2016 World Crops Research Update - Okra and Eggplant

Transcription

1 2016 World Crops Research Update - Okra and Eggplant Vineland is publishing Issue 3 (August/ September 2016) in a series of four research updates evaluating various varieties and the effect of different management practices on the growth of okra and eggplant. Temperature and precipitation It has been a hot and dry summer in southern Ontario and eastern Canada. According to Environment Canada, the highest temperature recorded in July was 34.1 C with humidex values well above 40 C. August s highest temperature recorded was 33.4 C. Precipitation was below seasonal average with only 48 mm of rain in July and 41 mm in August. Drought conditions have persisted since April and the lack of precipitation and high temperatures have been hard on various crops. Vineland s research farm is equipped with drip irrigation, providing plants a sufficient amount of water and nutrients for optimal production. In this environment, okra and eggplant, being subtropical plants, grew well. Okra postharvest practices As discussed in previous research updates (Issues 1 and 2), okra needs to be harvested daily in order to maintain a high quality production. In a matter of a day or two, okra becomes woody and unmarketable. To provide accurate postharvest information to growers, a fact sheet on postharvest best Picture 1: Okra plant in full production (August 3, 2016). practices has been developed and can be found at It discusses proper storage procedures for okra including: Temperature: 7 C to 10 C Relative humidity: 95 to 100 per cent Quality can be maintained for up to 10 days depending on the specific okra variety Okra should be harvested during the morning and cooled down immediately using an appropriate cooling method. Okra should then be transported to a sorting facility to remove damaged and diseased produce. Chilling injury and injury-enhanced rots are common causes of postharvest loss in okra which can be prevented by handling produce with care and avoiding overpacking containers.

2 Okra fertigation and irrigation Nitrogen fertility trials were conducted for a second year at Vineland (see Picture 2). The objective of these trials was to establish a nitrogen response curve for okra by testing five different rates of nitrogen from 50 to 150 kg/ha. In 2015, the best growth and yield response were obtained when one third of the total nitrogen fertilizer was applied in the spring before beds were formed and the remaining nitrogen applied through drip irrigation after the first flower appearance. Regular irrigation and fertigation are key components to a successful production system. Okra responds best to 7.5 kg/ha of nitrogen per week. This rate of nitrogen fertilization is generally recommended for good crop management. Also, to ensure an adequate water and nutrient supply, okra was irrigated two to three times a week for a total of 50 to 75 mm of water. At the end of the growing season, Vineland will have a better understanding of okra s response to different fertilizer rates and whether the growth trend is similar to that observed in Picture 3: Okra hybrids from East West Seed grown at Vineland s research farm (August 3, 2016). New okra varieties Several new varieties of okra from East West Seed were tested. Since the seeds arrived in late June, they were directly planted into black plastic-covered beds. However because of the short growing window, it was not possible to assess their full yield potential. Instead the focus was on evaluating growth habit and pod structure and determining overall suitability to the short Canadian growing season. In general, plants emerged quickly and demonstrated fast growth and fairly high yield potential. More information will be available once harvest is completed. Picture 2: Fertigation trials at Vineland s research farm (August 3, 2016). 02

3 In Asia, as a result of insect and disease pressures, short-season okra hybrids are used to maximize yield and achieve premium quality. Three successive crops of short-season okra are also often grown in the same field in one growing season. These short-season, high yielding okra hybrids have great potential owing to the limited growing season in Canada. Picture 4: Okra pods damaged by thrips (September 16, 2016). Cucumber beetles sometimes feed on okra seedlings and chew holes in leaves and pods. Okra diseases Fusarium wilt caused by a soil-borne fungus can lead to severe crop loss if the level of fungus in the soil is high enough. Infection can occur at any time during the life cycle of the plant and can have devastating effects when soil temperatures reach 25 to 32 C. The fungus usually enters through feeder roots and colonizes the vascular system. Initial symptoms include yellowing and wilting of leaves with leaves eventually drying out and dropping prematurely. Plants are often stunted, producing limited fruit, if any. The fungus can persist in soil for a number of years due to its ability to colonize a wide variety of crops and weeds. It can be controlled by fumigation or planting varieties that are tolerant or resistant, especially if inoculum levels in the soil are low. Okra pests Thrips are a serious pest. Damage caused by their feeding leads to curving of okra pods tips (see Picture 4). During hot and dry summers, thrips populations can grow exponentially and cause severe damage to okra pods making them unmarketable. Thrips feed on okra flowers but rarely kill or affect the survival of the plants. Stink bugs feed on okra and can cause malformation of pods and wart-like growths on the surface. Japanese beetles also feed on okra leaves and in severe cases cause skeletonization. They also occasionally feeds on pods. Picture 5: Healthy okra plants (left) and plants showing Fusarium wilt symptoms (right) (September 15, 2016). 03

4 Eggplant irrigation Irrigation is an essential element of a successful vegetable production operation, especially during hot and dry summers. Eggplant are 80 to 95 per cent water, so a loss in water weight equals a loss in revenue when produce is sold by weight. Whether using overhead or drip irrigation, it is important to provide enough water to the crop for a high quality yield production. For eggplant, the most critical period in terms of irrigation is during flowering and fruit formation. Stress due to a lack of water during this period can lead to the development of blossom-end rot and malformed fruit. Fruit size and yield are also reduced by moisture stress. Picture 6: Long purple eggplant grafted on Kaiser rootstock (August 3, 2016). Powdery mildew was seen in some okra varieties although it has not been a concern this year. Symptoms first appear as white powdery spots on the leaves. In severe cases leaves curl, turn yellow, die and fall off. Severely infected plants may have reduced yield, shortened production times and fruit with little favour. Eggplant bruising Eggplant bruising can be a serious problem for Chinese long eggplant, making fruit unmarketable in some cases. To minimize bruising, it is important to avoid planting in windy locations. Bruising can be minimized by removing bottom leaves and trellising eggplant to limit plant movement. Grafting eggplant Since Chinese long eggplant is susceptible to Verticillium and Fusarium wilts, this year plants were grafted onto various disease-resistant rootstocks for field production. Results speak for themselves as seen in Picture 6. Although the cost to establish grafted plants is higher than non-grafted plants, this can be balanced with increased production. Picture 7: Eggplant bruising (August 3, 2016). 04

5 Vineland Research and Innovation Centre 4890 Victoria Avenue North, Box 4000 Vineland Station, ON L0R 2E0 tel: VinelandResearch vinelandresearch.com About Vineland s Feeding Diversity: Bringing World Crops to Market As part of a collaborative group of partners determined to build a local ethno-cultural vegetable marketplace, Vineland is leading research on new crop varieties (okra, Asian and Indian eggplant), production technologies, postharvest innovations, consumer insights and market development. Vineland s production team is trialing new varieties to assess agronomic performance and disease resistance. Picture 8: Ramesh Eerpina, Senior Research Technician in Vegetable Production harvesting eggplant (September 22, 2016). Takeaway messages Okra and eggplant reach full production in August while production volumes in September are steadily decreasing Proper postharvest practices are critical to maintain high quality and a long shelf life Thrips can be a serious problem in okra and can lead to misshapen unmarketable pods Regular irrigation and fertigation during hot summer months are important to achieve high production potential Short-season Asian okra varieties tested at Vineland show great promise Eggplant grafting may be a viable option to prevent losses due to soilborne pathogens To review other research updates, visit vinelandresearch.com/research programs/ feeding diversity. If the information contained in these research updates is of interest to you or if you have any questions, please contact: Dr. Michael Brownbridge, Research Director, Horticultural Production Systems x798 or michael.brownbridge@vinelandresearch.com 05