Answer #1 ·
Maple Tree's Answer · Hi Rafael-Bacillus thuringiensis (or Bt) is a soil-dwelling bacterium that is used as a biological pesticide. There are several types of Bt that can be used for killing a specific insect. Bt applied to the soil can can kill insect larvae that feed on the plants roots and enter the plant from beneath the soils surface but can also kill insects that feed on the foliage. You would need to know the specific insect you want to kill in order to acquire the proper strain of Bt. In your case other insecticides can normally be used to kill the insects that may be causing the damage.
The yellowing, browning, holes in the leaves, and leaf curling can be caused by serveral things. I would first check the foliage closely for insects. Holes in the leaves may be caused by sap sucking insects such as aphids, mites, and others. Holes can be made by these insects in the foliage causing yellowing and browning of the leaves. Other insects such as leaf miners which bore into the leaves and lay their eggs can cause the yellowing and curling of the leaves. Look closely for any tunneling on the surface of the leaves. These insects are normally found on the new tender leaves and not the older leaves. The tunnels appear as undulating white or yellow lines on the leaf surfaces. Other insects may be seen in grouping on the underside of the leaves only so make sure you inspect both sides of the foliage carefully as many of these insects are very small. Most insects that may have damaged your lime can be taken care of with treatments of a horticultural oil or Neem oil.
Environmental factors can also cause the yellowing, browning, and curling of the leaves. Too much water can cause yellowing and browning. Fungal diseases can cause spotting throughout the leaves and their margins eventually causing yellowing then browning with small holes in the center of some spots.
With the leaves curling and holes showing I'm thinking it may be a pest problem possibly with a nutrient deficiency also. Are the leaves yellowing with possibly the veins staying green? Check the leaves especially the new young tender leaves for signs of pests. Also check the soil and make sure it is not too wet. Eight inches or so below the surface should feel cool and moist but never too wet. If possible upload a picture of the tree and an upclose picture of the infected or damaged leaves. This may help to identify the problem. Above this answer and to the right of your name below your question you will see where you can upload a picture. Let me know what you find after inspecting the tree.
I noted a few links below that will give you some facts about Bacillus thuringiensis and its usefullness and how it works.
http://www.bt.ucsd.edu/index.htmlhttp://npic.orst.edu/factsheets/BTgen.pdfJohn)