Optimizing insecticide sprays for plum curculio

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

The plum curculio is an important early season pest on pome and stone fruits. There is an array of insecticides available for control of the plum curculio, but their performance characteristics vary greatly compared to our traditional broad-spectrum chemistries. These 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 curculio injury via their oviposition (egg-laying) deterrence and anti-feedant modes of activity. Neonicotinoids and OP’s 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.

For organic growers, Surround WP can reduce plum curculio injury to fruit if applied to attain a heavy coating on the tree canopy; this kaolin clay product works as a plum curculio repellent. The following table is designed to summarize several key variables that can help growers determine how to optimize the performance of various insecticides for integrated pest management (IPM) programs.

Several other compounds, like Rimon, Esteem and Delegate, are commonly used in tree fruit pest management programs, and have modes of 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 sub-lethal effects will not prevent injury to fruit from adults, but will result in non-viable plum curculio eggs, thus no live larvae. Delegate, when ingested by plum curculio adults will cause moderate levels of mortality on this pest. Esteem, when used post-harvest in cherries (San Jose scale crawler timing) will reduce female plum curculio overwintering viability. Rimon, Esteem and Delegate are not labeled for 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.

Compound trade name
Chemical class
Activity on adult plum cuculio
Curative activity on PC larvae or eggs
Guthion, Imidan
Organophosphate
Lethalvia contact
curative
Asana, Warrior, Danitol, Baythroid
Pyrethroid
Lethal via contact,
Repellent
none
Avaunt
Oxadiazine
Lethal via ingestion
minimal curative on larvae in cherries
Actara, Assail, Calypso, Clutch
Neonicotinoid
Lethal,
Oviposition deterrent,
Antifeedant
curative
Surround
Particle film
Repellent
none
*Delegate
Spinosyn
Lethalvia ingestion
none
*Rimon
Insect Growth Regulator
Sub-lethal, egg sterilization
none
*Esteem
Insect Growth Regulator
Sub-lethal, reduced overwintering viability
none

* Not currently labeled for PC control.

Optimal timing and order selection of insecticides for plum curculio management is based on matching the performance characteristics of each chemistry (Table 1) with plum curculio life-cycle development (Figure 1) and tree phenology (Table 2). 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 too as they are toxic to mite predators. Because plum curculio adults are feeding on tree parts during bloom and petal fall, we recommend Avuant be used at this petal fall timing. The performance of neonicotinoids is optimized when sprays are made after fruit set (pome fruits) or suck-split (stone fruits), so that fruit and foliage are both covered. Surround will not work unless tree is completely covered, so multiple sprays are needed on the tree prior to plum curculio oviposition activity. 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. Please make sure to read the footnotes in Table 2 to help with the proper order of insecticides.

Table 2. Labeled Control Materials for Plum Curculio

Compounds2
Crop
Rate
Crop Stage and Initial Control Timing (DD50)
Guthion 50W
Pome fruit Cherries
2 lb
2 lb
Petal fall (approx. 250 DD)
Petal fall (approx. 175 DD)
Imidan 70W
Pome fruit
Stone fruit
3 lb
2½ lb
Petal fall (approx. 250 DD)
Petal fall (approx. 175 DD)
Actara 25WG
Pome fruit Stone fruit
4½ oz
4½ oz
Petal fall + 3-5 days (approx. 300 DD)
Shuck-off (approx. 250 DD)
Calypso 480SC
Pome fruit
4 oz
Petal fall + 3-5 days (approx. 300 DD)
Assail 30SG
Pome fruit
Stone fruit
8 oz
Petal fall + 3-5 days (approx. 300 DD)
Shuck-off (approx. 250 DD)
Clutch 50WDG
Pome fruit
3 oz
Petal fall + 3-5 days (approx. 300 DD)
Avaunt 30WG
Pome fruit 1
Stone fruit 1
5 oz
Petal fall (approx. 250 DD)
Petal fall (approx. 175 DD)
Surround WP
(not
recommended
for cherries)
Pome and
Stone fruits
Usually
16 lb by
First Cover
Multiple applications starting before
bloom to achieve complete coverage
Pyrethroids
Pome fruit Stone fruit
-
-
Petal fall (approx. 250 DD)
Petal fall (approx. 175 DD

1 Avaunt should be used first when in a program combination with a neonicotinoid. Avaunt’s lethal activity on plum curculio is enhanced with adult ingestion. Neonicotinoids are antifeedants, which if applied first may reduce Avaunt’s primary mode of activity.
2 For a complete list of insecticides registered or recommended for plum curculio control, see the 2009 MSU Fruit Management Guide MSUE bulletin E-154.

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