Category Archives: Parasitic wasps

Vegetable Gardening the Natural Way

Do you grow vegetables at home? If so, I’m sure you don’t welcome wildlife into your veggie patches. Rabbits, groundhogs, deer, slugs, you name it, there’s some animal just waiting to devour your plantings and destroy all your hard work. Fencing (or a resident dog on duty 24/7) is usually the only way to keep the four-footed animals out, but what about the tomato hornworms, the slugs and the beetles that can’t be kept out with fencing?

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The kitchen gardens at circa 1730 Salem Cross Inn in West Brookfield, MA. Colonial farmers knew that food gardens interplanted with lots flowering plants helped keep pests under control.

Walk into any hardware or big-box store and you can take home a variety of cheap but toxic concoctions that will kill upon contact. Although this might stop some of the pests for the moment, spraying ultimately does more harm than good. Crop pests are well-adapted to the various poisons farmers have used for decades, and they’ll usually stage a quick comeback. Not to mention, do you really want to use increasingly complicated chemical compounds — mostly untested for long-term health impacts and their interactions with other common chemicals — on the food that you eat?

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If you spray for pests, you’re also killing the natural predators of the pest, such as this hoverfly (aka syrphid fly), a common non-biting fly that visits flowers for nectar – their larvae eat large numbers of our garden pests.

So how can you grow food without resorting to harmful chemicals? It requires a bit more thought than just just spraying something from a bottle, but it’s not complicated.

Basically, you enlist the help of the natural world…and tap into its natural checks and balances.

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Vegetable gardens at Tower Hill Botanic Garden – colorful, whimsical, functional, and “friendly” to the “good bugs” that eat garden pests.

When dealing with pests, think prevention, not cure. Here are a few Golden Rules:
  • Provide habitat for beneficial insects and birds who are natural predators of your garden pests. Give them what they need, and they’ll help keep pest populations under control.
  • Confound pests by companion planting your vegetables with plants with strong scent or other characteristics that confuse or repel pests, and rotate crop plants from year to year to stay one step ahead of pests.
  • Grow your plants in healthy, living soil that is rich in beneficial soil organisms – healthy soil means healthy plants that can withstand a bit of pest damage. Avoid synthetic chemical “power” fertilizers that kill soil life – these actually encourage the sappy, weak leaf growth that attracts pests.

In and around your veggie gardens, plant a variety of flowering annuals, perennials, shrubs, vines and trees to attract nectar-and-pollen seeking pollinators and predatorial insects such as hover/syrphid flies, soldier beetles, lady beetles, parasitic wasps and flies, and many, many more. Your aim is to keep the area buzzing with a variety of beneficial insect activity right through the seasons.

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Ring your beds with single-flowering marigolds (Tagetes spp). The bright, nectar-rich blooms attract beneficial insects right until first frost. Plus, the strongly-scented foliage seems to repel (or confuse) many pests, and they are less likely to find your plants.

The nectar found in flowering plants is what keeps those insects flying – it’s the fuel that keeps them patrolling your garden for pests, so make sure there’s something blooming all through the seasons to keep them fed. Yes, some flies are pests and certain wasps do sting, but most of the bugs flying out there are beneficial – preying on other insects, pollinating plants, and as a food source for other wildlife.

Check out this braconid wasp, which is in the process of laying its eggs inside a gypsy moth caterpillar – which means this caterpillar is doomed:

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Photo by Scott Bauer/USDA Agricultural Resource Service (Courtesy of bugwood.org)

You don’t have to worry about these wasps hurting you – they don’t have a hive to defend and they don’t sting! If you grow tomatoes, you’ll want to attract another type of braconid wasp that uses tomato hornworm caterpillars as its host:

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Above
: The rice-like cocoons on this tomato hornworm caterpillar are from a braconid wasp that will eventually consume the caterpillar. If you see a caterpillar like this, don’t kill it! You want the wasp to complete its life cycle and continue controlling hornworms every year.

If you are reading this because you have problems with hornworms skeletonizing your tomatoes, resolve to start adding plants for parasitic wasps for next year’s tomato crop. They’ll do a fine job keeping the hornworms under control for you.

Above: Rudbeckia and great blue lobelia bloom their heads off in the rich soil next to our veggie beds - at the same time attracting lots of parasitic wasps and flies who prey on garden pests.

Above: Rudbeckia and great blue lobelia bloom their heads off in the rich soil next to our veggie beds – at the same time attracting lots of parasitic wasps and flies who prey on garden pests.

Other common predatorial bugs that you want to attract to your habitat include assassin bugsambush bugs and certain types of stink bug, who feed on insect eggs, caterpillars and other creatures that can harm plants. You’ll find all of these in and among flowering nectar plants, weeds and wherever bugs hang out.

A garden buzzing with insect life also brings in the “big guns” of bug control, including birds, dragonflies, bats, amphibians (toads & frogs) and other wildlife whose diet consists largely of flying insects and/or insect eggs, caterpillars and grubs. Healthy local populations of these predators will cut WAY down on your pests:

Nesting boxes for birds and other winged wildlife at Garden in the Woods, Framingham MA. Nesting birds can feed their hatchlings hundreds of caterpillars every day, so provide them with nesting opportunities near your gardens.

Nesting boxes for birds and other winged wildlife at Garden in the Woods, Framingham MA. Nesting birds can feed their hatchlings hundreds of caterpillars every day, so provide them with nesting opportunities near your gardens.

Include some locally native plants in your landscaping- these are best for attracting nesting birds because they tend to support the most diversity in herbivorous insects — in other words, plenty of caterpillars to feed hungry baby birds!

Even if you don’t like the taste of cilantroparsley, fennel or dill, always try grow lots of these culinary herb plants – they are cheap and easy to grow from seed, and make good companions for tomatoes. Allow some plants to flower – their clusters of numerous tiny flowers (called umbels) contain individual portions of sweet nectar for small beneficial insects. These fellow members of the carrot family of plants are also a host for the caterpillars of the beautiful black swallowtail butterfly:

Don't kill these caterpillars! They turn into beautiful butterflies. Give them their own patch of dill or parsley to eat, or relocate them to queen anne's lace or wild carrot plants.

Don’t kill these caterpillars! They turn into beautiful butterflies. Give them their own patch of dill or parsley to eat, or relocate them to queen anne’s lace or wild carrot plants.

The tiny white flowers of cilantro attract parasitic wasps and many other beneficials

The tiny white flowers of cilantro attract parasitic wasps and many other beneficials

Leave some areas of bare ground in the vicinity of your vegetable beds to provide nesting opportunities for squash bees (important pollinators of squash and cucumbers) and other native bees that excavate tiny tunnels in the ground to build their nests:

Not ant hills, but nesting sites under construction by a metallic-green digger bee. Photo by Beatriz Moisset.

Not ant hills, but nesting sites under construction by a metallic-green digger bee. Photo by Beatriz Moisset.

 

Hang wooden blocks for wood-nesting bees and beneficial insects near your gardens. Many native bees and insect predators use tunnels in old wood or tubular plant stems as a snug winter home for their offspring:

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Nesting block for bees and other insects – showing telltale signs of use by mason bees, grass-carrying wasps and other beneficial insects.

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Bumble bees are crucial pollinators for many food plants such as tomatoes and blueberries. Although they do raise a communal hive, they are very gentle and won’t sting unless physically threatened. Give them lots of nectar plants (right through the season) and a place to nest near your gardens.

Problems with slugs? Slugs LOVE the moist conditions of well-mulched, well-watered vegetable gardens and can decimate plants in just a few nights of feeding. Bring in the toads – who hunt the soil at night for slugs, grubs and worms – by giving them a cool, damp place to spend their days:

Give slug-gobbling toads a "toad abode".

Give slug-gobbling toads a “toad abode”.

Feed the soil, not the plants! In other words, provide habitat for the soil food web, or the (mostly micro-biotic) wildlife that lives in the soil. Each year, amend your vegetable beds with compost, farm-animal manure, leaf mold, seaweed or fish-based fertilizer – whatever you can get your hands on locally:

Pests tend to attack stressed plants. Encourage healthy plants by amending your soil with good quality compost (above) and mulch well with organic materials to help retain soil moisture and build soil tilth.

Pests tend to attack stressed plants. Encourage healthy plants by amending your soil with good quality compost (above) and mulch well with organic materials to help retain soil moisture and build soil tilth.

Try to rotate your crops each year to stay ahead of pests. Many pests lay their eggs in and around their host plants – in the spring, when pests emerge, they won’t have such an easy time finding their favorite plants if they are growing elsewhere, and are more likely to be eaten by a predator if they have to travel in search of food. Another way of doing this (assuming you have the room) is to scatter a crop around your property instead of a single location or bed. If a pest infests one area, they may not reach them all.

These raised veggie beds on our small Massachusetts farm may look a tad weedy, but the surrounding plants attract so many beneficial insects and bird predators that pest damage is minimal. 

These raised veggie beds on our small Massachusetts farm may look a tad weedy, but the surrounding plants attract so many beneficial insects and bird predators that pest damage is minimal.

I hope this gives you some ideas of how to keep your vegetable gardens healthier for you, your children and pets, and the planet! Gardening with and for wildlife may mean your gardens might look a little messier than the “not a petal out of place, not a weed to be found” landscaping tradition, but free, natural pest control and the amazing array of predators and prey that will take up residence in your backyard? I hope you will agree, those are worth taking up a new beautiful wildlife gardening aesthetic

 NOTE: This is a reprint of my 24/Sep/2012 article “Can Vegetable Gardens be Wildlife-friendly” from Beautiful Wildlife Garden.

Japanese Beetles, Chickens and the Habitat Farm

Here on our small farm, we love our small flock of chickens – their delicious and healthy eggs, their comical antics and their expert bug control are all reasons why we’ll always keep a few chickens around. One additional bonus? Chickens LOVE to eat Japanese beetles!!!

Anybody who gardens in New England is almost definitely familiar with the damage that Japanese beetles can do to plant foliage and lawns. Their grubs (juvenile form) eat plant roots and wreak havoc on the shallow roots of chemically-treated lawns.

japanese beetle damage on plum IMG_0681_2The adult beetles cause extensive damage to foliage when they congregate in throngs during July and August, mating and feeding on plants.

The frustration for gardeners and landscapers is that Japanese beetles are not simple to control. Because they are an imported pest, very little local wildlife are adapted to use them as a food source and they have few natural enemies to keep their numbers in check. Even if you spray all the grubs and beetles dead with a toxic concoction, very soon they will be back, usually arrived from neighbors’ properties. It’s not worth it, especially because the poisons also kill the beneficial insects that you want to encourage.

The encouraging news is that natural predators of Japanese beetles introduced by biologists do appear to be having an impact on their populations. Parasitic wasps and microscopic nematodes attack beetle grubs during the time they spend in the soil. A parasitic (tachinid) fly imported from Japan by biologists targets the adult beetle and does appear to be having an impact on breeding populations. I don’t think we’ll ever see Japanese beetles disappear completely from our landscape, but from these natural controls I do notice fewer beetles each year in the gardens of central Massachusetts.

In the picture below, the Japanese beetle on the left has a white dot on its thorax (behind its head), which is the egg of the parasitic tachinid fly. Many beetles will “wear” multiple dots. These eggs hatch into larvae that burrow into the beetle and consume its tissue from within, eventually killing the beetle within 5-6 days. Don’t kill these beetles! You want the eggs to hatch and the fly to complete its life cycle to continue its work on beetle populations.

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The beetle on the right has no spots on its thorax – but does have rows of 10-12 white spots on both its sides – these are NOT the eggs of the parasitic fly.

So what can you do if a favorite plant is swarming with adult beetles? The least-impact method of controlling adult Japanese beetles is manual removal. In the morning when the beetles are lethargic, sweep them (with your fingers or a small brush) right off the foliage of infested plants into a jar of water. They will thrash around in the water but can’t fly away. You can then flush them down a toilet or, if you have a chicken coop, throw them into the coop! Your chickens will go crazy for them! Because adult beetles lay eggs in the soil where they mate and feed, the more beetles you can remove from your property during their mating stage, the fewer grubs that will hatch out into beetles next year.

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My hens Millicent and Betty follow me around during my “beetle sweeps” so they can gobble the beetles right from my collection jars:

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As for grubs (the juvenile form of the Japanese beetle that eat grass roots), avoid at all costs the chemical grub control based upon Imidicloprid (sold in the US by the trade name Merit) a chemical that’s been banned in several European countries due to links between its use and the collapse of honeybee populations (aka Colony Collapse Disorder). If parts of your lawn are dying and you suspect grub damage, your lawn is under stress and chemical treatments will not fix the problem. You can try applying beneficial nematodes (microscopic wireworms) to attack the grubs in the short term, but longer term, if you convert to an organically-maintained lawn where grass roots can grow deep into the soil, the impact of the grubs will decline. And, supply suitable habitat for ground-feeding birds and the parasitic insects, and let them do their thing. It’s healthier for your lawn, your family, the bees and the planet.

To support those tiny parastic flies and wasps, make sure you have lots of nectar plants blooming to supply the sugary substance these beneficials need to fuel their flight. Without nectar when they need it, they won’t stick around. Pictured below are New England native plants boneset, Joe Pye weed and goldenrod blooming in late summer:

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Raising Herbert – Part 3: Free to Fly (or be Eaten)

Good news from Turkey Hill Brook Farm! The monarch butterfly chrysalis shed its skin and finally metamorphosed into its adult butterfly form about a week after Herbert the caterpillar turned himself into a cocoon on August 8th:

I missed a few days of checking his progress on the milkweed plant, but on August 14th, you could clearly see the orange and black markings forming on the butterfly’s wings inside the chrysalis:

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I never saw the adult butterfly emerge, but on the evening of the 16th, I checked the leaf and Herbert was gone, and all I could see of this amazing metamorphosis was his tattered skin, showing that he had emerged and flown away!monarch-chrysalis-final

I’ve seen some fresh-looking monarch butterflies flying around our butterfly gardens this week, so I’m hoping that Herbert is one of them and hasn’t already been eaten by a hungry bird or other predator. As for whether he is male or female, I’ll never know, but a recent garden visitor pointed out a tiny monarch butterfly caterpillar about 1/2″ long and perhaps 3mm wide dining on a leaf of the same milkweed plant where Herbert did his changeover. Could Herbert have used the same plant to lay her eggs? If so, she might need a name change…maybe Hebe?

Since then, I haven’t seen the second caterpillar again, so it could have been parasitized by a tiny predatorial wasp that uses the bodies of caterpillars as a host to lay their eggs, which then hatch and begin feeding on the caterpillar from the inside out. Kind of gruesome, I know, but nature isn’t always pretty, and the predator/prey relationship is what keeps nature in balance. Without parasitic wasps to keep monarch caterpillar populations in check, the cats would probably eat their own milkweed food plant right out of existence. And no milkweeds? No monarchs!