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Pest: Cucumber Beetle

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Note: I'll do a real thread on this pest that disguises itself as a beneficial ladybug later, but thought anyone doing an outdoor should know about them now. Update: It's done,  this article is still a good read

 

 

Grow Guide: 7 Organic Ways to Defeat Cucumber Beetles

0 By Allie Beckett on

July 11th, 2017

 

The first time I saw these guys wandering around our outdoor plants I thought, “Aww, yellow lady bugs, how cute!” Man, was I wrong. While they might try to disguise themselves as beneficial ladybugs, these yellow scoundrels will chomp their way through your garden in no time.

 

While they may seem like a simple pest, these beetles are surprisingly stubborn. But we’re all about organic cannabis cultivation at Marijuana.com, so while there may be chemical pesticides out there that will eradicate cucumber beetles, those same pesticides will also kill everything they touch, throwing off the balance of the ecosystem and creating a worse problem in the long run.

 

There are two kinds of cucumber beetles, ones that are spotted (Diabrotica) and ones that are striped (Acalymma). Both are members of the Chrysomelidae family. I’ve found that the spotted ones seem to be more attracted to cannabis while the striped ones stick to cucurbits (squash, cucumbers, pumpkins, etc.).......

 

 

 

 

 

https://www.marijuana.com/news/2017/07/grow-guide-7-organic-ways-to-defeat-cucumber-beetles/


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                                        Pest: Cucumber Beetle

 

220px-Diabrotica_undecimpunctata_howardi

 

( Acalymma vittatum, A. trivittatum, Diabrotica undecimpunctata )

 

 

 

 

 

Special Species Notes

 

Often thought as a beneficial yellow ladybug, but these are pests trying to fool you by disguising themselves. Don't be fooled, the real beneficial ladybugs comes in red or solid black ( the Mite and Mealybug destroyers).

 

Adult and larval stages of the cucumber beetle transmit several plant diseases, including bacterial wilt and various types of mosaic virus. Cucumber bacterial wilt and cucumber mosaic can survive in the digestive system of a cucumber beetle and as a cucumber beetle moves from plant to plant to feed, it spreads these diseases to all the plants it eats. Once a plant is infected with either bacterial wilt or cucumber mosaic, it cannot be cured and will either die or become unproductive after they are infected. It's best to remove and destroy the plant by fire.

 

CukBtlSpotdN6337s_348x380.jpg

 

spottedcucumberbeetle_Raupp1-498x325.jpg

 

Spotted cucumber beetle

 

Identification/ Common Species:

 

 

 

Cucumber beetles are native insects and found across the United States from Canada to Mexico, east to west coast. They are members of the Chrysomelidae family. There are six species of cucumber beetle in the United States.

 

spotted_cucumber_beetle02.jpg

 

Larval and adult banded cucumber beetle,

Photograph by Lyle Buss,

Entomology and Nematology Department, University of Florida.

 

There are two types of striped Cucumber beetles: the Acalymma vittatum in the eastern U.S. and A. trivittatum in the west.   The spotted  Cucumber beetles (Diabrotica undecimpunctata howardi)  are more attracted to cannabis. Another name for the spotted cucumber beetle is “southern corn rootworm”.  The banded cucumber beetle  (Diabrotica balteata) is more common in southern Florida. These beetles are not troublesome in sandy soils (Sorensen 1999).

 

stripedcucumberbeetle_1000_Raupp.jpg

 

Striped cucumber beetle

 

Adult cucumber beetles are 1/4 inch long. They are yellowish-green or orange-green in color with dark heads, legs and antennae. They have distinct black spots or lengthwise stripes on their wings.

 

Adult striped cucumber beetles are yellowish-green or orange-green with three black stripes down its back in color have a yellow-and-black–striped abdomen. The lengthwise black stripes on the backs of striped cucumber beetles are more distinct and extend to the tip of the wings. They have beaded black antennae about 1.6 mm long. The spotted cucumber beetle are the same length, but have 12 black spots on a yellow abdomen. The striped cucumber beetles have black abdomens below, and pale colored legs with black "knees". They are sometimes confused with the western corn rootworm (striped cucumber beetle) which has a pale-colored abdomen and more uniformed dark legs. Adults are most active in the morning and late afternoon.

 

Eggs of both species are pale orange-yellow and are laid in groups, they darken with age, up to 800 eggs in the soil near the base of plants, or 20 or so on the underside of a leaf.

 

SquaBugEggYeN6324s_350x398.jpg

 

5.1-cucumber-beetle-eggs.jpg

 

198-13.jpg?itok=WePnYaIp

 

Eggs

 

 

The slender white larvae are 3/8 inches up to 1/3 inch long, have brown ends. The larvae are worm-like, creamy white, dark-headed, and have three pairs of legs on the thorax.

 

220px-Diabrotica_virgifera_virgifera_lar

 

Western corn rootworm

 

 

12_spot_larvae.jpg

 

Spot Beetle larvae

 

The Pupae are white initially, but turn yellowish with age and start looking like adults. They are about 7.5 mm long and 4.5 mm wide. A pair of stout spines are on the tip of the abdomen and smaller spines are found on the dorsal side of other abdominal segments.

 

Host plants:

 

During the growing season, they are found feeding on seedlings, foliage, vines, pollen, flowers and fruits causing greatly reduced yields and sometimes plant loss. The larvae feed on the roots of the host plants.

 

Spotted cucumber beetles feed on over 200 different crop and non-crop plants (includes cannabis), whereas striped cucumber beetles have a much stronger preference for cucurbits and rarely feed on other plants. Spotted cucumber beetles seem to be more of a pest farther south in the US, whereas striped cucumber beetles dominate farther north.

 

Cucumber beetles damage cucurbit crops in at least three ways. First, their feeding directly stunts plants and, when flowers are eaten, can reduce fruit set. Second, cucumber beetles transmit bacterial wilt disease. Wilt disease is from the Erwinia bacterium that spreads rapidly through the vascular system of the plant, creating resins which restrict the movement of water and nutrients. This causes the plant to wilt and die, sometimes in a little as seven days. It's a serious concern in central and eastern United States. Cucumber beetles can also spread Squash mosaic virus, Cucumber mosaic virus, Bean mosaic virus, and Maize chlorotic mottle virus (Alston and Worwood 2008). As well as lead to an increased incidence of powdery mildew and black rot, and a predisposition to fusarium wilt.

 

8-cb-adult-damage.jpg

 

Cucumber beetle adult damage on a melon fruit

 

 

Third, adults scar the fruit reducing its marketability. It is primarily young cucurbit plants that are vulnerable to stunting and bacterial wilt disease, whereas damage to older plants primarily comes from fruit scarring.

 

The primary host plants are Cucumbers, Pumpkins, Gourds, winter and summer Squash, Beans, and Melons. Some examples of alternate hosts plants are beans, peas, corn, peanuts, cannabis, potatoes, zucchini,  grasses, tomatoes,  eggplant, asparagus, apple, pear, okra, tree and shrub blossoms.

 

 

 

 

spotted_cucumber_beetle03.jpg

 

Larvae of the spotted cucumber beetle, Diabrotica undecimpunctata howardi Barber.

Photograph by Clemson University - USDA Cooperative Extension Slide Series

 

First signs:

 

The stems and roots of your seedlings are being eaten off and/or have been bored into. The leaves have holes and are yellowing. The plant is wilting. The plants future yield provided it didn't die will be low; for veggie plants, they will produce yellow and stunted fruits.

 

Larvae eat roots and burrow in young plant stems, causing wilt or death.  Adults eat seedlings, and chew holes in leaves, flowers and fruit. Adults gouge and rasp fruit, especially smooth melons, and damage may be worse on the shaded undersides of fruit contacting soil since beetles congregate there to avoid heat.

 

spotted_cucumber_beetle04.jpg

 

 

Feeding damage from the spotted cucumber beetle

Photograph by Gerald Holmes,

Valent USA Corporation, Bugwood.org.

 

 

Spotted cucumber beetle (also known as the Southern corn rootworm) eats roots of beans and corn as well as cucurbits.

Both striped and spotted beetles are serious vectors of plant diseases, including Fusarium wilt, various mosaic viruses, muskmelon necrotic spot virus, and cucurbit bacterial wilt, although spotted beetles are considered less important vectors of this devastating disease than striped beetles. Cucurbit bacterial wilt causes sudden wilt and death, mainly of cucumber and muskmelon, but also of summer squash.

 

CukeBtlDmgStemN6345s_700x530.jpg

 

The arrow points to two eggs

You can see the scarring on the stem

 

The leaves will show the biggest evidence of the damage from cucumber beetles. You will see holes on the surface. This causes a deficiency in the nutrients that the plant requires for survival. the green leaf will turn to yellow.

 

damage.jpeg

 

Spot Beetle damage to beans

(Photo by Pamela Opfer)

 

Plant stunting is also a common symptom. Plant stunting is where the plant does not grow fully. It appears smaller than the usual. The leaves will also appear sickly, which is evident in color and vigor. Some would say a sickly runt.

 

12_spot.jpg

 

Spot Beetle adult  

(Photos by Ken Gray)

 

Life cycle

 

The cucumber beetle sex ratio is highly skewed toward females. There is a very good reason for this since the females are larger bodied than the males and are more likely to survive overwintering. Adult cucumber beetles overwinter above and below ground.  They can be near buildings, in your house, attic,  in fence rows, in wood lots, weeds, garden debris/trash, and woody areas. The diseases they carry can also overwinter in their gut and can be passed onto plants the next spring through fecal matter or when feeding.

 

Overwintering adults become active once the temperature reaches 59-68°F (15-20°C). Capinera (2008) reported that adults are long lived: 60 days in summer and up to 200 days in winter.  Cucumber beetles overwinter primarily as fertilized females and become active in early spring.

 

Adults leave their hiding sites in late March. Dispersal flights occur during warm periods in April and May searching for food and mates. The adult females start ovipositing 2-3 weeks after emergence usually from late April to early June.  Cucumber beetles quickly locate host plants in the spring. They feed on blossoms of flowering plants and/or on seedlings right as they are emerging, usually killing them.

 

The female mates and lays up to 800 orange-yellow eggs in cracks in the soil at the base of host. The females can lay up to 1500 eggs each over the course of several weeks. After depositing their eggs, the female beetles die. The spotted cucumber beetle primarily laying its eggs on corn and other grasses. In spring, spotted cucumber beetle prefers to deposit eggs in wet, coarse soil. Striped cucumber beetle deposits eggs around the base of plants, on vines, or just below soil surface. During June, the number of above ground adult beetles drops significantly. At this point, the beetle population is mostly underground. 

 

The eggs are oval shaped laid in clusters of 25-50 on the underside of leaf, or up to 800 at the base of the host plant. They are about 0.7 mm long and 0.5 mm wide. Freshly laid eggs are completely dependent on soil moisture for their survival. The eggs hatch in about 6-10 days. however it can take up to 30 days with low temperature conditions. The eggs hatch and the larvae dig down and nibble away at the roots of those plants.

 

The larvae start feeding on roots and underground stems. Spotted cucumber beetle larvae feed on roots, stem base, or fruit surface (thus the name "rindworm"). Striped cucumber beetle larvae feed mostly on roots and stems. The larvae of spotted cucumber beetles are not as damaging to cucurbit crops whereas the striped cucumber beetles lay eggs at the base of cucurbit plants and their larvae then feed on the roots of these plants. Seedlings will most likely die whereas a plant with established root system can survive if the infestation isn't too server.

 

The larvae feed for roughly three weeks before they pupate. The larvae require seven days for development of first instar, five days for development of second instar, and four days for development of third instar. During the third instar, the larva constructs a small chamber in the soil and pupates within that chamber.

 

Larvae pupate in the soil for 6-10 days before emerging as adult beetles. Pupae are white initially, but turn yellowish with age and start looking like adults.

 

After the larvae pupate in the soil, they emerge later in the summer as adults.  The adults return to cucurbit/host plants and feed on the foliage later in the summer.

 

In early July, the first summer generation matures and begin to emerge from the soil. The beetle population rises and eventually peaks in mid-August. The emergence of the first summer generation is marked by a return by the beetle population to a normal (1;1) sex ratio.   Beetle populations tend to be relatively high from August through October, when the second summer generation emerges from the soil, the cycle repeats. This population overwinters and reemerges the following spring.

 

A complete life cycle takes about 40 to 63 days for this insect to go from an egg to an adult. Up to four generations can be produced in a single growing season depending where in the U.S you are. For example in Minnesota, the Striped cucumber beetles overwinter as adults whereas the spotted cucumber beetles do not overwinter. In the southern regions, up to three generations of striped cucumber beetles can be produced in one growing season. Two generations has been reported in Oregon peeking in late July and in October, and three in southern California and Alabama.

 

 

What to do: For preventative use

 

 

Select resistant varieties whenever possible.

 

Inspect plants frequently for beetles and handpick any that are discovered. Knock beetles to the ground and catch them with a piece of cardboard placed under the plant. Or, use a handheld vacuum to suck up the beetles. They are very hard to hand pick, but it is easier to hand pick them with yellow gloves coated in petroleum jelly.

 

Floating row covers are extremely effective when placed on seedlings and left in place until plants are old enough to tolerate beetle damage. Make sure you securely fasten row cover edges to ensure that beetles do not find a place to enter. If you are using these for a veggie garden, you must remove during blossoming time several hours each day to allow for pollination.

 

Yellow sticky traps. For added effect, attach a cotton swab soaked in the oil of clove, cinnamon, cassia, allspice or bay leaf, all of which act as a powerful floral attractant.

 

If you till your garden in the late fall and early spring, this will expose cucumber beetles hiding there to harsh winter conditions and reduce their populations next year.

 

Use trap crops such as Hubbard and buttercup varieties of Cucurbita maxima, and zucchini (C. pepo), are very attractive to cucumber beetles. Trap crops should be planted a week or two earlier than your primary garden on the perimeter of the field in multiple rows if beetle pressure is particularly severe. Once the pests are there, insecticides can be applied to the trap crop only, reducing total insecticide use.

 

Straw mulch can help reduce cucumber beetle problems in at least 3 different ways. First, mulch might directly slow beetle movement from one plant to another. Second, the mulch provides refuge for wolf spiders and other predators from hot and dry conditions, helping predator conservation. Third, the straw mulch is food for springtails and other insects that eat decaying plant material; these decomposers are important non-pest prey for spiders, helping to further build spider numbers.

 

Results of a study in Virginia (Caldwell and Clark, 1998) suggest that metallic-colored plastic mulches repel cucumber beetles, reducing beetle feeding damage and the transmission of bacterial wilt.

Diatomaceous Earth . To us it looks like a fine powder, but to insects its broken glass that cuts them and they lose moisture and die.

Kaolin Clay: it's a protective film to ward off early damage from striped cucumber beetles. A brand of kaolin clay is Surround that comes in a powdered form, which is then mixed with water and sprayed on the seedlings. When the seedlings are planted out in the field, the clay acts as a sticky barrier to hungry cucumber beetles, causing what some call “excessive grooming”. This keeps the beetles busy when they would otherwise be eating your seedlings and searching for mates. When applied to plants, Surround WP (kaolin clay) leaves a fine powdery film that insects find unattractive for feeding and egg-laying

 

Using mulch and drip irrigation helps reduce soil moisture under fruits, reducing beetle feeding as well (Alston and Worwood 2008).

 

Remove garden trash and other debris after you are done working in your garden and shortly after harvest to reduce overwintering sites.

 

Using a combination of companion plants such as radish (Raphanus sativus L.), tansy (Tanacetum vulgare L.), and nasturtium (Tropaeolum spp. L.) and aluminum plastic mulch.

 

Use of row crops like buckwheat (Fagopyrum esculentum Moench), cowpea (Vigna unguiculata (L.), and sweetclover (Melilotus officinalis (L.)) was also effective at controlling cucumber beetle populations by attracting beneficial insects.

 

 

 Insecticides

 

There is no solid evidence that pathogens effectively control adult beetles, but fungal pathogens and predatory nematodes are available commercially to control larvae. Chemical sprays must be directed at the adult beetle.

 

Spinosad, the active ingredient in Monterey Garden Insect Spray is approved for organic use and works on a long list of insects found on vegetable crops.

 

Pyrethrin is a natural pesticide that is extracted from the chrysanthemum flower. While it is natural, it contains neurotoxins that can affect humans and shouldn’t be used in excess.

 

Organic insect soap will work Ok on cucumber beetles but due to their tough outer skin, soap isn't your best option.

 

Neem oil

 

 

Biological control

 

 

Braconid wasps

 

http://freemygreenpdx.com/topic/14456-beneficial-parasitoid-wasp/

 

 

Tachinid flies

 

A tachinid fly and a braconid parasitoid wasp parasitize striped cucumber beetle.

 

 

 

Ground Beetle  (Coleoptera)

 

http://freemygreenpdx.com/topic/14351-beneficial-bug-ground-beetle/

 

 

Green Lacewings/Eggs (Chrysopa rufilabris)

 

http://freemygreenpdx.com/topic/14337-beneficial-bug-green-lacewing-larvaeeggs/

 

 

Ladybugs (Hipodamia convergens)

 

http://freemygreenpdx.com/topic/14338-beneficial-bug-ladybugs/

 

 

Spined soldier bugs (Podisus maculiventris)

 

http://freemygreenpdx.com/topic/14834-beneficial-bug-spined-soldier-bugs/

 

 

above feed on pest eggs.

 

 

Predatory Nematodes (Steinernema/ Heterorhabditis) eat the immature stages developing in the soil.

 

 http://freemygreenpdx.com/topic/14383-beneficial-predatory-nematodes/

 

 

Wolf Spiders

 

harvestmen or "daddy long legs"

 

rove beetles

 

bats

 

Chickens

 

 

 

 

 

 

 

The link below will take you to "An Intro to beneficial bugs and beneficial insect food" it has a list (been worked on) to pests and beneficial insects

 

  http://freemygreenpdx.com/topic/14334-an-intro-to-beneficial-bugs-their-food-and-the-pest-they-take-care-of/


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Cucumber beetles are found throughout North America and they can cause some damage as flea beetles do. They are attracted to Cucumbers vegetables, namely cucumbers, squash, pumpkins, and beans. They not only affect the Cucumbers plant, but also Squash, Zucchini, Pumpkins and Beans plants too. It is very important to take some eco-friendly pesticides that will be only harmful to beetles but to the plants. But, before using any pesticides it is necessary to get some exterminator Brooklyn experts help who will make you assured that your plant will be safe from the pesticides.

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