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Be on the Lookout for Asparagus Beetles

Elaine Roddy, Vegetable Crops Specialist, OMAFRA Ridgetown
May 18th, 2007

It is easy to take note of asparagus beetle activity in harvested fields.  However, the 1 and 2-year old plantings may actually be the most susceptible fields on the farm.  The beetles survive the winter in crop residue, windbreaks and fencerows.  They emerge in early spring and seek out green asparagus on which to lay their eggs.  The lush fern of new plantings is very attractive to the adult beetles. 

While beetle feeding in harvesting fields can cause damage to the spears and grade-outs due to the presence of eggs; the largest losses can be caused by the defoliation of immature plantings due to larval feeding.  Defoliation during the crown establishment stage places additional stress on the crop, potentially impacting future yield potential.  High populations in the young plantings may also act as a reservoir, allowing beetles to move onto the commercial fields as they fern out later in the spring.

Beetles are most active in the afternoon.  Critical thresholds may be missed by early morning scouting activities as the beetles may be present, but not yet active in the crop.  The adult beetles are blue-black with four yellowish patches on the wing pads. The wings have bright red margins.  They are approximately ¼” long.  Asparagus beetle larvae vary greatly in colour, ranging from a greasy translucent grey to darker green. They have black heads and a slug-like body shape.  The Spotted Asparagus Beetle is much less common.  They are red with 12 black dots (six on each side of the wing pad.)

Thresholds:

• Eggs: 2 eggs on 100 spears
• Larvae: 10% defoliation
• Adults: 5-10% of plants infested

Controls:
Apply one of the products listed below as soon as one of the thresholds above has been met.  During harvest, select a product with a low PHI.  Always rotate between chemical groups to avoid the development of resistance. 

Product	Chemical Group	Rate	PHI1	Notes
Decis 5 EC	pyrethroid	80 mL/ac		Apply after cutting Apply in min 20 gal/ac water
Ripcord 400 EC	pyrethroid	34 mL/ac	1
Sevin XLR2	carbamate	1-2.5 L/ac	2	Do not use more than once every 3 days
Malathion 500 E	organophosphate	1 L/ac	1
Malathion 25 W	organophosphate	2.2 kg/ac	1