Dayton "Dirt" - February 10, 2017

As February rolls along, work in the greenhouse intensifies as rooted cuttings now must be transplanted into pots and hanging baskets while more unrooted cuttings are to arrive from Costa Rica and Guatemala. Strict sanitation controls are in place at the foreign greenhouses where
the stock plants for the plant cuttings grow.

        

In 2013, a virus called tobacco mosaic virus or TMV was found in our greenhouse on petunias grown from cuttings in Central America resulting in their disposal after the plants were potted and growing nicely. The Dummen company sent out a warning that some of their stock that they had  shipped tested positive for the virus that is evident by a slight streaking or mottling of the normally evenly dark green leaves. The virus is spread by handling the cuttings while sticking them into the  rooting cells and then by trimming the plants. TMV will cause a collapse of the plants when the weather begins to warm up in spring. This collapse during warm weather is similar to a once common malady that geraniums are prone to call Xanthomonas. This geranium killer is actually a bacteria that is spread by water. Some plants, such as vining geraniums show little or no signs of the disease and yet can be a carrier that results in the infection of the zonal (regular) geranium. Today with virus testing and better sanitation methods, disease like Xanthomonas and TMV are relatively rare.

In the greenhouse too continues the application of the microscopic worms called nematodes. These small creatures move in water so that the foliage of the plants must be kept wet for no less than 2 hours so they are able to hunt down and kill the destructive thrip insect. Surprisingly, there are no restrictions by EPA as far as entry into the greenhouse once the nematodes are applied as they already exist in nature and are completely harmless to humans. Soon the hanging baskets just recently planted will need to be hung up so that two small packets of predatory mites will have to be attached to the plant’s foliage. These packets called mini-sachets contain two mite species called Amblyseius californicus and Amblyseius curcurbitae. The californicus mite seeks out the nasty European two spotted spider mite while curcurbitae prefers the lousy thrip insect. Everyday several of the mites walk out of a hole in the sachet for a total of 6 weeks that will protect the plant from destructive greenhouse pests without chemicals! With the help of a technician form the Biobest Company that produces and supplies these critters to the greenhouse and food crop industry, the complicated process of using “good” bugs to “fight” bad bugs should be well under  way this spring.

With more and more greenhouse growers and possibly farms using beneficial predators will pesticides largely be a thing of the past? I hope so.

Tom