Macadamia Moth Pests in California:

Known and potential

Reprint from CMS 1963

There are substantial published reports of various insect species recorded as pests of the Macadamia. These are primarily from Australia and from Hawaii, Florida and California in the United States. Since the larvae (worms) of moth Lepidoptera constitute an economically potential hazard to Macadamia production and since the author is closely associated with this group of insects, this discussion will be restricted to the known and potential Macadamia moth pests in California orchards

A. Inflorescence and nut feeders.

The larvae of the filbertworm, codling moth, raisin moth and navel orangeworm have been identified from injured nuts sent in. The orange tortrix has been identified from injured nuts. It has also been observed building nests in the nut clusters causing some of the nuts to drop (Ebeling, 1959).

B. Foliage Feeders.

In this foliage-feeding group, the orange tortrix and black scavenger caterpillar have been observed feeding on the new flush of foliage and attacking the inflorescence clusters. The citrus looper is a native southern California species which is sometimes an economic pest of citrus (Atkins, 1960). It is known as the kiawe moth and the algaroba moth in Hawaii where it was introduced and was first detected during World War II (Van Zwaluwenburg, 1946). This species has been observed feeding on young Macadamia foliage (Ebeling, 1956; Namba, 1957). The omnivorous looper has been found infesting the foliage of Macadamia trees in California (Ebeling, 1959). This looper is a common place pest in all California avocado groves. The larvae of the tobacco budworm was once observed devouring the leaves of 3 to 8 inch Macadamia seedlings in a lath house nursery (Ebeling, 1956; 1959).

A. Inflorescence and nut feeders.

One would not be surprised to find the Peach twig borer attacking nuts on the tree. The almond moth, tobacco moth, Mediterranean flour moth and Indian meal moth will undoubtedly he found infesting Macadamia nuts both in the shell and shelled in storage.

B. Foliage Feeders.

This group of moths occurs commonly in most areas, are somewhat general plant species feeders. They can be expected to become occasional economic pests of Macadamia trees.

A. Nut feeders.

The koa seedworm is a native Hawaiian moth, which is the most important Macadamia pest in Hawaii occasionally causing a loss of up to 15% of the crops. It has been variously known as the klu tortricid, koa seed moth, koa seedworm, litchi moth, litchi borer, Macadamia nut moth, Macadamia nut borer and Macadamia nut husk borer. The koa seedworm is somewhat like our codling moth in appearance and habits. Damage to Macadamia by the koa seedworm is confined to the nut. Nuts one-half inch up to mature size are attacked. If the damage is extensive enough in the young nuts, development is stopped and the nuts may drop from the tree or dry upon the tree. When there is only slight damage, which is confined to the husk the nut may mature without any apparent effect. Often when the shell is damaged at an early stage but development continues the shell is distorted and undersized at maturity. The kernel is then undersized but not distorted.

C. illepida larvae usually damage the kernels only partially, lowering their sale price. However, an important consideration is that a hole through the shell provides an entry path for fungi, dried fruit beetles and ants which then may completely destroy the kernel (Namba, 1957).

B. Foliage feeders.

Both of these moths have been reported attacking leaves (Namba, 1957). The Mexican leaf roller is common in Central America (Mexico) and in Hawaii and is a pest of young trees.

SUMMARY—To briefly summarize the current worm picture on the Macadamia in California we can state that there is currently some economic damage to the nuts from five species of moth pests and some damage to the foliage from another five moth pests—a total of ten species. In addition to these ten species there arc twelve additional moth species which can be expected to become pests in the future. There is always a chance of other moth pest introductions and of other moth species already present becoming pests of the Macadamia.