Two species of "cucumber beetles" [striped cucumber beetle, and spotted cucumber beetle] feed on cucurbits. Two additional species [northern corn rootworm, and western corn rootworm] invade late in the season. Within this complex, the striped cucumber beetle is present in the highest density and over the longest time span. Adult feeding during early plant growth can cause stand reduction and rind-feeding by adults or larvae later in the season renders crops unmarketable and may serve as routes of entry for pathogens. Larval feeding also impacts root development and has been correlated with fusarium wilt. More importantly, the striped cucumber beetle vectors bacterial and viral pathogens. The major pathogen is Erwinia tracheiphila, the causal agent of bacterial wilt. Disease management currently relies on vector management. Even a low beetle density during colonization of young plants can result in significant plant disease and the severity of disease over time correlates to beetle density during early plant growth. Disease development is strongly influenced by inoculum dose. Cultural methods can manage the problem in machine-harvested, short-season processing pickles that have high plant populations, but the vector/disease complex presents very difficult risks for long-season, fresh-market vine crops that are grown at much lower plant populations. Bacterial wilt is most severe on melons and cucumbers. It was rare to see bacterial wilt in squash and pumpkins in the past, but recently this disease seems to be infesting some squash and pumpkin plantings.

Timing and cultural controls: The striped cucumber beetle overwinters as an adult both inside and outside of cucurbit fields. Adults invade fields soon after transplanting, and lay eggs at the base of plants. The hatching larvae feed on the roots of vine crops, pupate, and then emerge as new adults in about 25-30 days. There are at least 2, and probably more, generations per year in Pennsylvania.

Early immigration can be the most serious. Up to 10% of the immigrating adults have tested positive for carrying the pathogen that causes bacterial wilt using ELISA tests. Where this immigration has traditionally occurred very soon (within 3 days to a week) after transplanting, we recommend an application of insecticide to the transplants. Roots of these young plants may not be sufficiently established to take up material applied through drip irrigation. After transplanting, the roots are training to the drip lines, and a single application through the drip irrigation at that time (about 10 days to 2 weeks after transplanting) should control the immigrating adults. We anticipate that no, or only 1 or 2 foliar insecticide applications would be needed if that early immigrating population is prevented from establishing. If this approach is successful for several years, we may no longer see this dramatic invasion of fields soon after transplanting. Should that occur, scout fields and add insecticide when immigration starts.

An effective cultural control method is the use of row covers. Put the covers on right at transplanting. The row covers effectively exclude the beetles for as long as you have the crop covered. If you can find a self-pollinating cultivar (there are some good ones now for cucumbers), then you can leave the floating row cover on until harvest. Otherwise, you need to remove the cover to allow bees to pollinate the crop.

Admire 2 F. - Imidacloprid, the active ingredient of Admire, is a relatively new systemic neonicotinoid insecticide now labeled for striped cucumber beetle in vine crops. Admire is intended for soil applications and translocates to new leaf tissue when taken up by the roots. The foliar formulation - Provado - is NOT labeled for cucurbit crops. In a gallon of formulated product, Admire 2F contains 2 pounds active ingredient Vegetable growers must correct for application rates when using plasticulture and applying materials through drip irrigation since the effective treated area is reduced to that of a "mulched acre". Smaller growers will need low application rates, which require measuring volumes of less than one fluid ounce.

To control cucumber beetles invasion at transplanting with Admire, use a very low rate (0.02 ml/plant) to treat transplants about 1 day prior to planting in the field. To treat a flat of 200 transplants with Admire, dilute 4 ml (0.135 oz) of Admire in a volume of water sufficient to soak to soil mix evenly. This treatment will protect the plants for about 2 weeks, and can be followed by field application if needed. To help make conversions: multiply 0.02 ml per plant times the number of plants in your flat. For example, use 20 ml to treat 1000 transplants. This rate is just a little higher than suggested for tomato transplants, which is - 15 ml - or 0.5 ounce - per 1000 transplants. You can convert ml to oz by dividing by 29.6 (there is 29.6 ml in a fluid oz). Be careful of phytotoxicity (burning the plants) at higher rates. We observed burning of leaf margins at 0.04 ml/melon plant at the 2-leaf stage, although these plants did grow out of this in about 2 weeks.

The best way to apply Admire to the field is through an injector connected to a drip irrigation system. As with all chemical injections, the irrigation system should be primed with water prior to beginning the injection, and the material should be injected slowly to provide even distribution. Remember: the more evenly distributed the material is, the better job of protection, and the chance of phytotoxicity will be reduced (i.e. the more emitters on your drip tubing the better). It is also important that the zone of moisture created by the drip tubing be within the root zone of the crop because it is the roots that will move the material into the plant. Below is a table which shows the number of ounces (oz) or milliliters (ml) of Admire that need to be applied per 100 row-feet of a cucurbit crop for a application rates of 16-24 oz/A. The amount required to treat a 100 ft row is very small and not easily achieved by commonly available measuring devices. We recommend that growers with small fields use milliliters as a measurement unit, and use syringes if available (without a needle to avoid plugging up the syringe, and to help with safety) for extracting these amounts. A syringe without a needle will provide a very accurate and safe method of measuring these small quantities.

If a drip irrigation system is not available to deliver the pesticide to the root zone, it can be applied by directing a spray or drench into the soil at the base of the plant. It is important that the material be applied when the soil is moist, or with enough water to soak the soil to the depth of the root zone. If it is applied only to the surface of the soil, the roots will not have good access to it. Apply the material directly to the base of the plant when the soil is moist and with at least 10 ml of water per plant for young plants (<4 true leaves) and 50 ml of water for larger plants. This can be achieved with a backpack sprayer rather efficiently, but you need to calculate how much time it takes for your backpack sprayer to deliver a 10 ml volume of water. To calculate the total volume of water to put in your backpack sprayer, multiply the number of plants you want to treat by the volume of water per plant. For example, let's say you wanted to treat a 100 foot row of cantaloupe with 16 oz/A of Admire. If your plant spacing were 2' then there would be 50 plants in that row. If the plants were young you would only need 10 ml of water per plant (minimum - please feel free to increase this amount if you wish). Multiply 50 plants by 10 ml and you will discover you need 500 ml of water to treat this row. Add 500 ml of water to the backpack sprayer and then add 3.26 ml of Admire (see Table 1), mix well, and apply. The trick with this type of delivery system is to estimate how long it takes to deliver 10 ml (a very small quantity) from your backpack sprayer. Often this is just a quick shot from the trigger. Remember to keep the nozzle close to the soil and direct the spray toward the base of the stem. Please test the output of your sprayer with water prior to performing these calculations, and remember - do not apply Admire within 21 days of harvest.

Read the label. You should always read the label. Information on the label supercedes anything written here, and good information about rates per 1000 linear feet is on the label.

Pesticides are poisonous. Read and follow directions and safety precautions on labels. Handle carefully and store in original labeled containers out of the reach of children, pets, and livestock. Dispose of empty containers right away, in a safe manner and place. Do not contaminate forage, streams, or ponds.

*** Disclaimer ***

Authored by: Shelby Fleischer, Professor
Lew Otjen, Horticulture

February 2002

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