17 articles tagged "Greens and Salad Crops".

Figure 1. Cercospora leaf spot of beet.

This disease was observed in a home garden recently on table beet (Figure 1). I was surprised considering how dry it has been.  Cercospora leaf spot also affects swiss chard. Symptoms include circular leaf spots that may have a reddish margin. The center of the lesions may start off a light brown and turn to gray after the fungus (Cercospora beticola) begins to sporulate. Under conditions conducive to disease, the lesions can coalesce and result in loss of foliage. Yield and quality of the crop can be reduced.  Cercospora leaf spot is favored by rainy weather or overhead irrigation and temperatures from 77 to 95°F.  The spores are readily dispersed in rainy, windy weather. One reference I found said that Cercccospora leaf spot can start with 90% relative humidity—that is, leaf wetness may not be necessary.  That might be why this disease is present in this dry spell.   Cercospora may in survive crop residue over winter. The fungus may also be seed borne.  Resistant cultivars are available.[Read More…]


xxxx

While many growers use high tunnels to extend the growing period for warm-season crops such as tomatoes or cucumbers, it is also possible to grow cool-season crops such as spinach well into winter. The winter over much of Indiana has been rather mild; spinach and other cool-season crops should be doing well. However, disease and insect pests may be a problem. In the first week of March, I observed leaf spot on spinach growing in a high tunnel (Figure 1). Note that the lesions occur on a cluster of plants indicating possible spread of a fungus. A closer look shows that the center of the lesion may be dark with fungal sporulation (Figure 2). I was able to confirm the disease as Cladopsorium leaf spot of spinach. Little is known about the biology of the fungal pathogen. However, the disease is favored by rainy or at least moist weather. The[Read More…]


Figure 1: Bottom rot of lettuce often causes stunting and wiling.

Although Indiana is not known for lettuce production, an increasing number of growers find that augmenting retail sales with leaf lettuce can be profitable. Since lettuce is a cool season crop, field planted leaf lettuce around Indiana may be reaching harvest stage. Leaf lettuce can generally be grown with few pests. However, lettuce drop was recently observed in a field of mixed lettuce varieties. Lettuce affected with lettuce drop often first appears stunted. A closer inspection may reveal that outer leaves are wilted and necrotic (Figure 1).  Eventually, the entire plant may die. If the plant is removed from the ground and observed, the leaf ribs that touch the ground may exhibit dark, rotten appearing lesions (Figure 2). The lesions may be associated with dark fungal bodies known as sclerotia (Figure 3).  Fortunately, lettuce drop does not often spread from plant to plant. The plants that are diseased will most[Read More…]


Bolting of crops overwintered in high tunnels is common in the spring. ‘Bolting’ refers to lengthening and blooming of the flowering stalk. Bolting is often a problem because the quality of the marketable part of the plant declines. Also, plants subject to bolting are programmed to die once they complete flowering and seed production so yield will decline in quantity as well as quality. Sometimes bolting is not a problem because the stalk, buds, and flowers can be sold as a new product while they last; this is often the case with kale,  mustards and related crops. Crops susceptible to bolting include those in the mustard family such as kale, mustards, tatsoi, bok choy (pac choi), mizuna, turnip, radish, etc.; carrots; beets and in some cases Swiss chard; onions; lettuce; and spinach. (Figure 1)   Bolting is triggered by environmental conditions. Some plant types are triggered to develop flowers by[Read More…]


It’s that time of year, where we are prepping high tunnels and getting back into the full swing of production, slowly, here in the Midwest. Many of you have already begun to transplant and may have encountered your first pests on these new crops. Aphids are one that remain a problem in high tunnels, and may even have plagued your winter production (Figure 1,2,3). Some keys to preventing or controlling these pests rely first on sanitation and then careful scouting. Try to remove any green bridge material that may already be infested before transplanting into the space. This includes weeds, lingering winter crops or residues. Having a week without vegetative hosts should get rid of any overwintering residents. After transplanting scout diligently, at least weekly, or more often on susceptible young transplants. Aphid infestations tend to begin on the growing points or younger tissues of the plant. Be sure to[Read More…]


Figure 1. Breakdown of young leaf tissues in the heart of a celery plant

Blackheart of celery is a physiological disorder that causes significant crop loss in major celery production areas. It is characterized by the breakdown of young leaf tissues in the heart of the plants (Figure 1). The affected young tissues turn black, which give it the name “blackheart”.  The cause of blackheart of celery is related to calcium deficiency in the fast expanding tissues, similar to the cause of blossom-end rot of tomato and tip-burn of lettuce. The symptom is more severe as plants approach maturity. Fluctuation in soil moistures; excessive soil fertility, especially nitrogen and potassium; and high soil salinity favor the development of blackheart. Varieties may show different tolerance to the physiological disorder. In addition, the problem can be prevented by avoiding wide fluctuation of soil moisture and over-fertilization. Drench application and foliar spray of soluble calcium direct to the heart of the plant may help to prevent the[Read More…]


Figure 2. Multi-leaf lettuces grown in a high tunnel (photo credit: Liz Maynard)

Winter farmers markets are becoming more and more popular. Lettuce is a primary type of vegetables grown for the market. As we are finishing up summer crops, it is a good time to learn and refresh knowledge about lettuce. This article discusses some of the basics of growing lettuce in high tunnels, as well as the lessons we learned from a trial conducted at Southwest Purdue Ag Center in fall 2016. Lettuce Types Lettuce has multiple morphological forms major types include crisphead (iceberg), butterhead (bibb), romaine (cos), Batavian (summer crisp), and multi-leaf lettuce (salanova). The first decision about growing lettuce is whether to harvest full-size heads of lettuce, or to harvest ‘baby-leaf’ lettuce (Figure 1). These harvest methods require very different production practices. Full-size heads are harvested one time as a single head of leaves. Baby-leaf lettuce is first harvested when single leaves reach about 4 to 5 inches, and[Read More…]


Figure 1. Lettuce in high tunnel showing symptoms of lettuce drop caused by the fungus Sclerotinia sclerotiurum. Photo by Erin Bluhm.

Some of the red and green multi-leaf lettuce plants in Figure 1 are wilted and closer inspection reveals death and soft decay at the crown and well as freeze damage (Figure 2). Getting even closer as in Figure 3 we see white fuzzy mold and find hard black sclerotia 1/8 to ¼ inch across and up to ½ inch long at the base of the plants and in the soil. These sclerotia confirm that the plants have succumbed to white mold or lettuce drop caused by the fungus Sclerotinia sclerotiorum. The lettuce was transplanted in September or October 2016 and the photos taken in mid to late January. We continue to see more plants succumbing to the disease. Infection by this fungus begins when sclerotia buried in the soil produce small mushroom-like apothecia and spores from the apothecia land on susceptible plant tissue, germinate, and invade the plant. Sclerotia can[Read More…]


Figure 1. Aphids on kale crop. Photos courtesy Liz Maynard.

Aphids can be one of the most damaging and hard to control pests during the winter months in high tunnels. The first step to managing aphids is to develop a scouting plan. Aphids reproduce clonally and develop quickly leading to very large population build-up in a short period of time. Therefore scouting is recommended at least three times a week. When examining plants be sure to look at the growing point and underside of leaves, where aphids prefer to colonize (Figure 1). Outbreaks commonly begin on the outer rows or the start of the row so these are places to be sure to include when scouting. In the summer months, successful control has been achieved using a soap/mineral oil spray consisting of 1.5% castile soap and 0.25% mineral oil. Cornell University also reports grower success using the biopesticides Mycotrol O and BotaniGard. These are commercially available formulations of the aphid-attacking[Read More…]


Figure 1. Flea beetles on Brassica (photo credit: John Obermeyer)

Many of our vegetable crops are subject to feeding by one or more species of flea beetles (Figure 1). Flea beetles get their name because they have enlarged hind legs that allow them to jump like fleas. Most species are quite small, and with their ability to jump, often seem to just disappear when disturbed. Flea beetles tend to feed on the leaves, chewing small round holes. When populations are high, the feeding holes with overlap, creating larger holes. Flea beetles tend to be early season pests, primarily because smaller plants are more affected by their feeding. Treatment thresholds vary from crop to crop. For example, eggplants, on of the most commonly damaged vegetable crops, should be treated when there is an average of 4 beetles per plant. For tomato, the threshold is when leaves are 30% defoliated. Crucifers have no particular threshold, so treatment should be made when leaves[Read More…]


Vegetable Crops Hotline - Department of Horticulture and Landscape Architecture 625 Agriculture Mall Dr. West Lafayette, IN 47907

© 2020 Purdue University | An equal access/equal opportunity university | Copyright Complaints | Maintained by Vegetable Crops Hotline

If you have trouble accessing this page because of a disability, please contact Vegetable Crops Hotline at guan40@purdue.edu.