The natural trend of the insect community can be observed in an almond orchard that has been neglected for years. This is the case of one which I bought last winter. I have not used insecticides here to get insight on what is beneficial, neutral or detrimental. Most insects have turned out to be either neutral or beneficial. Some make the trees look worse, but do not reduce growth or fruit production significantly, especially when other insects control them. But a nasty caterpillar has proved to be a dangerous enemy of almond trees.
His name describes it in a few words: the almond tree skeletonizer moth, aglaope infausta. This Lepidoptera is endemic in South Western Europe. Its presence can be easily detected in the orchard because of its characteristic pine nut like cocoon. I observed those empty cocoons in the branches of one tree in winter. In late March, I noticed that small black and yellow caterpillars were present in tress near that of the cocoons. They were voracious and some trees lost all their leaves. In May they formed the cocoons and small black butterflies emerged.
This pest has affected either healthy or weaker trees. The damage to those trees is intense. The good news is that the attack was confined to a small group of 10 trees out of 130 almond trees in the orchard. New green shots are again observed in mid August.
After having read about this insect, I realise that nothing can be done until next spring. It seems to be the case that the caterpillars are very sensitive to insecticides. This pest used to be serious in Spain years ago, but the practice of systematically treating with insecticides has made it no longer a threat.
The strategy that I am to follow is different. The intervention will be limited to trees that show clear caterpillar activity in late March or early April, while leaving the rest of the trees free from insecticides. I have seen the importance of beneficial insects that control potential pests, as explained in the entry “Aphids”. I truly appreciate the value of keeping a living insect community in the orchard.
I have followed this strategy in 2016 an treated only the trees that showed caterpillar damaged with an insecticide in late March. The weakened trees have recovered in a very impressive way. Some trees showed caterpillar presence in mid June. Damage was low and did not seem to affect production. However moths were plentiful at this time, so it is important to keep watching.