Page Intro: Mostly the larval forms of other pests inhabit the depths in one form or another during at least some of their life — most of them, anyway. On this page we’ll start with some background, then we’ll take a look at a variety of pests (like leafminers, and cutworms, grubs, gnats, and more), learn how they become a problem, talk about some serious pests, get some advice, find out what’s available to the scout, then finally get some solutions.
Some Background
Roughly ninety percent of all insects spend at least some portion of their lives in the confines of the dirt kingdom. This number is inclusive of good bugs, bad bugs and those in between. There are basically three types of insects, at least as it applies in this text, which can be found down-under: good bugs, which we will not concern ourselves with on this web page; bad bugs, which are bad because they cause damage to plant roots, bulbs etc.; and bad bugs which do not cause damage to roots and the such, but are merely developing in the soil so they can once again rise and become above-ground phytophagous or plant-eating pests. [Intro]
A Variety of Pests
These pests, regardless of which category they fall into, are members of several insect orders: Coleoptera, which are beetles; Lepidoptera, which are moths and butterflies; Diptera, which are flies; and others of equal importance. We’re talking about thousands of insects — wow! This all equates to one very important fact: the soil is a good place to practice pest control. Time of year will be one of the only variables you’ll be concerned with as not all the pests you may wish to target will likely be in the dirt kingdom at the same moment. Some pests spend dwell in the soil several times during every season. Some are always present, while others visit only once a year. Some natural biocontrols frequent Dirtropolis, too, in one form or another, but tend not to be as affected by the biocontrols discussed on this website as the pests which are discussed herein. Moreover, many beneficial creatures, such as earthworms, are not targeted at all — at least, again, by the biocontrols mentioned in this book. Now let’s take at look at a small fraction of the pests, in no particular order, you may be concerned with which may be conquered in the soil. [Intro]
Leafminers
As mentioned in the page, Leafminer Pests, those critters which are members of two orders, Lepidoptera and Diptera, can be pests which aren’t considered pests in the soil. Again, leafminers, as larvae, when they are through tunneling through your leaves, drop to the ground to pupate — at least the Dipteran leafminers do. Timing isn’t too critical when it concerns these pests as there are likely to be pupae present at any given time in greenhouses, but more seasonally outdoors. If you see the mines beginning to develop, an immediate implementation of leafminer parasitoids would be appropriate, followed soon after with an appropriate soil-pest biocontrol. Give them the old one-two punch combination. [Intro]
Cutworms
Cutworms, one of the pests mentioned in Caterpillar Pests, are extremely vulnerable in the soil. And this is good as this is when and where they exhibit their undesirable behavior — they are soil pests. Cutworms stay in the root-zone of target plants during daylight hours and are of little concern to growers. At night they are of great concern — especially to gardeners and farmers (they are not really a greenhouse pest in most cases). They come to the soil’s surface and wrap their bodies around the stems of newly emerged plants. There they feed on the plant’s stem, often severing it. At sunup they go down back down to the safety of the dirt kingdom. When the gardener heads back out to garden he or she will notice a plant, or plants, laying over with its stem chewed and nearly cut off at, or very near, ground level. The plant will be doomed unless it can send up new shoots. Targeting cutworms under most circumstances requires a preemptive action, before the plants are lost. With some crops the gardener or farmer gets a second chance. [Intro]
Beetle Grubs
Not previously mentioned on this web site are Japanese beetles, pests with which gardeners, orchardist and nurserymen are all too familiar. Japanese beetles, members of Coleoptera, devour the leaves of many popular plants, shrubs and trees. Common hosts include bush beans, roses and flowering crab trees, for starters. Moreover, they not only have their larval stage in the soil, they’ve been known to deaden patches of lawn if their “grub” numbers are significant. This makes Japanese beetles unique sort of pests, being in their glory above and below ground. Non-chemical means of controlling the adults once they’re seen on the foliage is difficult and time-consuming at best, and the ever-popular Japanese beetle trap can be really bad news as I mentioned in The I in IPM and Scouting Goods pages. The larvae or grubs are a different matter. There are generally two times to target the grubs: spring and late summer into fall — as that’s when they’re in their larval stage and residing in the soil. [Intro]
Fungus Gnats and Flies
One important pest — or category of pests — very common to greenhouses and other indoor areas, and the main focus of this chapter, would be fungus gnats, or mushroom flies as they’re called in that industry. This is especially true where artificial, sphagnum peat-based, manure-rich or compost-laden growing media are being used. These pests are generally from three genera (a taxonomical grouping) belonging to the order Diptera: Lycoriella, Sciara, and Bradysia spp. They were thought of as merely nuisance pests, like shore-, moth- and humpbacked flies (in my opinion), as recently as the 1990s. (Yeah, way back then.) It is now common knowledge that fungus gnats can actually be quite devastating to crops. They are known to feed on root hairs — which are essential to a plant’s uptake of nutrients — they vector root rot — causing bacteria and viruses and other soil borne diseases, and can actually kill plants outright if not kept in check. I know, when I was a grower they were my worst pest (it’s how I was introduced to biocontrol). [Intro]
And More
Other pests which can be fairly easily controlled underground, but more difficult to deal with above ground include the following: Black vine, carrot and strawberry-root weevils; sod webworms, wire- and potato-tuber worms; apple, carrot-rust fly, onion and cabbage maggots; and flea, June/May and cucumber beetle larvae. There are many species of pests which can be dealt with more easily when in their vulnerable subterranean stages, way too many to list here. Why, even fleas can be dealt with, and filth-breeding flies, and…? Well, you get the point. [Intro]
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