Effectively controlling plum curculio in stone and pome fruits

With the recent warm weather and wet conditions, plum curculio will be on the move into orchards. Be prepared to control this pest at this time.

Plum curculio life stage control timing chart
Figure 1. Plum curculio life stage control timing for reduced risk and OP-replacement insecticides.

With stone fruits at shuck split and apples in bloom in the north and sizing further south, and the warm and humid weather this week, plum curculio is moving out of overwintering sites and beginning egglaying in fruit. Michigan State University Extension educators and agricultural consultants have been observing higher than normal numbers of insects in the orchards. In recent years, plum curculio may have been on the back burner for Michigan cherry growers as spotted wing Drosophila (SWD) has become the key pest in cherry orchards. However, we have seen challenges in isolated orchards with plum curculio in the past two years, and this article is a reminder that plum curculio is a pest that still needs management in both apples and cherries.

There are many insecticides available for control of plum curculio, but their performance characteristics vary greatly compared to our traditional broad-spectrum chemistries. Conventional insecticides, such as organophosphates and pyrethroids, work primarily as lethal contact poisons on plum curculio adults in the tree canopy. Avaunt also works primarily by lethal activity, but ingestion is the important means for delivering the poison. Neonicotinoids are highly lethal to plum curculio via contact for the first several days after application, but as these systemic compounds move into plant tissue, they protect fruit from plum curclio injury via their oviposition (egglaying) deterrence and anti-feedant modes of activity.

The rotation of these two modes of action is critical to successful plum curculio control. Avuant needs to be used prior to any neonicotinoids because Avaunt must be ingested to work effectively, and the neonicotinoids have that anti-feedant characteristic. If needed use Avaunt first followed by neonicotinoid insecticide. Neonicotinoids and organophosphates (OPs) can also be used as rescue treatments because they have a curative action that can kill eggs and larvae that are already present in the fruit. If plum curculio infestation occurs and a rescue treatment is needed, organophosphates and neonicotinoids can provide curative action up to two weeks after plum curculio infestation, although in some cases dead cadavers can still be found in fruit. Growers should not rely on this curative mechanism for most effective plum curculio control.

At this time in the season, cherry growers should be using the neonicotinoid and indoxacarb (Avaunt) chemistries as these materials are not effective at controlling SWD. Save Imidan and the pyrethroids to target and potentially overlap these materials to control late season plum curculio and early SWD emergers. Imidan and pyrthroids are rated excellent for SWD, and neonicotinoids are only rated as fair against this pest. To make the most out of a cherry insecticide program, the more broad-spectrum materials, like pyrethroids and Imidan, should be used later in the season to do double duty on these two pests.

In apples, optimal timing and order selection of insecticides for plum curculio management is based on matching the performance characteristics of each compound with plum curculio life cycle development (Figure 1) and tree phenology (Table 1). Because organophosphates and pyrethroid insecticides are contact poisons, they can be used as early as petal fall to knock beetles out of the tree canopy. However, we do caution the use of pyrethroids, as they are toxic to mite predators. The performance of neonicotinoids is optimized when sprays are made after fruit set (pome fruits) or shuck split (stone fruits), so that fruit and foliage are both covered. Surround will not work unless the tree and fruit are completely covered, so multiple sprays are needed on the tree prior to plum curculio oviposition activity.

Voliam flexi can be used for plum curculio control but only the neonicotinoid (Actara) component will be effective against plum curculio. Also, remember that 4.5 to 5.5 ounces of Actara is the recommended rate for plum curculio control, and Voliam flexi is labeled at 4 to 7 ounces; be sure to apply an adequate amount of Voliam flexi to meet these recommended rates. Leverage (imidacloprid plus cyfluthrin) and Voliam Xpress (Chlorantraniliprole plus Lamda-cyhalothrin) are other pre-mix materials labeled for plum curculio control. Venerate, an OMRI approved product, acts as a stomach poison and reduces egg viability and has been shown to provide good control. Apta is labeled for plum curculio control and is active against adults by contact.

The following table is designed to summarize several key variables that can help you determine how to optimize the performance of various insecticides for integrated pest management (IPM) programs. Several other compounds, like Exirel, Verdepryn, Venerate, Rimon and Delegate, are commonly used in tree fruit pest management programs and have activity on plum curculio worth noting. Rimon, when targeted to control obliquebanded leafroller or codling moth at petal fall, will effectively sterilize plum curculio eggs when adults are exposed to residues in the tree canopy. These sublethal effects will not prevent injury to fruit from adults but will result in nonviable plum curculio eggs, thus no live larvae.

Delegate, Exirel and Verdepryn have been shown to provide fair to good activity, but ingestion by plum curculio adults is important for optimal control. Esteem, when used approximately two weeks post-harvest in cherries (San Jose scale crawler timing), will reduce female plum curculio overwintering viability. However, Rimon, Esteem and Delegate are not labeled for standalone plum curculio control, but when used in pest management programs may contribute to overall plum curculio population management.

Table 1. Insecticidal modes of activity on plum curculio life stages.

Compounds2

Chemical class / activity

Crop

Rate

Crop stage and initial control timing (DD50)

Imidan 70W**

Organophosphate

Pome fruit

3 lb

Petal fall (approx. 250 DD)

Lethal via contact

Stone fruit

2.125 lb

Petal fall (approx. 175 DD)

Actara 25WG**

Neonicotinoid

Pome fruit Stone fruit

4½ oz

Petal fall + 3-5 days (approx. 300 DD)

Lethal, Antifeedant and Curative

4½ oz

Shuck-off (approx. 250 DD)

Assail 30SG**

Neonicotinoid

Pome fruit

6 oz

Petal fall + 3-5 days (approx. 300 DD)

Lethal, Antifeedant and Curative

Stone fruit

 

Shuck-off (approx. 250 DD)

Belay 2.13SC**

Neonicotinoid

Pome fruit

6 oz

Petal fall + 3-5 days (approx. 300 DD)

Lethal, Antifeedant and Curative

Peach

Shuck-off (approx. 250 DD)

Exirel 10SE

Diamide

Pome fruit

6 oz

Petal fall (approx. 250 DD)

Lethal via ingestion

Stone fruit

Petal fall (approx. 175 DD)

Verdepryn 100SL

Diamide

Pome fruit

8.2 – 11 oz

Petal fall (approx. 250 DD)

Lethal via ingestion

Stone fruit

Petal fall (approx. 175 DD)

Delegate 25WG*

Spinosyn

Pome fruit

6 oz

Petal fall (approx. 250 DD)

Lethal via ingestion

Stone fruit1

Petal fall (approx. 175 DD)

Avaunt 30WG

Oxadiazine

Pome fruit

5 oz

Petal fall (approx. 250 DD)

Lethal via ingestion

Stone fruit

Petal fall (approx. 175 DD)

Venerate XC

 

Biopesticide

Lethal via ingestion and egg sterilization 

Pome fruit

4-8 qts

Petal fall (approx. 250 DD)

Stone fruit

 4-8 qts

Petal fall (approx. 175 DD)

Apta

METI 1

Lethal via contact

Pome fruit Stone fruit

21-27 fl oz

Petal fall (approx. 250 DD)

Shuck-off (approx. 250 DD)

Pyrethroids

Asana, Warrior, Baythroid

Pome fruit Stone fruit

Variable

Petal fall (approx. 250 DD)

Lethal, repellent

Petal fall (approx. 175 DD)

Rimon* (targeting codling moth, OBLR)

IGR

Pome fruit Stone fruit

20-40 oz

Petal fall (approx. 250 DD)

Egg sterilization

Esteem* (targeting scale)

IGR

Pome fruit Stone fruit

5 oz

Post-harvest

Adult sterilization

Leverage 2.7F

Pyrethroid + Neonicitinoid

Pome fruit

4.4-5.1 oz

Petal fall (approx. 250 DD)

Lethal, Repellent, Curative

Stone fruit

4.5-5.1 oz

Shuck-off (approx. 250 DD)

Voliam Xpress

Pyrethroid + Diamide

Pome fruit

6-12 oz

Petal fall (approx. 250 DD)

Lethal, Repellent

Stone fruit

6-12 oz

Petal fall (approx. 175 DD)

Voliam flexi

Neonicotinoid + Diamide

Pome fruit

6-7 oz

Petal fall (approx. 250 DD)

Lethal, Antifeedant, Curative

Stone fruit

6-7 oz

Shuck-off (approx. 250 DD)

*Not labeled for plum curculio (or just for plum curculio suppression)
**Have curative properties that can kill eggs and larvae that are already present in the fruit.
Modified from John Wise, Nikki Rothwell, and Mark Whalon, 2017.

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