Increase Onion Yields by Reducing Sunburn and Heat Stress

INCREASE ONION YIELDS BY REDUCING SUNBURN AND HEAT STRESS

Use of Surround® to Control Sunburn and Heat Stress

Surround® is a recognized tool to protect onions from the damage caused by sunburn at harvest. Early season use of SURROUND also can protect plants when temperatures exceed optimum ranges. Heat stress can inflict financial losses that frequently go unseen by growers.

 

SURROUND is specially formulated to reflect harmful infrared and ultraviolet radiation from plant surfaces while allowing penetration of beneficial Photosynthetically Active Radiation (PAR). SURROUND-treated plants are typically several degrees cooler than untreated plants and a cooler plant leads to:

  1. reduced heat stress and more efficient water use,
  2. increased photosynthesis and greater plant vigor, and
  3. potentially higher yields.

And, SURROUND does not block leaf stomata so gases (O2 and CO2 ) and water continue to move in and out of the plant, maintaining natural photosynthetic and cooling processes.

The effective light filtration properties of SURROUND result in cooler plant surfaces and higher rates of photosynthesis (expressed as carbon assimilation)

  • INCREASE ONION YIELDS BY REDUCING SUNBURN AND HEAT STRESS
  • INCREASE ONION YIELDS BY REDUCING SUNBURN AND HEAT STRESS

  • For Heat Stress and Insect Suppression

    • SURROUND must be applied prior to heat stress/sunburn conditions.
    • Reapply 5-7 days later or as necessary to maintain coverage and protect new growth. In overhead irrigated fields this may require weekly sprays.
    • Use of SURROUND also can suppress insect activity, especially thrips. Apply SURROUND before insects enter the field. If insect pressure exceeds acceptable thresholds then a knockdown insecticide should be used.

  • For Post Lifting Sunburn Protection

    • First applications must be made immediately after the onions are rolled — when bulbs are first exposed to the sun.
    • Thorough coverage is needed to protect the bulbs from sunburn.
    • Apply 50 pounds per acre in 50 gallons of water or equivalent.
    • A second application should be made 5-7 days after the first for best coverage.
    • A third spray may be needed if the onions are kept in the field longer than two weeks.

 

Problem Pounds / Acre Application Instruction
Sunburn and heat stress 25-100 Provide thorough coverage of all plant surfaces prior to sunburn-causing conditions with one to two full-rate applications 7 days apart. Depending upon the length of the high heat period, three to four applications in total often are needed, with subsequent applications every 7 to 21 days.
INCREASE ONION YIELDS BY REDUCING SUNBURN AND HEAT STRESS

Application Tips

  • Apply SURROUND to near-drip. Avoid foliage run-off.
  • Change the direction of travel on alternate applications for best coverage.
  • SURROUND can be tank mixed with most pesticides. When tank-mixing, always add SURROUND to the tank first. A pre-mix tank is suggested for sprayers without mechanical agitation.

Aerial Application

  • Use no less than 10 gallons per acre. Best mixing results are achieved when mixing no more than 1lb per gallon of water.
  • SURROUND may be applied using standard aerial application nozzles.
  • Make applications not more than 10 feet above the top of the largest plant unless a greater height is required for aircraft safety.
  • When spraying at low relative humidity, increase droplet size to compensate for evaporation.