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NC State Extension

Control Based on Treatment Windows – March


interplanting-200Stages of pests. March is the time for twig aphids to start hatching. What other pests are active depends a lot on the weather. During warm springs, mites and adelgids will become active. In cooler years, they won’t.

  • RBM — Mites in buds.
  • EHS — All stages present though still few males and crawlers. There will be more crawler activity if the weather is warm.
  • BWA — Nymphs may start to molt to the adult. Eggs are typically still not present.
  • BTA — Eggs are starting to hatch by the second week in March if the weather is warm or by the end of March in years with cold weather.
  • Cinara aphids — Cinara aphids may be very active.
  • SSM — If the weather is warm, SSM eggs may start to hatch, though typically there is not much activity from spider mites until April.
  • HRM — Eggs present. In some years mites active. Numbers continue to increase.
  • Predators — Predators may be becoming more active if the weather is warm.

Advantages to March applications. March is a good of year to treat for pests if the weather cooperates. Typically there are still many nights with temperatures below freezing, so be sure to protect sprayers. Typically in March, the BWA is either in the nymphal stage or just starting to molt to the adult and so products like oil, Lorsban and Provado still work. Because predators are still not very active, pesticides still have fewer impacts on the natural predators of mites and scales.

This is the best time of year to use horticultural oil for control of virtually all pests. Eggs of twig aphids and spider mites are close to hatching, and they are more likely to be killed by the oil spray. A much lower percentage of adult mites and aphids are killed by oil treatments, so be sure to use oil early enough in the month. Control of pests with oil is determined by how thorough the coverage is, so be sure to cover all plant surfaces including the trunk, branches, and all needles. For more information on the use of oil see:Organic Pest Control in Fraser Fir Christmas Trees.

Bees will typically not be active if the temperature is below 55 degrees. However, if weeds such as purple deadnettle and yellow mustard are blooming and temperatures are higher than the mid-50s, bees may be present. Be sure to protect pollinators by applying materials during cooler periods or at night if using a mistblower.

Disadvantages to March applications. Besides issues with freezing temperatures and sprayers, there are other problems that cold weather presents with pest control. One problem with treating this time of year is that mite control will be variable. The HRM is often active during winter months, and therefore may be readily controlled, but if temperatures dramatically decrease after application, control may be reduced. The SSM is less likely to be active than the HRM. Products like Talstar may or may not last long enough on the foliage to kill spider mites once they hatch. Miticides which kill the eggs such as Envidor probably won’t work as the eggs are not active enough for the chemical to be effective. Therefore if SSM eggs are present and mites will be a problem, it would be better to wait until later in the spring to treat.

March is still too early to control RBM and control of EHS is still poor.

Materials That Can Be Used in March
Pesticides RBM EHS BWA BTA* Cinara** SSM HRM
Bifenthrin products(Talstar, Sniper) None None Excellent Excellent Excellent Variable. Mites may not be active enough for control. None
Asana None May be some suppression but not long lasting control. Excellent Excellent Excellent if aphids are active. None None
Horticultural oil None May be some suppression but not long lasting control. Excellent if coverage adequate. Excellent as long as eggs haven’t hatched. Control declines as aphid matures. Good if aphids are active. Good Excellent
Dimethoate None May be some suppression but not long lasting control May give control if eggs are not present. Excellent Good if aphids are active. Little as mites are not active. Excellent control of active mites but eggs not controlled. Population may rebound.
Lorsban None None Excellent as long as eggs are not present. Excellent Good if aphids are active. Little as mites are not active. Poor
Provado None None Excellent as long as eggs are not present. Good Good if aphids are active. None None
Safari None Is probably too early to get good control. Excellent None Good if aphids are active. None None

*BTA control is for that spring. Control will not carry over to the following year.

**Cinara aphid control is for that spring. If trees will be cut in the fall, trees will have to be retreated that time.

For more information on mite control see: Focus on Mite Control.

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