Cucumber Beetle, Striped
Feeding damage from striped cucumber beetle on underside of squash cotyledon.
Feeding damage from striped cucumber beetle on squash cotyledons and first leaf.
Fact Sheets Available for Striped Cucumber Beetle:
PERIMETER TRAP CROPPING IN WINTER SQUASH AND PUMPKIN
Two-row perimeter of buttercup squash around a main crop of butternut.
MANAGING STRIPED CUCUMBER BEETLE IN VINE CROPS
Managing Striped Cucumber Beetle in Vine Crops 
All over the Northeast, striped cucumber beetle is our most serious early-season pest in vine crops. These beetles spend the winter in plant debris in field edges, and with the onset of warm days and emergence of cucurbit crops, move rapidly into the field. Densities can be very high, especially in non-rotated fields or close to last year’s cucurbit crops. Adult feeding on cotyledons and young leaves can cause stand reduction and delayed plant growth. More importantly, the striped cucumber beetle vectors Erwinia tracheiphila, the causal agent of bacterial wilt. This disease overwinters within the beetle and is transmitted by contact of beetle feces with the open wounds in leaf tissue caused by beetle feeding. Bacteria multiply and block the vascular system of the plant, causing vines to wilt. This disease can be effectively managed only by preventing feeding by the beetle. Vine crops vary greatly in their susceptibility to wilt.
Avoid early season infection with wilt. Cucurbit plants at the cotyledon and first 1-2 leaf stage are more susceptible to infection with bacterial wilt than older plants, and disease transmission is low after about the 4-leaf stage. Wilt development is strongly influenced by the dose of the pathogen that the plants receive. It may be a relatively small proportion (1-10%) of overwintering beetles that carry the Erwinia pathogen and are able to infect plants. The higher beetle density during early plant growth, the more severe the incidence of wilt. Male beetles that discover a host plant will release an aggregation pheromone that calls others to their spot. Groups of beetles feeding, wounding and defecating on a single plant are more likely to transmit disease, and to acquire the pathogen and transmit it to other plants.
Cultural Controls: Crop rotation. Because beetles spend the winter in field borders close to last year’s crop, planting into the same field encourages rapid invasion by high numbers of beetles. Rotating to a field at a distance from last year’s cucurbits reduces beetle numbers significantly. Of course, crop rotation has many other benefits as well – in vine crops, it is critical for disease management. Any barriers between the fields – woods, buildings, fallow fields or other crops, roadways and waterways – help delay the arrival of beetles.
Cultural Controls: Using Transplants. Several studies in the Northeast have shown that three-week-old transplants, set out in the field at the same time as a direct-seeded crop, will produce not only earlier but higher yields. These studies were done with both summer and winter squashes. Transplants have multiple benefits. Germination of untreated seeds in cool soils can be spotty, while transplanting ensures a good stand. Transplants provide a jump on the weeds. Plants are bigger when cucumber beetles arrive so that they are less vulnerable to both feeding damage and to wilt. An insecticide or repellent can be applied to flats before plants are set out, making it less costly. Planting dates are more flexible – for some crops, it may be possible to delay planting until late June and avoid the worst of the beetles. Plants can be held inside to avoid late frost or wait until fields are dry (or wet) enough to plant. Of course, it is not advisable to hold transplants too long. If they are already flowering or have been stressed when they are set out, they tend to develop into small plants with early but small fruit. Standard seedling production methods work well for vine crops, but large cell sizes (72, 36 or 24) or peat pots are recommended as roots should not be disturbed when transplanting.
Cultural Controls: Floating, or spun-bonded, row covers are very ffective barriers that keep beetles off the crop during the critical early growth stage. They have the added benefit of enhancing growth and reducing wind damage in the early season, for an earlier yield. Studies have also shown an increase in yield with row covers. Covers must be removed at flowering to allow for pollination. Wire hoops are very helpful, to prevent damage from abrasion; these are usually used on single rows, but can also be used under wide sheets of 15 or 25 or 50 feet. Black plastic adds warmth and solves the problem of weed management under the covers.
Thresholds and foliar controls. Beetle numbers should be kept low, especially before the 5-leaf stage. Conventional IPM systems have relied onscouting frequently (at least twice per week) and treating after beetles colonize the field. To prevent bacterial wilt, we recommend that beetles should not be allowed to exceed one beetle for every 2 plants in susceptible crops. This is a lower threshold than is needed to prevent significant foliar damage. Less wilt-susceptible crops (butternut, most pumpkins) will tolerate 1 or two beetles per plant without yield losses.
Proper timing is key. There are a number of broad spectrum insecticides which can be used for foliar control (including Capture 2EC, Decis 1.5EC, Thoinex 50W, Asana, and Sevin). See 2006-2007New England Vegetable Management Guide for more details.
Organic insecticides. Insecticides available for organic growers include kaolin clay (Surround WP), pyrethrin (Pyganic Crop Spray 5.0 EC)), and spinosad (Entrust). Pyrethrin is primarily a contact toxin, while spinosad acts both as a contact and a stomach poison. None of these provides a highly effective ‘knockdown” of beetle populations. No rotenone products are approved under the National Organic Program.
Surround WP should be applied before beetles arrive because it acts as a repellent and protectant -- beetles do not “recognize” the plant and so do not feed -- not a contact poison. It can be tricky to mix and use. One approach is to mix a slurry in a bucket and then add the slurry to the tank, as the dry powder can cake if added directly to the tank mix. Another approach is to add the powder to water and allow it to settle slowly. Once the powder is fully wet, agitate gently. Regular agitation is needed during spraying. With direct-seeded crops, apply as soon as seedlings emerge if beetles are active. Transplants can be sprayed before setting out in the field. Surround can also be used on the main crop of a PTC system, creating a “push-pull” dynamic. Ensure good coverage of the foliage (it will look like it was sprayed with white latex paint), including, if possible, the undersides of leaves (not easy when cotyledons are close to the ground). Reapply after a heavy rain and on new growth. And, wear a respirator or mask when mixing and spraying. Although kaolin is very safe in terms of skin exposure or ingestion, handlers should take precautions to avoid breathing the powder.
Perimeter trap cropping. This strategy saves time and money – and it works! See the June 1, 2006 Vegetable Notes Newsletter or articles above on pertimeter trap cropping.
Systemic controls. Two systemic neo-nicotinoid products, Imidacloprid (Admire) and thiamethoxam (Platinum), are registered for use in cucurbits; in New England, Platinum is labeled for use on striped cucumber beetle only in MA and CT. Note that Admire is being sold in two different formulations now: Admire 2F (21.4% active ingredient) and Admire Pro (42.8% active ingredient). Rates for Admire Pro are approximately half that of Admire 2F, because it is twice as concentrated.
Because of the systemic activity when applied to soil or seed, these products are taken up through the roots and transported into new leaf tissue where they persist through the critical early plant stages. They can be applied in the furrow or as a surface band at planting, which simplifies control efforts especially in fields where a sizable invasion of cucumber beetles is likely. Some may also be applied through drip irrigation, which allows application to be timed shortly in advance of the expected arrival of the pest, and is suited to crops grown on plastic. They can be applied as a transplant drench prior to setting out in the field. Also, they are very well suited to a perimeter trap crop system – which dramatically reduces the cost per acre for pest control.
Using systemics in direct seeded crops. It is important to get the insecticide into the soil to avoid photochemical breakdown; placing it in the furrow or irrigating it in can accomplish this. One of the most efficient systems for an in-furrow treatment is to attach an injector to the planter for placement at the seed level after the furrow is opened and before the seed drops. This has the advantage of one trip through the field and very precise targeting of material. Where it is applied to the soil surface, it should be watered in with irrigation (or rainfall) to move it to root depth for seedlings. For growers who plant by hand on a two-way grid for cross-cultivation, apply in a twelve-inch band at the time that fertilizer is incorporated.
Platinum rates are recommended at 5 to 8 oz per acre. The label provides a chart of recommended rates per 1000 feet of row at various row spacings. For example, at 3 foot spacing, the recommended range is 0.34 to 0.55 oz/1000 liner feet, while at 7 foot spacing, the rates range from 0.8 to 1.29 oz/1000 feet. It may be possible to use a similar approach as for Admire (see table below) in calculating rates per row feet. In a trial conducted at the UMass research farm this summer, both high and low rates gave comparable levels of control compared to imidacloprid.
The Admire label gives a range of 16 - 24 oz per acre or 0.9 to 1.3 oz per 1000 feet of row. Studies have found a rate of 1.0 or 1.1 oz per 1,000 feet to be sufficient for controlling cucumber beetle in the critical early weeks. Given the wide range in row spacing with these crops and the fact that this is a banded application, we have suggested that growers calculate rates based on the number of row feet to be treated per acre.
Using systemics on transplants: This method of application is, obviously, less expensive than a furrow drench. The best time to treat is about 1 day prior to planting in the field. We have seen effective results with a rate of 0.02 ml/Admire 2F per plant, although this is lower than the rates for some plant populations listed on the label. Be careful of phytoxicity at higher rates. In Pennsylvania, burning of leaf tissue in cucurbits was observed at 0.04 ml/plant. Use half the rate for Admire Pro. Note: You can convert ml to oz by dividing by 29.6 (there are 29.6 ml in one fluid oz).
Another way to apply imidacloprid to transplants is through a water wheel planter. Use the same rate of Admire 2F per plant (0.02 ml) and the rate of water per plant that fits your planter (e.g. 8 oz). Multiply by the number of plants and mix the total Admire needed with the total water needed in the tank. Make sure your workers wear protective gloves and allow time for uptake (1+ days) into leaves Note that the highest rate of uptake will be into new growth.
Drip application: A drip system can be used for Admire or Platinum applications to either direct seeded or transplanted crops. Know your system well enough to know how long it will take to inject a given amount of concentrated solution (eg one bucketful) and to soak the area between emitters. Apply early enough to allow the plant roots and leaves to take up the material before beetles arrive. The system should be primed with water first, and imidacloprid injected slowly for even distribution. Make sure to use enough water to soak the area between emitters. More emitters provide more even distribution of product.
Calculate the rate needed per 100 or 1000 ft of row. Place the total amount in the bucket with enough water for 20-30 minutes of injection. Charge the system with water first to get the soil wet. Turn on the Venturi or other injector, to inject slowly for even distribution (20 or 30 minutes). Then flush lines with clear water and to move product out and down.
Non-target effects: Bees are very susceptible to imidacloprid and thiamethoxam and could be affected by its presence in pollen if it is still at high levels in the plants at the time of flowering. Bees intoxicated by Admire or Platinum, like beetles, show unusual behaviors such as tremors, staggering, and falling over before dying. This could happen with bees at excessively high rates of these insecticides. We have not observed it at the rates suggested in this article. The foliar formulation of imidacloprid (Provado)is not labeled for cucurbits, and the foliar formulation of thiamethoxam (Actara) has a label for cucurbits but may not be sprayed during bloom. Carbamates such as Sevin and synthetic pyrethroids should not be used during bloom to avoid killing bees.
Resistance from overuse. The down side of systemic products might be that they are ‘too easy’. That’s not necessarily a bad thing for growers who are always too busy! However if these are overused on a routine basis, these products may well be lost to resistance in a fairly short time. Furthermore, they are not cheap. For a truly IPM approach, combine or alternate these materials with crop rotation, perimeter trap cropping, and field scouting followed by foliar sprays with other classes of insecticides to reduce the likelihood of resistance and keep use rates low. Perimeter trap cropping provides a large, untreated refuge which can delay resistance.
Updated June 2006
- Ruth Hazzard, Vegetable Extension Program, Department of Plant, Soil and Insect Sciences, University of Massachusetts, Amherst
Where trade names or commercial products are used, no company or product endorsement is implied or intended. Always read the label before using any pesticide. The label is the legal document for product use. Disregard any information in this newsletter if it is in conflict with the label.
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