Guess the Pest! Week 1 Answer: Cabbage White

David Owens, Extension Entomologist, owensd@udel.edu

Congratulations to Joe Streett for correctly identifying last week’s Guess the Pest challenge as cabbage white, also known as the imported cabbageworm. Joe won a heavy duty sweep net for catching the butterflies and will be entered for the end of season raffle along with all others who submitted correct answers. This is one of the early harbingers of spring. I saw my first April 1 and it is now the most common butterfly out. It is a Brassica specialist. Females lay eggs on wild mustard, brassica cover crops like turnip or radish, and cultivated brassicas such as broccoli and cabbage which are being transplanted now. Larvae are green, about an inch long, and fuzzy. They are easiest to find when ‘hiding’ on the leaf’s upper midrib. Pre heading, brassicas can tolerate a good deal of defoliation (30% infested plants), but once heading initiates, thresholds for this and other defoliating worms drop to 5%.

Recent Vegetable Trends

Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu

Vegetable growers that direct market or that target marketing programs to entice buyers should be on the leading edge of food trends.

Food trends are driven by many factors such as health benefits, dietary shifts, public values, celebrity recognition, and customer diversity.

The great thing about food trends is that you, as a grower and marketer, can help to start trends, invent new ways to market your produce, develop tastes in your customer base, and help define new eating habits.

One of my goals as a vegetable specialist located in Delaware is to reinvent one of our most important regional crops, the lima bean, by promoting different specialty types. We have been testing a range of potential specialty lima beans from our breeding program and other diverse sources that have different sizes, shapes and colors for cooking, eating, and taste attributes.

In recent years other vegetable trends have waxed and waned. The word on the street is that kale’s best days are now behind it. However, Brussels sprouts are still going strong, cauliflower is being put into everything, arugula is still hanging in there, and beets are on the upswing (2018 was the year of the beet).

Beets are an interesting study in trendiness. Five years ago, you would see small sections of beets in the fresh, canned, pickled, and frozen sections of the supermarket, maybe 10 selections at most. Now there are beet products in the juice, snack, and health product sections. Why? Because beets are being promoted by the “health” industry as a superfood.

A current question that is being asked by trend analysts is what will replace kale in the “greens” arena. One group that is gaining traction is chard and beet greens. Chard is now being sought by chefs as the new greens item to add menu selections. Other trend followers suggest that “wild” tasting plants will be part of the new trend driven by chefs. This includes sorrel, dandelion, an amaranth.

There are dozens of types of dandelions from the common weed to cultivated types. All parts of the weedy dandelion can be used as food and as a medicinal. Dandelion greens are very nutritious and can be added to salad and soups or cooked as a greens side dish. I expect to see some growers start to provide this as an actual crop. It is also perennial.

Edible amaranth is close relative to pigweed and makes a rich flavored cooked green. It is very easily grown and loves the summer heat. In addition to this new trend, it is a favorite of many immigrants from the Caribbean and Africa.

Sorrel is lemony flavored and there are selections that have been made for specific leaf attributes. It is this flavor that has brought it back to the table. Expect to see it more on plates in the future.

Other interesting trends include:

Vegetable “steaks” – these are vegetables that can be sliced and grilled like steaks (eggplant, squashes, tomatoes). This is a new way to market “old” crops.

Small sizes – small versions of popular vegetables. Snack peppers, snack cucumbers, mini eggplants, mini squashes and much more are becoming more and more popular. This follows the past baby vegetable trend but with new crops.

Color and color blends – Colorful vegetables are very trendy, especially in blends or mixtures. Everything from chard to cauliflower, carrots to peppers.

Fermentable foods – Grow foods for your customers to ferment. Cabbage, Napa, Pak choy, daikon, cucumbers, peppers, and many more.

Ugly produce – Off shapes and types are now sought. An example would be the ugly tomato that has been marketed as such in grocery stores.

Hot Water Treatment of Seeds

Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu

We have had an increase in bacterial diseases of vegetables that are seed transmitted such as black rot of cole crops.

Hot water treatment of seeds is a method to eliminate certain seed borne diseases of vegetable crops. This treatment has the benefit of killing pathogens that may be found on and within the seed coat.

From the Mid Atlantic Commercial Vegetable Production Recommendations:
“Seed heat-treatment follows a strict time and temperature protocol, and is best done with thermostatically controlled water baths. Two baths are required: one for pre-heating and a second for the effective pathogen killing temperature. The initial pre-heat treatment is 10 minutes at 100ºF (38ºC). The effective temperature treatment and time in the second bath differ between crops; protocols for several important crops are listed in Table E-10. Immediately after removal from the second bath, seeds should be rinsed with cool water to stop the heating process and dried on screen or paper. Seeds may be re-dusted with fungicide if desired. Pelleted seed is not recommended for heat treatment. Heat treat only seed that will be used during the current season. See crop sections for specific seed treatment recommendations.”

List of seeds that can be treated, treatment times and temperatures, and diseases controlled can be found at https://ag.umass.edu/vegetable/news/hot-water-treatment-of-seeds

The University of Delaware Extension Vegetable program has the equipment to hot water treat seeds. Please contact Gordon Johnson gcjohn@udel.edu or Emmalea Ernest emmalea@udel.edu to arrange to hot water treat seeds.

Cabbage Maggots are Out and About

Jerry Brust, IPM Vegetable Specialist, University of Maryland; jbrust@umd.edu

The unceasing wet weather we have had this summer has made some fall planted cole crop fields vulnerable to cabbage maggots, Delia radicum (CM). The flies that are attacking cole and radish fields now are most probably 4th generation CM. We usually see some damage from this late generation of flies in our area, but it is usually scattered around. This year it is much more pervasive throughout the area. This widespread damage is due to how wet it has been, which has a dramatic cooling effect on the soil, CM larvae are better able to survive in the wet, cooler soils vs the drier hotter soils that we normally have in the summer and early fall. Adult flies are most active from 10 am to 2 pm and are inactive at night, in strong winds and when temperatures are below 50°F or above 80°F. Female cabbage maggot flies seek out and lay eggs on the lower portions of stems of young host seedlings or in nearby cracks in the soil. Within a few days the eggs hatch and the tiny maggots burrow down to the roots or bulb (radish and turnip) and begin feeding. The maggots usually feed for 2 to 3 weeks before pupating in the soil. Most of these pupae will overwinter in the soil, so it is important to be sure to rotate any cole crops out of the fall planted area for spring planting. A Diazinon, Lorsban or Verimark soil application pre- or at-planting will help reduce CM problems. Using row-cover over the newly planted seed would also control CM. Once damage is found in radish or turnip bulbs there is no rescue treatment.

Figure 1. Turnip with feeding damage

Heat and Moisture Effects on Cole Crops

Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu

September-maturing cole crops have been negatively affected by the high August and September temperatures and uneven moisture (dry to wet). While cabbage, kale, and collards can tolerate high temperatures; Brussels sprouts, broccoli, and cauliflower are more sensitive to excess heat. These three crops do best under moderate and even temperatures and even water supplies. They do not develop properly when temperatures are in the 90s.

In broccoli, high temperatures can lead to uneven development of the crown leading to a bumpy appearance and looser head. This reduces the grade and price potential. In Brussels sprouts high temperatures can caused sprouts to be very loose, elongated and unmarketable. In cauliflower high heat can cause loose curd.

The following are some other disorders that can be prevalent when cole crops are exposed to uneven moisture and excessive heat.

Tipburn of Cauliflower, Cabbage, and Brussels Sprouts
This problem can cause severe economic losses. Tipburn is a breakdown of plant tissue inside the head of cabbage, individual sprouts in Brussels sprouts, and on the inner wrapper leaves of cauliflower. It is a physiological disorder which is associated with an inadequate supply of calcium in the affected leaves, causing a collapse of the tissue and death of the cells. Calcium deficiency may occur where the soil calcium is low or where there is an imbalance of nutrients in the soil along with certain weather conditions. (High humidity, low soil moisture, high potash and high nitrogen aggravate calcium availability). Secondary rot caused by bacteria can follow tipburn and heads of cauliflower can be severely affected. Some cabbage and cauliflower cultivars are relatively free of tipburn problems.

Cabbage Splitting
Cabbage splitting can develop when moisture stress is followed by heavy rain. The rapid growth rate associated with rain, high temperatures and high fertility cause the splitting. Proper irrigation may help prevent splitting and there are significant differences between cultivars in their susceptibility to this problem.

Lack of Heads in Broccoli and Cauliflower
During periods of extremely warm weather (days over 86°F and nights over 77°F) broccoli and cauliflower can remain vegetative since they do not receive enough cold for head formation. This can cause a problem in scheduling the marketing of even volumes of crop.

Cauliflower Purple Coloring and Yellowing
The market demands cauliflower which is pure white or pale cream in color. Heads exposed to sunlight develop a yellow and/or red to purple pigment. Certain varieties are more susceptible to purple off-colors, especially in hot weather. Self-blanching varieties have been developed to reduce problems with curd yellowing. For open headed varieties, the usual method to exclude light is to tie the outer leaves when the curd is 8 cm in diameter. Leaves may also be broken over the curd to prevent yellowing. In hot weather blanching may take 3 to 4 days, but in cool weather, 8 to 12 days or more may be required. Cauliflower fields scheduled to mature in cool weather (September and October) that are well supplied with water and planted with “self-blanching” cultivars will not need tying. Newer orange cauliflower and green broccoflower varieties are being planted. They are less susceptible to off-colors but still can develop purpling under warm conditions.

Cauliflower Ricing
“Riciness” and “fuzziness” in cauliflower heads is caused by high temperatures, exposure to direct sun, too rapid growth after the head is formed, high humidity, or high nitrogen. “Ricing” is where the flower buds develop, elongate and separate, making the curd unmarketable.

Development of Curd Bracts in Cauliflower
Curd bracts or small green leaves between the segments of the curd in cauliflower is caused by too high of temperature or drought. High temperatures cause a reversion to vegetative growth with production of bracts on the head. In a marketable cauliflower head, the individual flower buds are undeveloped and undifferentiated.

Calcium and Boron Deficiencies in Brassica Crops

Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu

Calcium Deficiency
Calcium deficiency is most commonly seen as tipburn of cauliflower, cabbage, and Brussels sprouts. Chinese cabbage (Napa cabbage) is also susceptible to tipburn. This problem can cause severe economic losses. Tipburn is a breakdown of plant tissue inside the head of cabbage and Chinese cabbage, individual sprouts in Brussels sprouts, and on the inner wrapper leaves of cauliflower. It is a physiological disorder which is associated with an inadequate supply of calcium in the affected leaves, causing a collapse of the tissue and death of the cells. Calcium deficiency may occur where the soil calcium is low or where there is an imbalance of nutrients in the soil along with certain weather and soil nutrient conditions, such as high humidity, low soil moisture, high potash or high nitrogen all of which can reduce calcium availability. Secondary rot caused by bacteria can follow tipburn and heads of cauliflower can be severely affected. Some cabbage and cauliflower cultivars are relatively free of tipburn problems. Green cabbage varieties with good resistance to tipburn include Blue Vantage, Bobcat, Cecile, Emblem, Padok, Platinum Dynasty, Quick Start, Royal Vantage, Solid Blue 780, Superstar, Thunderhead, Vantage Point and Viceroy. Red cabbage is less susceptible to tipburn. Check with your seed supplier for tipburn ratings for other varieties.

Controlling tipburn starts with managing liming so that soil pH is above 6.0. Limit ammonium forms of nitrogen, and ensure an adequate and even supply of water. Adjust planting date so that head maturation occurs during cooler temperatures. Plant a cultivar that is less susceptible to the disorder. In general, calcium foliar sprays have not been shown to be effective for controlling tipburn incidence.

Severe tipburn in cabbage. Photo credit David B. Langston, University of Georgia, Bugwood.org

Boron Deficiency
Cole crops have a high boron requirement. Symptoms of boron deficiency vary with the cole crop. Cabbage heads may simply be small and yellow. Most cole crops develop cracked and corky stems, petioles and midribs. The stems of broccoli, cabbage and cauliflower can be hollow and are sometimes discolored. Cauliflower curds become brown and leaves may roll and curl. It is important to note that cole crops are also sensitive to boron toxicity if boron is over-applied. Toxicity symptoms appear as scorching on the margins of older leaves.

It is recommended in broccoli and kale to apply 1.5-3 pounds of boron (B) per acre in mixed fertilizer prior to planting. In Brussels sprouts, cabbage, collards and cauliflower, boron and molybdenum are recommended. Apply 1.5-3 pounds of boron (B) per acre and 0.2 pound molybdenum (Mo) applied as 0.5 pound sodium molybdate per acre with broadcast fertilizer. Boron may also be applied as a foliar treatment to cole crops if soil applications were not made. The recommended rate is 0.2-0.3 lb/acre of actual boron (1.0 to 1.5 lbs of Solubor 20.5%) in sufficient water (30 or more gallons) for coverage. Apply foliar boron prior to heading of cole crops.

Boron deficiency in broccoli causing hollow stem. Photo credit Gerald Holmes, California Polytechnic State University at San Luis Obispo, Bugwood.org

New Technology for Reducing Transplant Shock

Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu

A new tool is available for reducing transplant shock. The chemical 1-methylcyclopropene (1-MCP) which is marketed as the product LandSpring by the AgroFresh company reduces ethylene production and stress on young plants. Ethylene in the plant hormone released when plants are injured or are under stress, as is common during transplanting. Excess ethylene can cause leaf drop and wilting and can increase transplant losses. The way 1-MCP works is that it has a similar molecular structure to ethylene but without the negative effects on the plant. It binds to ethylene receptors in the plant and thus blocks ethylene from causing damage.

LandSpring is labelled on broccoli, brussel sprouts, cabbage, cantaloupe, cauliflower, cucumber, eggplant, muskmelon, bell pepper, nonbell pepper, summer squash, tomato and watermelon. According to the company “When applied to seedlings 1-5 days before transplanting, LandSpring WP helps decrease transplant shock enabling plants to more rapidly establish and grow. Observed benefits include increased crop biomass due to better root and shoot development when plants are subjected to stress.in the weeks following transplantation”.

The label can be found at this site: https://agrofresh.octochemstore.com/wp-content/uploads/2017/04/LandSpring-_epa-approved-seedling-label.pdf

More information can be found at: http://www.landspring.info/

Timings for Late Summer and Fall Harvested Vegetables Revisited

Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu

Plantings for fall harvested vegetables are underway and will continue through August. Timing these plantings can be a challenge, especially where multiple harvests are needed. Plantings from early July through the beginning of September may be made, with cutoff dates depending on the crop, variety, and season extension methods such as row covers, low tunnels, and high tunnels.

These plantings can be divided into 2 groups: 1) warm season vegetables for harvest up to a killing frost and 2) cool season vegetables for extended harvest in the fall.

The three main factors influencing crop growth and performance in the fall are daylength, heat units, and frost or freeze events. A few days difference in planting date in the summer can make a big difference in days to maturity in the fall.

Warm season vegetables for fall harvest include snap beans, squash, and cucumbers. July plantings of sweet corn can also be successful to extend seasons for farm stands. Mid-July plantings of tomatoes and peppers also are made for late harvests, particularly in high tunnels.

Cool season vegetables for fall harvest include cabbage, broccoli, and cauliflower; the cole crop greens, kale and collards; mustard and turnip greens; turnips for roots; spinach; beets; lettuce; leeks; green onions; and radishes.

To extend harvest in the fall, successive plantings are an option. However, days between plantings will need to be compressed. One day difference in early August planting for a crop like beans can mean a difference of several days in harvest date.

Another option to extend harvest in the fall is by planting varieties that have different days to maturity at the same time. This is particularly successful with crops such as broccoli and cabbage where maturity differences of more than 30 days can be found between varieties.

Another way to get later harvests is to use row covers or protecting structures (high tunnels). This can allow for more heat accumulation and will aid with protection against frost and freezes. Decisions on what type or combination of covers/protection to use and when to apply the protection will influence fall vegetable maturation and duration of harvest. In general, plantings of cool season crops can be made 30-45 days later in high tunnels than in outside production.

A final factor for summer planting for fall production is on planting cutoff dates. For example, a crop such as cucumber may produce well with an August 2 planting but poorly with an August 8 planting; broccoli has a wider planting window than cauliflower; turnip greens have a wider planting window than kale.

Planting Window for Fall Harvested Warm Season Vegetables
(harvest September through Frost)

Snap Beans: July 10 through August 10

Lima Beans: June 15 through July 20

Cucumbers: July 10 through August 7 (high tunnel transplanted up to September 1)

Peppers: Transplant up to July 10 (high tunnel up to July 30)

Pumpkins and Winter Squash: Direct seed through June 30, transplant up to July 7

Summer Squash: Direct seed July 15 through August 15 (high tunnel up to September 1)

Sweet Corn: Direct seed July 1 through July 30

Tomatoes: Transplant up to July 10 (high tunnel up to July 30)

Planting Window for Fall Harvested Cool Season Vegetables
(harvest September – December)
For transplants, seed 3-6 weeks prior to desired planting date (8 weeks for leeks and onions).

Beets: Direct seed July 1 through August 10

Swiss Chard: Direct seed July 15 through August 20 (high tunnel up to September 30)

Broccoli: Transplants July 15 – August 20

Brussels Sprouts: Transplants through July 10

Cabbage: Transplants July 1 – August 10

Cauliflower: Transplants July 20 through August 15

Kale: Transplants July 15 through August 30

Kale: Direct seed July 1 through August 15 (high tunnel up to September 30)

Collards: Direct seed July 15 through August 15

Carrots: Direct seed through July 10 (high tunnel up to August 30)

Turnip Greens: August 1 through September 10 (high tunnel up to September 30)

Turnip Roots: August 1 through August 30 (high tunnel up to September 20)

Mustard Greens: August 1 through September 10 (high tunnel up to September 30)

Leeks: Transplant July 20 through August 10

Lettuce (full head stage): Direct seeded August 1 through August 20

Lettuce (full head stage): Transplants August 10 through August 30

Lettuce (baby stage and cut salad mix): Direct seed August 1 through September 15 (high tunnel up to October 15)

Onion (green bunching): Direct seed July 1 through August 30 (high tunnel through September 30)

Parsley: direct seed July 15 through August 15 (high tunnel through September 15)

Radishes (salad): Direct seed August 1 through September 30 (high tunnel through November 30)

Radishes (Daikon): Direct seed August 1 through September 10 (high tunnel up to September 30)

Spinach: Direct seed August 10 through August 30 (high tunnel up to September

Cole Crops Affected by Heat, Uneven Moisture

Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu

September-maturing cole crops have been negatively affected by the high August and September temperatures and uneven moisture (dry to wet). While cabbage, kale, and collards can tolerate high temperatures; Brussels sprouts, broccoli, and cauliflower are more sensitive to excess heat. These three crops do best under moderate and even temperatures and even water supplies. They do not develop properly when temperatures are in the 90s.

In broccoli, we are seeing knuckling, that is the uneven development of the crown leading to a bumpy appearance and looser head. This reduces the grade and price potential. In Brussels sprouts high temperatures have caused sprouts to be very loose, elongated and unmarketable. In cauliflower we are finding ricing, purpling, and loose curd.

The following are some other disorders that can be prevalent when cole crops are exposed to uneven moisture and excessive heat.

Tipburn of Cauliflower, Cabbage, and Brussels Sprouts
This problem can cause severe economic losses. Tipburn is a breakdown of plant tissue inside the head of cabbage, individual sprouts in Brussels sprouts, and on the inner wrapper leaves of cauliflower. It is a physiological disorder which is associated with an inadequate supply of calcium in the affected leaves, causing a collapse of the tissue and death of the cells. Calcium deficiency may occur where the soil calcium is low or where there is an imbalance of nutrients in the soil along with certain weather conditions. (High humidity, low soil moisture, high potash and high nitrogen aggravate calcium availability). Secondary rot caused by bacteria can follow tipburn and heads of cauliflower can be severely affected. Some cabbage and cauliflower cultivars are relatively free of tipburn problems.

Cabbage Splitting
Cabbage splitting can develop when moisture stress is followed by heavy rain. The rapid growth rate associated with rain, high temperatures and high fertility cause the splitting. Proper irrigation may help prevent splitting and there are significant differences between cultivars in their susceptibility to this problem.

Lack of Heads in Broccoli and Cauliflower
During periods of extremely warm weather (days over 86°F and nights 77°F) broccoli and cauliflower can remain vegetative (does not head) since they do not receive enough cold for head formation. This can cause a problem in scheduling the marketing of even volumes of crop.

Cauliflower Purpling
The market demands cauliflower which is pure white or pale cream in color. Heads exposed to sunlight develop a yellow and/or red to purple pigment. Certain varieties such as Snow Crown are more susceptible to purple off-colors, especially in hot weather. Self-blanching varieties have been developed to reduce problems with curd yellowing. For open headed varieties, the usual method to exclude light is to tie the outer leaves when the curd is 8 cm in diameter. Leaves may also be broken over the curd to prevent yellowing. In hot weather blanching may take 3 to 4 days, but in cool weather, 8 to 12 days or more may be required. Cauliflower fields scheduled to mature in cool weather (September and October) that are well supplied with water and planted with “self-blanching” cultivars will not need tying. Newer orange cauliflower and green broccoflower varieties are being planted. They are less susceptible to off-colors but still can develop purpling under warm conditions.

colecrop6

Purpling in cauliflower

Cauliflower Ricing
“Riciness” and “fuzziness” in cauliflower heads is caused by high temperatures, exposure to direct sun, too rapid growth after the head is formed, high humidity, or high nitrogen. “Ricing” is where the flower buds develop, elongate and separate, making the curd unmarketable.

colecrop3

“Riciness” in cauliflower

colecrop4

“Fuzziness” in cauliflower

Development of Curd Bracts in Cauliflower
Curd bracts or small green leaves between the segments of the curd in cauliflower is caused by too high of temperature or drought. High temperatures cause a reversion to vegetative growth with production of bracts on the head. In a marketable cauliflower head, the individual flower buds are undeveloped and undifferentiated.

Loose Heads in Cauliflower, Loose Sprouts in Brussels sprouts and Premature Flowering or Knuckling in Broccoli
Loosely formed curds in cauliflower can be due to any stress that slows growth making them small or open. Fluctuating temperatures and moisture will also cause less compact growth. In contrast, excess vegetative growth caused by excessive nitrogen can also cause loose heads in cauliflower and broccoli. Knuckling in broccoli is uneven growth in the crown leading to a bumpy appearance. Premature flowering and open heads in broccoli can be brought on by high temperatures. High temperatures can cause loose sprouts in Brussels sprouts.

colecrop2

Knuckling, loose heads and discoloration in broccoli

Harlequin Bugs and Blister Beetles Damaging Late Summer Vegetables

Jerry Brust, IPM Vegetable Specialist, University of Maryland; jbrust@umd.edu

This has been a tough growing season for most of our vegetable crops. Some crops were planted late and had problems setting fruit later on in the summer heat while others that were planted on time were 2-3 weeks ahead of harvest schedule. Some crops have done OK and a few have done well, but most others have suffered due to the weather. Late summer/early fall crops are not fairing much better. I have received several reports of mysterious feeding on plantings of tomatoes and carrots, and reports of damage by pests that were easily seen, because there were so many of them. In many of the cases it was probably two common late summer pests: the blister beetle and Harlequin bugs.

Blister Beetles (family Meloidae)
Blister beetles are commonly seen in fields starting in late June going through the fall. There seems to be a great deal of them this year feeding on just about every new and even old vegetable planting. Adult blister beetles vary in color and size. Most are one-half to one inch long with long, soft bodies and wide heads. The area between the head and the body is narrow and looks like a neck. The wing covers are leathery with the abdomen often times extending beyond the end of the wings (Fig. 1). The legs are relatively long for the body size. The beetles come in a variety of dark or bright colors that are variegated, striped or flat. Striped blister beetles are shades of gray and brown with yellow stripes running lengthwise on its wing covers. Others are gray to black with a gray or white margin around each wing (Fig. 1).

Adults begin laying eggs in the spring and continue through most of the season. Females will lay one to two hundred very small eggs just beneath the soil surface. White larvae hatch from these eggs in about two weeks and have relatively long legs which they use to find their main prey–grasshopper eggs (so the larvae are beneficial, while the adults are a pain). Most larvae will go through 4-5 instars but some go through 6-7. Adults emerge from the pupae stage after ten days.

If you look up blister beetles most of the literature deals with the beetles as a threat to horses and livestock. The beetles secrete and contain within them a blistering chemical called catharidin. Catharidin is toxic if ingested and it persists in dead beetles long after the hay they infested was dried and baled. Horses are particularly susceptible to the poisoning. Humans who ingest the beetle can suffer severe damage to the urinary tract and gastrointestinal lining.

Blister beetles will feed on just about any plant: tomato, potato, eggplant, peppers and other solanaceous vegetables as well leafy greens. Often times in late summer, they arrive in swarms, seemingly overnight and can feed heavily on plants and then just as suddenly disappear — often leaving growers perplexed as to what came in and did the feeding damage. A beetle will feed for a time and then usually move on to another spot not causing a great deal of damage unless there are a significant number of them or they stay in one place for an extended period of time. Covering plants with a row cover or with kaolin clay (product called Surround) BEFORE the beetles start to feed has worked pretty well, but the row cover or clay must be applied before they start to feed. If applied after they are found feeding it is not as effective. Pyrethroids also will work well if beetles are directly contacted.

BlisterBeetle

Figure 1. Two adult Margined blister beetles Epicauta funebris

Harlequin Bugs (Murgantia histrionica)
Adult harlequin bugs are red- or orange-and-black-spotted bugs about 3/8 of an inch long, with flat, shield-shaped bodies (Fig. 2). Nymphs are similar in general color and shape to the adults (Fig. 3). The eggs of harlequin bugs are distinctive and look like no other stink bug eggs—or anything else. The eggs look like tiny white barrels standing on end, typically in a double row (Fig. 4). Twelve to eighteen eggs are usually laid together in one batch on the underside of the leaves of the host plant. Each egg is marked by two broad black stripes near the ends of the “barrel” (egg) with one black spot in the middle of the egg and a black mark on top of each egg. Harlequin bugs over winter as adults (rarely large nymphs) in old cabbage stalks or any other crop debris.

HarlequinBug1

Figure 2. Harlequin bug adult

HarlequinBug2

Figure 3. Harlequin bug nymph and damage-white spots

Plants commonly attacked by harlequin bugs include crucifers such as horseradish, cabbage, forage radish, collards, mustard, Brussels sprouts, turnip, kohlrabi and radish. If these are not available hungry bugs will feed on tomato, potato, eggplant, okra, bean, asparagus, beet, weeds, and even fruit trees and field crops. The harlequin bug feeds by injecting salivary secretions into plants that liquefy plant tissue so they can ingest it. This feeding at first results in white spots (Fig. 3) and then progresses to browning, wilting and eventual death of the plant. New plantings of crucifers can be heavily attacked in the spring but more commonly in the fall and this is what I have heard about and seen happening in several areas of Maryland. As with blister beetles, harlequin bugs can be managed by using a row cover or kaolin clay BEFORE they show up and start feeding. Once they start feeding these two controls do not work very well. Pyrethroids will reduce the damage, but there is often a 7-day pre-harvest interval (phi) with many of the chemicals depending on what the crop is. So be sure to check the label to find the correct phi for the product you are using on the particular crucifer you are using it on.

HarlequinBugEggs

Figure 4. Harlequin bug eggs