Pickleworm Control: How to Identify, Prevent, and Manage Pickleworms in Your Garden

Early scouting and early intervention, with squash fruit young enough to be infested by pickleaf or affected larvae (before larvae overwinter in the plants), together with cultural, biological pickleworm organic control and, if necessary, chemical pickleworm control is the best pickleworm management program. Pickleworm (Diaphania nitidalis) populations can be serious for summer squash due to the larva's consumption of leaves as well as its feeding on fruits. These can enter flowers, buds, shoots and developing fruit, where it will be difficult to get to them on target and apply insecticides. Proper management for growers begins with correct identification and knowledge of the pest's life stage and the proper timing and stage of monitoring on the crop and intervening prior to the completion of the larval life stage when it is protected in the plant's tissues. Pickleworm shows a preference at certain times to summer squash; it makes an excellent sentinel crop.

When assessing an agricultural management problem, each squash plant that is damaged by fruits is often too late in the season to be considered a treatment candidate. Monitoring flowering plants, and searching carefully for eggs and young larvae in flower buds and flower is a better strategy. There is a current recommendation from Virginia Cooperative Extension to treat when larvae are first observed in blossoms and buds and prior to entering fruit.

Pickleworm and the garden crops it attacks

Pickleworm is the larva, or caterpillar, of the moth, Diaphania nitidalis of the family Crambidae. It is a main pest on cucurbit crops, and may infest cucumber, squash, pumpkin, cantaloupe, muskmelon and winter squash. It is deemed a favorable host for pickworms, and is significant for early detection if a grower desires to determine if the pressure of pickworms is building up in an area.

What is pickleworm? Pickleworm (Diaphania nitidalis) is a moth pest whose larvae bore inside the buds, blooms and incipient fruit of cucumbers and can feed on cucurbits as squash and particularly summer squash are favored hosts.

The correct identification is important as there are a number of pests of cucurbits that may cause similar damage initially. Pickleworm is a species of caterpillar which usually bores flowers and fruit. Squash bugs (Anasa tristis) are sucking insects that often cause plants to wilt and injure leaves, and squash vine borers are caterpillars, which bore into the stems. Being closely related to the pickleworms, melonworms may also feed on and damage maturing fruit, but they tend to be much more diligent in devouring foliage.

When making management decisions for pickleworm organic control before identification of trouble pests may be present, it is easy to make a wrong choice and make unnecessary applications that disturb beneficial insects. Insects that inflict damage on the tree are always the key point: What species is the pest, where is it feeding, and how to get rid of pickleworms?

Organic methods for pickleworm treatment​

Pickleworm adults are small moths, 3cm long. The wings are translucent yellow, with a brown border, creating a distinctive pattern, and their anterior halves are larger than the posterior. anterior and hind wings are larger than each other, the anterior wings being translucent yellow and the edge a brows colour. They are nocturnal, active at night more than during the day; it is during this night that growers will most likely notice plants being active at them. In single or small clusters of active growing plant tissues, such as shoots, buds and flowers. The eggs are white before they hatch but turn to yellow color in the process of hatching, which typically takes around 5 days.

Golden yellow white or cream coloured with rows of dark spotting on their back and a brown head which also forms a row of spots. The spots will fade as they grow and grow like caterpillars will generally turn green as they age, but can vary in color depending on the host plant. Larvae can grow to be about 25–30 mm long when mature. The flowers, buds, tender shoots and young fruit are therefore the most useful scouting locations as they allow for better assessment, especially for scab.

One of the scouting practices that can help is the careful examination of flowers and fruit development instead of damage manifested on the top of the leaves. An infestation that may get a lot more difficult to control when the larva burrows into fruit has begun with a small caterpillar in a blossom. In the coming sections, we will discuss how bt for squash bugs can help prevent pickleworm control.

When are the seedlings in the pickleworm damage to squash?

The larvae of pickleworms will sometimes start eating in buds and blossoms. Feeding in these structures may lead to reduction of fruit growth and in older plants small, round feeding holes may be seen on young squash. A good field clue is wet, pulpy frass around the entrance hole. The frass, or ‘poop’ of the caterpillars can make it easy to see otherwise very tiny damage.

Inside a maturing squash the larva bores through the fruit, living within it. This can quickly bring down the marketable quality and might lead so far as second deterioration. When the vines have been badly attacked by flowers and fruit, heavy infestations can occur as well. They can have a problem on the central vines after blossoms and fruits have been eaten, says Virginia Tech.

What growers should take note of for the practical application is that having a hole in fruit is not an aesthetic loss. It can be a sign that the caterpillar has already infested a safe feeding spot for the insect pests and contact will be difficult in this area.

Pickleworm Life Cycle and Why Treatment Timing Matters

How to get rid of pickleworms? Pickleworm's life cycle—egg, larva, pupa and adult. Females lay eggs on the growing parts of the plants and in about three to four days the eggs begin hatching. Larvae subsequently eat and change color several times in a couple of weeks to pupae. The pupa stage takes place in protected places like in folds of leaves or plant debris and adult females can emerge for around 8 to 9 days.

Larvae are the most important management target since this is the life stage which causes the direct damage to the crop. Most important, the most critical life stage for intervention is the early larval stage. Exposed buds and flowers are easier to access by the young larvae than are larvae when tunneled into developing fruit.
 

What's the Best Treatment Time for Pickleworms?

If you detect young larvae, especially when they are in the blossoms and buds, and before larvae are in the developing fruit, treat. The current recommendations from Virginia Tech suggest starting treatment in the early stages, as soon as the larvae are spotted in blossoms and buds and prior to fruit-set.

This is one reason why scouting the field on a frequent basis is desirable as compared to a defined calendar. Arrival of adults and egg deposition may vary, depending on crop stage, local pest infestation, weather. Shoot the plants several times per week to see if a plant is infested at the point when the larvae are exposed.

Pickleworm Organic Control - what can gardeners do first?

Address prevention and monitoring then only consider an insecticide as a step in an integrated program. Physical exclusion can be achieved through rows of row covers or screens before adult moths start laying eggs and early planting can minimize exposure in some production areas. Flowers, buds and young fruit should be regularly inspected for infestation, and if possible the removal of heavily damaged fruit with larvae present. Crop sanitation and control of alternate hosts of cucurbit crops can help limit the opportunity for the pest to endure.

The organic options recommended by Virginia Cooperative Extension include insecticidal soaps, and pyrethrins; and kaolin clay sprays are included among the crop-protection options. Growers using certified organic crops, however, should check with their certified crop advisor to make sure that a specific material, formulation and application rate is approved for organic certification. Growers always should adhere to the usage direction on the product label.

However, physical exclusion will need a little planning as squash is highly reliant on pollinators. The use of row covers can be very useful at critical points of early growth but usually have to be removed or properly managed with flowers in need of bee access. It's not about the mere exclusion of insects past a certain time, but about preventing pickleworm adults from establishing and allowing the necessary pollination to occur.

A Step-by-Step Integrated Pest Management (IPM) Strategy for How to Get Rid of Pickleworms

An effective Integrated pest management solution depends on 7 steps:

Step 1: Selective examination of plants for squash during flowering and incidence of fruit set

This is when the pickleworm eats his favorite food, usually young fruit, flower and bud.

Step 2: Search for eggs and develop larvae

Be sure to examine actively growing tissue closely. The caterpillars may be hard to locate in the early stages when they are young-size, but at least as difficult is the damage they will cause later.

Step 3: Prune away severely injured fruit and visible pests, as far as possible

But, for small plantations or home gardens picking of damaged fruits will assist lowering the residual harvest of larvae.

Step 4: Physical exclusion of young people is a symptomatic response, and should be implemented early

Row covers, screens will help limit moth access prior to flowering, as long as pollination needs are taken into account.

Step 5: Highlight young larvae of the hashish plant

Control with an appropriate biological insecticide or see the product label and local regulations for registered insecticide for the appropriate pest/crop.

Step 6: Re-scout (after Pickleworm Treatment​)

Even after one application, don't think the problem is solved. Please watch and look for any new entryways, larvae or fresh eggs again.

Step 7: Make adjustments to the program

When re-emergence occurs, consider both the scouting interval and window of application and the crop's development/maturity more than just simply increasing the level of treatment.
The main aim is to prevent larvae from being protected in the fruit. With internal feeding beginning, even otherwise effective insecticides may give disappointing control as it is no longer easily reached.

When to pickleworm spray?

Timing is the most important factor to consider rather than going for a more powerful spray when it comes to pickworm applications. Applying to larvae at the newly hatched up to the early or second instar stage, when they are engorging themselves on exposed flowers, buds and tender plant tissues is effective. Larvae bore into fruit where they are more resistant to foliar treatments. Thus it is recommended that treatment be applied at the first sign of larvae in blossoms and buds in advance of fruiting in Virginia Tech.

Coverage also matters for pickleworm control. To target application of the product to the feeding site of young larvae and also to follow all spray (bt for squash bugs) instructions on the label for application rate, spray interval, and harvest and personal protection restrictions. Products registered for one crop or pest cannot be assumed to be considered as suitable for another one.

Generating A Pollinator Safe Squash Pest Management Plan

Bees and other pollinators like the squash flowers, so high care must be taken when applying insecticides during flowering. Growers need to be mindful of the following pollinator precautions on the product label and avoid wanton exposure. Time of application can be chosen to deplete some exposure to the active pollinators if allowed by the label. With IPM, growers are particularly beneficial in this situation as good scouting can help target insecticide application when it is appropriate.

Options for biological control of pickleworm

Biological pickleworm organic control is best used in the context of an integrated programme and should not be considered as a complete solution. Broad-spectrum insecticide use can be minimized and lead to ecological suppression by beneficial predators/parasitoids. Native predators can eat eggs and early stage pickleworms and biological and cultural controls can be used along with early detection of pickleworms, according to UF/IFAS.

The seed carries a bacterium that is harmless to all other insects and beneficial organisms, but deadly to young pickleworm larvae. Bacillus thuringiensis (Bt) is relevant because it is one of the biological insecticides that is utilized for control of susceptible caterpillar larvae. The action of Bt is by ingestion - the susceptible larvae eat the treated plant material, and the Bt toxin interferes with its gut. This is why it is all the more important to get exposed.

That is significant in the case of pickleworm treatment. UF/IFAS discusses Bt insecticides, which are effective against pickleworms and melonworms, but explains the problem caused by the endophytic feedingstyle. A similar recommendation is made by Virginia Tech, who advised killing larvae prior to entering fruit.

Predator, Parasitoids and management - Ecology

Predaceous insects help to limit egg and early larval populations. By creating a variety of gardens and only using broad spectum insecticide in the instances listed above, these helpful insects will be retained in the garden. Intensive investigations on strategies like trap cropping and push-pull approaches also offer scope for further avenues of integrated approaches, but the outcomes may differ depending on crop, environment and pest pressure and production system.

The rationale of using Bt against all squash bugs (P. aculeata): understanding what Bt really targets.

The term “bt for squash bugs” is confusing because pickworms and squash bugs are different insects. The pickleworm is the caterpillar, or larval form of a moth while the squash bug is a true bug that sucks plant fluids. Avoid using Bt as a control for squash-bugs because Bt is meant to control susceptible caterpillar larvae, and therefore may not control the squash-bug.

The thing about Bt that I'm happy about is that as long as the caterpillar eats treated plant tissues, the biological insecticide will be effective on pickleworm. That is why the timing of the application is of great importance. The young exposed larvae that feed on treated flowers or on other available tissue are more appropriate targets than protected larvae in the blooms or in squash fruits. UF/IFAS mentions that Bt based insecticides are one of the biological control methods for pickleworms and/or melonworms.

If squash bugs are present, all management practices need to be carefully planned for a squash bug program and should not follow a caterpillar program.

How to apply BT thuricide as a part of a pickleworm management program?

Is BT thuricide a Direct Pickleworm Insecticide? 

Pickleworm – Diaphania nitidalis is a caterpillar that is a problem on cucurbit crops, such as squash and cucumbers. Bacillus thuringiensis var. kurstaki (Btk) is a biological insecticide that targets larvi caterpillars susceptible to Btk. Bt produces proteins when ingested which disrupt the gut of the larva and eventually ceases feeding and kills the larva.

Novobac says that BT Thuricide contains Btk, and is formulated for caterpillar control. Bt will control pickleworm larvae but it is important to time applications correctly. Pickleworm larvae may enter the flowers and fruits, and are thus hard to reach with spray treatment. So treatment will be most beneficial when there is an active feeding cycle in the young larvae and is used before the larvae have bored into the fruit. Approval of product efficacy, intended crop use and suitability should be verified prior to application. 

How Bacillus thuringiensis controls Pickleworm?

Bt is not systemic, therefore must be ingested by the targeted caterpillars and are not effective against most flies. As a damaging insect feeds on treated plant matter, Bt proteins have damaging effects on its digestive tract and eventually kill the pest by stifling its feeding.

To the farmer, this translates to spraying coverage and application time are critical. Bt should be on the surface of the plant on which young larvae are eating. After bloom or fruit has been bored, the pickleworms are not exposed to direct spraying and it becomes much harder to control the infestation.

Read and follow the very important directions below for managing pickleworms:

• Monitor on a regular basis: Check flowers, buds, leaves and immature fruits for eggs and small caterpillar damage.
• Synchronize timing of application: Aim for recently hatched / young actively feeding larvae before entering into fruits.
• Provide complete coverage: Spray product’s labeled surfaces of crop to the extent indicated by the product label at the recommended rate and by the recommended application method.
• Repeat as directed: Monitor the crop and apply the treatment only as directed by the label especially when new larvae appear or weather degrades the effectiveness of the treatment.
• Eliminate host plant material: Remove and destroy the infested fruits and other heavily-pested materials on planted host plant materials where possible, to minimize continuing pest pressures.

If you are using Novobac BT Thuricide to control pickleworm, verify you are using it on a recommended label crop and the registered pest or appropriate caterpillar group (AKA pest group).

In addition to being effective, pickleworm control can be done using BT Thuricide, as part of an integrated pickleworm management program.

When approved for the intended use, BT Thuricide will be a biological option for an integrated pest management (IPM) program. But should not replace the other method especially if larvae are already present in the fruit.

Insect scouting, coordinated with timely Bt applications and removal of infested fruit and other local control tactics can help the farmer control pickleworm in his crop. The main concept is to kill the pest in an accessible and active feeding state prior to the time when feeding damage is hard to rectify.

The choice is yours on how much you would like to protect your squash before pickleworm starts

How to get rid of pickleworms? Successful pickleworm management starts before the infestation becomes obvious, as damaged fruit. By regularly scouting for the eggs and young larvae during the flowering period and early fruit development of the squash, growers can locate eggs and young larvae at a time that they are exposed. Then physical exclusion, sanitation, removal of infested fruit, conservation of beneficial organisms and suitable selection of a biological and/or chemical product can be used together in accordance with the pest pressure level and crop stages.

The biological pickleworm controll tool of Bacillus thuringensis is applicable to the susceptible pickleworm larvae, especially in their early life stages and when they are taking up plant foliage that is exposed. It is highly dependent on time of application as the larvae are difficult to access within the fruit.

Scout during flowering, exclude/pick early infestations, except/add young larvae before entering fruit to control pickworm effectively.

Reference:

• de Baptista, Gilberto C., et al. "Deltamethrin residues applied in different formulations in staked cucumber and the actions of insecticides on the pickleworm control." Horticultura brasileira 26 (2008): 321-324.
• Dougherty, D. E., and D. J. Schuster. "Compatibility of fungicide-insecticide combinations for disease and pickleworm control on honeydew melon." Proceedings of the Florida State Horticultural Society. Vol. 97. 1984.