I ’ve grownbearded irisin my garden for years ; in fact , these perennial are one of my favorite springtime bloomers . But in recent age , my bearded iris have been harry by a troublesome pesterer : the iris borer .
In early leap , my iris heyday bloom attractively , but by mid - July the foliage begin to turn yellow and vile . Brown splotch come out all over the steel - alike leaves , and when the plants are disturbed , sometimes there ’s an unpleasant odor . These are all pretty clear sign of an iris borer infestation .
Spotting The Iris Borer
Iris borers ( Macronoctua onusta ) are the cat of a specie of moth . These caterpillars spend their entire larval stage inside of an iris flora , munch on the foliage and rhizomes . The brown , unworthy leaves are have by their feeding . Eventually , all the damage leafage will ferment completely brown and shrivel up , possibly impacting next class ’s flower production .
Adult iris rock drill moths fly around the garden at night . They ’re fairly non - descript , and the females lay eggs on iris leaf in August or September . These diminutive orchis sit on the leafage all wintertime long , and the larvae hatching the following spring . The young cat tunnel into the newly emerged leaves and spend weeks feeding . They move down toward the base of the works as the time of year progresses , and by the time July get in , the bore bit are feeding on the rhizomes .
When they reach the rootstock , the borers tunnel through these fleshy root and often stimulate the rhizome to waste . That ’s what makes infested iris plants smell so poorly . I think they smack like lousy potatoes or onion .
In other August , the mature caterpillars start to pupate in the soil around the iris plants . Pupation takes only a few weeks before a fresh contemporaries of adult moths come forth and start to lay more eggs .
Protecting Your Irises
Trim Back Foliage
The rationality these pests have begun to plague me the preceding few year is because I ’ve neglected to turn off my sword lily plants back in the late free fall . Because the eggs overwinter on the foliage , it ’s very important to spend some metre every fall removing all the leave-taking from the plants , all the manner back to the rootstalk , and toss them into the refuse or burying them . This is best done after we get a few arduous frosts and the adult moths have stop over laying eggs . I have n’t gotten to this chore the past few season , and as a upshot , my sword lily plants are paying the price .
Discard Infested Rhizomes
If you have flag plants that are already infest with borer , you’re able to dig up the plants and crack launch the rhizomes to reveal any stone drill housed inside . Throw aside any soft , rotted rhizome and replant the healthy ones . If you bechance to amount across any chubby , pinkish , hairless caterpillars in the operation , be sure to slop them or run them to yourducksorchickens .
Apply Beneficial Nematodes
Another option for those gardeners who , like me , have neglected to trim back the foliation in the fall , is to apply beneficial nematode worm to your plants in the springtime . The correct mintage of this beneficial , microscopic roundworm are Heterorhabditis or Steinernema . These little critters are mixed with water and spread over the iris plants where they look for out and kill any iris borer larvae . They ’re best applied when the iris diaphragm leave-taking are to the full grown but the plants have yet to bloom .
The Silver Lining
Although I ’d like to rid my whiskered iris plants of borers to keep the plants looking and do their respectable , it ’s crucial to mention that an sword lily borer plague seldom kills an established iris plant life . Even if a handful of the rootstock are damaged , the rest will go on to produce healthy flowers the next year . Except in extreme cases , iris borers do n’t signify the remainder of the road for your barbate iris diaphragm plants . Gardeners like myself just need to put in a little effort to keep them in check .
Jessica Walliser
Jessica Walliser
