Controlling common asparagus beetle during harvest season
Print
EmailCommon asparagus beetle egglaying during harvest can cause major financial loss; get updated on products available for control.
Sources of beetles during harvest
In late summer, larvae of common asparagus beetle, called grubs or “slugs,” hatch from eggs and feed in fern. They then pupate in the soil and develop into an adult beetle. As winter approaches, these beetles seek out overwintering sites to protect them from cold weather, including loose bark in logs and trees surrounding asparagus fields, as well as hollow asparagus stems. As it warms up in spring, beetles emerge from overwintering sites ready to feed, mate and lay eggs during the asparagus harvest season.
Asparagus beetle control during harvest
Michigan State University Extension offers the following suggestions to help control asparagus beetles during harvest:
Apply insecticides on warm, sunny days. Asparagus beetles are typically not active during cold weather. Unfortunately, this is also the time it is easiest to fit in insecticide applications. However, if beetles are not active, contact with insecticide may be limited. Applying insecticides during warm, sunny days may increase the number of beetles coming into contact with insecticide residues.
Control asparagus beetles in the fern season. This year’s beetles come from last year’s fern, making fern-season control important. Experience suggests problems during harvest can be reduced when beetles are kept in check the previous season. Some growers have even used later-than-normal insecticide applications in late summer to early fall with the goal of reducing the overwintering population’s size.
Consider banded applications to keep rates up and reduce cost. Asparagus beetles contact insecticides on the spears. Some growers apply insecticides in a band over the row by placing plug tips in nozzles that would hit between rows. This reduces application cost by lowering the broadcast rate, while keeping the rate in the band high.
There is some flexibility on timing. There will be spears of varying length during any insecticide application. Spears that are just emerging will only have their tips treated. However, spraying just the tip of the spear as it first emerges from the soil is enough. This works because asparagus beetles naturally move to the tip to mate and lay eggs. As long as the tip has insecticide residue, it will kill the beetles when they move there. Full coverage of spears that are almost ready to harvest isn’t necessary for effective control.
Labeled products and notes on their use
There are at least five insecticide active ingredients (AIs) from four modes of action (MOA) with one-day preharvest intervals (Table 1). Generic forms are labeled for all products including acetamiprid and chlorantraniliprole. Note, methomyl is a restricted use pesticide.
Table 1. Conventional insecticides with one-day preharvest intervals labeled for asparagus beetle control during asparagus harvest, their mode of action number (MOA), application rates, number of applications allowed during harvest at the highest rate, and minimum days allowed between applications.
|
Tradename |
AI |
MOA |
Formulated rate/ac |
# apps at high rate |
Retreatment interval (days) |
|---|---|---|---|---|---|
|
Carbaryl 4L |
carbaryl |
1A |
1 qt |
3¹ |
3 |
|
Lannate LV |
methomyl |
1A |
1.5-3 pt |
5 |
5 |
|
Perm-up |
permethrin |
3A |
2-4 fl oz |
4 |
7 |
|
Assail 30SG |
acetamiprid |
4A |
2.5-5.3 fl oz |
2 |
10 |
|
Coragen |
chlorantraniliprole |
28 |
1.2-2.5 fl oz |
4 |
3 |
¹Only 3 are allowed during harvest; 5 total are allowed per season in harvest and fern season applications combined.
Carbamates (1A): Carbaryl has been a grower standard for years. During harvest use the cheapest formulation available since spears are frequently harvested, there is little benefit from the extended residual activity advertised for Sevin XLR Plus. Lannate is also labeled, but has a two-day reentry interval. Given this, and the fact it is the same mode of action, there may be little incentive to use methomyl instead of carbaryl. Carbaryl is very effective at controlling both adults and preventing egglaying on spears.
Resistance to carbaryl has not been detected in several recent trials conducted in Oceana County.
Pyrethroids (3A): Permethrin (e.g., Perm-Up) has also been used, but some growers feel it is not as effective at controlling adult beetles compared to larvae. This has led to a preference for conserving this product for the fern season, where it can also be used for Japanese beetle and tarnished plant bug management.
Neonicotinoids (4A): Acetamiprid (e.g., Assail) is effective at controlling both adults and preventing egglaying on spears during harvest. It has similar efficacy to carbaryl, but it offers a different mode of action.
Chlorantraniliprole (28): Coragen is a newer insecticide that can be used during asparagus harvest because it has a one-day preharvest interval. It is a contact insecticide and is good at stopping adult beetles from feeding and laying eggs. However, field trials showed it does not kill beetles, it just keeps them from laying eggs.
Organic products: Pyganic and Entrust are two organic insecticides approved for use during asparagus harvest. In field trials, Pyganic did not greatly reduce beetle numbers but it did reduce eggs on asparagus spears, though it was not as effective as carbaryl or acetamiprid. Entrust, however, was not effective—it did not reduce beetles or eggs compared to not spraying at all.
