Vegetable Garden Updates

Allium leafminer

HGIC received its first allium leafminer (Napomyza gymnostoma) question from a Baltimore gardener. The pest symptoms were discovered on chives growing in a window box. If you observe this pest please send photos and information through Ask an Expert.

The white spots are feeding punctures where adult leafminer flies  fed on plant sap. Photo credit: Lawrence Barringer, Pennsylvania Department of Agriculture, Bugwood.org

The white spots are feeding punctures where adult leafminer flies
fed on plant sap.
Photo credit: Lawrence Barringer, Pennsylvania Department of Agriculture, Bugwood.org

Mated female flies lay eggs on lower leaves and the hatched larvae feed on leaves, creating visible trails (mines) between leaf surfaces. They pupate in protected plant parts (bulbs. leaf sheaths) and a second generation of adults emerges in September and lays eggs. Larvae feed and overwinter in the pupal stage inside infested plants and adjacent soil.

A floating row cover can be used to exclude adults in spring and fall when they are flying and searching for host plants. Neem oil and spinosad are organic insecticides that may be effective in controlling allium leafminer. Here is some detailed information from Penn State (this European pest got its U.S. start in PA in 2015) and UME about the allium leafminer.

Tomato Planting Tips

Last year’s blog post has 5 tips for people who are ready to plant!

 

Spring Weather Is Tough on Seedlings and Transplants

And for those who could not wait…erratic spring weather is hard on the tender transplants of warm-season vegetable crops. Leaves that are yellowed, bleached, bruised, torn, punctured, spotted, and discolored are showing symptoms associated with challenging spring growing conditions. These include high winds, cool night temps, cloudy and rainy weather, and rapidly fluctuating air temperatures, etc. In addition, soil temps are relatively low, so root systems are slow to grow, pick up nutrients, and become established. Under such harsh conditions plants just sit and get beat up by the elements.

Tomato leaf tem that has been battling the April elements.

Tomato leaf stem that has been battling the April elements.

Pepper grows more slowly than tomato so expect plants to struggle for a while as they get established. The recent cool nights will not have much effect on later flowering and fruit set, but do pinch off pepper blossoms for 3-4 weeks to get strong root systems.

For tomato, night temperatures below 50-55 degrees F. typically cause pollination and fruit development problems (even though only buds are exposed) resulting in “catfacing” of tomato fruits (crevices, hollows and holes).

Catfacing on an un-ripe tomato

Catfacing on an un-ripe tomato

There is no way to prevent this other than holding off on transplanting until late May. Cultivars vary in the degree to which low night temps will negatively affect fruit. It’s typically best to immediately remove these fruits as they don’t develop or ripen well – only a small portion of each affected fruit may be edible.

Here’s additional information on vegetable seedling and transplant problems.

New Basil Cultivars with Resistance to Downy Mildew

Four new basil cultivars with downy mildew resistance are available for home gardeners- ‘Obsession’, ‘Devotion’, ‘Prospera’, and ‘Amazel’ (sold as plants). Seeds can be ordered from some online vegetable seed suppliers. ‘Amazel’ plants may be difficult to find at this time.

‘Prospera’ and ‘Amazel’ may be the best bets at this point, based on 2018 results from a Cornell University research trial.

Fabric Grow Bags

Many more types and sizes are coming on the market and gardeners seem to really like them. They are versatile, reusable, and affordable. Plant roots are air-pruned when they reach the breathable fabric. This promotes root branching and a larger overall root system. Here’s a 5-gallon bag (with handles) that we planted with herbs for Maryland Day on April 27th:

Photo credit: Jon Traunfeld

Photo credit: Jon Traunfeld

 

Summer squash growing happily in 20-gallon fabric bags.

Summer squash growing happily in 20-gallon fabric bags.

 

What’s in the Bag?

Be selective when buying growing media to fill containers. Products can vary greatly and carry an assortment of names- potting soil, topsoil, planting mix, etc. Look for products that are soilless (no sand, silt, or clay), are homogeneous in appearance, fairly lightweight when dry, and smell earthy.  A 1:1 mixture of compost and a soilless growing medium works well for most container gardens. Our “Soil for Containers” web page has more information.

The label on this bag lists “aged forest products and perlite” as the components.  The clods and lack of uniformity suggest it might hinder the growth of container plants. Photo credit: Jon Traunfeld

The label on this bag lists “aged forest products and perlite” as the components. The clods and lack of uniformity suggest it might hinder the growth of container plants.
Photo credit: Jon Traunfeld

By Jon Traunfeld, Extension Specialist

One Comment on “Vegetable Garden Updates

  1. The last year I grew rainbow Swiss chard and Russian kale I was plagued, PLAGUED, with leaf miner. I drowned my veggies in spinosed to no avail. It didn’t work. I finally pulled the plants in utter frustration. As much as I love these veggies, I will not be growing them again any time soon.

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