Posts Tagged ‘pepper’

Stip Disorder in Peppers

Friday, September 7th, 2012

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

As fall approaches and late pepper crops mature, pepper stip disorder can be a problem in bell, pimento, and elongated peppers (chilies, bananas, sweet frying types) causing them to be unmarketable. It is particularly a problem on peppers taken to ripe stage such as red bells, but can also be an issue on green immature fruit. Pepper stip, also called color spotting or black spotting, is a physiological disorder of pepper fruit. It causes gray, brown, black, or green spots that are slightly sunken and are ¼ inch or smaller in diameter. Spots may be single or in groups and can resemble damage from stink bugs. Microscopic examination of affected areas shows dead collapsed cells with no evidence of cell puncture or insect damage. It is primarily a fall disorder and occurs most often when temperatures drop into the 40s and 30s. It can also occur after peppers are moved into cold storage. This is similar to what is seen with blossom end rot, only the affected areas are isolated and can occur throughout the fruit, not just on the ends.

The exact cause of stip is not known; however, it is thought to be a nutrient imbalance involving lower calcium (Ca) in fruit and high levels of nitrogen (N) and potassium (K). Research has shown that stip was most common in fields with low soil calcium or low pH and in fields with very high N and K fertilization.

Pepper varieties vary considerably in their susceptibility to stip. Research has shown that resistant cultivars consistently had lower N and K, and higher Ca concentrations than susceptible cultivars in leaf or fruit tissue samples. In 2011 red bell pepper variety trials conducted in New Jersey by Rutgers University, it was found that Camelot, Paladin, Classic, Patriot and Vanguard all were susceptible to stip. Additional trials are underway this fall.

In late summer and fall, there is reduced transpiration, and Ca movement in the fruit can be reduced. Excess N can cause rapid growth and extra foliage further limiting fruit transpiration and excess K can compete with Ca for plant uptake and cation exchange in the fruit.

Managing stip starts with using resistant varieties for fall production. Maintain high soil calcium levels and reduce nitrogen and potassium in fall production. Additional calcium through the drip system may help reduce stip. Foliar calcium applications have shown little or no effect on reducing stip.

 

Brown Marmorated Stink Bug in Peppers

Friday, August 31st, 2012

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

There has been a large and rapid increase in brown marmorated stink bug (BMSB) in some pepper fields in the past week in central Maryland. Numbers just two weeks ago in these areas were very low with just a few nymphs observed. We know that BMSB populations tend to increase in August and through the fall into the first frost, but this was such a rapid increase that a great deal of damage was done to bell and banana peppers.

These peppers had been treated with chlorantraniliprole (Coragen) and this took care of any worm problems very well, but the growers did not think stink bug. There were 8-10 nymphs and 2-3 adult BMSBs per plant in these fields. Damage to peppers as you might guess was extensive (Fig. 1). Much of the feeding appeared to be done by nymphs (Fig. 2). BMSB nymphs have a white stripe on all six of their legs, which is unique compared with our most common native stink bug species. This white stripe fades when nymphs become adults.

Besides the white ‘cloudy spots’ on fruit, many peppers had dark brown and red as well as bright white areas (Fig. 1). These bright white areas were found to have yeast growing within the wound that from previous studies we learned has been injected by the BMSB when it feeds.

One odd thing from the BMSB outbreak was that tomato fields that were next to or very close to the pepper fields had almost no BMSBs in them. Whether this would have changed soon we are not sure as the growers did not take any chances and treated.

 Figure 1. BMSB damage to bell and banana pepper, brown spot (yellow arrow) and bright white areas (green arrows)

Figure 2. BMSB nymphs feeding on pepper

Hot Year Means More Blossom End Rot

Friday, July 20th, 2012

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

Blossom end rot (BER) is showing up again this year in peppers and tomatoes. BER is a disorder where developing fruits do not have enough calcium for cell walls, cells do not form properly, and the fruit tissue at the blossom end collapses, turning dark in color. Calcium moves through cation exchange with water movement in the fruit, so the end of the fruit will be the last to accumulate calcium. Larger fruits and longer fruits are most susceptible. With fruits, the rapid cell division phase occurs early in the development of the fruit and if calcium accumulation in the fruit is inadequate during this period, BER may occur. While it may not be noticed until the fruit expands, the deficiency has already occurred and cells have already been negatively affected. We most commonly see signs of blossom end rot on fruits many days after the calcium deficiency has occurred.

Understanding blossom end rot also requires an understanding of how calcium moves from the soil into and through the plant. Calcium moves from the soil exchange sites into soil water and to plant roots by diffusion and mass flow. At plant roots, the calcium moves into the xylem (water conducting vessels), mostly from the area right behind root tips. In the xylem, calcium moves with the transpirational flow, the movement of water from roots, up the xylem, and out the leave through stomata. Calcium is taken up by the plant as a divalent cation, which means it has a charge of +2. It is attracted to negatively charged areas on the wall of the xylem, and for calcium to move, it must be exchanged off the xylem wall by other positively charged cations such as magnesium (Mg++), potassium (K+), ammonium (NH4+), or additional calcium cations (Ca++). This cation exchange of calcium in the xylem requires continuous movement of water into and up through the plant. It also requires a continuous supply of calcium from the soil.

In general, most soils have sufficient calcium to support proper plant growth. While proper liming will insure there is adequate calcium, it is not the lack of calcium in the soil that causes blossom end rot in most cases. It is the inadequate movement of calcium into plants that is the common culprit. Anything that impacts root activity or effectiveness will limit calcium uptake. This would include dry soils, saturated soils (low oxygen limits root function), compaction, root pathogens, or root insect damage. In hot weather on black plastic mulch, roots can also be affected by high bed temperatures. Low pH can also be a contributing factor. Calcium availability decreases as pH drops, and below a pH of 5.2 free aluminum is released, directly interfering with calcium uptake. Again, proper liming will insure that this does not occur. Applying additional calcium as a soil amendment, above what is needed by normal liming, will not reduce blossom end rot.

In the plant, there is a “competition” for calcium by various plant parts that require calcium such as newly forming leaves and newly forming fruits. Those areas that transpire the most will receive more calcium. In general, fruits have much lower transpiration than leaves. In hot weather, transpiration increases through the leaves and fruits receive lower amounts of calcium. High humidity will reduce calcium movement into the fruit even more. Tissue tests will often show adequate levels of calcium in leaf samples; however, fruits may not be receiving adequate calcium. In addition, in hot weather, there is an increased risk of interruptions in water uptake, evidenced by plant wilting, when transpirational demand exceeds water uptake. When plants wilt, calcium uptake will be severely restricted. Therefore, excess heat and interruptions in the supply of water (inadequate irrigation and/or rainfall) will have a large impact on the potential for blossom end rot to occur. Proper irrigation is therefore critical to manage blossom end rot.

As a positive cation, there is “competition” for uptake of calcium with other positive cations. Therefore, if potassium, ammonium, or magnesium levels are too high in relation to calcium, they can reduce calcium uptake. To manage this, do not over-fertilize with potassium or magnesium and replace ammonium or urea sources of nitrogen with nitrate sources.

Applying additional soluble calcium through irrigation, especially drip systems, can reduce blossom end rot to some degree if applied prior to and through heat events and if irrigation is applied evenly in adequate amounts. Foliar applications are much less effective because fruits do not absorb much calcium, especially once a waxy layer has developed, and calcium will not move from leaves into the fruit (there is little or no phloem transport).

In conclusion, the keys to controlling blossom end rot are making sure roots are actively growing and root systems are not compromised, soil pH is in the proper range, and irrigation is supplied in an even manner so that calcium uptake is not interrupted. Supplemental calcium fertilization will only marginally reduce blossom end rot if water is not managed properly.

Another calcium disorder that is found in peppers is called “stip”. These spots on peppers occur later in the year, commonly in the late summer or fall, during cool, humid conditions. Under these conditions, calcium movement into the fruit is uneven, leading to localized collapse of cells, causing the spotting. Again, making sure adequate calcium is moving in the plant is critical to control stip.

Sunburn in Fruits and Fruiting Vegetables

Friday, July 6th, 2012

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

High temperatures, clear skies and high light radiation, and long daylengths are a recipe for developing sunburn in fruits and fruiting vegetables. We commonly see sunburn in watermelons, tomatoes, peppers, eggplants, cucumbers, apples, strawberries, and brambles (raspberries and blackberries).

There are three types of sunburn which may have effects on the fruit. The first, sunburn necrosis, is where skin, peel, or fruit tissue dies on the sun exposed side of the fruit. Cell membrane integrity is lost in this type of sunburn and cells start leaking their contents. The critical fruit tissue temperature for sunburn necrosis varies with type of fruit. For cucumbers research has shown that the fruit skin temperature threshold for sunburn necrosis is 100 to 104°F; for peppers, the threshold is 105 to 108°F, and for apples the critical fruit skin temperature is 125-127 °F. Fruits with sunburn necrosis are not marketable.

The second type of sunburn injury is sunburn browning. This sunburn does not cause tissue death but does cause loss of pigmentation resulting in a yellow, bronze, or brown spot on the sun exposed side of the fruit. Cells remain alive, cell membranes retain their integrity, cells do not leak, but pigments such as chlorophyll, carotenes, and xanthophylls are denatured or destroyed. This type of sunburn browning occurs at a temperature about 5°F lower than sunburn necrosis (115 to 120° F in apples). Light is required for sunburn browning. Fruits may be marketable but will be a lower grade.

The third type of sunburn is photooxidative sunburn. This is where shaded fruit are suddenly exposed to sunlight as might occur with late pruning, after storms where leaf cover is suddenly lost, or when vines are turned in drive rows. In this type of sunburn, the fruits will become photobleached by the excess light because the fruit is not acclimatized to high light levels, and fruit tissue will die. This bleaching will occur at much lower fruit temperatures than the other types of sunburn.

Genetics also play a role in sunburn and some varieties are more susceptible to sunburn. Varieties with darker colored fruit, those with more open canopies, and those with more open fruit clusters have higher risk of sunburn. Some varieties have other genetic properties that predispose them to sunburn, for example, some blackberries are more susceptible to fruit damage from UV light.

Control of sunburn in fruits starts with developing good leaf cover in the canopy to shade the fruit. Fruits most susceptible to sunburn will be those that are most exposed, especially those that are not shaded in the afternoon. Anything that reduces canopy cover will increase sunburn, such as foliar diseases, wilting due to inadequate irrigation, and excessive or late pruning. Physiological leaf roll, common in some solanaceous crops such as tomato, can also increase sunburn.

In crops with large percentages of exposed fruits at risk of sunburn, fruits can be protected by artificial shading using shade cloth (10-30% shade). However, this is not practical for large acreages. For sunburn protection at a field scale, use of film spray-on materials can reduce or eliminate sunburn. Many of these materials are Kaolin clay based and leave a white particle film on the fruit (such as Surround, Screen Duo, and many others). There are also film products that protect fruits from sunburn but do not leave a white residue, such as Raynox. Apply these materials at the manufacturer’s rates for sunburn protection. They may have to be reapplied after heavy rains or multiple overhead irrigation events.

Early Season Pythium and Phytophthora Control in Pepper and Tomato Crops

Thursday, April 19th, 2012

Andy Wyenandt, Specialist in Vegetable Pathology, Rutgers University; wyenandt@aesop.rutgers.edu

With the dry spring we’ve had thus far, it’s easy to forget about Pythium and Phytophthora! The same question always comes up about this time of year when growers begin to start thinking about transplanting their tomato and pepper crops. “What should I do to help prevent Pythium and Phytophthora?”. In years past, the answer was simple, apply mefenoxam (Ridomil Gold SL, Ultra Flourish, 4) or metalaxyl (MetaStar, 4). Problem solved, right? In the past, that answer was right, but with resistance development in Phytophthora (P. capsici) to both mefenoxam and metalaxyl, the correct answer isn’t so simple anymore. It’s important to remember that both chemistries will work very well as long as resistance hasn’t been detected on your farm.

How do you know if you have resistance? The easiest way is to follow efficacy. If the chemistries no longer provide the control they once did, then there is a good chance you have mefenoxam-insensitive Phytophthora populations present on your farm. There are also lab services which test for resistance. Remember, once resistance develops it can linger around for a very long time. Therefore, proper crop rotation and resistance management is critical before resistance has the chance to develop.

Our options for pre-transplant applications include a Ranman (cyazofamid, 21) drench one week before transplanting for Pythium in tomatoes as well as Previcur Flex (propamocarb HCL, 28) for the suppression of Pythium and Phytopthora in tomatoes and peppers. Phosphite fungicides, such as ProPhyt and K-Phite (FRAC code 33) can also be applied as a pre-transplant drench in the greenhouse. Additionally, there are a number of biologicals such as Trichoderma, Streptomyces, and Bacillus products which can also be used in the greenhouse to help suppress soil-borne pathogens. Remember, the biologicals need to be applied without conventional fungicides.

At transplanting applications now include Ranman (cyazofamid, 21) in the transplant water or through drip irrigation for Pythium control. There is a section 2ee for the use of Previcur Flex (propamocarb HCL, 28) + Admire Pro (imidacloprid) in transplanting water for Pythium control. Presidio (fluopicolide, 43) now has a label for drip application for Phytophthora control when conditions are favorable for disease development. Additionally, phosphite fungicides, Pro-Phyt and K-Phite (FRAC code 33) can also be applied through drip irrigation at transplanting to help suppress Phytophthora blight. Unlike in the past, there are a number of good options for early season control of these pathogens, it just takes a little bit more planning ahead of time. For further details on use and crop labeled please refer to the specific fungicide label. Remember the label is the law.

Brown Marmorated Stink Bug Populations This Season

Thursday, July 28th, 2011

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

Brown marmorated stink bug populations were a big concern early this spring (and also all of last year) as their numbers were found to be pretty high in and around fruit orchards and a few vegetable fields. These were the BMSB that had overwintered that were coming out of their hibernation mode and moving out for something to eat. Their populations grew a bit more in May, but then seemed to hold steady, except for some scattered hot spots throughout the Mid-Atlantic where their numbers and damage were much greater. For the most part, growers were ready for the onslaught and did a good job of limiting the bug’s damage, but at the cost of a heavy spray schedule and the loss of many of their IPM programs. The adult BMSB population has declined over the last few weeks in many areas of the Mid-Atlantic. I am guessing that some of the overwintering adults are dying off and that soon the nymphs will start to be seen in greater numbers than before. This is just what I see happening in some pepper fields. Where before we were finding few adults or egg masses, we now are finding 4-6 nymphs/plant (Photo 1). The nymphs are feeding on both large and very small fruit causing damage that looks much like what the adults would do to peppers (Photo 2). BMSB eggs were looked for earlier in the season and not found to any great extent, but the eggs of any stink bug are very difficult to find. That is why there still are no good thresholds for green and brown stink bugs in many vegetable crops—they are just too difficult to monitor accurately. These medium-size nymphs we are now seeing are easy to spot as they tend to be on the top or edge of the pepper plants in the morning and even during early afternoons. Growers should be looking for the nymphs now in all their vegetables, but especially in peppers and sweet corn even if they have not seen many BMSB adults before this time. These medium to small nymphs while not particularly easy to kill are much easier to control than large nymphs or the adults and this would be the time to control them.

Photo 1. Brown marmorated stink bug nymph

Photo 2. BMSB feeding damage on small and medium size pepper fruit

Summer Vegetable Plantings for Fall Harvest

Thursday, July 28th, 2011

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

Plantings for fall harvested vegetables are underway. Timing these plantings can be a challenge, especially where multiple harvests are needed. Plantings from mid-July through the end of August 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 this time of year 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 with planting different maturing varieties 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 by use of row covers or protecting structures. 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.

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.

Sunscald Very Prevalent in Peppers This Year

Thursday, July 21st, 2011

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

I know this seems very obvious to most growers, as we have sunscald every year in our vegetable plantings. This year just seems to be especially bad as I have gotten several calls from growers about a strange problem in their peppers that looks like sunscald, but couldn’t be. The reason given that it could not be sunscald is because the plants have thick foliage and the fruit seem well covered. Sunscald occurs when peppers or other vegetables are exposed to the direct rays of the sun during hot weather; the damaged areas may become papery and bleached or tan colored, and these areas often are covered with a black fungal growth (Photo 1). It is more apparent on plants that have sparse foliage or that have lost a large proportion of leaves to a leaf-defoliating disease. But almost all the farms I visited had plants that looked very good (Photo 2). The problem is that pepper plants often lean to one side or the other because of winds blowing them in certain directions. When this occurs sunscald can be especially prevalent on previously shaded pepper fruit that are suddenly exposed to the sun, even for a short period time. Photo 3 shows one of these leaning pepper plants and several fruit that were damaged by this sudden exposure resulting in sunscald. The damaged areas are vulnerable to infection by fungi (Black mold), and bacteria, so that at times a pepper fruit will be found that is a soupy, smelly watery mess. Sunscald is most prevalent on green fruit. Staking and tying pepper plants will greatly decrease the leaning plants and greatly decrease sunscald. The pepper plants do not have to be tied often, usually once is all it takes and stakes do not need to be any taller than the pepper plants (so broken tomato stakes work well) (Photo 4). Peppers in a tied vs. non tied section of field had vastly different sunscald problems. The stake and tied section had less than 2% of fruit sunscald damaged; the non-tied section had 17% sunscald damaged fruit for the same variety planted the same day.

Photo 1. Pepper fruit with small and large areas of sunscald

Photo 2. Pepper plant that appears to have good foliage and fruit cover but still has sunscald fruit

Photo 3. Leaned-over plant exposing covered peppers, resulting in several sunscald fruit

Photo 4. Staked and tied pepper plants, 4-5 plants between stakes, one string

Vegetable Disease Updates – July 8, 2011

Friday, July 8th, 2011

Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu

Late Blight
There have been no new late blight detections in DE or VA on potatoes. The disease apparently is under control and the weather has not been very favorable, especially where the temperatures have been over 90°F. Besides the two finds in DE and VA the only active late blight at present appears to be on Long Island, NY on both potato and tomato.

Downy Mildew on Cucurbits
As most of you know by now downy mildew was found in Sussex County on Tuesday and Dorchester County, MD. Both finds were on pickling cucumber. Since then downy mildew was found in an additional field near Bridgeton, NJ, Talbot County, MD, Wyoming County, PA, and several more cucumber fields in NC. Now is the time to be spraying specific fungicides for downy mildew on cucumbers. Continue to check the IPM pipe website for more information on the spread of downy mildew: http://cdm.ipmpipe.org.

Root Knot Nematode
Root knot nematode can be a very yield limiting pathogen on very susceptible crops like cucumbers and other vine crops, lima beans, snap beans and tomatoes to name a few. They are often worse in very sandy soils or sandy knolls in fields. With the temperatures that we have seen here in DE you can begin to see the swellings or galls on the roots in about 21 days from seeding or transplanting. Plants in infested areas of the field will be stunted and if the plants are dug carefully, if root knot is present, you will see galls of varying sizes on the roots. We have no chemical controls except for vine crops once the nematodes are seen. Vydate should be applied preventatively in fields with known root knot infestations at seeding and/or later when plants are still small. See label for details. Treating early is always better than waiting until galls can be seen.

Root knot galls on baby lima bean roots, 23 days from planting

Pepper Anthracnose
Be on the lookout for anthracnose on peppers. It has been reported in southern NJ. Anthracnose fruit rot can be a very difficult disease to control if it gets established in a field. Fields should be scouted frequently especially if peppers or tomatoes have been planted in the past. It is best controlled by preventative fungicide sprays beginning at flowering. Apply Bravo or another chlorothalonil product every 7 days and alternate with a stroblilurin fungicide (FRAC code 11) like Cabrio or Quadris plus Bravo. If anthracnose fruit rot appears, removing infected fruit from heavily infected areas will help to reduce spore loads and reduce spread if done early and often enough. Fruit will need to be removed from the field and not just thrown on the ground.

Anthracnose on pepper fruit

 

Physiological Leaf Cupping and Rolling in Vegetables

Friday, July 1st, 2011

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

Leaf cupping and rolling in vegetables can be caused by virus diseases, aphid infestations, herbicides and growth regulators. However, late spring and early summer is the time of the year that we often see leaf cupping and rolling disorders appear in vegetable crops that are not related to pests or chemicals. This can be seen in tomatoes, peppers, potatoes, watermelons, beans, and other crops. This is a physiological disorder that may have many contributing factors.

In tomatoes, leaf roll starts at the margins which turn up, then roll inward, most commonly on the lower leaves. Upward cupping is also found commonly in watermelons and potatoes. Beans, peppers, and other vegetables may cup downwards. Leaves may stay in this rolled or cupped state for a short period of time and then return to normal, or they may remain permanently rolled or cupped. Rolled leaves may become thicker but are otherwise normal. Physiological leaf roll or cupping is often variety dependent with some varieties being more susceptible than others.

There are several possible causal factors for physiological leaf roll or cupping. Water relations are suspected in many cases where there has been a reduction in water uptake or increased water demand placed on the plant. The plant responds by rolling the leaves which reduces the surface area exposed to high radiation. High temperatures, excessive pruning, cultivation, and vine moving activities may also trigger leaf rolling. High nitrogen fertility programs followed by moisture stress may also trigger this type of leaf roll. Inadequate calcium moving to leaf margins may also cause a different type of leaf cupping. This is also related to interrupted water movement.

In most cases, yields are not affected by physiological leaf rolling or cupping. However, growers may choose to select varieties that are less susceptible to this disorder.