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Commercial Horticulture > Comm Hort Blog > Posts > Pest alert for high tunnel crop producers with crucifer crops

This article was originally published in 2014 but has been updated in 2016 with new information (like the resources  listedat the end). For any high tunnel pest management question, call a Regional Extension Agent or the author at 251-331-8416 for immediate consultation. Remember that majority of restricted use pesticides cannot be used inside the high tunnel due to the special environment that excludes direct sunlight and rainfall. Pest prevention is the critical strategy for conventional or organic high tunnel crop producers. One of the most recent research projects in the Alabama Vegetable IPM project has been the use of shadecloths and fabric for pest exclusion/pest prevention that works for medium to large insects. Check out the resources section for more information. 

Flea beetles (early season pest):

Usually not a major issue in fall crops, but it is worth mentioning because populations will become active early in spring, esp. in south Alabama where outbreaks occur. For prevention, stagger planting of leafy greens may serve as trap crops (note: okra and eggplants in early spring can attract flea beetles) or use low tunnels with light fabric (SUPERLITE) to delay infestations. Spinosad (ENRTUST) does well to stop flea beetles on small plants and is a good rescue insecticide (Cadillac treatment though). Pyrethrin (PYGANIC, AZERA) treatments may slow down flea beetles but not completely stop them. Don’t know the efficacy of kaolin clay (SURROUND) but it may deter some feeding as it confuses insects.

Aphids (early- to mid-season pest):

For prevention, stagger planting of leafy greens to serve as trap crops (note: okra in early spring can attract aphids) or use low tunnels with light fabric (SUPERLITE) to delay aphid infestation in high tunnel. Your best treatment options at LOW POPULATIONS are NEEM (WITH AZADIRACHTIN – NEEMIX, MOLT-X), MYCOTROL-O, PYRETHRIN (PYGANIC) and PARAFINNIC OIL (SUFFOIL-X). Neem and Mycotrol can be tank-mixed and rotated with Pyganic or Paraffinic oils. Check the labels for USAGE RESTRICTIONS. USE on few plants first to check for phytotoxicitiy. AT HIGH PEST PRESSURE, THESE INSECTICIDES MAY NOT GIVE FULL APHID CONTROL. Use a good sprayer and treat the underside of leaves for full canopy penetration.

Biological control agents include lacewings and ladybeetles released multiple times (at the first pest detection). Do not use pyrethrin or spinosad directly over the beneficial insects.

Caterpillar complex:  Cross-stripped cabbageworms, diamondback moth, imported cabbageworm, armyworms, and loopers 

Collards planted early or staggered can serve as trap crops. Eggs are laid singly by most except cross-striped cabbageworm and armyworms. Use light fabric to block moths from laying eggs (laid in masses under the leaves) without blocking too much sunlight and airflow. Remove egg-masses from leaves. SANITATION AND WEED CONTROL are very important in high tunnels to prevent insect buildup. Harvest timely and start insecticide treatment on late season crop immediately after detection to prevent rapid defoliation. Early stage caterpillars may not have the stripes and look similar to other caterpillars (remember we have diamondback moth, imported cabbageworm, armyworms, and cross-striped cabbageworms feeding together in late season high tunnels due to warm conditions which cause rapid growth of pests). Below is an example of diamondback moth feeding. 


A large number of cross-striped cabbageworms can cause a window-pane feeding and/or rapid skeletonization in outbreak situations. Control of caterpillars should be targeted when they are newly hatched and aggregated under the leaves. Make sure to do targeted applications with a good quality sprayer.


Yellowmargined leaf beetle (YMLB): Stay alert for this pest as it comes on suddenly. The beetles are about 0.2 inch long with dark brown wings and yellow margin all around the forewings (see picture below - click for a larger image). From our experience, it appears that YMLB is very good at finding new plantings of turnips and napa cabbage very quickly leading to complete defoliation of those crops. It also feeds on other common crucifer crops (e.g., cabbages) if there is nothing else to feed. Numerous black larvae may be seen on leaves along with the beetles. The eggs and larvae may look like the beneficial insects - so correctly identify the pest first before taking any control measure. Read more about this insect here

YMLB injury1.jpg

Management tactics:  Insecticides for SMALL-SIZED caterpillars include Bt (Dipel, Xentari), pyrethrum (Pyganic), and neem (Molt-X). Insecticides should not be used when the pupae or cocoons are present (it is too late by then). If Dipel (easily available at the Coop stores) doesn’t work too well, then switch to Xentari which can be easily bought online. Bt (esp. Xentari) + Pyrethrin tank mix does well but growers need to keep spraying the crop at weekly intervals or sooner depending on pressure. Cadillac treatments include spinosad (ENTRUST) and AZERA (NEEM+PYRETHRIN). Entrust is a good RESCUE INSECTICIDE but use sparingly and stop spraying once the crop is clean. For any of the insecticides, first CHECK THE LABEL and then use them in a small area to check for phytotoxicity.  Adjuvants to spinosad may increase efficacy but check label for crops.

Biological control agents include lacewings and ladybeetles that can be released multiple times at pest detection. Producers using pest exclusion systems (see below) have great potential to integrate natural enemies that can be constrained in a small area with the netting for managing insect pests like aphids, thrips, and whiteflies. 

Overall, it is easier to do organic or sustainable pest management in high tunnels than open field crops where sunlight and rain ruins organic treatments. Producers should consult the REAs for correct insect identification because some products are selective in action. Remember that your smart phone has a camera - shoot pictures and text them to use for rapid identification. If the pictures are poor quality or the insect is too small to be captured with commong devices, then a sample of the insect and the crop injury is very helpful. 

Additional crucifer IPM resources for gardeners and farmers:

High tunnel pest exclusion (HTPE) training module

High tunnel pest exclusion (HTPE) system for vegetable production - SARE Bulletin

Pest exclusion system for high tunnel producers and gardeners (Baldwin County Blog, April 1, 2016)

Insect Pest Scouting for Crucifer Crops (2016) - ANR-2241

If you are a new crop producer in Alabama, then visit the Alabama Beginning Farms website for resources and assistance.

Ayanava Majumdar

Ext. Entomologist


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