Radish-Armyworm and cutworm

Includes

Beet armyworm (Spodoptera exigua)
Bertha armyworm (Mamestra configurata)
Western yellowstriped armyworm (Spodoptera praefica)
Black cutworm (Agotis ipsilon)
Variegated cutworm (Peridroma saucia)

Pest description, crop damage and life history

See:

Armyworms

Pest monitoring The bertha armyworm is considered a "climbing cutworm" because it spends little time near the ground. It can be easy to miss while scouting, because eggs and young instars tend to be clustered, but later in the year disperse actively. Larvae also tend to drop quickly from plants when disturbed, avoiding detection. Populations can explode due to an influx of overlapping generations of migrating moths along with overwintering populations.

Pheromone traps are useful for determining when major flights occur, but not for predicting damage. A 5-minute timed search is useful in determining the need for treatment. On average, if one or more larvae or egg masses are found in 5 minutes, treatments may be justified.

In those rare instances when control measures are required, the beet armyworm is more difficult to control than the western yellowstriped armyworm. Insecticide applications are most effective if applied against small larvae.

Management-biological control

Common natural enemies of armyworms include several braconid and ichneumonid wasps; many general predators including assassin bugs, damsel bugs, and spiders; and a nuclear polyhedrosis virus, reported to have brought about excellent late year control in Canada. None of these natural enemies can be counted upon to achieve adequate control in any given year.

Management-cultural control

Weed control is important. Lambsquarters and wild mustard attract egg-laying females and provide a source of food for larvae. Fall tillage can help destroy overwintering pupae.

Cutworms

Pest monitoring Pheremone traps can be used to monitor for cutworms in conjunction with field scouting. Moth counts in excess of two black cutworm moths per trap per day indicate significant egg laying pressure. Intensify field scouting.

If the cutworm population is reducing the plant stand, treat during the seedling stage. Frequently, the damage is most serious at the edges of a field, but stand loss can occur in a spotty pattern throughout the field.

Usually, it is necessary to dig in the soil to find black cutworm larvae and to determine the extent of the infestation and the size of the cutworms involved. Larvae normally hide under debris on the soil surface during the day, but are active, voracious feeders at night.

Since extensive damage may occur in a short period of time, inspect plant beds and newly set plants frequently. In North Carolina, an economic threshold of 5% injured plants has been established for cutworms infesting newly set or young plants (within 3 weeks after transplanting). In Ontario, Canada, the guideline for black cutworm on many seedling vegetables is also 5% plants infested.

Management-biological control

Cutworms are attacked by a number of predators, parasites, and diseases. Many of these natural control agents are not effective on pale western and black cutworms because of their subterranean nature. It is not known if any of these natural enemies can control cutworm populations, but their presence should be noted.

Management-cultural control

Cutworms are most injurious in fields with high plant residue. Historically, cutworms are a problem in early, spring-seeded seedling fields. Tillage prior to seeding reduces cutworm damage. A thorough harrowing between rows may provide some control when cutworms are feeding actively in established fields.

Management-chemical control: HOME USE

Apply any one of these materials to the soil surface at first sign of cutworm activity. Consult label. Minimum preharvest interval (PHI) varies with crop. Difficult to control. Where cutworms are on the soil surface, a carbaryl drench, when bees are not present, may help.

  • azadirachtin (neem oil)-Some formulations are OMRI-listed for organic use.
  • Bacillus thuringiensis var. kurstaki (Btk)-Some formulations are OMRI-listed for organic use.
  • bifenthrin
  • carbaryl
  • cyfluthrin
  • delatamethrin
  • esfenvalerate
  • insecticidal soap-May require several applications. Some formulations are OMRI-listed for organic use.
  • kaolin-Applied as a spray to foliage, it acts as a repellent to some insect pests. Some formulations are OMRI-listed for organic use.
  • plant-derived essential oils (rosemary, peppermint, etc.)-These have some efficacy against lepidopteran larvae. Some formulations are OMRI-listed for organic use.
  • pyrethrins-Some formulations are OMRI-listed for organic use.
  • spinosad-Some formulations are OMRI-listed for organic use.
  • zeta-cypermethrin

Management-chemical control: COMMERCIAL USE

  • alpha-cypermethrin (Fastac EC) at 0.008 to 0.025 lb ai/a. PHI 1 day. REI 12 hr. Retreatment interval 4 days. Do not exceed 0.075 lb ai/a per season.
  • Bacillus thuringiensis (Javelin) at 0.12 to 1.5 lb/a. PHI 0 days. REI 4 hr. Acts slowly; may need multiple applications. Add an appropriate spreader-sticker to enhance control. Most effective on small larvae. Some formulations are OMRI-listed for organic use.
  • beta-cyfluthrin (Baythroid XL) at 0.013 to 0.022 lb ai/a. PHI 0 days. REI 12 hr. Retreatment interval 7 days. Do not exceed 0.11 lb ai/a per season.
  • beta-cyfluthrin/imidacloprid (Leverage 360) at 0.056 to 0.066 lb ai/a. PHI 7 days. REI 12 hr. Retreatment interval 7 days. Do not exceed 0.022 lb ai/a beta-cyfluthrin or 0.044 lb ai/a imidacloprid per season.
  • bifenthrin (Brigade WSB) at 0.08 to 0.1 lb ai/a. PHI 21 days. REI 12 hr. Do not exceed 0.5 lb ai/a per season. Retreatment interval 7 days.
  • bifenthrin/zeta-cypermethrin (Hero) at 0.025 to 0.1 lb ai/a. PHI 21 days. REI 12 hr. Retreatment interval 21 days. Do not exceed 0.44 lb ai/a per season. Oriental radish (Daikon) only.
  • Burkholderia spp. (Venerate XC) at 1 to 8 quarts/a product. PHI 0 days. REI 4 hr. OMRI-listed for organic use.
  • carbaryl (Sevin 4F) at 1 to 2 lb ai/a. PHI 7 days. REI 12 hr. Retreatment interval 7 days. Do not exceed 6 lb ai/a per season. Limit 6 treatments per season.
  • carbaryl (Sevin 5 Bait) at 2 lb ai/a. PHI 7 days. REI 12 hr. Retreatment interval 7 days. Limit 3 treatments.
  • Chenopodium ambrosioides extract (Requiem 25EC) at 4 to 6 pints formulated product per acre, soil application. REI 4 hr. OMRI-listed for organic use.
  • chlorantraniliprole (Coragen) at 0.045 to 0.098 lb ai/a. PHI 1 day. REI 4 hr. Retreatment interval 3 days. Do not exceed 4 applications per crop or 0.2 lb ai/a per crop.
  • Chromobacterium subtsugae (Grandevo) at 0.3 to 0.9 lb ai/a per 100 gal. PHI 0 days. REI 4 hr. OMRI-listed for organic use.
  • cyfluthrin (Tombstone) at 0.025 to 0.044 lb ai/a. PHI 0 days. REI 12 hr. Retreatment interval 7 days. Do not exceed 0.22 lb ai/a per season.
  • cyfluthrin/imidacloprid (Leverage 2.7) at 0.074 lb ai/a. PHI 7 days. REI 12 hr. Retreatment interval 7 days. Do not exceed 0.03 lb ai/a cyfluthrin or 0.04 lb ai/a imidacloprid per year.
  • deltamethrin (Delta Gold) at 0.012 to 0.028 lb ai/a. PHI 3 days. REI 12 hr. Retreatment interval 3 days. Do not exceed 0.14 lb ai/a per season.
  • diazinon (Diazinon 50W) at 2 to 4 lb ai/a broadcast before planting and incorporate into the soil. REI 3 days.
  • esfenvalerate (Asana XL) at 0.03 to 0.05 lb ai/a. PHI 7 days. REI 12 hr. Do not exceed 0.1 lb ai/a per season.
  • GS-omega/kappa-Hxtx-Hv1a (Spear Biological Insecticide) at 0.8 lb ai/a. PHI 0 days. REI 4 hr. Do not exceed 2 lb ai/a per year.
  • methoxyfenozide (Intrepid 2F) at 0.12 to 0.25 lb ai/a. PHI 1 day. REI 4 hr. Retreatment interval 14 days. Do not exceed 0.5 lb ai/a per year.
  • spinetoram (Radiant SC) at 0.047 to 0.0625 lb ai/a PHI 3 days. Retreatment interval 4 days. Do not exceed 3 applications or 0.188 lb ai/a per season. Limit 3 treatments.
  • spinosad (Success, Entrust SC) at 0.047 to 0.094 lb ai/a. PHI 3 days. REI 4 hr. Retreatment interval 5 days. Do not exceed 0.28 lb ai/a per season. Limit 3 treatments. Entrust SC is OMRI-listed for organic use.
  • zeta-cypermethrin (Mustang) at 0.05 lb ai/a. PHI 7 days. REI 12 hr. Retreatment interval 7 days. Do not exceed 0.3 lb ai/a per year.

Note: Using diazinon as recommended for cabbage maggot control also helps control cutworms.

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