  

• Apply after planting pumpkin seeds and before soil cracking. 
• For pre-transplant: Apply after soil preparation and bed shaping but before laying plastic. Delay transplanting for 7 days after application.
  
• Avoid applying it right before heavy rainfall or during cool weather, as that may cause crop injury after application. Watch the weather forecast and try to plan your planting and herbicide application accordingly. 
• Once the pumpkin seeds have germinated, do not reapply Sandea until the pumpkin crop as 2 or more leaves.

 

For postemergence activity: 

• Use low rates (0.5 oz) if applying after pumpkin seeds have emerged 
• Apply before pumpkin seed germination, or when the pumpkin crop has 2 or more leaves but before flowering.
  
• If applied outside of these window, it can cause crop injury, reduced size and color, and reduced yield.

Weed size: As with many herbicides, weeds are generally more susceptible to Sandea when they are smaller. As a general rule of thumb, most broadleaf weeds should be sprayed when they are less than 6 inches tall in order to be effectively controlled. You may have heard of the "pop can rule" that says to spray weeds before they reach the height of a pop can for best results.

Combining modes of action: Sandea can be applied on its own or in a tank mix with other products. Herbicide trial results at Purdue University showed good weed suppression with 0.5 oz Sandea + 4 pts. Strategy (preemergent), and Sandea at 0.5-0.75 oz + Poast or Select (postemergent). Herbicides should be chosen based on the weed species present. 

 

Injury symptoms: Sandea causes yellowing of the leaf and leaf cracking (see photos). These are the symptoms most obvious to the naked eye. If you have observed these or similar symptoms, consider your application timing and weather condition at the time of application. For more information, see Halsulfuron injury by University of Kentucky.

These symptoms may be confused with mosaic virus symptoms. If unsure, send a plant sample to the Plant Disease Clinic. It is critical to identify what is causing the symptoms before attempting to correct them.

 

Photos: Dr. Bernard Zanstra and University of Kentucky.

 

Sandea is an ALS herbicide, and the active ingredient is halosulfuron. ALS herbicides work by entering the plant tissue and being translocated through the xylem and phloem to the growing points on the plants, where they impact plant growth. Therefore, injury symptoms on pumpkin plants will appear on new growth or close to the growing points. 

 

Reading the label: The Sandea label includes important information about how to apply it to pumpkins and winter squash, including sprayer volume, maximum oz/acre, and soil type considerations, among other things. Always refer to the label on the specific product that you are applying. Below is a screenshot from a Sandea herbicide label: 

 

Screenshot of the Sandea herbicide label, showing directions for use for pumpkins and winter squash (page 8). See: http://www.keystonepestsolutions.com/labels/Sandea.pdf