Every growing season brings a variety of inquiries into the UConn Home & Garden Education office, either by snail mail, email, or in person. This year was no exception and I would like to share some that I found particularly interesting.

As we are entering the Christmas season I will start with an image of a Christmas cactus with raised bumps on its leaves. Although they were the same color as the leaf they had a translucent appearance when viewed with the light from behind. These blisters are edema (oedema)are the result of a disruption in the plant’s water balance that causes the leaf cells to enlarge and plug pores and stomatal openings. Moving the plant to a location with more light and watering only when the soil is dry can control edema.

Edema on Christmas cactus

Christmas cactus with edema symptoms

The cold of winter can cause problems that sometimes aren’t apparent until later in the year. Tree trunks that are exposed to southern light during the winter can suffer from sunscald and frost cracks. Sunshine and warm daytime temperatures can warm a tree enough so that the sap begins to run but the nighttime temps will cause the sap to freeze and expand, weakening the bark and resulting in vertical cracks. Dogwood with sunscald (on left) and willow with frost crack (on right) are among the susceptible species.

 

There were several incidences of huge populations of black cutworm larvae emerging in the spring including a group that appeared to be taking over a driveway! The Noctuidae moth can lay hundreds of eggs in low-growing plants, weeds, or plant residue.

The wet spring weather that helped to alleviate the drought of the past two years also had an effect on the proliferation of slime molds, those vomitus-looking masses that are entirely innocuous. The dog stinkhorn (Mutinus caninus) is another fungus that made several appearances this year.

Hosta plants exhibited several different symptoms on its foliage this year and the explanations were quite varied, from natural to man-made. The afore-mentioned wet spring and summer or overhead watering systems can cause Hosta to have the large, irregular, water-soaked looking spots with dark borders that may be a sign of anthracnose (the below left and center images). In the image below on the right the insect damage that shows up as holes that have been chewed in foliage may be caused by one of Hosta’s main pests, slugs.

But one of the more enigmatic Hosta problems presented itself as areas of white that appeared randomly on the foliage. Several questions and answers later it was determined that the Hosta in question was very close to a deck that had been power washed with a bleach solution! Yeah, that will definitely give you white spots.

Bleach damage 3

That bleach bath also affected a nearby coleus (below on left). Coleus downy mildew (Peronospora sp.) also likes the cool the cool temperatures and humidity of spring (below on right). The gray-purple angular blotches of this fungal disease were first observed in New York in 2005. Fungicides can be helpful if used early and thoroughly, and overcrowding and overhead watering should be minimized.

The grounds of the residence where my in-laws live have a lot of flowering plants in the landscape and as we walked one evening I noticed that the white roses had spots of red on them. These small, red rings are indicative of Gray mold (Botrytis cinerea), a necrotrophic fungal disease that is also a common problem in grapes called botrytis bunch rot. The disease is a parasitic organism that lives off of the dead plant tissues of its host.

The fungus Gymnosporangium clavipes, cedar-quince rust, on Serviceberry warranted several calls to the center due to its odd appearance. The serviceberry fruit gets heavily covered with the aecia tubes of the rust which will release the aeciospores that infect nearby members of the Juniper family, the alternate host that is needed to complete the cycle of the infection.

Two other samples that came in, goldenrod (below on left) and sunflower (below on right), shared unusual growths of foliage. Sometimes plant aberrations can be the result of a virus (such as rose rosette disease), fungus (such as corn smut fungus), or, like these samples, phytoplasma. Phytoplasma is the result of bacterial parasites in the plant’s phloem tissue and can result in leaf-like structures in place of flowers (phyllody) or the loss of pigment in flower petals that results in green flowers (virescence). Phytoplasma parasites are vectored by insects.

A frequent question revolves around ‘growths’ of a different kind, in particular the white projections that can cover a tomato hornworm. These are the pupal cocoons of the parasitic braconid wasp. The female wasp lays its eggs just under the skin of the hornworm and the newly hatched larvae will literally eat the hornworm to death. As the larvae mature they will chew their way to the outside where they will spin their cocoons along the back and pupate. As the hornworm is effectively a goner at this point they should be left undisturbed so that the next generation of wasps will emerge to continue to help us by naturally controlling this tomato pest.

Tomato hornworm 3

Tomato hornworm with braconid wasp pupal cocoons

 

Another wasp that was caught in the act was the cicada killer wasp (Sphecius speciosus), a large, solitary, digger wasp. Cicada killers, also called cicada hawks, are so called because they hunt cicadas to provision their nests. It is the female cicada killer that paralyzes the cicada and flies it back to her ground nest. The male cicada killer has no stinger and although its aggressive nature can seem threatening to humans, the male spends most of its time grappling with other males for breeding rights and investigating anything that moves near them.

Cicada killer wasp

A cicada killer wasp paralyzes a cicada

 

Speaking of noticing what’s going on around you, as my husband was walking past a False indigo (Baptisia australis) in July he heard a strange cracking sound and called it to my attention. The plant in question was outside of a gym on the Hofstra University campus where our son’s powerlifting meet had just ended. As many lifters exited the building amid much music and commotion we stood their staring at the Baptisia, heads tilted in that pose that is more often found on a puzzled dog. The bush was indeed popping and cracking as the dried seed pods split open!

 

But none of our inquiries approach the level of oddity reported by a retiree in Karlsruh, Germany, who thought that he had found an unexploded bomb in his garden in September. Police officers called to the scene discovered not a bomb but in fact an extra-large zucchini (11 lbs.!) that had been thrown over the garden hedge.

skynews-courgette-germany_4146311

This is not an unexploded ordnance!

 

I look forward to next year’s growing season with great anticipation!

Susan Pelton