Insect Control

NOTES:  For the insecticides listed below, one product trade name and formulation is provided for each active ingredient (AI) as an example of rates, preharvest interval (PHI), restricted entry interval (REI), and special instructions. In many cases, there are other products available with the same AI. Please see Table 26 and Insecticides Alphabetical Listing by Trade Name for more information on these insecticides.

The designation (Bee: L, M, or H) indicates a bee toxicity rating of low, moderate, or high. See the Protecting Honeybees and Native Pollinators section for more details.

The symbol * indicates a product is a restricted use pesticide. See Pesticide Safety and Use for more details.

The symbol OG   indicates a product is listed by the Organic Materials Review Institute (OMRI) as approved for use in organic production. See Organic Certification section for more details.

Allium Leafminer (Phytomyza gymnostoma)

The Allium leafminer (ALM) is a relatively new invasive pest species associated with many allium hosts. The ALM is a true fly species. It was first detected in Lancaster County, PA in 2015. Currently the distribution of the fly is limited within New England. However, the northern expansion of the fly has been rapid with several positive identifications in MA in 2019.

Within the Northeast, ALM populations exhibit two flights per season. These flights are separated by a summer aestivation (“summer hibernation”) period that often precludes the fly from causing significant damage in crops grown and harvested during the summer months (i.e. garlic and bulb onions). The first flight (overwintering population) begins in mid-to-late April, ending in May. The second flight does not begin until September and typically extends into early October. Female flies will make multiple punctures on leaves with their ovipositor (apparatus for laying eggs) that leaves a distinct line of easily visible white dots. These oviposition “scars” are the primary diagnostic indicator for the presence of the pest. Eggs are laid singly inside of leaves where the oviposition marks are made. When ALM eggs hatch, larvae enter the leaves and actively “mine” the plant tissue. After several days, larvae move towards the center and base of plant. After several weeks of active feeding, larvae typically pupate near the base of the plant within the foliage or may exit the plant and pupate in the soil. 

The most vulnerable allium hosts plants tend to be those plants harvested during the early spring and fall (primarily leeks and scallions). The removal of infected host plants and other allium residues from earlier harvested alliums is an important practice for reducing potential outbreaks in fall allium crops. Insect exclusion netting or other types of row covers can effectively exclude ALM flies if securely applied before the second flight begins. Foliar chemical applications have also been shown to be effective for reducing ALM damage. 

abamectin (Agri-Mek* SC): 1.75 to 3.5 fl oz/A; PHI 7d, REI 12h, Bee: H, Group 6. Make 2 consecutive applications then rotate to a different mode of action. Make at least 2 consecutive applications of another mode of action before making additional Agri-Mek SC applications. Insect control can be reduced if used with a sticker or binder type product.

azadirachtin (Azatin OOG): 4 to 16 oz/A foliar or drench, 4 to 16 oz/100 gal in greenhouses; PHI 0d, REI 4h, Bee:L, Group un. When using lower rates, combine with adjuvant for improved spray coverage and translaminar uptake.

cyantraniliprole (Exirel): 13.5 to 20.5 fl oz/A; PHI 1d, REI 12h, Bee:H, Group 28. Use with an adjuvant to maximize efficacy. Spreading and penetrating adjuvants can cause negative crop response.

cyromazine (Trigard): 2.66 oz/A; PHI 7d, REI 12h, Bee: H, Group 17. Apply when leafminers first appear. Do not apply more than 6 times or 1 lb/A per calendar year.

dinotefuran (Scorpion 35SL): 5.25 to 7 fl oz/A foliar, 8.75 to 10.5 fl oz/A soil.; PHI 1d, REI 12h, Bee: H, Group 4A. Do not apply more than a total of 10.5 fl oz/A per season.

Isaria fumosorosea Apopka Strain 97 (PFR-97 20% WDGOG): 1 to 2 lbs/A; PHI 0d, REI 4h, Bee: M, Group M.

mineral oil (SuffOil XOG): 1 to 2 gal/100 gal water; PHI 14d, REI 4h, Bee: L, Group M.

pyrethrins (Pyganic EC5.0IIOG): 4.5 to 17 oz/A; 0.25 to 0.50 oz/gal, 3 gal/1000 sq ft in greenhouse for backpack sprayers; PHI 0d, REI 12h, Bee: M, Group 3A.

spinetoram (Radiant SC): 6 to 10 oz/A; PHI 1d, REI 4h, Bee: M, Group 5. Efficacy improves with the addition of an adjuvant. Do not make more than 2 consecutive applications of Group 5 insecticides. Do not make more than 5 applications per year per crop.

Leek Moth (Acroleopiosis assectella)

Though leek moth feed upon most cultivated alliums, leeks are the most preferred and susceptible host species. Because garlic and onions are generally harvested for their bulbs, leek moth feeding damage tends to be less of a concern in these crops, as even moderate damage to the above-ground foliage typically does not lead to significant reductions bulb size or yield.

There are three flight periods of leek moth per season. The first flight (the overwintering generation) begins in mid‐late April, ending in mid‐May. The second flight period (the first generation) begins in mid‐June, ending in early to mid‐July. The third flight period begins in late July, ending in mid‐to late August. Although leek moth activity slows down after the last flight period, the damage can still develop on remaining allium vegetables, especially leeks, in the field. These larvae are considered to be the third generation and become the overwintering adults or pupae.
Eggs are laid singly on lower leaf surfaces whenever night temperatures are above 50-54°F.  Females lay up to 100 eggs over a 3-4-week period. After hatching larvae begin to burrow into the stem and move towards the center of the plant where young leaves are formed. In onions, leek moth larvae enter the hollow leaves and continue to feed on the inner cuticle of the leaf leading to the characteristic “window-paning” damage. After several weeks of active feeding, larvae exit the foliage and initiate pupation on the outside of leaves. Pupation lasts about 12 days, depending on weather conditions. 

Pre-harvest strategies: For smaller plots, insect exclusion netting can be an effective strategy for reducing leek moth damage by directly reducing exposure to egg laying female moths. Chemical applications are typically well-suited for larger growing areas and are best applied 1-2 weeks following peak moth flights, which can be monitored using traps baited with pheromone lures. In addition, research has shown that the timely release of the parasitoid wasp, Trichogramma brassiceae, can significantly reduce leek moth damage in leeks and other alliums. 

Post-harvest strategies: The primary concern for garlic and onion growers is the potential damage that may occur during post-harvest curing and/or storage. Damage during curing and storage is generally the result of larvae being brought into the storage area following harvest. A simple low-risk strategy for reducing the prevalence of leek moth larvae in these areas is to remove as much of the foliage as possible prior to curing. This “topping” strategy leaves larvae in the field where they no longer can access the bulbs. Research has also shown that topping prior to curing or storage does not affect bulb quality or shelf life.

lambda-cyhalothrin (Warrior* II): 0.96 to 1.60 oz/A; PHI 14d, REI 24h, Bee: H, Group 3A.

methomyl (Lannate* LV): 3 pt/A; PHI 7d, REI 48h, Bee: H, Group 1A. For green and dry onions. Add wetting agent to improve coverage. Begin application before populations reach 3 to 5 thrips per plant.

spinetoram (Radiant SC): 6 to 10 oz/A; PHI 1d, REI 4h, Bee: M, Group 5. Thorough coverage is essential. Efficacy improves with the addition of an adjuvant.

spinosad (Entrust SCOG): 4 to 8 oz/A; PHI 1d, REI 4h, Bee: M, Group 5. Use adjuvant for better control.

Onion Maggot (Delia antiqua)

For more information on this pest and for cultural and biological controls, see onion maggot in the Onion section.

diazinon (Diazinon* AG500): 2 to 4 qt/A; REI 3d, Bee: H, Group 1B. Broadcast and incorporate just before planting. Will not control organophosphate-resistant onion maggots. DO NOT make more than one application per year.

Onion Thrips (Thrips tabaci)

Thrips are favored by hot, dry weather. Heavy rain or overhead irrigation can lower populations quickly. Lacewing larvae, pirate bugs and predatory thrips are important natural enemies. Reduce populations by cleaning up crop residue after harvest to limit overwintering sites. Do not plant leeks near other Alliums (onion family) or alfalfa, clover, cucurbits or brassica crops that can harbor large populations of thrips, which may migrate to leeks when these crops are cut or harvested. Begin applications when damage is first noticed. Repeat applications at 7- to 10-day intervals. Use a shorter interval in hot, dry weather. Use a spreader-sticker for better coverage. Apply in early evening, using high pressure and 100 gal water/A for best results. See onion thrips in the Onion section for more information.

acetamiprid (Assail 30SG): 5 to 8 oz/A; PHI 7d, REI 12h, Bee: M, Group 4A.

Beauveria bassiana (Mycotrol ESO): 0.25 qt to 1 qt/A; PHI 0d, REI 4h, Bee: L, Group UN. Treat when populations are low and thoroughly cover foliage. Takes 7 to 10 days after the first spray to see control. Repeat applications may be needed.

Burkholderia spp. strain A396 (Venerate XCOG): 1 to 8 qt/A; PHI 0d, REI 4h, Bee: M, Group UN. Suppression only.

Chromobacterium subtsugae strain PRAA4-1 (GrandevoOG): 2 to 3 lb/A; PHI 0d, REI 4h, Bee: M, Group UN.

deltamethrin (Delta Gold*): 1.5 to 2.4 oz/A; PHI 1d, REI 12h, Bee: H, Group 3A.

dinotefuran (Venom): 3 to 4 fl oz/A foliar, 5 to 6 fl oz/A soil; PHI 1d foliar, 21d soil, REI 4h, Bee: H, Group 4A.

imidacloprid (Admire Pro): 14 oz/A; PHI 21d, REI 12h, Bee: H, Group 4A. Soil applications only.

kaolin (Surround WPOG): 25 to 50 lb/A or 0.25 to 0.5 lb/gal; PHI 0d, REI 4h, Bee: L. Suppression/repellence only. Good coverage into plant crown is essential. Generally compatible as a tank mix with other insecticides.

malathion (Malathion 57 EC): 1.5 to 2 pt/A; PHI 3d, REI 24h, Bee: H, Group 1B.

pyrethrin (PyGanic EC5.0OG): 4.5 to 17 oz/A; 0.25 to 0.50 oz/gal, 3 gal/1000 sq ft in greenhouse for backpack sprayers; PHI 0d, REI 12h, Bee: M, Group 3A.

spinetoram (Radiant SC): 6 to 10 oz/A; PHI 1d, REI 4h, Bee: M, Group 5. Thorough coverage is essential. Efficacy improves with the addition of an adjuvant.

spirotetramat (Movento): 5 oz/A; PHI 7d, REI 24h, Bee: M, Group 23. Must be tank-mixed with a spray adjuvant with spreading and penetrating properties to maximize leaf uptake and sytemicity; don't use sticker adjuvants. Controls immature stages; may also reduce adult fertility.

zeta-cypermethrin (Mustang*): 3.2 to 4.3 oz/A; PHI 7d, REI 12h, Bee: H, Group 3A.