Plum curculio organic control

Effectively controlling plum curculio in stone and pome fruits

With stone fruits at shuck-split and apples sizing, and the warm temperatures predicted for this week, plum curculio is likely to begin egglaying in fruit. There are many insecticides available for controlling 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 curclio injury via their oviposition (egglaying) deterrence and anti-feedant modes of activity. Neonicotinoids and organophosphates 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.

Voliam flexi can be used for plum curculio control, but only the neonicotinoid (Actara) component will be effective against plum curculio. Also, 4.5 to 5.5 ounces of Actara is the recommended rate for plum curculio control, and Voliam flexi is labeled at 4-7 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. For organic growers, Venerate has been shown to provide good control.

The table below 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 Exirel, Rimon, Esteem 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 sub-lethal effects will not prevent injury to fruit from adults, but will result in nonviable plum curculio eggs, thus no live larvae. Delegate and Exirel have been shown to provide fair to good activity, but ingestion by plum curculio adults is important for 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 stand-alone plum curculio control, but when used in pest management programs may contribute to overall plum curculio population management.

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 (see photo) and tree phenology (see table). 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, Michigan State University Extension cautions using pyrethroids as they are toxic to mite predators. Plum curculio adults feed on tree parts during bloom and petal fall, so Avaunt can be used at this petal fall timing.

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. 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.

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

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 pounds

Petal fall (approx. 250 DD)

Lethal via contact

Stone fruit

2.125 pounds

Petal fall (approx. 175 DD)

Actara 25WG**

Neonicotinoid

Pome fruit

4.5 ounces

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

Lethal, Antifeedant and Curative

Stone fruit

4.5 ounces

Shuck-off (approx. 250 DD)

Assail 30SG**

Neonicotinoid

Pome fruit

6 ounces

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 ounces

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

Lethal, Antifeedant and Curative

Peach

Shuck-off (approx. 250 DD)

Exirel 10SE

Diamide

Pome fruit

6 ounces

Petal fall (approx. 250 DD)

Lethal via ingestion

Stone fruit

Petal fall (approx. 175 DD)

Delegate 25WG*

Spinosyn

Pome fruit

6 ounces

Petal fall (approx. 250 DD)

Lethal via ingestion

Stone fruit1

Petal fall (approx. 175 DD)

Avaunt 30WG

Oxadiazine

Pome fruit

5 ounces

Petal fall (approx. 250 DD)

Lethal via ingestion

Stone fruit

Petal fall (approx. 175 DD)

Venerate XC

Biopesticide

Pome & stone fruits

4-8 quarts

Petal fall (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, obliquebanded leafroller)

IGR

Pome fruit

20-40 ounces

Petal fall (approx. 250 DD)

Egg sterilization

Stone fruit

Esteem* (targeting scale)

IGR

Pome fruit

5 ounces

Post-harvest

Adult sterilization

Stone fruit

Leverage 2.7F

Pyrethroid + Neonicitinoid

Pome fruit

4.4-5.1 ounces

Petal fall (approx. 250 DD)

Lethal, Repellent, Curative

Stone fruit

4.5-5.1 ounces

Shuck-off (approx. 250 DD)

Voliam Xpress

Pyrethroid + Diamide

Pome fruit

6-12 ounces

Petal fall (approx. 250 DD)

Lethal, Repellent

Stone fruit

6-12 ounces

Petal fall (approx. 175 DD)

Voliam flexi

Neonicotinoid + Diamide

Pome fruit

6-7 ounces

Petal fall (approx. 250 DD)

Lethal, Antifeedant, Curative

Stone fruit

6-7 ounces

Shuck-off (approx. 250 DD)

*Not labeled for plum curculio (or just for PC suppression)
**Have curative properties that can kill eggs and larvae that are already present in the fruit.
Modified from John Wise, Nikki Rothwell, David Epstein, Larry Gut, and Mark Whalon, 2009.

Drs. Wise and Rothwell’s work is funded in part by MSU‘s AgBioResearch.

Plum curculio (Conotrachelus nenuphar Herbst) is a primary pest of tree fruit east of the Rocky Mountains. Traditionally, plum curculio has been controlled using organophophates, but increased government regulation of pesticides has forced reevaluation of these control strategies. Additionally, the increased popularity of organic tree fruit production has necessitated the need for novel control strategies, as organic tree fruit growers name plum curculio as their biggest insect threat. A number of behavior related strategies have been developed for this pest, including traps baited with plant volatile lures and the use of kaolin clay. Pyganic is an organc insecticide that is currently the best chemical organic growers have to control plum curculio. A strategy that integrated the tools that organic growers already have available has been field tested in apple and cherry. This strategy involves attracting plum curculio to the outer rows nof the orchard and utilizing pyramid traps to monitor their population. When plum curculio catches were sufficient, the outside rows were sprayed with Pyganic. Success of this strategy was measured with comprehensive damage sampling. This strategy may prove to be a viable option for both conventional and organic growers.

Plum Curculio

Plum curculio is a native pest of North America that can cause considerable problems in orchards throughout Kentucky. While it has only a single generation in Kentucky, it can cause serious early-season fruit damage to apple, pears, peaches and other stone fruits.

Life History

The adult is a typical snout beetle, 1/4 inch long, dark brown in color with patches of white or gray. There are four prominent humps on the wing covers. The snout is 1/4 the length of the body, with mouth parts located at the end. Plum curculio overwinters in the adult stage in ground litter or soil usually outside the orchard. Adults migrate into the orchards each spring. Often border rows near woods are the first to show injury.

Figure 1. Adult plum curculio on young apple

The adult curculio becomes active in the early spring where it flies to trees and feeds on buds, flowers and newly set fruit over a five to six week period. This results in cat-facing facing of the fruit because of plum curculio feeding and egg-laying injuries. The female adult cuts a hole in the fruit with her mouthparts and hollows out a small cavity then turns and deposits an egg in the cavity. She then cuts a crescent-shaped silt which extends beneath the egg so as to leave the egg in a flap of flesh. Injury will appear as a 1/8 inch crescent-shaped cut on the fruit. This prevents the egg from being crushed by the rapidly developing fruit. After about five days, the larvae will hatch and burrow into the fruit. The larva is a legless grayish white grub with a brown head. Its length will be about 1/3 inch when full grown.

When the larvae are fully developed, they will leave the fruit through clean exit holes. No frass or webbing will be evident. Frass is usually found around the calyx end on codling moth damaged fruit.

Figure 2. Late season fruit scarring by plum curculio

Surface feeding and egg-laying by the overwintering adults can scar or misshape the fruit by harvest, while feeding by the larvae causes premature drop of the fruit. In peaches, gummy material can often be seen at the location of the wound. These insects are active primarily at night and serious damage may appear in orchards that have been scouted rigorously even though the adults were not detected. Currently there are no methods to accurately predict when damage will occur.

Emerging adults in the late summer feed on apples for a short period of time. They cause round, cylindrical feeding wounds in the side of the fruit that penetrate about 1/4 inch that often lead to rots on the fruits.

Control

Adults control is accomplished by insecticide applications timed at the petal-fall and/or first-cover stage for apples, and the shuck-split and first-cover stages in peaches and cherries. Serious plum curculio damage is usually restricted to orchards that do not use an insecticide application that is effective against plum curculio in this period. To improve timing, commercial growers can use a beat sheet to monitor for the adults, or monitor for the first signs of curculio damage to the fruit. Generally, the adults begin to damage the fruit when the night time low temperatures begin to reach 60°F.

Figure 3. Fresh egg-laying wounds to young fruit.

Home gardeners can help reduce future problems by picking up these damaged apples as they fall off the tree and destroying them before the adults emerge. In apples, the larvae will only complete development in fruit drops.

For more information on reduced insecticide apple management programs, see ENTFACT-201, Controlling Apple Insect Pests with Reduced Insecticide Usage.

Revised: 11/19

Problem type: Insect
Name of problem: Plum and Apple Curculio
Plant name(s): Plum, apricot, cherry, apple, pear, gooseberry and chokecherry
Symptoms / Characteristics:
Symptoms of plum curculio damage include small irregular puncture wounds, semi-circular scars and crescent-shaped cuts on fruit, as well as misshapen fruit and premature fruit drop.
Plum curculio damage may be attributed to early season adult feeding, fruit injury during egg laying and summer adult feeding. The plum curculio is a snout beetle (Conotrachelus nenuphar), which overwinters in the adult stage under leaf debris and in piles of wood or brush near the host plant. Emergence occurs during spring flowering and lasts up to four weeks during which time the adult beetles feed on leaves, flowers and immature fruitlets. Early season fruit injury is characterized by small irregular puncture wounds and semi-circular scars. Following the emergence phase, the females lay eggs inside the fruit by making crescent-shaped cuts on the fruit surface. Multiple deposits can result in misshapen fruit if the injured fruit should remain on the tree until harvest. Once the eggs hatch, the larvae feed on the developing fruit resulting in premature fruit drop. Mature larvae drop to the ground to pupate and, after 2-3 weeks, emerge as summer feeding adults, which continue to feed on the fruit until early fall.
In the adult stage, the plum curculio is 4-6 mm long and is dark grey to brown in colour, with grey and white patches on the back. Other identifiable features include 4 bumps on the back and a long, curved snout. Depending on maturity, the grub-like larvae can range from 1-9 mm in length. They lack functional appendages and are greyish-white with a brown head.
Apple curculio (Anthonomus quadrigibbus) is very similar in both appearance and life cycle. Injury symptoms are similar to that of the plum curculio, with the exception of the crescent-shaped scar. Host plants include apple, crabapple, saskatoon and hawthorn.
Control / Preventions:
All susceptible fruit trees in the immediate area should be monitored before and during fruit set. Fruit should be inspected for semi-circular and crescent-shaped scars and insecticides may be applied once an injury is detected. Guthion may be used when populations of plum curculio are high, but should be handled with care due to its toxic properties. It should be substituted with Imidan when populations are low. Avoid summer adult infestations via regular collection and disposal of fallen fruit.

USING NEW TOOLS TO MANAGE THE PLUM CURCULIO

(Harvey Reissig, [email protected] Entomology, Geneva)

Biology and Traditional Chemical Control Programs

The plum curculio, Conotrachelus nenuphar (Herbst) (PC), is a native pest of stone and pome fruits that has plagued orchardists since the first settlers planted fruit trees. The PC flourishes in wild, unsprayed habitats, because population levels and fruit infestation levels are not regulated effectively by natural enemies. In natural habitats, unsprayed apple and plum fruit is usually heavily damaged by this pest. Therefore, the prospects of developing an effective biological control for PC by conserving natural enemies in commercial apple orchards does not appear to be feasible.


Plum curculio adult

Adult PC overwinter under ground debris, often along hedgerows or along the borders of woodlots. Although a few adult PC may overwinter in commercial orchards, the majority survive in adjacent overwintering sites. In the spring, as soon as ambient temperatures begin to reach 50°F, adult PC emerge from their overwintering quarters and begin to move into orchards. Beetles can be found in apple orchards even before apples bloom, but the adults are usually most numerous after blossoms begin to open. New adults may continue to immigrate into orchards for a 4—6-week period in early spring. Although adults are present in apple trees during Bloom, developing apple fruit is not susceptible to PC injury until after petals have dropped from the young fruitlets. After Petal Fall, beetles damage apples either by feeding (making holes in the apple with their beak-like mouthparts) or by ovipositing (cutting crescent-shaped oviposition scars in the fruit).


Dried sap produced by plum curculio feeding and oviposition wounds on apple

There is only one generation of PC annually. Since there are no resident populations of PC in most commercial apple orchards in NY, it is only necessary to control overwintering adults during their oviposition cycle. Usually, feeding damage from surviving adults emerging late in the summer is not found in commercial orchards.

PC activity and oviposition are greatly affected by temperature. Adults are relatively inactive when temperatures remain below 50°F. During cool springs, adult movement and oviposition may be lengthy (4—6 weeks), but in warmer seasons, the oviposition period may be relatively short (2—3 weeks). Growers using traditional chemical control programs usually apply a protective insecticide to the whole orchard to maintain a protective residue on apple fruit and foliage during the entire PC oviposition cycle in the spring. Since insecticide residues are usually effective for 10—14 days, depending upon the amount of rainfall, traditional control programs usually require an initial spray at Petal Fall, followed by 2—3 insecticide sprays depending upon the weather and precipitation during the spring.

Control and Management Options

Compared with many other insect pests, the PC is not highly mobile and capable of dispersing uniformly throughout an entire orchard during one growing season. Damage from curculio tends to be extremely spotty, and is usually confined to the outer rows of commercial orchards. Since most PC problems result from immigration into orchard borders from outside sources, past history of damage is very useful in deciding whether or not any particular orchard or portions of an orchard are likely to be severely injured by this pest. Sprays of broad spectrum insecticides, such as organophosphates, applied to control PC will also provide control of the first generation of codling moth. Traditionally, growers in NY who treated entire orchards with organophosphate insecticide sprays for plum curculio have not had to apply special sprays against the first generation of codling moth. Growers opting to control PC with reduced insecticide schedules should also be aware that this strategy may require more consideration of management of the first generation of codling moth. In addition, growers in the Hudson Valley and Champlain Valley should also be aware that petal fall sprays of organophosphates have also usually prevented early season damage from the European sawfly.

Standard Control, Timing of Sprays Using PC Oviposition Model

Most studies in western NY have shown that applying a spray of insecticides at the Pink bud stage is no more effective in protecting apples from PC damage than starting control sprays at Petal Fall. However, some trials in the Hudson Valley have suggested that a Pink spray does help in preventing subsequent PC fruit injury in programs in which additional treatments are applied at Petal Fall. Although growers realize that initial post-bloom sprays for plum curculio control should begin at Petal Fall, they are often unsure how many additional sprays will be necessary to maintain protective chemical residues to prevent subsequent damage throughout the PC oviposition cycle, which varies according to temperatures and weather patterns after Petal Fall.

Recently, researchers at the Geneva Station have developed an oviposition model to determine when control sprays after Petal Fall are no longer necessary to protect fruit from PC damage. This model is based on the assumption that residues from control sprays after Petal Fall only need be maintained on fruit and foliage until about 40% of the oviposition cycle is complete, which is predicted by the model to occur at 340 DD (base temp 50°F) after Petal Fall. A more detailed discussion of this model and its validation can be found in the article published in the New York Fruit Quarterly Vol. 2, No 2: “Timing Insecticide Applications for Controlling Plum Curculio Using a Predictive Model”. No one knows exactly why it is not necessary to apply PC control sprays after 40% of the oviposition cycle is complete. This parameter was chosen from initial experiments designed to compare the effectiveness of different schedules of control sprays after Petal Fall in protecting fruit from PC injury. Probably, this strategy works because, after 40% of PC oviposition is complete, adults usually are not moving into the orchard from outside sources, or moving around within orchards from tree to tree. Therefore, by this time, adults residing in treated trees have already been killed by insecticide residues and are unable to complete the remainder of their normal oviposition cycle.

In order to use this strategy: (1) Treat the entire orchard at Petal Fall with a broad spectrum insecticide. (2) Start calculating the accumulation of DD after Petal Fall (Base temp 50° F). (3) No additional sprays are necessary whenever the date of accumulation of 340 DD falls within 10—14 days after a previous spray.

This conventional strategy is probably only necessary for commercial apple orchards in which PC fruit damage has been observed frequently, or for orchards thought to be particularly vulnerable to infestation from codling moth or the European apple sawfly. Usually, orchards that chronically suffer fruit damage from PC are relatively small blocks located next to abandoned orchards or surrounded by woods or woodlots, which are favorable sites for overwintering of PC adults. Some larger orchards bordered by woods on one or more sides may also be at risk for chronic infestations of PC.

Petal Fall Spray, Oviposition Model Border Sprays

This program is similar to the previous program, except that after the Petal Fall spray is applied, additional sprays as determined by predictions from the oviposition model are applied only to the border rows of the orchard (outer 2—4 rows). When using this strategy, it is difficult to treat the ends of orchards in which rows are perpendicular to hedgerows or wooded areas. The only practical way to protect these edges is to drive along the edge of the end trees, with only one side of an airblast sprayer activated to attempt to blow spray back into the block to cover as many trees near the end of the row as possible. Usually, depending upon the size and spacing of trees, at least 2—4 of the end trees in each row will be adequately covered by the single-sided sprayer application. Using this strategy assumes that any PC that have migrated into an orchard prior to Petal Fall will be killed by the Petal Fall spray, and any additional adults coming in after Petal Fall will be killed by border row sprays before they can damage fruit in the outer rows of treated trees or migrate into the interior of the block. This strategy will probably be effective in controlling plum curculio in typical commercial apple orchards that have had no previous history of observed fruit damage from plum curculio at harvest.

Border Sprays, Petal Fall and Oviposition Model

In this program, only the border rows and end trees within each row are treated at Petal Fall for control of the PC. Subsequent sprays are applied only to border rows and end trees according to oviposition model predictions. This strategy can be used in orchards having no previously observed history of plum curculio damage in which there is a desire to use only selective pesticides to encourage the buildup of natural enemies for biological control of mites and other foliar pests. In orchards in which this strategy is used, it may be necessary to consider applying a limited program of selective insecticides for control of the first generation of codling moth. It is also a good idea to closely examine fruit from both border rows and interior rows for damage at harvest from PC. If traces of PC damage are observed in fruit harvest evaluations, it may be necessary to apply one of the more conservative PC control programs during the subsequent growing seasons until PC damage is eliminated.

WHITE APPLE LEAFHOPPER STOPPER

(Art Agnello, [email protected] Entomology, Geneva)

WALH nymphs can be numerous in some blocks, especially in the eastern part of the state. Provado has proven itself effective against this pest, and a petal fall application also gives leafminer control. Furthermore, it will have an added effect on green aphid populations, which could be problematic, depending on the availability of succulent green tissue. Growers using Sevin in their thinning sprays will get some control at the 1 lb rate. Alternative choices for control include Thiodan and Lannate; Agri-Mek or Carzol used for mites now will also do the job, but Carzol will be harmful to predator mites. The damage potential of this first generation should be evaluated carefully before deciding on the need for a specific control of this pest.

BROTHERS UNDER THE SKIN

(Art Agnello [email protected], Entomology, Geneva)

Codling Moth

Most New York apple growers have traditionally ignored the potential threat to their crop posed by this widely endemic orchard resident, as the regular OP sprays for plum curculio and apple maggot between petal fall and mid-August make fruit infestations by codling moth relatively rare. During the past few years, however, with the advent of trapping-based spray decisions for apple maggot, and a resulting decrease in cover sprays in some cases, there have been more opportunities for an unwelcome return of the worm in the apple, which is all the more unacceptable because it is a fairly easy problem to prevent.


Internal apple injury caused by codling moth larva

To that end, we will again publicize suggested codling moth treatment windows this season, for those growers who don’t necessarily spray certain blocks for maggot each year, and who have evidence (or suspicion) that codling moth is starting to pose a significant threat.

The Michigan model for predicting this insect’s development gives fairly accurate predictions of codling moth activity in N.Y. As many as two insecticide applications may be made for each of the two generations per year, depending on the severity of pressure. Degree days are accumulated from the date of first sustained moth catch, and the first spray is applied at 250 DD (base 50°F), which corresponds with predicted 3% egg hatch. A second spray may be applied 10—14 days later. If pressure is not too severe, one spray will suffice, applied instead at 360 DD after the biofix date (which we’re calling May 13 in Geneva and May 2 in Highland). To control the second generation, the timing is 1260 DD after this same biofix date. We will be providing regular updates to identify imminent spray dates.

Oriental Fruit Moth

(This just in from Debbie Breth of the Lake Ontario Fruit Team:)

Oriental fruit moth trap catches in peach orchards in the Niagara region appeared to have peaked on May 8. A predictive model from Ontario would have called for a spray 6 days later. However, trap catches are increasing with the resumption of warm weather, and it is unclear when the “true” peak will have occurred. Therefore, she recommends that growers apply control sprays no later than shuck split, regardless of model predictions. Of primary concern is terminal shoot damage in non-bearing blocks. In some bearing orchards it may be necessary to control the first generation to prevent a buildup of numbers in subsequent generations that can attack the fruit.


Oriental fruit moth internal injury to apple.

Past Insect columns: 4/5 | 4/12 | 4/19 | 5/3 | 5/10

Top

Leave a Reply

Your email address will not be published. Required fields are marked *