Allium Leaf Miner (ALM)

Allium leaf miner (ALM) adults (flies) continue to be captured on yellow sticky cards in chive plantings in Hunterdon and Mercer counties.  Numbers have declined somewhat this week (Milford, Hunterdon County 21, Princeton, Mercer County 13) relative to the week prior (Milford 27, Princeton 45), but it is still too soon to stay whether the first flight has peaked.  We will report the captures over the next two weeks, with hopes for signs that the flight is ending.

Growers should consider maintaining the control method of their choice at this time.  Affected crops include chives, scallions, garlic, onions and leeks.  Look for neat rows of white spots descending from the upper tips of allium leaves (photo at left).  Initial injury often occurs on the tallest leaves.  Under warmer, less breezy conditions, adults may be seen near the tips of leaves (see photo of adult at lower right).

Floating row covers, kept on until this flight ends will help minimize access to plants.  Insecticide applications targeting adults may be helpful as well, although frequency of applications is uncertain.  Spinosyn materials (Radiant, Entrust (OMRI approved)), pyrethroids (Mustang Maxx, Warrior), neonicotinoids (Scorpion, Venom), the diamide Exirel (section 2ee recommendation) and the insect growth regulator Trigard are labeled for miner control.

Allium Leaf Miner (ALM)

Allium leaf miner (ALM) feeding/egg laying scars have been detected in Cape May County as of 4/3/22 (see photo at left).  It is likely that this pest is active, and depositing eggs in alliums throughout south Jersey at this time.  Many weather stations in southern and central counties  exceeded 250 growing degree days (GDD) base 39˚F over a week ago, with northern counties surpassing this threshold more recently.  39˚F is close to the lower developmental temperature (38.3˚ F) which our colleagues at Penn State recommend for predicting the first emergence of ALM adults.  Last year, initial feeding/egg laying scars were detected within a few days of local weather stations recording the 250 GDD threshold.

Growers should consider initiating the control method of their choice at this time.  Affected crops include chives, scallions, garlic, onions and leeks.  Look for neat rows of white spots descending from the upper tips of allium leaves.  Initial injury often occurs on the tallest leaves.  Under warmer, less breezy conditions, adults may be seen near the tips of leaves (see photo of adult at lower right).

Floating row covers, kept on until this flight ends will help minimize access to plants.  Insecticide applications targeting adults may be helpful as well, although frequency of applications is uncertain.  Spinosyn materials (Radiant, Entrust (OMRI approved)), pyrethroids (Mustang Maxx, Warrior), neonicotinoids (Scorpion, Venom), the diamide Exirel (section 2ee recommendation) and the insect growth regulator Trigard are labeled for miner control.

Adult activity and observations of feeding will be reported on in the IPM Update as they occur.  At this time, all growers should prepare to respond to the first adult generation.  We will deploy yellow sticky cards and attempt to identify the end of the first flight so that growers know when the risk of infestation has abated.

Allium Leaf Miner (ALM)

Many weather stations in southern and central counties have exceeded 250 growing degree days (GDD) base 39˚F within the past week.  39˚F is close to the lower developmental temperature (38.3˚ F) which our colleagues at Penn State recommend for predicting the first emergence of ALM adults.  Last year, initial feeding/egg laying scars were detected within a few days of local weather stations recording the 250 GDD threshold.  Limited inspections (Hunterdon, Morris counties) have not revealed scars yet, but feeding and egg laying is sure to come with the next series of warmer days.   Growers in southern counties may reasonably assume there is ALM activity in their area currently.

Photo: Sabrina Tirpak. Allium leafminer oviposition scars on onion

Growers should consider initiating the control method of their choice at this time.  Affected crops include chives, scallions, garlic, onions and leeks.  Look for neat rows of white spots descending from the upper tips of allium leaves (see photo at left).  Initial injury often occurs on the tallest leaves.  Under warmer, less breezy conditions, adults may be seen near the tips of leaves (see photo of adult at lower right).

Floating row covers, kept on until this flight ends will help minimize access to plants.  Insecticide applications targeting adults may be helpful as well, although frequency of applications is uncertain.  Spinosyn materials (Radiant, Entrust (OMRI approved)), pyrethroids (Mustang Maxx, Warrior), neonicotinoids (Scorpion, Venom), the diamide Exirel (section 2ee recommendation) and the insect growth regulator Trigard are labeled for miner control.

Adult activity and observations of feeding will be reported on in the IPM Update as they occur.  At this time, all growers should prepare to respond to the first adult generation.  We will deploy yellow sticky cards and attempt to identify the end of the first flight so that growers know when the risk of infestation has abated.

Allium Leaf Miner

Allium leaf miner (ALM) feeding/egg laying scars continue to increase in chive plantings near Milford, Hunterdon County and Lawrenceville, Mercer County as of this Tuesday.  Chives in home gardens in central Morris County and southern Cape May County were also found to be infested this past weekend, with adults actively flying in plants.  The first (spring) flight of these flies appears well underway.  Yellow sticky cards have captured low, but consistent (range 1-5/card/week) numbers of adults in Hunterdon and Mercer County plantings.  Foliar insecticide applications temporarily suppress catches on the cards.  Growers throughout the state should assume there is egg laying activity in their area currently.

Growers should consider initiating (continuing) the control method of their choice at this time.  Affected crops include chives, scallions, garlic, onions and leeks.  Look for neat rows of white spots descending from the upper tips of allium leaves (see photo at left).  Initial injury often occurs on the tallest leaves.  Under warmer, less breezy conditions, adults may be seen near the tips of leaves (see photo of adults at lower right).  Click on photos to enlarge the images.

Floating row covers, kept on until this flight ends will help minimize access to plants.  Insecticide applications targeting adults may be helpful as well, although weekly sprays have not stopped foliar injury.  Spinosyn materials (Radiant, Entrust (OMRI approved)), pyrethroids (Mustang Maxx, Warrior), neonicotinoids (Scorpion, Venom), the diamide Exirel (section 2ee recommendation) and the insect growth regulator Trigard are labeled for  leaf miner control.

Adult activity and observations of feeding will be reported on in the IPM Update as they occur.  At this time, all growers should continue to respond to the first adult generation.  We will attempt to identify the end of the first flight so that growers know when the risk of infestation has abated.