Time to watch for pests

The season is warming up and insect pests are jumping into action. Here’s some old foes and some new ones to watch out for, and some friends too.

Gray garden slugs, Deroceras reticulatum, with chewing damage and slime trails on leaves.
Photo UC IPM

Slugs and Snails

We have very few snails, and compared to some other places I’ve lived, few slugs. But the slugs we do have really like the hoophouse. I found two this morning on the cucumber plants. (It was an overcast morning – they don’t like high temperatures.) My reaction was to flip them onto the path and stomp on them. We rarely have to take stronger action. If we do, we sink shallow plastic dishes into the soil, with the rim at soil level and fill the dishes with a dilute version of beer or soda, or sugary water. I don’t know if it has to be fermenting to be attractive to slugs, but any sugary liquid in our hoophouse warmth is going to start fermenting after a day. If numbers are really high and damage is extensive, we need to hunt the slugs down. Do this at dusk or later, with a headlamp and either a pair of scissors or a bucket of soapy water.

There is a good blog post by Joe Kemble on the Alabama Commercial Horticulture website:

Slugs or Snails in Your Greenhouse or High Tunnel? What Do I Do?

The post helps us understand our foe:

“Slugs are very sensitive to ambient temperature and can detect temperature changes as gradual as 2°F per hour. Slugs prefer to remain at 62 to 64°F although they lay eggs and develop normally (but slower) at lower temperatures. Development ceases below 41°F. Slugs can withstand slight freezing temperatures although their tendency to take shelter in cold weather protects them from freezing. Slugs try to escape from temperatures higher than 70°F. “

Joe Kemble offers  4 approaches to dealing with them: trapping, hunting, iron phosphate (Sluggo) and metaldehyde bait. Metaldehyde works very quickly, but it can poison and even kill dogs, cats and other mammals that might feed on it. So I don’t recommend that! Iron phosphate is much safer but also much slower – snails can take up to seven days to die. Neither should be used near waterways. Use of Sluggo has been allowed if conditions leave no less toxic option, under the National Organic Standards since 2006

Another good resource is the UC IPM site which takes the IPM steps one at a time and applies them to slugs. How to Manage Pests/ Pests in Gardens and Landscapes/ Snails and Slugs which has good photos.

Grow Smart Grow Safe  looks at many options. See their Table of Molluscicides. It explains all the current options.

Jumping Worms

Invasive Jumping Worm
Photo Wisconsin Department of Natural Resources

A new troublesome  invasive earthworm has arrived from East Asia. Here is a handy ID card

“Jumping worms (Amynthas spp.) dwell on the soil surface and eat leaf litter.  They can turn up almost anywhere from urban parks, to suburban backyards, to rural forests. Because they reproduce on their own, a single worm can start a new population. You can help prevent jumping worms from spreading to new areas by knowing what to look for.”

The Wisconsin Department of Natural Resources has good information, including photos.

These worms eat up all the leaf litter under trees, causing desert-like conditions. The surface soil becomes grainy, with a texture like dry coffee grounds, and no longer supports the growth of under-story plants.The 1.5″-8″ worms thrash around if picked up. Visually they can be distinguished from other earthworms with a clitellum (saddle), because theirs is cloudy white and smooth.

Use the jumping worm identification card [PDF] and brochure [PDF] and watch for this pest. Report finds to the DNR or your Extension Office.

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Spotted Lanternfly.
Photo from Virginia Cooperative Extension

Spotted Lanternfly

Another invasive alien is the Spotted Lanternfly, a pretty hopper. Lycorma delicatula (White), an invasive plant hopper, has been discovered in Berks County, Pennsylvania. It is native to China, India, Vietnam, and introduced to Korea where it has become a major pest.  As well as Eastern Pennsylvania, the pest has been found in Virginia, Maryland and New York.

The red bands on the hind wings are not visible when the insect is at rest with the wings folded up over the back. It can easily blend in on tree bark. Note that the earlier stages of this pest look very different. The first nymphs are black and white, later ones, red, black and white. All stages are spotted.

Adult Spotted Lanternfly (pinned). Photo USDA Aphis

This insect has the potential to greatly impact almonds, apples, apricots, cherries, grapes, hops, nectarines, peaches, plums and walnuts, as well as these trees: maples, oaks, pines, poplars, sycamores and willows.

The signs and symptoms of a possible infestation include

  • Plants that ooze or weep and have a fermented smell
  • Buildup of sticky fluid (honeydew) on plants and on the ground underneath infested plants
  • Sooty mold on the infested plants

If you find a spotted lanternfly, report it to your Extension Office.

Click here to learn more from Pennsylvania Department of Agriculture, and here to read more from USDA APHIS.

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A zipper spider on a tomato plant, catching anything that lands on its web. Photo Wren Vile

We mostly have good bugs. While working in the hoophouse this morning, harvesting scallions out of the way of advancing enlarging cucumber plants, I also found many tiny zipper spiders and their tiny webs. These will get impressively huge. We made a point of saving their egg-cases on the bows of our hoophouse over the winter.

Zipper spider egg cases overwintering in our hoophouse.
Photo Wren Vile

I also saw a tiny praying mantis, another creature whose egg-cases we make a point of storing in the hoophouse over the winter.

And I saw a tattered Monarch butterfly. I had to check the Monarch or Viceroy? Page to be sure.

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